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Direct On-Demand DHW with Weil McClain Ultra 155

I had an indirect on the DHW priority 1. I replaced it with an electric On-Demand that occasionally trips the breaker when it draws cold well water in the winter. Can I just flush my boiler and use the priority 1 for a DIRECT on-demand DHW supply (open loop system)? All of my other loops can be run at close to the same temperature (Mid 120's)? My boiler is undersized for my house and we are superinsulated.


  • Henry
    Henry Member Posts: 998
  • Ironman
    Ironman Member Posts: 7,379
    Absolutely NOT! You cannot run potable water from the boiler system.
    Why did you get rid of the indirect for an electric on demand?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
    kcoppJean-David Beyer
  • hot_rod
    hot_rod Member Posts: 22,261
    You could add a HX package, treat it as a zone. There are some prebuilt modules available for doing DHW via a plate style HX
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Zman
    Zman Member Posts: 7,573
    I am not sure why you switched away from the indirect and went to electric. Now that you have the electric, why is it tripping the breaker? The unit should have an amp rating and the circuit should be sized accordingly. If you post all the details, we can attempt to get you out of trial and error mode.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein