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Hydronic heating problem

Hello, I have a Dettson Hydra20. Two days ago we woke up to 17C inside the house instead of the 21C set on the thermostat. The water temp on the boiler was at 40C and not moving. I also have a gas fired boiler (dual energy setup), I switched to gas and the water temp quickly went up to 80C.

Today I did some troubleshooting on the electric boiler. I changed a relay that I think was faulty (I wasn't hearing clicking, though in retrospect, I should have checked voltage at the heating elements to be sure). After that, I ran the electric boiler again, water temp got up to about 55C after thirty minutes or so. The problem is that the water temperature is set for 75C using the set screw. Even after an hour, it never gets past 60C. Pressure stays at around 18psi. From what I recall, before it was getting up to 75C and about 25psi. The radiators seemed hotter before, though I don't have temperature readings to prove it.

I tried rolling back the set screw water temperature control and the boiler turned off as expected. Rolling it back up turned the boiler back on. So this seems to be working normally.

All four heating elements check for continuity and do not have shorts (touching terminal and other metal on the element with meter). Each shows ~12 Ohms resistance and when running, ~240V.

Is it possible that I have a bad or under-performing element? Anything else I should check? Thanks a lot!

Comments

  • hot_rod
    hot_rod Member Posts: 21,854
    An Amprobe is the best way to check elements, or the total current draw when they are all energized. Many of the VOM have an accessory to allow you to clamp around the wire to check current draw.
    Voltage at the element does not guarantee the element is good. A resistance check usually does if you disconnect both wires from each element.
    Power off of course.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • HVACNUT
    HVACNUT Member Posts: 5,744
    Is the outdoor sensor used on the electric boiler?
    Is it piped with the 3 way valve as shown for dual fuel?
  • Intplm.
    Intplm. Member Posts: 1,797
    @qwertyyul I would suggest looking at the heating element(s).
    They are probably corroded or burnt out to the point that they may need replacing.
  • hot_rod
    hot_rod Member Posts: 21,854
    good point by @HVACNUT It looks like ODR can keep elements off.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream