Honeywell AMX 300 install questions

Discussion in 'Water Heater Forum, Tanks' started by 1audio, Jan 27, 2017.

  1. 1audio

    1audio New Member

    May 17, 2015
    I installed one of these and its a well done kit. However I have questions about integration with a recirculation system. The directions say to connect the recirculation to the tap on the thermostatic valve. Its currently going in to the water heater drain connection. I need to service it because the flow is to low so the whole system fills with untempered water at around 140 when it runs. Makes for a bit of a surprise when a tap is first turned on. The datasheet says I need 1/2 GPM for the valve to work. I will be opening it up and replacing some components that are probably 60 years old (steel pipes and backflow preventor). The pump is a recent Grundfos UP 15-42 SF that per their docs should deliver 3.5 GPM. Clearly its not.

    So if I redo this and redirect the recirc. to the mixing valve I have the following questions-
    1) Location for air bleed valve? The connection to the mixer valve will be the highest point. Do I move the air bleed up there?
    2) Redirect the pump. Its pushing water down and this would redirect the flow up up. I don't think it matters but I don't want to do something dumb.
    3) Backflow preventer- vertical instead of horizontal- any issue?
    4) Components- The piping except for this stuff is all copper. Should I use brass or steel + dielectric for this stuff?
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    To ensure that you get tempered water, you need to relocate the recirculation line return to the port on the mixing valve. You do NOT need an air bleed valve anywhere in the system. I'd use a brass or copper threaded female fitting to make the recirculation line connection to the mixing valve.

    As to the checkvalve's position and orientation, it would depend somewhat on the type of valve you have.

    The pump you have is (I think) way bigger than needed, will cost more to run and was to buy. Most recirc system's pumps are small, 1/25th HP or so that don't actually move all that much water. You can slow it down by putting a valve after the pump (not before or you could cause cavitation and damage the pump) to create more head.
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