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Add on additional instantaneous electric hot water heater to oil boiler that also does hot water bot

I am a plumbing contractor, 
Customer wants to add an additional water heater to existing oil boiler set up.

He has an existing oil boiler that supplies hot water to radiators and  coils that provide hot water to showers faucets etc..
Also in addition there are two recirculation pumps.
There is a amtrol storage tank and digital aquastat in the situation .
We are looking to connect a instantaneous electric hot hot water heater.
Customer dosent want any gas etc...

How do they connect together,
What can I install, so that when the temperature in the tank goes down, it should open up the valve on the instantaneous hwh side, sonce its triggered by flow...and close if the demand is reached,
Also since its electric and being used as an add on he dosent want it to be on all the time.
Want both to work one after the other.


  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,117
    I would like to se a picture of the boiler coil and Amtrol. Model numbers if you are not on the job site. Maybe a hand sketch of the piping from the boiler to the Amtrol and the tankless coil in the boiler. But pictures would be better.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • Jamie Hall
    Jamie Hall Member Posts: 23,447
    I, at least, will need some more information on this...

    First, is the Amtrol tank strictly a storage tank for hot water? Or is it an indirect? And if it is a storage tank, how is the hot water in the tank replenished and reheated -- since it will cool off. Is there a circulator thought the tankless coil on the boiler for it?

    Where to the existing recirculation pumps tie it?

    In fact, a piping diagram would be very helpful...

    Now having gotten that far, the real question:

    What, exactly, is the objective of this addition? Is there a specific problem which he's trying to solve? And if so, what is it?

    The reason I ask is that yes, I can think of ways to do this -- though it's going to be an interesting set of valves and controls -- but unless your client's electric rates are stupid cheap and the amount of hot water involved is quite small, I'd find it difficult to come up with a more expensive approach...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,886
    Electric tank or indirect (assuming the amtrol isn’t already one?) would be the way to go. 
  • Larry Weingarten
    Larry Weingarten Member Posts: 3,337
    Hi, Maybe it's a crazy idea, but how about running the piping from tank to tankless? Set the tankless to fire up when temperature drops ten degrees or so. That way plumbing and controls remain simple. This probably won't work if line pressure is too low. Also, I'd put in three valve bypasses so either heater can be taken off line without affecting hot water availability.

    Yours, Larry

    And, I agree with Jamie... What problem are you working to solve?