Please refer to our Heating Blog Library for additional details.

Just what is a “Neo-Gravity Hydronic (FHW) Heating Appliance (TM)”?

By definition a Hydronic FHW (Forced Hot Water) Heating Appliance fully integrates a boiler, hydronic distribution and controls into a pre-built, free-standing product. The “heart” is a dedicated, variable speed, “smart” circulator along with the boiler control (aquastat) that combine to generate and distribute 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. The manufacturer, Taco Comfort Solutions® publishes that their Delta-T ECM Hydronic Distribution System dramatically reduces system electrical power requirements  by up to 85% while further reducing your fuel consumption by up to 15%. We actually do even better than this by optimizing natural (gravity) hydronic convection within our appliance, thus the naming.

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, such as:
  • Design – It’s fully engineered and proven, optimized for heating water generation and distribution.
  • Performance – All Premium American Components, configured with the latest hydronic technology provide optimum performance in your heating application. So much so that we will challenge ANY “built-on-site” hydronics technician or installer to match its performance!
  • Quality – All the historically best performing, readily available American components are tested and proven on our monitored “beta sites”.
  • Value – State-of-the-art design, purchasing, assembly methods and logistics combine to provide the maximum economic benefit. The result is a premium appliance that exceeds contemporary “built-on-site” systems in cost, performance and longevity.
  • Delivery – What we refer to as TAT (Turn-Around-Time) is minimized. Whether you are scheduling a future new, a current replacement or an emergency heating requirement, your system is there when you need it.
  • Availability –The “Appliance” is an open-marketed product available to any end user (consumer, tradesman or contractor).
  • Installation –  Skill level requirements are dramatically reduced, allowing many user installation options. Our Appliance comprises over 95% of the materials required. Place it, pipe it and power it!
  • PRODUCT NOTE: Our “Enhanced Convection Delta-T ECM Hydronic (FHW) Heating Appliance™” is now under Intellectual Property Protection (U.S. Patent 10,690,356 with Canada to follow).

Who benefits from a Hydronic Heating Appliance?

  • Our “Appliance Advantage” is beneficial to any trade 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 or priced to sell!  Compare our specifications with others, 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).  Measure and detail the pipe sizes supplying to and returning from 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.  Installation into a lower height clearance site for instance 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, and we highly recommend it!

What services do we offer?

Boilers On Demand LLC is a Heating Appliance Manufacturer. We build and stock our “modular” appliance with a variety of supporting modules that configure to fulfill most hydronic heating applications.

Currently full product installations are available only within our local geographic region (NH), but this is subject to change. Installations beyond this will be executed under the authorization and supervision of an appropriately trained, 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.

We can assist an installer along with delivery where logistically practical. In 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 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.

  • Our NH Region Contractors and Consumers are delivered directly to site by us, or by their arrangement.
  • All products are F.O.B. Antrim, New Hampshire, USA 03440.  Depending upon your terms of service, differing transit or shipping options are available.
  • Your sales and excise taxes do not apply from our NH shipping point. It is your post-sale responsibility alone.

What “Neo-Gravity Hydronic (FHW) Heating Appliance (TM)” benefits can I expect?

We now have accrued over thirty system operating-years on our multiple “Beta-Site” installations that we closely monitor. Currently all are oil-fired appliance systems with varying end use applications. From these we can derive the following:

  • NO APPLIANCE-RELATED SERVICE CALLS TO DATE – NONE! We have had two fuel/fuel tank related outages, however. (These were serviced, treated and corrected.) A recent severe power surge substantially damaged much of a client site, including our appliance. Service was reestablished within a day.
  • Extended System Maintenance Intervals. Our Monitored No Service Trials – up to three years. Not recommended by the manufacturers however (nor us), but no incidents to report.
  • 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 with an Indirect Water Heater provides uninterrupted DHW priority and reduced, but continued heating under selective fail conditions. Proven on our beta sites.
  • Installed system costs of 60 to 80% of contemporary “high-end” installs in our NH Area.

From our Beta Sites and other Trade Experience of over some sixty-five years we can project the following:

  • Our Delta-T ECM Hydronic (FHW) Heating Appliance has an expected economic life of well over thirty (30) years, twice or more that of contemporary systems, and at less cost. (Buy two (2) of theirs to one (1) of ours?)
  • Its heavy cast-iron and steel construction has superb contaminated water tolerance vs. any low-mass or condensing technology system. No Magnetite Alleviation typically 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 over a decade of appliance development, installation and performance histories. Similarly with Taco Delta-T ECM Hydronic Distribution ….. no equals.

Specifically, the Weil-McLain UO Series boiler is the highest thermal mass (weight and water content) residential boiler in the world! Weil-McLain is now promoting it in Commercial Multi-Boiler Applications (as we have). It is a “beast”! Its near-boiler piping attributes optimize both Delta-T ECM Hydronic and our patented Natural Convection Distribution performance. Additional attributes include packaging, assembly, handling, installation, durability and serviceability ease.

Many years in development ….. we have done our homework!


All individual manufacturer component warranties apply!

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


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 Max All-Stainless Indirect Water Heaters are Fully Owner Lifetime Warranted!

Taco, Inc. Products are typically 1 to 2 Year Warranted, but check specific items on their website. They typically live much 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 Economic 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?

Our Design Policy is based on the KISS Principle (Keep It Simple, Stupid)! All elements are industry standard, i.e. no manufacturer-specific controls or third-party add-ons. Everything is in Trade or Box Store Stock ….. everything. All controls, gauges, valves and adjustments are within an arm’s reach of the appliance front.

As a Heating Appliance Manufacturer we “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 or Certified Heating Technicians.

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-purchase.

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

Note: Our Pre-purchase or pre-pay Methods include ONLY:

  • Cash
  • Certified Check
  • Wire Transfer

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