Temp and Pressure very very high

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  #1  
Old 05-26-17, 11:19 AM
T
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Temp and Pressure very very high

I have a Biasi boiler. Just started having a serious problem. I first noticed the pressure relief valve leaking. I capped it while I went to get a new one but on return I saw that the the pressure was 65 psi! I didn't notice the temp high at that time. I first shut off the water supply to make sure the pressure reducing valve wasn't leaking but that didn't correct it.
After I bled and got back to 20 psi and started up again the pressure went back up to 65. I felt it must be the expansion tank after much reading so I replaced that since not much money. Well that wasn't it and afterwards saw that the temp was getting well above 250 degrees even as my aquastat was set at 190. Off to Blackman and got a new aquastat. Set it to 190, bled to reduce pressure and tried again. It shut off at about 210 but afterwards the temp continued to climb to above 250 and pressure back to 65.

I'm stumped! I do have an indirect hot water tank and wonder if a leak in that system could be an issue... Both that zone and the heating zone are working fine with both circulaters flowing and shutting off as normal. There is no air in the system.

Help!

Update: so, I shut off both valves on the inderect hot water loop, then I turned up the thermo on the heating loop, and the system worked as normal. It got to 210, shut down, and the pressure never got above 19 psi.

I waited 20 minutes and all was steady, then I opened the valves on the indirect hot water loop and the pressure went up quite quickly.
So I guess I need a new hot water tank unless I'm missing something.....
I still don't understand why the temp also builds.
 

Last edited by tomfmal1; 05-26-17 at 11:53 AM. Reason: Update
  #2  
Old 05-27-17, 06:01 AM
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Definitely sounds like a pressure leak from indirect tank into boiler loop. Not sure why temp goes so high. I think it's pretty common for temp to continue to rise after boiler shuts off, I know mine does it.
But not "well over 250 degrees". I'm no expert, but I think if it was my system, I'd replace the indirect tank first, and then keep an eye on the temp. Good luck- Steve
 
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Old 05-27-17, 10:03 AM
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Thanks for the support/opinion! I'm gearing up to replace. I may go with a propane this time and just eliminate it from my boiler.

I'll update when done.
 
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Old 05-27-17, 10:14 AM
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I wonder if the temp is rising because the 130 degree hot water is mixing with the boiler water adding to the total temp.
It doesn't rise like that when I close that loop off.
I hope the boiler water was not getting into our drinking water by the same way.
Wouldn't boiler water be escaping into the tank? If so I suppose it would just affect the hot water only, but there is no back flow on a water tank like there is on a boiler feed so seems possible in theory.
 
  #5  
Old 05-27-17, 10:26 AM
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Normally pressures in the potable system are higher than in the boiler system. But if you had some sort of malfunction that caused the potable pressure to drop- I guess anything's possible. Steve
 
 

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