Please refer to our Heating Blog Library for additional details.

What is a DELTA-T ECM Hydronic (FHW) Heating Appliance?

A Hydronic FHW (Forced Hot Water) Heating Appliance fully integrates the boiler with distribution and controls into a pre-built, free-standing product. The “heart” is a single, variable speed, “smart” circulator along with the boiler control (aquastat) that distributes heating water very efficiently.

This “smart” circulator continuously regulates heat distribution by maintaining the ideal temperature differential between hot water going to and from your radiation under all conditions. Liken it to having an “automatic transmission” on your boiler as in your car. The more power (heat) you need, step on the gas. Need less, let up on the gas ….. that simple!

Circulation is further managed by the latest high efficiency, low energy ball valves. Taco Comfort Solutions® (the manufacturer) publishes that their Delta-T ECM Hydronic Distribution System dramatically reduces system electrical power requirements (up to 85%) while further reducing your fuel consumption (by up to 15%) — and we agree!

“DELTA-T”: “Delta” is the Greek letter ∆ used by science as “difference” and “T” as “Temperature”. Therefore, Delta-T (∆-T) = Temperature Difference.

ECM: “Electronically Commutated Motor”. A powerful electronic pulse-driven motor that also dramatically reduces energy. It virtually eliminates “stall” or “sticking”, the primary fail modes of all heating circulators.

The result is simple, durable and efficient heating ….. Period!  Follow this link to a more in-depth description.

Why purchase a Hydronic (FHW) Heating Appliance?

  • A Hydronic (FHW) Heating Appliance has innate advantages, as follows:
  • Design – A fully engineered hydronic appliance, optimized for heating water generation and distribution.
  • Performance – Top-rated American Components, configured with the latest hydronic technology provide the most efficient performance in your heating application. No “built-on-site” heating installation can match it.
  • Quality – The historically best performing, readily available American components assembled and tested using our proven in-house and field assembly methods.
  • Value – State-of-the-art design, purchasing, assembly methods and logistics achieve the maximum economic benefit. The result is a premium appliance more than comparing with lesser-performing, contemporary “built-on-site” systems.
  • Delivery – What we engineers refer to as TAT (Turn-Around-Time) is minimized. Whether you are scheduling a future new, current replacement or emergency heating requirement, your system is there when you need it.
  • Availability –The “Appliance” is a product with open availability, thus unconstrained by trade access or influence. The end user (consumer, tradesman or contractor) controls the sale.
  • Installation –  Skill level requirements are significantly reduced, providing additional consumer installation options.
  • PRODUCT NOTE: Our Packaged “Enhanced Convection Delta-T ECM Hydronic (FHW) Heating Appliance™” is currently under Intellectual Property Protection (Patents Pending – USA & Canada).

Who can benefit from a Hydronic Heating Appliance?

  • The “Appliance Advantage” is beneficial to any user or end-user, and not limited to:
  • Fuel Dealers, Plumbers & Heating Contractors – A proven performance & service package, available “on demand” – no stock on hand, less time on the job. Customer satisfaction.
  • Building Contractors – A performance package, delivered & installed to a short interval schedule. Very competitively priced, it requires lower trade skills and content to complete a heating system installation.
  • DIY’s (Do-IT-Yourselfers) – Our package “takes all the fun out of it”.  No complex control wiring, piping and system layout.  Just finish connections to your current utilities, fill with water and fire per our Planning & Installation Guide.  Price and Performance!
  • You, the Customer – Whether you have the DIY skills required or not, by specifying our heating appliance you know precisely what you are getting.  No lesser, prior generation products poorly installed and priced to sell!  Compare specifications, then solicit your completed installation quotes, as necessary.

How do I determine what I need?

  • Heat Loss Requirement – You must know reasonably well your building “Heat Loss” (heating requirement), preferably by calculation.  Refer to our “Using a Heat Loss Calculator” Blog for more detail.  If replacing a boiler, don’t assume the same size is required by merely reading off the current unit nameplate! Building efficiency improvements (insulation, doors, windows, etc.) have effectively reduced your boiler size requirement over the years – and it was probably generously sized by practice at prior installation.  If your architect/builder/heating-engineer can’t provide a calculation – go on-line and use the several available!
  • DHW (Domestic Hot Water) Requirements – DELTA-T ECM Hydronic (FHW) Heating Appliance™ system boilers have no internal DHW Coil provisions as you may currently have!  They are “Heat-Only” Boilers to attain their efficiencies.  However they can supply DHW with an Indirect Water Heater at field installation, current or future.  The Indirect Water Heater by design provides the ultimate in DHW generation efficiency.  Sizing is typically determined by number of baths, bedrooms, family size and additional DHW requirements.  (You could also retain your current separate DHW heater — your choice.)
  • Number of Zones – Specify the number of heating zones (thermostats) required both currently and planned (plus one for DHW).  Detail the initial pipe sizes supplying all of your zones.  Residential zones are typically ¾” or 1” supply and return piped.  Indirect Water Heaters typically require 1” piping.
  • Installation Placement – System Dimensional Details must be qualified for installation compatibility.  A lot of flexibility is afforded in our design.  Height in a lower height clearance site can be accommodated by design modification, utilizing an on-floor expansion tank (option) if necessary.
  • Access Restraints – Refer to our System Dimensional Detail and determine:
    • Can you get it into the building, and safely?  Check widths (26″) and weights in particular!  These systems knock down vertically, so access height is usually not an issue, but weights on stairs can be! The Weil-McLain UO is the HEAVIEST RESIDENTIAL BOILER ON THE MARKET!
    • Door widths and swings must be qualified.
    • Surface quality across yards, etc.
  • The Weil-McLain Boiler Replacement Guide (link) is an excellent planning resource. We highly recommend it!

What services do we offer?

We are essentially an “Appliance Manufacturer & Provider” and therefore our services can vary within our market outlets.

As a “modular” product we build and stock a variety of components, readily configurable to fulfill most applications.

Currently full product installations are within our local geographic region (NH) only, but subject to change.

Installations beyond this will be executed under the authorization and supervision of an appropriate, Locally-Licensed Installer. Typically this can be a Fuel Dealer Tradesman or Agent, a Licensed Tradesman Client or one engaged by a Customer (Consumer or Contractor) for this purpose. In all these cases a “Save Harmless Affidavit” of Code Compliance must be provided to us prior to initiation.

To potential Boilers On Demand Licensed Installers we will provide first delivery and subsequent training on our products.

Our website www.BoilersOnDemand.com contains Product Support Resources as follows:

  • Product Brochure(s)
  • Product Planning and Installation Guide
  • User Supplement(s)
  • Extensive Heating Blog Library
  • On-line Inquiry
  • Contact Information
  • Installer Training and Licensing Opportunities

How do I get it delivered to my location?

This is wholly dependent upon the Contracting Party and Site Location.

  • Trade Dealers and Professionals are provisioned from their and/or our stock by prior arrangement.
  • Our NH Regional Direct Contractors and Consumers are delivered to site by us.
  • All products are F.O.B. Antrim, New Hampshire, USA 03440.  Depending upon your terms of service, differing transit or shipping options are available.
  • Sales taxes do not apply from our shipping point.

What Delta-T ECM Hydronic (FHW) Heating Appliance benefits can I expect?

We now have over twenty (20) system operation-years accrued on our six (6) “Beta-Site” installations that we closely monitor. They are all oil-fired burner systems with similarly configured Appliances. From these we can derive the following to date:

  • NO APPLIANCE-RELATED SERVICE CALLS TO DATE! NONE! (We have had two fuel/fuel tank related outages, however. (These were serviced, treated and corrected.)
  • Extended System Maintenance Intervals. Our Monitored Trial Procedure – up to three (3) years. Not recommended by the manufacturers however (nor us)!
  • Quiet and infrequent (Oil) Appliance Operation. Directly attributable to the very high-mass (Weil-McLain UO Series) boiler employed that operates at lower system temperatures.
  • Fuel consumption reductions of 40 to 50% on most replacements, depending upon the individual application. No Guarantees however.
  • Integrating an Indirect Water Heater provides uninterrupted DHW priority and extended heating under fail conditions. Our Trial Procedure.
  • Installed system costs of 60 to 80% of prevailing in our NH “Beta Site” Area.

From our Beta Sites and other Trade Experience of over some sixty (60) years we can project the following:

  • Our Delta-T ECM Hydronic (FHW) Heating Appliance has an economic life of well over thirty (30) years. Twice or more that of contemporary systems, and at less cost.
  • Its heavy cast-iron and steel construction has superb contaminated water tolerance vs. any low-mass or condensing technology system. No Magnetite Alleviation System required.
  • Our High-Mass Delta-T ECM Distribution Appliance eliminates the need for hydronic boiler water return temperature management, a “must-do” on condensing systems.
  • Smoothed hydronic distribution profiles projected upon radiation increase heated area comfort levels while reducing fuel consumption, as also noted by Taco Comfort Solutions®.

Will you provide Appliances utilizing other than a Weil-McLain Boiler?

Absolutely not. Our component selections are predicated on many years of appliance development, installation and performance histories. Similarly with Taco Delta-T ECM Hydronic Distribution.

Specifically, the Weil-McLain UO Series boiler attributes of high thermal mass (weight and water content), boiler pipe and flue tappings optimize Delta-T ECM Hydronic and Natural Convection Distribution performance. There are additionally complimentary packaging, assembly method, handling, installation, durability and serviceability attributes.

Many years in development. We have really done our homework!


All individual manufacturer component warranties apply!

There is no warranted differentiation between our “Appliance” and any “Built-On-Site” Heating System.


Weil-McLain Ultra UO Boilers are all 20 Year Heat Exchanger Warranted, 2 yrs on other parts.

Beckett Oil Burner(s) are Parts & Workmanship 5 Year Warranted.

HTP Products SuperStor All-Stainless Indirect Water Heaters are Fully Lifetime Warranted, and Transferable!

Taco, Inc. Products are typically 1 to 2 Year Warranted, but check specific items on their website. They live longer in use however.

Watts Water Technologies Valves are typically 1 Year Warranted, but check specific items on their website.

We additionally warrant our assembly workmanship for one year.


  1. From our own and manufacturer’s field experience we would expect a 30 year plus Service Life on the Weil-McLain® UO Series Cast Iron Boiler. Although not warrantied, Weil-McLain® intimates this in some of their other product videos and we certainly concur from our field experience.
  2. We have installed All-Stainless HTP Products “SuperStors” exclusively for over 20 years now, with not a single incident. They will likely out live us all!
  3. Taco Comfort Solutions® Hydronic Products are our components-of-choice. We love them and they love us.
  4. We don’t like service calls, and neither do our customers.


What about on-going maintenance and service thereafter?

As a Heating Appliance Manufacturer we must “service what we sell”, and always will. Similarly we do so as a regional (NH) installer.

Beyond this our Appliance(s) are installed, maintained and serviced by our Licensees.

If the situation ever necessitates, Weil-McLain also maintains a nation-wide Service Referral Program on their site. Our On-Line System User’s Guide has Specialized Service Notes included that should be readily interpreted by any competent serviceman.

We also suggest reading our Heating Blog entry on “Selecting a Serviceman”.

Terms of Payment?

As a Heating Appliance Manufacturer, products and related services are pre-pay.

Further, Trade System Installation Services are customary pre-pay, or other by prior arrangement.

Note: Our Pre-payment Methods include ONLY:

  • Cash
  • Certified Check
  • Wire Transfer

Credit Card, PayPal & other Card Services are not currently accepted due to their transaction restrictions.

What about Sales Taxes?

New Hampshire is truly a Tax-Free State.

We have no applicable income, sales or excise taxes.

Further, the NH Supreme Court has ruled that a N.H. Franchised Business selling a product inter-state has no responsibility to assess or collect taxes for other States or Principalities. It is therefore solely the client’s responsibility.