Prv releases after 3 or 4 days

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Dwellonroof

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Here is the background; we have an old Weil McCain boiler that was oil converted to natural gas quite a few years ago then suddenly it tripped the prv and snapped the drain pipe connected to it. Upon inspection the old pipe from the prv to floor was full of corrosion and blew apart at the weakest point which was the threads at the prv itself so I replaced the prv (30 psi) and it tripped again so after more inspection I found it had the wrong fill valve so we replaced it also but now it's still releasing so onto the compression tank. We removed the tank and had it tested by adding air and submerging and it passed the test. So apparently since the prv drain piping was blocked with corrosion I'm thinking the problem existed quite a while ago. also there is an old water heater connected but the potable side has been disconnected for years and no longer needed. I'll try to post pictures or video.
Any thoughts??
 

WorthFlorida

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How old is old? Is the hydronic system cast iron pipes/rad or all copper? If copper the corrosion is probably from the boiler. Is the expansion tank all steel or a bladder type. It could be filled with crud. Put a pressure gauge with a tattle tale needle on a drain valve. See where the pressure is going.
 
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Dwellonroof

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This is the only pic it will let me post because it says too large.
WorthFlorida, 50 to 70 year old??, copper fin, steel tank with airtrol.
 

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Dwellonroof

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I'm guessing your compression tank is undersized.
The tank is 14”x60” which is 40 gallon. I drained it 3 different times and only got 14- 16 gallon out of it. The building is only 1 story and basement. We also replaced the aquastat controll.
The main lines are what looks like black iron.
 
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Fitter30

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Dwellonroof

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no picture of tank since it was drywalled in as per the fire department but we did remove it and had it air/pressure tested.
 

Dwellonroof

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Is there a remaining problem?

If water is coming out of the relief valve, try turning off the stop valve that feeds water to the makeup water fill valve.
Yes, that’s my next step after I get the tank reinstalled. I also picked up a camera so I can hopefully see what the gauges do when and if it does it again.
 

Fitter30

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Think that's funny that a fire dept would want a ex tank covered with dry wall for a fire hazard. That basically stays at room temp once system is up to temp. With tank empty and full of air adding water to system slowly most tanks stop filling at about 50-60% full which is a good water level. If the Airtrol fitting was installed at the tank manufacturer probably be the correct length could loosen the small nut on the bottom of the Airtrol when water would come out that would be a proper charge.Most of the time the tube is stopped up. If tank had a leak above the waterline after the air charge would of leaked out water would of followed. Commercial tanks are usually fitted with a sight glass the valve packing or the glass gaskets can leak air and not water but residential tanks don't have a sight glass. Fill to 10 lbs. Third pic down is the air scoop on top right is the auto air bleed loose cap on top hopefully it still ok.
 
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John Gayewski

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The tank is 14”x60” which is 40 gallon. I drained it 3 different times and only got 14- 16 gallon out of it. The building is only 1 story and basement. We also replaced the aquastat controll.
The main lines are what looks like black iron.
Then you don't have a compression tank you have an actual expansion tank. If the expansion tank isn't full during these episodes then you have something like a check valve blocking the expansion tank from the boiler. There should be no way the pressure could get high enough with room in the expansion tank. It could be time to get rid of the old style expansion tank and get a newer style compression tank with a bladder and precharge.
 

Dwellonroof

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That was my thought as well about the drywall. The airtrol was plugged when I first drained the tank so I cleaned it up and reinstalled.
Actually I replaced that auto bleed valve because I didn’t know if the old one would still work. Btw the tank doesn’t have a sight glass it’s just a steel tank.
 

Dwellonroof

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Update; I have everything reinstalled and also put a gauge at the expansion tank drain and wanted one before the prv but not enough room. Now just need to install camera so I can monitor the gauges also I think I'll turn off the autofill for the time beaning.
 

Dwellonroof

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Well: I checked the camera several times over the past few days and the gauges were holding steady but today I noticed the temp. gauge was over 200 degree and pressure rising so now I'm thinking it's the honeywell control board at the burner because the aquastat I already replaced when this problem first occurred.
Edit: After doing more research I'm thinking the gas valve is defective.
Any thoughts??
 
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John Gayewski

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Well: I checked the camera several times over the past few days and the gauges were holding steady but today I noticed the temp. gauge was over 200 degree and pressure rising so now I'm thinking it's the honeywell control board at the burner because the aquastat I already replaced when this problem first occurred.
Edit: After doing more research I'm thinking the gas valve is defective.
Any thoughts??
You need to find out specifically what is happening. Is the aquastat sending the signal, but the gas valve isn't shutting off? If the aquastat isn't shutting the valve then what is? Gas valves work with very low voltage some milivots some 24vols.

Do you think the gas valve is getting a signal to shut off, but overunning the signal, then runs for another five minutes and then shuts off?

You should bs able to call whomever makes the gas valve and they can run you through some tests.
 

Dwellonroof

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John, This is from the;
INSTALLATION AND SERVICE INSTRUCTIONS ECONOMITE MODEL RE32
VII. GAS FAILS TO SHUT OFF. A. Defective combination valve.
I'm thinking they should know but I might call the valve manufacturer.
 

Fitter30

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If valve stuck it would be blowing the relief and boiler would be a BOMB if it was red hot and you turned the fill back on. Water would flash to steam. Limit set to around 200°? What is the operating control set to? The water regulating valve needs to be replaced it's leaking through. Pur a meter across operating thermostat if calling for heat reading would be 0 vac. Not calling 24vac.
 

John Gayewski

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John, This is from the;
INSTALLATION AND SERVICE INSTRUCTIONS ECONOMITE MODEL RE32
VII. GAS FAILS TO SHUT OFF. A. Defective combination valve.
I'm thinking they should know but I might call the valve manufacturer.
Something has to be shutting it off or it would not stop running.
 

Dwellonroof

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Fitter, limit is set to 170 when we shut it down it was almost 240 .
I shut the gas valve off but let the pumps run in order to have it cool down.
John, That's the problem it's not shutting off the gas for some reason.
 
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