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  • WHAT IS A DELTA-T SYSTEM?

    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.

    VT2218+ZV

    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!


  • OUR UNPOWERED FORCED HOT WATER (FHW) GRAVITY HEATING SYSTEM

    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.


  • THE DELTA-T ECM CIRCULATOR POWERED HYDRONIC HEATING SYSTEM

    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