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Testing a tankless coil?

jrc2905 Member Posts: 98
What would be the correct procedure for testing a tankless coil?
This is a Peerless boiler no more than four years old. The owner had been going down and turning the Hi and low limits up to max temp so she could sterilize baby bottles; she ran a day care center at this house. I had to replace the aqua stat because the Hi limit was running the boiler to 230 when set to 180. Now the boiler is rising to 30 psi every few days, the water feed looks new. The new owner says the boiler relief valve is leaking and has been using the relief valve to reduce the 30-psi to 20 psi. I could shut off the water feed to the tankless but that would involve the homeowner monitoring the pressure and would leave them without hot water. So I think I will test the coil any suggestions?


  • tommyoil
    tommyoil Member Posts: 613
    Try some basics like

    closing the pressure reducing valve (feeder that LOOKS new)first making sure, of course, that there is water in the system BEFORE you do. Maybe the p.r.v. is no good. Also, when you do that, assuming you have a diaphragm expansion tank, check to make sure the charge on it is o.k.(charge on tank should match system pressure/12 p.s.i. on system = 12 p.s.i. on tank charge)You can do that by removing the tank and checking it with an ACCURATE tire pressure gauge. Is the tank properly sized to match the system? Also, if the H.O is relieving the p.s.i by dumping the system, maybe its loaded w/ air. Sometimes, checking for a coil leak is as simple as shutting off the supply valve to it. Sometimes its not. Have had to remove and pressurize coil while outside the boiler in worst case scenario. Sometimes the coil leaks are so slight that it may take days (as in your case) to overcharge the boiler.
  • jrc2905
    jrc2905 Member Posts: 98

    Thanks, everything else checks out, I was thinking of cutting two ball valves into the supply and return to the coil, brazing a schrader valve into the loop and pressurizing it with nitrogen and watch it using my refrigeration manifold.
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