• Tag Archives System

    BoilersOnDemand.com via its Principal, Paul D, Mercier, Sr., has filed for Non-Provisional Intelligent Property Protection (Utility Patent) in the United States of America and Canada on the: ENHANCED CONVECTION, DIFFERENTIAL TEMPERATURE MANAGED, HYDRONIC HEATING APPLIANCE.

    We deem this to be the first, truly integrated, free-standing, simple, durable Hydronic (FHW) Heating Appliance in the Market. Enabled by recent advances in Delta-T ECM Hydronic Distribution, the major elements of energy generation and distribution augmented by our optimization of natural convection (Gravity Heating) comprise the highest efficiency product available ….. bar none!

    A true “appliance”, merely coupling it to site utilities and radiation effects a completed hydronic (FHW) heating installation. Dramatic reductions in materials, labor & skill content, floor-space and maintenance have been realized. A truly “Value Engineered” product.

    Further detail will be made available on our web site www.BoilersOnDemand.com as we finalize our patenting process.


    An Indirect Water Heater (IWH) driven by an efficient hydronic boiler is the acknowledged cost-effective method for domestic hot water (DHW) generation. However, installing an IWH as a stand-alone (dumb) heating accessory can limit its potential and in fact reduce your overall annual heating system efficiency (AFUE) in practice. Let’s examine the elements comprising a complete hydronic system and their effects.

    The Indirect Water Heater (IWH) has experienced a renaissance with the availability and effectiveness of modern materials and manufacturing. Specifically Stainless Steel, Super-Insulation and Automated Manufacture provide a superb product-performance package, eclipsing its predecessors and current competition. Even so they are not “cheap” in a monetary sense, yet provide an outstanding service life while maintaining efficiency!

    Referring to our website www.BoilersOnDemand.com you will note that we integrate an IWH into our “Packaged Delta-T Hydronic FHW Heating Appliance” as standard equipment for overall performance. The HTP Superstor Ultra has been our exclusive IWH offering for over twenty years with stellar performance! There are many IWH Products available, even within HTP, but the SSU Series still exceeds.

    Referring to our “Packaged Delta-T Hydronic FHW Heating Appliance” image provided you will note four (4) basic system components:

    1. A “High-Mass” Weil-McLain Ultra Series UO Boiler.
    2. A “Green” Taco Delta-T ECM Circulator immediately above the boiler.
    3. Several Taco “Zone Sentry” Valves near circulator (for IWH) and @ top, center for heating zones.
    4. A HTP “Superstor” IWH, close-coupled to the right.

    As a standard feature on all systems utilizing an IWH as pictured, we provide a SPST (ON/OFF) Switch mounted on and in series with the IHW Aquastat. This allows selective engagement during system set-up, quick start-up, operation and diagnostics. It is visibly evident between the boiler and the IWH, placed for convenience.

    Our “System User’s Guide” refers to the IWH Selector Switch as a means of customer-inhibited operation with a two-fold purpose:

    1. Cycling only preparatory to demand DHW usage such as a dishwasher or shower(s), then “tailing” hot water via additional tasks to efficiently utilize remaining storage.
    2. Turn off DHW during protracted absences such as vacations, etc. while preserving primary area heating without risk or penalty.

    In either sequence boiler temperature is significantly reduced, ultimately approaching area ambient, reducing fuel consumption in the process.

    Using our SPST (ON/OFF) Switch as a junction box we also offer to our clients extension via another switch in series to a more convenient operating location. This is particularly helpful when considering site physicals and customer physical impairments or limitations.

    Carrying this to the next logical level is using at minimum a 1-Day or preferably a 7-Day Programmer, as may be applicable to your lifestyle. Keep in mind though that an IWH Zone uses a “dry” switch, i.e. no power applied, or you will “fry” something (your system aquastat!). Program your IWH Service to compliment your usage pattern for energy savings.

    Then you can proceed into the “wireless”, intelligent world via Wi-Fi Thermostats, Home Automation and the like. Like our “techie” customer on a work assignment in Hawaii who called us to advise he had a heating problem in his seasonal home up here in New Hampshire, the world is changing and beneficial technology is available to us all.

    By becoming “smart”, we can save ourselves a bit of trouble and a little money in the process.

    Author’s Note: Updated 01/10/2018

  • THE DELTA-T ECM CIRCULATOR — The “Automatic Transmission” for Boilers

    After speaking on-site  with a local customer about his system, he inquired as to what else we were doing. A mistake on his part.

    Both of us having differing technical backgrounds I launched into an inspired dissertation of our application of Delta-T ECM Circulation to Residential FHW Heating Systems. Obviously very interested, a running Q & A exchange of increasing technical depth ensued to the point of my noting he was developing that “deer in the headlights” look of incomplete understanding.

    We engineering types have a terrible habit of technically overloading our audiences, not as an “ego-trip”, but to inform as effectively as possible — we think!

    Needing to salvage the situation I paused, desperately searching for that inspired “bolt of lightening” to strike and clarify the atmosphere. By seeming grace, it came immediately! “I’m putting Automatic Transmissions on Boilers.” Yeah”, he responded, “that makes complete sense. Good idea!” Our further conversation became an analogy of FHW Heating Systems to Automobiles, surprisingly clearing our technical disparages. To expound …..

    After all, hot water boilers and automobile engines are both truly “heat engines”. An automobile engine must convert as much fuel combustion energy into mechanical propulsion power as possible via pistons, crankshafts, etc. Less than 60% becomes useful power, the remainder is dissipated as waste heat. The hot water boiler on the other hand necessarily converts its fuel combustion energy directly into useful heat at up to 97% efficiency!

    The automobile uses a transmission to adapt its mechanical power to control vehicle propulsion. A variety of gears, pumps, valves, etc. are used to accomplish this. The hot water boiler conversely needs only to move heated water (via a pump) exactingly to ideally acclimate our heated areas and (optionally) our domestic hot water (DHW).

    The Delta-T ECM (Differential Temperature) Variable Speed Circulator (Pump) is that ideal “boiler transmission” that delivers heated water most efficiently to maintain our comfort. So efficiently does it do so as to reduce system fuel consumption by up to 15% and electrical consumption by up to 85% as documented by Taco, Inc. Published Testing Results.

    No longer is heating system efficiency measured solely (and inaccurately) by the Boiler AFUE (Annual Fuel Utilization Efficiency) Rating, but the aggregate of Boiler, Distribution and Radiation Efficiencies. There are THREE (3) Elements in a hydronic heating system! Just as in Sulky Racing, it’s the combination of the horse, the jockey and the buggy that wins races.

    Even more exciting  is the opportunity provided by the Delta-T ECM Circulator to most efficiently configure a FHW Heating System, which we have done very effectively. Refer to our other, recently published Delta-T Blogs on this site that detail our development, field testing and observations of our systems.

    Our “Packaged Delta-T ECM Hydronic Heating Appliance™” (Patents Pending)exhibits the following attributes in direct comparison to the typical “conventionally installed” system:

    1. Has a higher Combined Boiler AFUE and Delta-T ECM Distribution (System) Efficiency than achievable with any “conventional” system configuration.
    2. Consumes less fuel and electrical power than any equivalently sized system.
    3. Our Integrated Boiler/Indirect Water Heater System occupies 1/3 to 1/2 the floor-space of others.
    4. Our proprietary Fully-Iron & Cast near-boiler piping maximizes durability and distribution performance while using fewer materials.
    5. Further, combining a High-Mass Boiler with an All-Stainless Indirect Water Heater assures a dramatically projected economic life (30 years or more?).
    6. A truly universal, multi-fueled Appliance. Just change the burner —– not the system!
    7. Provides, Simple, Durable, Efficient and Cost-Effective FHW Heating.

    So yes, we do put “Automatic Transmissions” on Boilers!

    Author’s Note: Updated 07/23/2018


    A Forced Hot Water (FHW) Heating System is designed to efficiently provide energy distribution to heated areas. This is accomplished by combusting fuel in a boiler and moving the heated water through radiation to warm the desired environment.

    However, to accomplish this most efficiently requires:

    1. A high-efficiency appropriately sized and fired boiler.
    2. Properly proportioned and positioned radiation for each heated area.
    3. Idealized, simultaneous energy delivery of heated water to all radiation, irrespective of heating demand patterns.

    Practically however, none of these elements are absolutely correct, nor can they be. Boilers and radiation are almost never idealized for efficiency, but the third (energy distribution) is typically the most poorly executed of all. You must deliver heated water at an ideal rate for maximum heating transfer efficiency.

    Common distribution systems typically consist of:

    1. Dedicated circulators for each zone, or
    2. A common circulator with a zone valve for each zone.

    These configurations do not perform efficiently in practice, and in particular zone valves.

    “Delta-T” is a technical connotation. “Delta” (from the Greek letter ∆) is difference, or differential. “T” designates temperature. Thus Delta-T (∆T) is “differential temperature”.

    The Delta-T Continuously Variable Speed Circulator  employs temperature sensors attached to the boiler supply and returns points. It measures and maintains the ideal temperature differential by infinitely adjusting its water delivery rate (pump speed) to suit. Coupling with the new Low Energy, High Flow Zone Valves this technology maximizes the efficiency of any hydronic system with dramatically reduced electrical power consumption.


    Additionally, this system also smooths the performance of your existing radiation by typically eliminating hydronic whistle from over-sped, heating lag and imbalance from under-sped zones.

    No costly control system is necessary! The innate intelligence of the Delta-T Circulator teamed with the self-diagnostic capability of this new generation “Green” Zone Valve simplifies wiring, installation and diagnosis.

    It’s a Terrible System. Terribly Simple – Terribly Efficient!


    Coal is our most plentiful yet most maligned source of energy. Generating the majority of our electrical power and fueling heavy industry, it has projected the United States from an agricultural to the predominant industrial society in less than a century. But with the EPA’s focus and regulatory squeeze, it has become the convenient “dog to kick”.

    However, the dog and the coal industry are not beaten yet. Witness the shift to exporting our coal to Eastern Europe, the Far East and resurgence of coal “parlor heaters’ supported by bagged fuel. This is not all, however. Economics Rule!

    We have recently through a series of coincidences come to acquaint a fellow tradesman whose specialty is automatic coal-fired hydronic (FHW) systems. His niche is larger, energy-intensive applications such as greenhouses, up-scale housing and “expansion mansions”. (The latter is a regional term denoting seasonal homes that are inordinately expanded and upgraded.) Greenhouses are typically gas, oil or wood heated at significant expense in an effort to survive economically. Upscale housing and “expansion” owners are motivated by pure economics in substituting or augmenting their heating system requirements. Again the latter is where we cross paths.

    Our market effort is providing a Premium, Optimized, and Packaged American Gas or Oil Hydronic Boiler System, ready to “plug & play”. We can also supply our systems pre-piped to interface with a coal/wood boiler as a fully integrated system. There is therefore in our view a very complimentary pairing of coal and wood boilers with gas or oil powered hydronic distribution systems.

    As a solid fuel system a coal fire must be maintained continuously while being modulated (adjusted) to suit heating demands. You don’t just turn a coal fire on and off with a switch, as with gas or oil powered burners. Thus you must utilize or dissipate the minimum fire energy, or let it extinguish. This relegates automatic stoker-fed coal systems to being effectively a heating-season-only appliance.

    The complimentary match is an integrated gas or oil burner boiler to provide the minimal heat and domestic hot water (DHW) requirements off the coal cycle. Thus is our affiliation with our coal systems guy. Whether it’s integrating an existing powered system with coal as previous or providing an overall solution, coal (or wood) systems can be very complimentary indeed.

    The surprise has been the economics of coal as a residential heating fuel, if you work around its physical attributes and distribution challenges. Idealizing its use can make coal more economical than even a sophisticated natural gas system. We have ‘run the numbers’ to our amazement! Let us elaborate.

    First, coal pricing is not necessarily a distribution determined commodity. You would not recognize this as a parlor stove, bagged coal user, but as a central heating system fuel you enter the bulk product market. Now you have options, similar in some regards to the cordwood vs. wood pellets scenario, with one notable exception ….. energy density.

    Coal has a moderately high energy density in comparison to wood for instance, being a necessarily granulated product for automatic stoker-fed coal FHW boiler systems. You can easily handle and pack a lot of it into a storage space. So the key is to ultimately source and deliver the product from its source location in bulk.

    There are two (2) means available, truck or train, or a combination of both. Your strategy is therefore predicated by your point-of-use transport and/or transfer site availabilities. Ultimately your option(s) will be driven by the nearest raw material source. In our case (North Central New England) we have no railhead or ‘coal shed’ facilities (truck under coal hopper car drop site). So we source typically from N.E. Pennsylvania. The ‘coal shed’ is likely the most efficient transit-transfer method, dictated by capacities:

    1. A coal train hopper car has a capacity of well over 100 tons.
    2. A tractor-trailer can legally haul about 22 tons maximum.
    3. A dump truck (for local drop) will vary depending upon its GVW.

    Now you must do the math, based upon your specific annual requirements, individual handling and available storage. Obviously you must work upwards from your system active hopper charge size, considering your refill frequency, etc. to optimize your pattern.

    Your opportunity is to move your fuel from the mine(?) yard at about $100+/- a ton to yours with minimum transit & handling cost. The local scenario is employing an independent Pennsylvania Semi-Trucker who delivers his 22-ton load here, and then back-hauls a bulk load home. This can be wood by-products, aggregates, scrap metal or whatever from this area. Obviously planning and scheduling are in order, and the resultant is a $250 per ton or less delivered cost.

    At $250 a ton or less coal trumps even natural gas (available or not) heating costs utilizing a 95% efficient Condensing Gas Boiler! This is in contrast to a $350+/- per ton cost of buying bagged coal from the local stove shop as a convenience (and handling it).

    The advantage as we see it of an integrated coal-oil or coal-LP (Propane) system is having your energy storage all on-site, and with a generator backup being totally unaffected by both electric outages and heating energy cost fluctuations.

    We must necessarily defer to the coal guy for technical and operational details. Our interest is solely to inform the consumer of all his options while noting our potential technical contribution to heating system integration and performance.

    Well, almost the only reason. Permit me a reflection.

    As a child at the end of WWII I vividly recollect our home being steam-heated with 11 cords of wood annually, and being cold in the process. Not to mention taking away cord wood from a whistling, open saw inches away from your hands and stacking it, seemingly forever. My Dad and a one-armed Uncle operated his saw, the same one that had taken his arm several years earlier. My Dad had had enough.

    We converted to an automatic coal stoker system with a large bin. Recall several nights being shaken out of sleep in a cold house to help my father fix the boiler. My task was to hurriedly dig to the bottom of the coal bin with my hands and remove a piece of chunk coal mixed into the bin that had stuck and sheared the auger feed pin. Meanwhile my Dad built a new fire and replaced the shear pin after my dislodging the chunk. Washing off all that coal dust with Lifebuoy Soap in cold water was the climax, and then hopping back into bed in a hurry.

    Otherwise we always had a nice warm house with radiators hissing that we could back up against, warm ourselves and dry our clothes. Loved that old coal stoker!

    Old, pleasant memories become more vivid as we age, don’t they?


    We recently upgraded an oil boiler for a single, elderly WWII Veteran and self-admitted perfectionist. He built his home in 1956 with a brother and friends from sawing the lumber to literally driving every nail in the place, and it is beautiful! It would be a candidate for the Better Homes & Gardens Showcase of its time.

    Thus it was no greater surprise to discover an American Standard Arcoliner, a premium vintage boiler in absolutely fantastic condition for its age. Along with it, our client’s dissertation on its history, maintenance, observed firing patterns, etc. (Every replaced nozzle was lined up on a shelf on his workbench!)

    Our customer had read the manuals, tech sheets et al related to our Weil-McLain Gold Boiler before start-up. Upon seeing the system come to life, he immediately focused on the Hydrolevel 3250 Master Aquastat that was brightly displaying boiler water temperature along with a series of red, yellow and green status lights. As the system warmed we monitored and explained all of the readings and light display changes and then its normal operating characteristics. Since then he has given us boiler temp and firing patterns that we will use to adjust his system.

    It is obvious that our customer will be fixated on his new “baby” forward. Not only is it a new area of interest, but will positively occupy him to a predictable economic benefit in the future. (We are awaiting a deep cold cycle to possibly adjust his boiler firing rate to suit.) These observations have led us to suggest that this FHW (Forced Hot Water) System Upgrade may be just the gift to not only occupy an inveterate “twiddler”, but also provide an economic benefit in the process. It’s “the gift that keeps on giving”, as the adage goes.

    Whether you the reader fit this profile, or a spouse, friend or whomever, the results should be the same. Installing this device on your applicable heating system will ultimately benefit the owner while keeping him out of mischief. You cannot blow anything up, but on the other hand your home and/or DHW (Domestic Hot Water) temperatures may be affected as low temperature adjustment limits are reached. The solution is obviously to readjust these, much as one (or more) plays with a thermostat. There is also a “factory default” feature that resets everything so that the twiddle cycle can commence again.

    So, check first that your particular system is applicable for upgrade to this truly modest cost and efficient device. Then decide whether your subject recipient is capable of installing it or have it done by a qualified tradesman. In any case you will hopefully benefit in more ways than just economically.

    Let the twiddling begin!


    Yes, we have an oil-wood (or coal) central heating system in our home that can fully function without ANY electrical power through outages and uses less power in normal operation as well. How? Gravity induced convection heating. It was initially installed in 1975 and been incrementally improved to date.

    We are unabashedly Weil-McLain Heating System Designers and Installers. This does not mean however that we kowtow to the heating fuel suppliers and pay-as-we-go! Living in rural, frosty New Hampshire our economic fuel options are limited to oil and wood only. (Propane is a substantial premium and Natural Gas is not available.) So it is not surprising that many of us use wood or a mix of fuels to survive economically. Therefore, wood, wood pellet, coal stoves and wood boilers.

    Particular evidence of this heating trend is the recent popularity of external wood boilers (Metal Storage Sheds with a smokestack sticking up out of them) that occupy many rural yards, next to a large woodpile. (Not to mention the well worn path from the house to the wood boiler!) As a facet of our enterprise we mention interfacing our Weil-McLain FHW Boilers and converting our Steam Boilers to accommodate them. Not surprisingly we get inquiries by sometimes frustrated users to assist in making the wood boiler work well with their central heating boiler. The stories can be a bit humorous, in fact.

    Let us first describe our subject system with the intent to provide you with the principles and applications we employed and from which you may benefit in your application(s).
    We have two (2) single-fuel boilers, centrally located in the basement level of a large split entry home that we built in 1970:

    1. A Weil-McLain Model 568 Oil-Fired Boiler, installed in 1995 and subsequently “tweaked” for performance.
    2. A 1935 Vintage National Heating Co. Economy No. 64 Wood Burner. Found, reconditioned and installed in 1975. A museum-piece that still runs very well.
    3. A 40 gallon “Hot Roc” Stone-lined Storage Tank coupled to the Old National that prevents a boil-off if it is overcharged with wood or used (carefully) for extra hot water (heating) storage.

    These boilers are commonly coupled to an overhead supply manifold and on-the-floor piping between return manifolds, physically separated by ten (10) feet. This layout provides for a simple, pure convection loop between them. NO CIRCULATOR IS REQUIRED!

    There are three (3) circulator driven heating zones off the Weil-McLain manifolds. These are FloChek Valved off the upper supply manifold with circulators on the return manifold.
    The two (2) upper (main) level Living and Bedroom Area Zones are of Split Loop Configuration (reference our recent subject blog for detail) and the lower level Office and Garage Loops are a Split Perimeter and Unit Heater configuration, respectively.

    Gravity Hot Water Central Heating has been around for over 150 years but was never too popular due to its restrictive design attributes. It is functionally a single zone, single level system where building characteristics allow. There is significant lag in response to a temperature change demand and if boiler control is not absolute, temperature control suffers as well. Nonetheless, where and when you can employ convective heating it can be beneficial from a distribution energy perspective (or a lack of it available).

    Our Split Loops are fed by 1” center tapped supplies and returns that feed conventional series 3/4” radiation loops on each halves. The loops are configured with conventional 1” FloChek, manually controllable seat, opening valves on the supply manifold taps. These FloChek Valves are always included in a hydronic (hot water) system to prevent natural continuous convective heating. If one fails you have continual heating in degree regardless of thermostat setting. Note: FloChek valves may also be incorporated within a supply side circulator.

    So we can use natural convective heating to our advantage. By employing a modest upward pitch to our Split Loop supply and return lines we augment gravity convection (hotter water rises, cooler water sinks) and opening the FloChek valves we have a “controllable” energy-free heating zone. The adjective “controllable” has to be qualified by trial and error settings over varying indoor and outdoor temperature demands.

    Let’s go through the four (4) Operational Modes available in our system:

    1. Powered, Oil-fired FHW “conventional” heating only.
    2. Powered, Oil and Wood-fired dual fuel heating.
    3. Powered Wood-fired heating only.
    4. Powerless Wood-fired heating.

    Powered, Oil-fired FHW “conventional” heating mode is conventional in all regards. There is an “open on rise” aquastat (adjustable) on the wood boiler that performs two (2) functions:

    1. Inhibits the oil burner boiler primary control when the wood boiler temperature setting is reached.
    2. Opens a motorized valve to enable the inter-boiler convection loop to operate.
      “Set it and forget it” applies.

    Powered, Oil and Wood-fired dual fuel heating is enabled when the wood boiler aquastat engages and disengages the oil burner and the convection loop valve as wood burning proceeds. There is a second aquastat on the wood boiler supply pipe that “closes on rise” as water temperature approaches the boiling point (set at 200F). It opens a zone valve that initiates a second close-coupled convective loop allowing room temperature (or above) water in the “Hot Roc” Tank to temper the boiler water temperature. So if you overfill the wood boiler and walk away there is no consequence. Works beautifully! This feature is referred to as a “Dumping Zone” – getting rid of the excess energy.

    Powered Wood-fired heating only operation is similar to the oil and wood mode excepting the oil burner is fully disabled by moving the wood boiler aquastat to its lowest setting nearing ambient room (and therefore water) temperature. We have another option on our particular oil burner primary control of a built-in switch-off feature. (A common switch could also be employed to open this wood boiler aquastat to primary control circuit.)

    Powerless Wood-fired heating is merely emulating the operation of the powered mode while adjusting FloChek Valves on your heating zones and maintaining your wood boiler temperature range. In fact you can strike a boiler charging pattern that can free you from full-time babysitting the “dragon”. Our Samson 5D (Expansion Slug Type) Boiler Controller will maintain a temperature setting reasonably well on the Old National excepting when you seriously overcharge the beast — then things start happening! When the pipes start banging you have to “expeditiously” open the “Dump Zone” Tank Valve manually to temper it down. You learn this lesson in a hurry!

    To summarize, we used the wood only mode (powered and powerless) continuously for nine (9) consecutive years, providing full-home corner to corner heating and providing our domestic hot water for our large family. (The summer season requires a little lifestyle scheduling.) Annual wood consumption was four (4) to four and a half (4-1/2) cords per year.

    Since that time our lifestyle changes have precluded wood-only operation, but it’s there if we need it. Evidencing a severe ice storm a couple years ago that crippled most of New England for over a week, it was a mere inconvenience to us.

    Unfortunately gravity convection heating has little applicability to the current external wood boiler rage. They require electrical power for operation. The internal wood boiler is another matter, such as is employed in our case. Hopefully some of our experience can be used in configuring your system or trimming a little operating cost from it.

    Author’s Update: 11/28/2020

    We have incorporated our gravity heating experience into what we believe to be the first, practical, efficient and affordable Pre-built “Delta-T ECM Hydronic (FHW) Heating APPLIANCE”. An extensive U.S. Patent 10,690,356 was issued to us on 06/23/2020 with all our Fourteen (14) Claims allowed. A Canadian Patent is to follow. Check it out at www.BoilersOnDemand.com.


    You have undoubtedly noted the creep of computer technology into most everyday home appliances. Everything has digital displays, clocks, menus, etc. that allow varied cycling options. These purportedly provide finite control over the appliance function (and yet another clock to blink 12:00 forever or to be reset after every power failure).

    The exception is your heating system. Home appliances are typically “closed-loop” systems, i.e. they execute a task in a contained environment.  However, if there is a digital display on a boiler, it is of temperature, operation status and failure modes as applicable. Furthermore these appear predominantly on gas-fired vs. oil-fired boilers. Why? They indicate boiler control system conditions only, not the performance of the total system, and they can’t.

    Hydronic (hot water) heating systems are comprised of three elements, a hot water generator (boiler) delivering through a distribution network to radiation (baseboards, radiators, heaters, etc.) that may exhibit infinite characteristics and combinations under varying climatic conditions and demands. Try to specify a boiler for any existing distribution network as a replacement item and you quickly realize that it is virtually impossible to “get it all right”. Reviewing our other blogs you will note the amount of effort given to remedying distribution network issues, particularly on existing installations. Headaches!

    Each zone (task) in a hydronic system must be supplied with the correct flow rate (gpm) of heated water for best performance. Currently this can only be done only with a properly selected circulator for each zone. The multi-zoned circulator distribution system is therefore the contemporary, preferred option.

    But what can be done with single-circulator, multiple zone valve systems? The short answer is that they by design can do nothing well. Their attraction has been initial cost offset by energy, performance and maintenance costs over system life. In fairness though, on smaller two (2) to three (3) zone systems they can perform respectably, if not perfectly. Hidden is the innate penalty of energy operating costs.

    Ironically, the direction to an efficient, reliable and cost-effective hydronic heating can be the single-circulator, multiple zone valve systems we just scorned — but with a very different circulator and very different zone valves!

    First and foremost a hydronic (hot water) boiler must be sized (capacity) to match and at worst case nominally exceed the heating demands of the total structure. (Refer to our blogs again.) This value must be determined through measurement and with the use of a Heat Loss Calculator. This value and this value only can determine the properly-sized hydronic boiler for your application. (Note: We specify and use Weil-McLain Ultra Series products exclusively, but we are terribly biased!)

    Link http://www.weil-mclain.com/en/assets/pdf/UltraSeriesBrochure.pdf

    It should be readily apparent that the objective is to supply the ideal amount of heated water to each zone, appliance or storage tank according to its current demand. This can now be accomplished by delivering the varying demand of heated water through an “intelligent” circulation system.

    There are two (2) variations of these, employing different principles:

    1. The Delta-P Method (Δ-P) where P = Pressure: Employs a full-demand capable conventional circulator pump configured within a by-pass loop containing a mechanically variable Pressure By-Pass Valve. Operationally the pump operates continuously and at full capacity providing a preset pressure delivery while returning the excess delivery to the boiler. We recently installed one of these systems. Works well so far, but additional pipe-fitting and valve required with continuous, fully powered circulator operation.
    2. The Delta-T Method (Δ-T) where T = Temperature: Employs an “Intelligent” Circulator on the output of the boiler that infinitely regulates delivery by maintaining a preset temperature differential between the supply and the return sides of the distribution system. Two (2) Temperature Sensors strapped to the supply and return lines near the boiler control the circulator speed (delivery rate). Taco Delta-T ECM Circulator found at this link: http://www.taco-hvac.com/uploads/FileLibrary/100-68.pdf

    Note: We strongly favor the Delta-T Method and thus the impetus for this blog.

    The other half of the Intelligent Hydronic Heating System is the Zone Valving that should be mounted beyond the System Circulator, after the air eliminator/air scoop at the end of the supply manifold. We strongly recommend and use only the new Taco Zone Sentry® Zone Valve Series found at this link: http://www.taco-hvac.com/uploads/FileLibrary/100-82.pdf. They feature:

    1. Well ported ball valving to minimize flow resistance.
    2. Quicker actuation.
    3. LED status indicator lamp.
    4. Very low energy consumption.
    5. Manual over-ride capability.
    6. High reliability.
    7. Low cost.

    Let’s define the specifics of the common system scenarios:

    1. New System Installation – Configure exactly per our prior discussion and details.
    2. Full Existing System Upgrade
      • Resize and replace boiler with a correctly sized and configured unit.
      • Replace all existing circulators with an intelligent “Delta-T” Technology Circulator.
      • Replace any zone valves with the specified “Zone Sentry” Valves.
    3. Partial Existing Zone Valve System Upgrade
      • Resize and replace boiler with a correctly sized and configured unit.
      • Replace individual zone circulators and valves as viable.

    System Design Notes:

    1. Intelligent Boiler Systems necessarily use “Cold Start” Hot Water Only Boilers. Immersion-style DHW Coils cannot be accommodated and therefore Indirect Water Heaters are typically used for domestic water generation efficiency.
    2. System Circulators employed by design in Condensing Gas and Multiple Boiler Systems must be retained! The Intelligent Circulator must be added to the distribution supply line outside of the “Boiler Loop” that maintains through-boiler circulation. READ AND FOLLOW YOUR BOILER MANUAL SPECIFICATIONS!
    3. Delta-T ECM Circulator selection is crucial not only for thermal flow capacity to match the boiler output, but for head (effective resistance) of the total system. Larger, multi-level systems need particular attention in this regard. Nominally over-sizing a Delta-T ECM Circulator will incur little penalty due to its innate efficiency and flexibility. However, under-sizing it will quickly exhibit a performance penalty.

    The Delta-T ECM System by design provides controlled, heated water within a preset, adjustable range to all distribution elements of a hydronic system. Moreover it does this irrespective of the number, size, duration and function of the distribution elements and their infinitely variable demand patterns. In so doing it becomes in effect a “self-balancing” system, eliminating hydronic noise (whistle) from over-driven zones while minimizing heating lag resulting from under-driven (lazy) zones.

    Note: The Delta-T ECM Circulator with its built-in controls is about three times that of a conventional one, but you need only one.

    The value of a Delta-T ECM System as a diagnostic tool, particularly as a replacement system upgrade should not be under-emphasized. If it doesn’t fix or improve existing distribution issues, it surely will point out any other deficiencies and isolate them for correction. As a radiation assessment tool in particular you can now properly balance rooms using the radiation dampers, and if not identify and supplement radiation as necessary.

    To summarize, it’s a terrible system:

    1. Terribly simple
    2. Terribly efficient
    3. Terribly inexpensive

    We encourage you to view our Packaged Delta-T ECM Hydronic (FHW) Heating System (Patent Pending) on this site for additional detail.

    Ed. Note: Updated 03/27/2017


    Legally, Plumbing & Heating Technicians are required to set the DHW (Domestic Hot Water) temperature at a maximum of 120 Degrees Fahrenheit at the faucet(s) (taps). The purpose is simple, to prevent personal injury particularly of children and when operating any water tap. It works, but is it ideal for the residential or commercial user? No.

    Like any regulation it has up and down sides. The down side is that some dedicated appliances need higher water temperatures or you pay it back in poorer performance and increased electrical energy costs. Dishwashers and commercial power washers are the primary examples.

    Commercial Dishwashers require a continuous 140 Degrees Fahrenheit supply to assure bacterial elimination and augment the sanitation cycle (electrical enhancement). We have had more than a few instances where clients have not been able to meet State Health Dept. Guidelines. In all cases there was a misapplication of DHW heating equipment involved. Shouldn’t a similar situation exist with residential DHW generation? It does.


    1. Local Dealer installed a Rinnai Demand Water Heater to supply a commercial dishwasher in a restaurant. Rinnai and others supply up to a 120 Degree F output as shipped. There is an internal switch to increase this to 140 Degrees F — and immediately void your Warrantee. There is a product application disclaimer on these and other Demand Heaters specifically excluding commercial dishwashers and other similar applications. Moreover they will not supply the volume of water over time (the Delta-T Problem). The only potential solution is to supply tempered water to the heater (see other blogs), but this can be iffy even for this application.
    2. Area Church installed a gas-fired 40 gallon water heater to supply their commercial dishwasher. Even if you could force the temp up to 140, there is not enough stored and resupply volume to operate through cycle(s). Being a single DHW source in a public structure, then what do you then do about tap water temperatures?

    Now, what about your residential dishwasher? The same process applies with similar results — but you don’t see it readily. That 120 Degree F (at best) water does its thing, but not as efficiently. Your initial wash temperature is low and efficiency suffers. The electricity-sucking water temp coil and sanitizing cycles are notorious energy users. (Look at the Wattage Data on the Appliance Nameplate.)

    The obvious solution in all cases is to supply hotter water to all dishwashers. In one manner or another you must provide a dual temperature source to accomplish this. The techniques vary depending upon your DHW source:

    1. Electric, Gas&Oil-fired and Indirect DHW Heaters – Increase your thermal switch or aquastat temps up to 140 Degrees F (the usual max allowable by design). Then separate your piping to the dishwasher (and other?) and install a good quality Tempering Valve into your other tap water supply line(s).
    2. Immersion (Tankless) DHW Coil in your Boiler – Ideal situation. Tee the output of your coil to dishwasher (and other?) for maximum temperature water. Careful – it is scalding hot!
    3. Provide a separate, high temperature & capacity DHW Heater to suit the particular appliance(s).

    Meanwhile do the “cheap tricks”:

    1. Insulate all your DHW lines from heater to use points, regardless and inasmuch as possible.
    2. Shut off your DHW immersion coil boilers between cycles to save energy during low heating season demands. It only takes about 15 minutes to reheat. Plan ahead.
    3. Open the nearest hot water tap to your dishwasher (kitchen sink?) to get water hot before cycling your dishwasher. This will minimize that initial wash temperature problem in the dishwasher.

    If you should decide to employ high temperature DHW taps for specialized use, do it safely. Secure them!

    Last Edit: 10/10/2012 pdm


    Well, we’re deep into the heating season and listening to that boiler run and run is not going unnoticed. Every time it starts we feel our wallets getting a bit lighter and our blood pressure going up. On top of this things are pretty tough economically. Believe us, we notice it too! Let’s go over some things we can do to lighten the load at least.

    Our remarks must be predicated by noting that the older your system, the more likely you are to benefit from this posting. Additionally refer to our other postings to gain insight to other improvement opportunities.

    Please note the green highlighted text links for referencing ease.

    Firstly, if your system has any age to it, most likely the boiler is over-sized for your application. This happened two ways. Your boiler was over-sized when originally installed, the “standard procedure” until recently, or you have made energy improvements over time to make it become that way, or both. Listening to your boiler cycling rate on that deep cold January morning will confirm this situation.

    Now we are assuming that your boiler has been THOROUGHLY CLEANED when serviced and properly tuned. If your serviceman shows up without heavy cleaning brushes and vacuum cleaner, trade him in!

    Opinion varies on this, but if your unit is running less than 50% of the time on your deepest outside cold point(s) you are likely over-sized.So much for peak demand assessment and tuning. The aggregate of the more subtle energy-stealer items is likely more significant overall.

    Applicable to your situation or not, the most common and most aggravating situation we find on older systems is incorrectly wired controls, particularly of circulators and the occasional zone valve. This winter again we have had several calls related to poor installation of controls and relays. (Refer to our blog ‘Plumbing Guys Plumb, Heating Guys Heat’ that vents our frustrations in this regard.) Additionally is having the wrong Master Aquastat for your system operating parameters.

    The Master Aquastat is the primary control on your heating system and defines its sequencing, correctly or not. To determine if yours is correctly defined we must go down a checklist.

    1. Do you generate your Domestic Hot Water (DHW) directly off your boiler by means of an Immersion Coil, internal to the boiler? If so your options are very limited. The boiler must be at temperature to produce DHW. Train yourself and users to switch the boiler on and off (seasonally) to produce DHW only when you need it. Don’t let your boiler run all summer to have on-demand supply! A waste of energy. (See other blogs.)
    2. If you generate DHW via a separate, detached water heater of any type and your boiler stays hot when no heat is required (as all summer long?), UPGRADE YOUR AQUASTAT from your current “Ranging Type” (keeping boiler water hot all the time) to a “Cold Start Type” that only warms the boiler when heat is demanded. Our favorite is the Hydrolevel 3250-Plus for oil and the 3200-Plus for gas fueled systems. Note that the additional use of their “Electro-Well” provides Low Water Cutoff (LWCO), a nice boiler safety feature. Nice display, easy to install & adjust; and reasonably priced to boot. Pays itself back in a hurry! Also check out their great videos!
    3. Now, are your aquastat and circulator or zone valves and controls wired properly? They must talk to each other electrically or your boiler runs erratically, zones don’t heat properly and circulators can circulate cold water. The quick way to tell is by removing the Master Aquastat Cover and looking at the “T-T” terminals, usually located near the upper right of the control board. What do you find?
      • If you have only one zone (thermostat) and one circulator, there should just be a pair of smaller wires from your thermostat to the “T-T” terminals. You should be good-to-go, otherwise it just won’t run.
      • If you have two or more zones (thermostats) with a circulator for each there should be a two-wire on the “T-T” terminals from a Multiple-Circulator Control Relay or to EACH of several individual Relays.
        • Case 1: If the wires on the “T-T” terminals are from one of your thermostats, IT IS WRONG! This is the most common condition we find. Someone has added additional zone(s) to your system using a SPST Switching Relay like a Honeywell RA89A, Argo, etc. The quick way to tell is to open the Relay(s) and see if it has terminals numbered 1, 2, 3&4 ONLY. You must use a DPDT Switching Relay like a Honeywell RA845A, Argo, etc. that has terminals numbered 1, 2, 3, 4, 5&6. Terminals 5&6 are not powered and are wired to the “T-T” terminals on the Master Aquastat to call for burner operation when any thermostat calls for heat. Changing them will allow the boiler to run ONLY when calling for heat. Energy and equipment saver.
        • Case 2: If the wires on the “T-T” terminals have a “jumper wire” across them, IT IS WRONG! Your system is running on a “Ranging Aquastat” that just keeps the water temperature in its setting range and from which the circulators pull heating water on-demand. This method is tough on equipment and effectively reduces both the capacity and the recovery of your system. Referring to preceding Case 1 go through the steps with Circulator Relay qualification and inter-wiring to bring the system up to peak, efficient operation.
        • NOTE: If in either Case 1 or 2 you are using a Circulator Switching Relay, or a Zone Valve Control the interior “End Switch” terminals are wired to the “T-T” terminals on the Master Aquastat only. Finished.
    4. If you are using Zone Valves in your system, are your aquastat and zone valves and controls wired properly? The first step is to verify that all of your zone valves have wiring to all THREE terminals (1, 2&3). Next is to trace and verify that there are leads from terminals 2&3 on all valves to the “T-T” terminals on the Master Aquastat. Refer to this Taco Zone Valve Link to verify wiring: http://www.taco-hvac.com/uploads/FileLibrary/ZoneValveBroch.pdf NOTE: If you are using a Multiple Zone Valve Control Relay, the interior “End Switch” terminals are wired to the “T-T” terminals on the Master Aquastat only. The 3 (R-W-G) wires from each zone valve and the 2 (R-W) Thermostat wires from each zone are wired to their respective interior relay locations. Refer to this Taco ZVC Relay Link to verify wiring: http://www.taco-hvac.com/uploads/FileLibrary/CAT100-5.1ZoneValveControl.pdf
    5. If you are using older Taco Zone Valves in your system consider upgrading them, particularly if they have Green-colored Heads (Tops). They were troublesome and Taco upgraded them with Gold-colored Heads. These Zone Valves are typically slow to actuate on & off, use measurable electricity to energize and maintain position and restrict hot water flow in the system. (Consequently we have preferred circulators.) Recently however Taco introduced a new, low power use, full-ported Ball Valve to replace these. Check this link: http://www.taco-hvac.com/uploads/FileLibrary/100-82.pdf The “Zone Sentry™” does it all well, very well, and with a useful indicator LED. By the way they are also less expensive than the older valves! Why repair it when you can swap it? Standard Ball-Porting will also definitely help out with those slow warm-ups, and lazy zones. Saves the circulator(s) a bit too. A winner.
    6. As you replace Circulators, necessarily or not, specify and utilize new generation products only! Recent advances in hydronic circulator and distribution technology are astounding! Despite a higher initial cost, they save lots of energy (electrical & some fuel) and extend service life. Two (2) basic examples. a. Single Circulator System with Zone Valves: Install a Delta-T ECM Circulator ASAP. It’s “thrice the price” but dramatically smooths out energy delivery and radiation pulsation. Swaps out directly with your little green Taco 007 (or other brand). Just attach the sensors to your boiler supply & return piping and go. b. Multiple Circulator Systems: Substitute the Taco 007e Circulator for existing, based on system usage. Again, about “twice the price”, but what a value! Your constant running “system circulator” where used is first, with your following based on zone sizes and usage. Note that radiant heating zones will benefit as well. (Weil-McLain now supplies Taco 007e’s only as their residential system circulators.)
    7. Perhaps the best investment a FHW System owner can make is installing an Indirect Water Heater for thermal efficiency and system value/performance. (Refer earlier in this blog and others to “Cold-Start Aquastats” and their benefits.) Don’t care what you are using for a heating fuel, the Indirect Water Heater tops them all in DHW generation. Problem is they are not cheap. You have to be serious about your energy management. There are two methods of getting there, however. a. The DIY or “Home Brew” Method: Your current boiler MUST HAVE AN IMMERSION COIL FOR DHW. Search out a very good, quality 80 Gallon Electric Water Heater that can be had cheaply, to be used as your storage tank. Strip out all the electrics. The only electrical function to be used is the (upper) thermostat terminals. Procure a Bronze or Stainless Steel bodied Taco 007 Circulator (or equivalent) ONLY! No iron-bodied ones — you are drinking the water going through it. Obtain a DPDT RA845A or equiv. Switching Relay (see prior above in this blog). Plumb a circulation loop from the boiler immersion coil taps to tees at the input and outputs of the 80 gal. water heater. Circulation direction is to the top tee. Wire in the relay as any zone addition, with a two-wire between both “T-T”‘s (relay and water heater). It isn’t a perfect solution, but a cost-effective one. b. The Professional Method: Applicable to any FHW Boiler configuration. Purchase a quality Indirect Water Heater Unit (we swear by, and not at, the HT Products “SuperStor Ultra”). Link: http://www.htproducts.com/literature/lp-81.pdf They use boiler water to heat DHW via an internal coil and therefore use iron-bodied system circulators. Other components are similar to the prior above. We would also suggest professional installation of these units. NOTE: Always put a small, correct “Thermal Expansion Tank” on the cold water feed side of any DHW Heater to prevent over-pressuring resulting from heating a cold tank of water.
    8. The final budget item must necessarily be a boiler upgrade. It’s also the point where you should review your heating fuel options. Refer to our extensive Boilers On Demand Heating Blog Library to assist you in this regard. Regardless of your selection, employ top-of-the-line appliances! Do your homework carefully but don’t select solely on a prior service relationship basis. The Weil-McLain Replacement Guide is invaluable in this regard! These new, high efficiency appliances are virtually self-diagnosing and trouble-free. Not only the Maytag Serviceman is lonesome these days.

    Last Edit: 12/31/2019 PDM