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    Heating and moving water (hydronics) is recognized as the most efficient method of creating and distributing warming energy. From the Roman Baths to Gravity Piped Hot Water Systems of a century ago natural convection of heated water provided a simple, if seemingly temperamental solution.

    Adding pumps (circulators) to heating water distribution has forever improved comfort an flexibility. However, their application has been less than ideal, utilizing only fixed-speed/capacity circulators, typically poorly applied to residential heating in particular. Using a “one size fits all” approach and swapping sizes to effect results has been a thorn to the trade suppliers.

    Applying switchable, multi-speed circulators has provided an interim solution to poor matching options. Further, measuring actual circulator zone supply and return temperature differentials with an infrared thermometer while selecting speed(s) has provided a more efficient solution. It’s still a less-than-ideal result, with a cost premium.

    The Delta-T (Differential Temperature Sensing) Variable Speed Circulator has been around for some years now, providing the idealized solution to heating distribution flow management. It has arguably fallen far short of its potential, burdened by high initial cost, audible operational “whine” and low speed “growling”. Occasional high load torque stalls further contributed to its unknown nature.

    Enter the ECM (Electronically Commutated Motor), the latest iteration of the “intelligent” Delta-T Variable Speed Circulator. The “heir apparent” is whisper quiet yet powerful, dramatically reduces power consumption with no “torque stalls”, displays great functional data and at a palatable cost. Taco® Comfort Solutions of Cranston, RI also claims up to 15% fuel savings along with an 85% energy drop with their 00e Series VT2218 ECM Circulator, pictured.

    Author’s Note: We former High-Tech Process Engineers were applying “Stepper Motors”, the ECM predecessors to Machine & Process Control over 40 years ago. Finally, the Heating World is getting some real tools to work with!

    The Delta-T Circulator is and has always been marketed as an enhanced replacement for a fixed or multi-speed circulator. Have a zone performance issue? Substitute a Delta-T and “tweak” it in. Problem fixed, within the constraints of the zone design and a 3X cost premium of course. This latest (and supplier exclusive) Taco® VT2218 is being very well received, breaking the “Cost-Performance Stigma” of its predecessors and counterparts. We love it!

    VT2218+ZV ultra-oil-1 HTPSuperstor

    As “High-Tech” Process and Manufacturing Engineers with a Heating Discipline we (Mercier Engineering) have further projected the Taco® Delta-T ECM VT2218 as a Dedicated System Circulator, the acknowledged INDUSTRY FIRST to do so! Reviewing its Technical Specifications the VT2218 is ideally suited to residential/light-commercial heating system applications, given that operational attributes can be accommodated. These are namely:

    1. Providing uniform heating performance under normal multi-zone demands.
    2. Simultaneously servicing an Indirect Water Heater (IWH) to optimize both domestic hot water (DWH) and heating water generation.
    3. Prioritizing DHW generation within varying area heating demands.
    4. Accommodating differential temperature branching such as radiant zone(s).
    5. Satisfying both current and future (planned expansion) demands without an efficiency penalty.
    6. Providing beneficial System Service & Reliability projections.

    Over the past fifty (50) years we have installed and monitored “conventional” hydronic (FHW) heating systems, focusing on component selections, their performance and service levels. This continual qualification process has yielded a set of Premium American Components with “zero-fail” histories, at the expense of other NAFTA, Euro & Chinese products.

    Recognizing the potential of Delta-T Hydronics Distribution as previously noted, about five (5) years ago began a concerted effort to select and qualify the dedicated system circulator application. Our independent work using three (3) successive iterations of Taco® VDT, HEC and VT/00e Products has yielded not only a viable, but a superlative Packaged Delta-T ECM Hydronic Heating Appliance™. Its performance is principally based on our Proprietary Near-Boiler Piping System that constitutes the basis of our Non-Provisional Intellectual Property Protection Submission (Patents Pending – USA & Canada).

    So what began as an “evolutionary” effort to apply a newly available “tool” in the resultant has approached a “revolutionary” one. Our Packaged Delta-T ECM Hydronic Heating System™ is actually a FHW Heating Appliance, an industry first! Placing the Delta-T ECM Circulator into a full hydronic (FHW) heating system we slogan as“Putting an ‘Automatic Transmission’ on a Boiler”. Coupling “intelligent” Taco Zone Sentry®valving (pictured), a “high-mass” boiler (Weil-McLain UOpictured)and an integrated IWH (HTP SSU45– pictured)dramatically reduce complexity and idealize hydronic system performance.

    In our introduction we referenced the “natural convection” (gravity heating) used by the Romans, et al that prefaced our “modern” hydronics. Our optimized Delta-T ECM System exhibits exceptional gravity convection qualities, continuing heating upon circulator disablement or with zone valve manual operation. Short of a full electrical outage significant gravity convection heating continues, providing a useful fail-safe protection feature.

    Now let us really “Raise The Bar”. Here is performance data taken from two (2) similar “beta test sites” in our grouping.

    100,000 BTUH System, Oil-Fired, 3-Heating Zones + IWH

    Attribute “Conventional” System Delta-T Hydronic System Comments
    System Efficiency (Est.) 87% (Boiler Only) 90++% (Aggregate) Combined Hydronic Efficiencies
    Mean Operating Temperature > 145°F (Est.) 132-140°F (Observed) Normal Heating Operation
    Distribution Power 165 Watts (Est.) 11-12 Watts (Observed) Equates to Taco® Claims
    Distribution Fuel Efficiency  N/A – 15% Consumption Per Taco® Claims
    Natural Convection  Minimal to Moderate Very Significant (Observed) Very Installation Dependent
    System Footprint < 35 Sq. Ft. 12 Sq. Ft. (Actual) Very Installation Dependent
    Construction/Life Low-Mass C.I. or Stl. + Copper High-Mass C.I. & Stl. Only  10 to 20 vs. 30+ Yrs. (Est.)
    Complexity/Maintenance/Skill Higher/Annual/Specialized Low/Bi-Annual/Standard Standard Controls Only
    System Installed Cost (Est.) $10,000+ (Est.) $7,500 (Quoted) Southern NH Region

    This is the new “Bar Height”.

    We challenge ANY Tradesman or System Installer to raise it.

    To Summarize:

    1. Delta-T ECM Hydronic Distribution is singly the most significant and cost-effective contemporary heating advancement.
    2. This technology is applicable to any fueled hydronic heating system with substantial packaging and cost benefits.
    3. System configuration using a Dedicated Delta-T ECM Circulator further reduces physical and technical complexity while idealizing hydronic performance.
    4. Our Packaged Delta-T ECM Hydronic Heating System™ is the first, true Hydronic Heating Appliance, considering its intrinsic architecture, performance and as-installed economics.
    5. This is the new Standard of Measure in Hydronic Heating.

    Author’s Note: Updated 06/12/2017


    When we think of heating systems it is logical to assume that the larger the building, the larger the boiler required to heat it. Most of us have seen the large central boiler systems employed in factories, commercial buildings or distributing heating to a campus. Some may have two boilers (or more) to assure continuity of service in an expanding campus as well.

    It is no secret that the larger a boiler, the less efficient it is both thermodynamically and particularly in seasonal operational efficiency. The efficiency spread between smaller and larger boilers has expanded in recent years to the point that our old and seemingly logical thinking has become fundamentally flawed.

    To develop this argument let us use a “two are better than one” scenario. (This can be extended to larger multiples as well, and applies to both gas and oil fired systems.)

    Firstly, all assumptions are predicated on the common denominator of structure heat loss (demand), not the size of the current boiler and its performance. Therefore the firing rate or capacity of your current boiler cannot be used for sizing comparisons. You must determine the actual heating requirement by using a “Heat Loss Calculator” of which several are available online.

    Furthermore, to arrive at a standard “Cost per Million BTU” for a particular fuel refer to our posting entitled “Using a Heat Cost Calculator — Carefully”. This will give you an accurate method of both selecting and applying values in the current environment. The heat content of fuels and their combustion efficiencies vary significantly and thus must be considered in any comparison.

    For our purpose we are assuming the published Annual Fuel Utilization Efficiencies (AFUE) of 87% and 95+% respectively of top end Weil McLain Ultra Oil and Ultra Gas products. These generally compare favorably with other competitive manufacturer product offerings and are the bases of our scenario.

    These modern, high efficiency heating appliances are limited technologically to sizing in the medium home to light commercial (and also the higher volume) market. They also vary significantly cost-wise by fuel utilized. To be more specific:

    1. The highest capacity of an 87% Ultra Oil Model nets at 172,000 BTUH

    2. The highest capacity of a 95+% Ultra Gas Model nets at 289,000 BTUH

    3. The cost of Gas vs Oil Models is significantly higher, offsetting some efficiency advantage.

    Where is the break point between a single, larger, less efficient boiler and two, smaller, more efficient ones? This is dependent upon the specifics of an application, but some general guidelines can be applied. It is generally accepted that about 70% of seasonal heating demand can be handled by one boiler of the duet. The second one is there to fulfill those peak, paralleled winter demands. A good exploratory starting point is if your heating demand is around 200,000 BTUH. Having additional demands such as Domestic Hot Water (DHW) generation, pool heating, etc. factor into the determination as well. Depending upon their quantitative and cyclical demand values they will lower the threshold between the size, number and possible dedication of boilers. Installation costs over single boilers will be somewhat higher, to be offset by efficiency gains.

    Historically the impact of Multiple Boiler Systems (MBS) can be dramatic. Common fuel usage drops of 40% are quoted in follow up reports. Their popularity in large commercial installations such as resorts, high-rise buildings and process installations are reflected in numerous trade journal articles. What is less recognized is their value in upscale housing, apartment buildings, low-occupancy, high-risk structures.

    Our personal experience with Municipal Facilities such as Libraries, Fire Stations and the like in rural areas is noteworthy. For instance, the loss potential of Rural Volunteer Fire Equipment in a freeze-up is very real, and substantial. Additionally, removal of combustion heating equipment from engine bays removes a very real high-hazard risk. The Insurance Underwriters love it!

    It must be understood that having a backup generator system is paramount to maintaining Multi-Boiler System operation.

    Beyond the efficiency claims of MBS, particularly in peaking efficiencies and managing seasonal standby losses, there are the additional benefits of alternating boiler usage (called “exercising”), automatic back-up for failures, increased boiler life and reduced maintenance. The “Boiler Manager” Control intelligence delivers idealized performance ….. always.

    For an analysis of your particular application, consult with an experienced heating engineer.

    Author’s Note: Updated 01/03/2018