GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Reviews on HTP Versa-Hydro?

Steve Mackay | Posted in Mechanicals on

I’m convinced that because of our low heat load in our basement for the radiant floor that using a DHW storage tank as an energy source via a heat exchanger is the way to heat our radiant floor. 

However my general contractor nor my radiant floor contractor are very familiar with the HTP Versa-Hydro. I wondered if anybody here has any reviews. 

They did mention that it’s the same brand that made the munchkin (?) Boiler that was plagued with problems. 

I emailed/ called the HTP customer service and they were not overly helpful – read the manual they said.  Those guys also said that they don’t recommend modern wifi connected thermostats.  Does anybody have experience with using the Versa-hydro with a thermostat I can set over the web?

Are there any other products you recommend I take a look at?



GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. Expert Member
    Dana Dorsett | | #1

    The Versa Hydro is overkill for most low-load homes. The HTP Phoenix Light Duty and an external plate type heat exchanger is a more affordable and likely bet. The rough schematic looks like this:

    Richard McGrath ([email protected]) could specify every valve, pump,, heat exchanger & thermostat on the system (for a design fee) if the local contractors need more guidance.

    The ill fated Munchkin product line is in no way related to their water heaters or combi appliances. HTP's UFT-series of wall hung boilers have a VERY good track record, a well engineered product developed a decade or so a go by Kiturami, a first-tier Korean boiler manufacturer.

  2. Expert Member
    Akos | | #2


    Are you using the tank only for heating the floor or also for DHW? If it is just for floor heat, you don't need a plate, treat the setup as a standard radiant loop. You can even skip the mixing valve if the tank can be set to low enough temperature to supply the floor heat.

    The important thing when using any tank type water heaters for space heating is to watch the return water temperature. You want this to be low enough that it doesn't upset stratification in the tank and cause excessive cycling of the burner.

    The wifi thermostat is nothing to do with the tank, the thermostat only runs the circulation pump. You can use any of the standard wifi thermostats for that. The tank water heater itself is one of those "just set it and forget it" items.

    1. Expert Member
      Dana Dorsett | | #3

      >"The important thing when using any tank type water heaters for space heating is to watch the return water temperature. You want this to be low enough that it doesn't upset stratification in the tank and cause excessive cycling of the burner."

      The auxiliary return port for space heating on the Phoenix Light Duty is intentionally designed and placed to not short cycle the burner- it doesn't inject the return water all the way to the bottom, utilzing only the top ~1/3 of the tank. (The burner boasts a 3:1 modulation range in any event.) This is far easier to deal with than many/most other water heaters.

      Similarly, the AO Smith Vertex space heating taps take the heating supply out the side at about the 1/3 point from the top, with the return side tap about 1/5 of the way from the bottom for similar reasons but using a different fraction of the cylinder. It's a glass lined tank and doesn't have a modulating burner, and while it's cheaper than an HTP Light Duty and works, it probably won't last half as long.

  3. Steve Mackay | | #4

    I have been in contact with Rich McGrath but with his schedule we've not yet set up anything official yet. I'm still hoping to contract with him.

    If things work out with Rich, that would be great but if he doesn't have the time then I'm not confident that my existing radiant floor guy can design a system with an external heat exchanger.

    We are using the tank for both DHW and radiant heat.

    I hadn't thought about stratification in the tank. If I understand typically cold water comes into the bottom of the tank so with the water returning from the radiant floor system being hotter it should enter the tank higher up? Where is the temperature probe in the tank that triggers the boiler? At the bottom?


    1. Expert Member
      Dana Dorsett | | #5

      I'd personally be reluctant to use a radiant heating contractor who couldn't figure out how to use an external heat exchanger. That part is one of the least complicated aspects of designing an efficient radiant heating system. This heat exchanger bit is not rocket science.

      If Rich isn't available, maybe you can convinced Morgan Audetat to take a vacation from semi-retirement to design a system around an Phoenix Light Duty:

      [email protected]

      Morgan has a lot of experience designing systems around water heaters.

      When using the water heater as a combi-appliance yes, you want the tepid return water to enter at some mid-point and leave the bottom of the tank as cool as possible, for both efficiency and potential short-cycling issues. Water heaters such as the Vertex or Light Duty which have been designed for potential combi-heater applications take care of that for you by design.

      Once upon a time it was popular to design radiant floor combi systems around American Water Heater's Polaris series stainless steel condensing water heaters, and many of those short cycled badly. Somebody figured out a hack swapping a resistor on the control board (voiding the warranty) as a work-around. The Phoenix Light Duty is a pre-engineered solution that doesn't need to be hacked into working.

  4. Expert Member
    Akos | | #6


    The good thing with a tank as a heat source for floor heat is that it is really hard to mess up. Practically the smallest plate HX would handle enough heat for a typical basement slab. Over sizing the HX actually helps with efficiency. Pressure drops are pretty low, even small the smallest pumps will do (I like the B&G ecocirc e3, low power, simple speed control)

    One low cost feature you can add with this setup is hotwater recirc.

    If you put the fresh water pump on it's own aquastat and feed it with return from the recirc loop (DHW tank -> fixtures ->recirc pipe->freshwater pump->Plate HX->Tank). Aquastat sensor after plate HX.

    If the basement is calling for heat, the aquastat will automatically keep the pump running, otherwise it will cycle the pump as need to keep the recirc loop warm. Preferably a programmable aquastat so you can have separate summer/winter time programs.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |