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  • THE ZONE VALVE VS. THERMOSTATS WAR – THE “POWER GRABBERS”

    There is a conflict (war) between the new energy-efficient zone valves and their thermostat counterparts. It is little understood and lesser recognized. The effect is erratic or non-operation of heating zones, frustrating both heating system owners and their servicemen.

    While discussing zone valve application specific to our “Package Delta-T ECM Hydronic (FHW) Heating System™” (Patents Pending – USA & Canada), Taco Engineering offered that there are disparages emerging between some “new generation” thermostats and proper zone valve operation. We were discussing specifically the Taco “Zone Sentry” Valve, a low power usage zone valve featuring extreme energy efficiency and operating life. This conflict is strictly a thermostat product design issue, evolving from the effort to incorporate more and more features into thermostats.

    The primary function of a thermostat is a “temperature sensing switch” presenting power (24VAC) provided by a transformer to operate a zone valve (or a circulator). The thermostat must also use a small amount of power to warm an “anticipating heater” that “tricks” its switch into closing earlier to smooth heating delivery by utilizing the heat stored in piping and radiation to “fill in” between thermostat cycles. A pure “temperature switch” has a high “hysteresis” or sensing lag and would have noticeable hot and cool periods in operation. A major advantage of the new Taco Zone Sentry Valve is now powering up to 12 valves from a standard 24VAC transformer vs. 4 of the prior generation “Power Head” or “Hot Head” valves as we cynically refer to them. The resulting electrical power savings benefits are dramatic (up to 85%)!

    Beyond the primary function of heating control modern thermostats incorporate more features that require using more power to execute them. Being effectively non-powered devices as designed they “borrow” their power from the zone-valve source 24VAC supply. This has generally worked with common “set & forget” and basic programmable thermostats with a battery backup. However adding features such as Wi-Fi and wireless inter-system controls require more and continuous power demands to maintain these communications features. Taco Engineering is experiencing ever more issues with these thermostats directly operating their zone valves and uses the term “Power Grabbers” in classifying them.

    Drawing down the 24VAC supply power will ultimately cause erratic Zone Sentry Valve behavior. This is typified by:

    1. Multiple “open” attempts, witnessed by viewing the Green LED Status Lamp, before finally opening.
    2. Occasionally the valve will not “close” after the zone thermostat demand is satisfied.
    3. The worst condition is the zone valve simply failing to operate upon a demand.

    Taco offers the following observations and possible solution:

    1. First, check your thermostat for correct mode switch settings for your system type, per the manufacturer’s instruction sheet. These are typically on the back of the thermostat, and match operation to your system type.
    2. If your thermostat manufacturer provided a resistor with the unit, install it per the instructions and retry operation.
    3. Taco otherwise recommends installing a 1.0-1.2 kohm, 2 watt or greater resistor in series with the power (red) lead. This will usually remedy the situation.
    4. If not, consult with your thermostat manufacturer to remedy, if possible.

    The more we demand of particularly digital temperature devices, the more potential control issues we incur. A sample of our observations:

    1. The Honeywell T86/T87 Series Thermostats (those old round ones you adjusted by turning the outer ring) were extremely durable, dependable and finitely adjustable, being “analog” devices. Their “anticipating heater” (as previously described) was infinitely adjustable and you could “tune” it to less than 1/2 Deg F. Resistor “tuning” range was from 0.2Amp to 0.6Amp, infinitely variable. They were banned due to containing a drop of mercury as the switching medium. (We advise our clients not to “upgrade” them unless they need a programming capability.)
    2. Digital Thermostats have selector switches prescribing a fixed “anticipating heater” value for each general system type and are non-adjustable. Thus you will have minor(?) control variations from the “correct” one.
    3. Zone Valves in particular require a higher “anticipating heater” setting than circulatory-driven systems, typically 0.5A (Zone Sentry) to 0.6 (Older Zone Valves) vs 0.35A+/- for aquastat/relay drives. This fine tuning is not available in a digital thermostat, thus minor(?) operational variations.
    4. Tuning a steam system upgrade to its robust radiation (cast-iron radiators) with a digital default thermostat can become a challenge.

    In closing we mention several of our customers being true “techies”, two of whom having commercial and home-built Wi-Fi Thermostat or Temperature Monitoring Systems. One recently called from a Hawaiian Job Site advising of an issue in his seasonal home in NH. Saved a potentially disastrous situation. Welcome to the “Digital Age”, but also be aware of its limitations!

     

     


  • BEYOND AFUE’S – TOWARD REAL HYDRONIC (FHW) HEATING EFFICIENCY!

    For the past year Mercier Engineering has been immersed in developing and preparing for market it’s Packaged Delta-T Hydronic (FHW) Heating System™, based on our past heating experience projected into the new world of “Delta-T Circulation”. You may have noted our preoccupation with this technology in “The Heating Blog” on our www.boilersondemand.com  website. Time to “put our money where our mouth is”, so to speak. The results of our efforts we deem noteworthy and are initially reflected in this writing.

    As the titling of this blog purposely implies, we must get beyond weighing hydronic heating system efficiencies solely upon the boiler’s Annual Fuel Utilization Efficiency (AFUE) Rating.  It is only one of multiple elements in an operational formulation that is seldom if ever approached, even more poorly understood, and we allege almost universally misapplied. Strong words which must be tempered by the reality that there has been little market incentive to change our approach to serving the residential FHW heating market in particular; but we ultimately must adapt and change it for the consumer’s benefit.

    AFUE is a regulatory, laboratory testing procedure intended to establish an efficiency value for a hydronic (hot water generating) boiler under a defined operating sequence and conditions. It can be presumed that it executes this comparison very effectively, under its terms. However, what it does not measure from our observations is in practice very significant. Specifically these Non-AFUE Test Attributes are:

    1. There are no provisions for qualifying or measuring between-cycle “stand-by” or “idle-time” losses. This is the time between burner firing cycles when the boiler is prone to radiated energy and convective exhaust (flue) losses, presumed to be non-productive.
    2. Similarly, the testing is “steady-state” in execution, providing no qualification or quantification of individual boiler attributes that may contribute to site application efficiency.

    These test attribute observations have been borne out in field applications, where system performances have not correlated well, boiler-to-boiler or system-to-system. To further complicate this is the variability of physicals to each application, however subtle. The forums and blog sites are rife with these seemingly “apples-to-oranges” commentaries. Our developmental efforts may be able to provide some explanations.

    From our observations there are necessarily five (5) elements contributing to total system energy efficiency:

    1. The boiler (heat engine) energy conversion efficiency or AFUE.
    2. The physical attributes of the specific boiler complimentary to system operation.
    3. The energy required to move heated water through the distribution system (radiation).
    4. The effective matching of radiation elements to heating demand.
    5. The control algorithm(s) to match energy creation with varying system demands.

    Our initial efforts have been with oil-fired hydronic systems and is the focus of this document, with gas-fired and solid-fuel applications to follow as resources permit. However, much of this effort is applicable as the basis of other heating systems.

    Varying the output (energy creation rate) of any heating resource is paramount. This has been readily achieved in gas-fired boilers by “modulating” combustion with sophisticated valving and controls. Typically they adjust from 20 to 100% of capacity, from “idle” to “full speed” to use the automotive analogy. However, direct modulation of oil-fired systems is not feasible using current technologies. A fixed (capacity) firing rate via pressurized, nozzle induced fuel atomization is the norm. Therefore, the only option is to adjust the operating temperature of an oil-fired hydronic boiler via controls to compliment heating demand. This is reasonably well-managed with modern “cold-start” aquastats, external temperature sensors, etc.

    The prior unaddressed penalty to particularly residential hydronic systems has been the toll on equipment and electrical energy requirements of circulating heating water with fixed-speed circulators. They are notoriously and arguably universally misapplied and inefficient in practice. Reducing water temperatures merely aggravates the situation by prolonging circulator cycling.

    Fortunately technology has come to the rescue in the form of the “Delta-T” Circulator, now becoming very applicable and affordable to the residential/light commercial markets. The undisputed pioneer and flag-bearer in this market is the Taco Viridian VT2218 found at this link: http://flopro.taco-hvac.com/media/Viridian_VT2218_100-114.pdf  To use the quote “This changes everything” is not an exaggeration! The Viridian is in fact the second generation, replacing the entry product Taco “BumbleBee” found at this link: http://www.taco-hvac.com/uploads/FileLibrary/100-101.pdf We mention the “BumbleBee” only because it has rapidly become a “cult product” in the HVAC Community, somewhat akin to the “Trekkies”. It was our initial “new tool” in developing and thence refining our product(s). Like our brothers, we hate to see it go as we move to the refined and more sophisticated “Viridian”.

    Referring back to our five (5) elements to total system efficiency, Delta-T Circulation is number three (3) on the list but is deservedly and necessarily the foundation of any hydronic system improvement. Taco reports system Delta-T Circulator-only swaps yielding 15% fuel usage reductions. It is the keystone of our Packaged Delta-T Hydronic (FHW) Heating System™, and should be the first improvement to any system! We caution however that this will require substantial near-boiler system re-piping and your installer must be knowledgeable. It is discouraging to note how few of our fellow tradesmen are cognizant of Delta-T or have used it beyond a radiant heat loop. We “Old Dogs must learn new tricks”, and we have!

    The second element of import is the necessity to employ “Cold-Start” Boiler/Aquastat Hydronic Technology, which overlaps Nos. 2 and 5 in our list. We are unabashed in our praise of the Hydrolevel 3250-Plus “Fuel Smart” Aquastat, found at this link: http://www.hydrolevel.com/new/images/literature/sales_sheets/fuel_smart_hydrostat_sales_sheet.pdf   It is now standard equipment on all our Weil-McLain Ultra Oil Boilers, and none too soon! The inter-action of the 3250-Plus with the VT2218 Circulator’s operational software is paramount to total system performance, as we have learned.

    Note: “Cold-Start” Technology applies to “heat-only” boilers. DHW (Domestic Hot Water) must be effected by an external Indirect Water Heater or another dedicated appliance. We combine the Indirect Water Heater in our design for optimized Heat and DHW Generation.

    Element 3: Our development indicates individual boiler attributes are significant. Specifically,

    1. Boiler supply and return tap placements are crucial to system “packaging”, i.e. the ability to compactly (efficiently) structure near-boiler piping. (We can pipe into a space as close as 11″ from the chimney, with all piping and controls behind the boiler, yet readily accessible.)
    2. A very high boiler mass (weight) for its capacity, i.e. for both thermal damping and storage.
    3. Favorable exchanger flue passage routing and exhausting.
    4. Burner type to compliment its attributes.

    The noted attributes lead us to our “Boiler-of-Choice”, the Weil-McLain Ultra Oil Series with the Beckett NX Burner. Refer to this link for detail: http://www.weil-mclain.com/en/assets/pdf/Ultra%20Oil%20Brochure_8%20Pg_web1.pdf   We have had “conventional” system design and installation experience with this boiler for over ten years now, with only one “no heat” service call, a failed aquastat. Weil-McLain has since upgraded it to the Hydrolevel 3250-Plus, thank God!

    The Beckett NX Burner has been likewise flawless in operation. Literally a “plug and play”. Its dual vent typing capability (direct & chimney) has proven beneficial to problematic venting applications, especially when encountering “cold chimneys” in our northern climate. Fully exposed exterior chimneys are sure to give a rough startup without utilizing its pre-purging and pressure firing features.

    The key attribute to system performance outside of Delta-T Distribution has proven to be Thermal Mass (Storage) provided by the sheer robustness (weight) of the Weil-McLain UO Series High-Mass, Triple-Pass Boilers. They are “The Heavyweight Champions” by far and as a result exhibit lower mean boiler operating temperatures and very less frequent burner cycling.

    As a matter of policy we do not cite or criticize our competitors, but we must make a single attribute comparison to emphasize our point. The approximate block weights of the top hydronic (approx. 100KBTUH, 87% AFUE) oil boilers are:

    Manufacturer/ModelApprox. Ship Wt.
    less Tare (lbs.)
    % of HighestComments
    Buderus G115/G21537560%Adjusted for 100KBTUH
    Burnham MPO-IQ11545072%
    Weil-McLain UO-3625100%

    AUTHOR NOTE: Very noteworthy, the Weil-McLain UO is also disproportionately the lowest cost per pound (by nearly half) of the three. Just what is the consumer paying for, we wonder? In our development experience increased boiler mass equates to improved system longevity and hydronic performance!

    Radiation (Element 4) efficiency is the remaining, but least controllable variable in a heating system. It is substantially outside the scope of our system application, yet there are some performance elements we can address.

    Existing hydronic radiation:

    1. Removal of unnecessary valving in zone supplies and returns. All zone supply functions are integrated into our system package.
    2. Zone interconnection and functionality can be optimized by correct pipe sizing and routing. It confounds us as to why some plumbers use virtually no 45° fittings! You can use 3-4 of them vs. a 90° elbow for the same flow resistance, and only 70% of the pipe required for a 90° elbow routing.

    New hydronic radiation:

    The contemporary approach to radiation varies widely, from simple radiation loop(s) for zoned heated areas to individually heated rooms throughout. The more finite the control, the more piping, fittings and control valving, the more hydronic distribution energy is required.

    Ironically, the same Delta-T Circulator Technology we employ to maximize our system performance has preceded us and become the darling in particularly radiant system applications. We have also employed them in these and they perform admirably. They reduce the energy requirements significantly but yet still camouflage that basic issue.

    If your concern is total energy consumption of a system, we would invite you to consider using less sophisticated radiation distribution schemes. A properly designed, installed and balanced series or split piping loop exudes simplicity and will likely be a lower installed cost. The KISS Principle applies — keep it simple ….. (Refer to our Heating Blog Library for additional detail.)

    To Summarize:

    1. Additional Boiler Attributes are important, beyond the AFUE Rating. In particular heat exchanger thermal mass (weight) will lengthen service life while minimizing repair costs. Burner attributes related to exhausting and tuning must also be considered.
    2. Delta-T ECM Hydronic Distribution Technology is key to improving any system’s energy performance, both heating fuel and electrical power consumption.
    3. Inter-related “intelligent” controls determine system operational performance. They are currently the Hydrolevel 3250-Plus Boiler Aquastat and the Taco VT2218 Delta-T Circulator Logic.
    4. Near-boiler plumbing in particular affects system performance. This is optimized in our system piping configuration to include fail-safe “natural gravity convection”.
    5. Interconnections between our system zone access points to existing radiation must be executed with the goal of minimizing flow anomalies.
    6. Existing and/or new radiation installations must likewise be executed by idealizing flow conditions inasmuch as possible.

    References:
    We strongly recommend referring to Taco’s website link http://flopro.taco-hvac.com/deltat_resources.html and refer to the various Delta-T resources therein. There’s a volume of resources here that will properly inform you of this new technology and its place in your Hydronic (FHW) Heating System.

    Author’s Note: Hyperlinks updated 08/27/2019


  • 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!


  • THE HYDRONIC REVOLUTION – The Intelligent Delta-T ECM Circulator FHW System

    We have witnessed many technological breakthroughs in the past fifty (50) years or so. My engineering career began manufacturing the first transistors, through integrated circuits, personal computers, parallel-processing supercomputers and their logical applications. Now witness the plethora of personal, mind-bending “high-tech” devices available to almost everyone. Similarly there are advances in energy, transportation, communications, etc. that will derive our future.

    OK. So what’s this Hydronic Revolution? Hydronics is the use of water as a medium in heating (or cooling) systems. Thus a Forced Hot Water (FHW) System is more correctly a hydronic system. As simple as they seem, Hydronic Systems need to be carefully designed to maximize their performance, both heating-wise AND electrically! Unfortunately most applications are incorrect hydronically and virtually all electrically, nor can they be using dated components and methods in particular.

    Heated water generated by a boiler must be pumped through “radiation” (baseboard, radiators, heaters, etc.) at an idealized rate to suit the heating demand. Pump it too slow and you have a wide temperature variation and “lazy” performance. Pump it too fast and you waste power and can create hydronic circulation noise. In both cases you waste energy, particularly electrical. The pump (circulator) either runs too long, or too hard.

    Enter the Variable Speed “Delta-T” Circulator some years ago. It measures the input and output temperatures of radiation piping and adjusts its pumping rate (speed) to maintain a “Delta-T” (temperature differential), usually set to 15-20°F with further adjustment to suit varying applications. It was a great advance from Taco® Comfort Systems, the premium American Hydronics Manufacturer with variants produced by others (U.S. & Foreign). It has never really “taken off” though, finding a niche in process control, radiant heating and other problem solving but little else to date ….. until now.

    Taco® has again “upped the ante”, and really upped it this time! Their newest offering, the Taco® VT2218 00e Series Delta-T ECM (Electronically Commutated Motor) Circulator is a marvel of Applications Engineering. An “Intelligent Circulator” is now an apt, if not a modest description. Kudos to our fellow engineers!

    Referring to the Taco® VT2218 00e Series Circulator Specification Sheet you can appreciate the sophistication of this device, and its flexibility to suit varied applications. It can do so much in fact that we must limit our discussion to its application as a simple Delta-T system circulator, its predominant application and the objective of this blog.

    Of equal or greater importance is what is not explicitly referenced in the Taco® specifications, how it attains its intelligence. Simply stated, the circulator logic “learns” its application pattern over a period of time, placing it in memory and executing it in the successive period. While executing, it continuously “observes” the pattern variations and adjusts its memory accordingly. Thus your programmable thermostat(s) cycles and heating load variations can be patterned and thenceforth satisfied efficiently.

    Similarly, observing pattern changes such as the length of a heating demand allows the Taco® VT2218 to empirically determine the relative outside temperature, emulating an Outdoor Temperature Sensor Option function. Being a passive measure, it would lag the correction time of an outdoor sensor, but to what overall effect?

    Utilizing a single system and/or distribution circulator such as the VT2218 Delta-T ECM vs. multiple fixed-speed circulators does require controlling individual thermostat demands via Zone Valves. Here again Taco has met the challenge. Again a little background is helpful.

    Taco® is the undisputed giant of the residential hydronic zone valve market. Their “Heat Motor” Zone Valve has dominated for decades and is available in most hardware and “box” stores as is their Model 007 Circulator. The combination of these power and control most residential hydronic systems, however poorly executed they may be. Referencing our Blog Library on this site (and on the internet in general) will evidence how much print is given to addressing hydronic distribution issues!

    The new Taco® Zone Sentry® Series Zone Valves are the “next generation” product to replace the old “Heat Motor” (energy hog) valves and be the ultimate companion to the VT2218 Delta-T ECM Circulator. They are both energy-efficient and intelligent by design as well. Whereas the old “Heat Motor” and “007” dominated and created their renowned application difficulties, the new Taco® Duo of Zone Sentry and VT2218 are their long awaited and performing successors (pictured).

    VT2218+ZV

    We among many other heating bloggers have derided simple “Zone Valves+Circulator Systems” as being an arguably cost-effective alternative to individual circulator zoned systems, and with justification. We in fact chide that zone valves+circulator systems “do nothing well”. True for the old, but not for the new generation!

    Thus, the titled “Intelligent Delta-T Circulator FHW System” consists of a Taco® VT2218 Circulator and Taco Zone Sentry® Valves coupled to a high-efficiency hydronic boiler for maximum performance. We have now and for over a generation specified and used Weil-McLain® Boilers in our applications with absolutely no regrets. Weil-McLain® is recognized as the premium All-American Manufacturer, with a growing market share. Their Warranties are fabled.

    So, to quote the old adage, “How do we get there from here?” From our perspective it’s all about education, particularly within the residential and light commercial market sector. You, the now hopefully more informed consumer, DIY (Do-It-Yourself-er), contractor, “week-end warrior”, tradesman, property manager or developer must drive this point forward in your interest.

    System specification is now relatively simple:

    1. Your total heating demand as determined by a heat loss calculation.
    2. A boiler selection by size and fuel type to suit.
    3. An intelligent Delta-T ECM Circulator(s) sized to your total heating demand.
    4. Energy-efficient Ball Zone Valves for your systems distribution controls.

    Notes:

    1. If your boiler selection has a “system loop circulator” you will employ the Delta-T System in series with it, per the manufacturer’s specification. (High-mass boilers typically don’t require a system loop.)
    2. If you wish to generate DHW (Domestic Hot Water) with your system, an Indirect Water Heater will be required. We exclusively specify and install the HTP® SuperStor Ultra, all-stainless and Lifetime Warranted.
    3. The new generation Zone Valves typically have built-in diagnostics and indicator lamp(s). Therefore you don’t need a Zone Valve Controller, as long as you can see the individual lamps. Significant redundant cost avoidance.

    Quoting Cesar Chavez 1927-1993 (American Activist and Labor Organizer): “We have seen the future, and the future is ours!”

    Mercier Engineering has seen its future as well. We have and are developing a series of “Intelligent Delta-T Circulator FHW Systems” PRODUCTS built upon Weil-McLain® Boilers, Taco® VT2218 Circulator and Taco® Zone Sentry® Valves that will provide the user with a very significant cost-performance advantage to built-on-site alternatives. They are a pre-built, assembled hydronic boiler package, ready for expedient on-site installation, with proven performance.

    Our dedicated website www.BoilersOnDemand.com is currently under complete re-construction to incorporate the latest technological innovations. It will be a significant resource to this end. Meanwhile please excuse us while we work by also taking advantage of our site’s extensive Heating Blog Library.

    Hopefully we have made you aware of hydronic FHW Heating progress and how it will definitely affect our immediate futures.

    Author’s Note: This Blog updated 08/18/2016 to reflect Taco’s new VT2218 Delta-T ECM 00e Series Circulator, replacing all prior.