Hydronic system pressure causing boiler leak

ek99

I have a pure fire boiler that supplies heat to 4 zones and indirect water tank.  I’ve had a plumber/hvac guy come and replace expansion tank, relief valve on boiler and Autofill valve.  I’ve also had someone take apart and service the pure fire boiler.  Everything seems to be in good working order.  The psi reads 20 when the boiler fires up and maintains this pressure for a few days.  Then all of a sudden the next morning it shows 25 psi.  And when the boiler fires up and circulators turn on the relief valve starts to leak. 

I’ve closed off the auto fill valve and let the psi back down to 20.  And again after a few days the psi will creep back to 25 and start to leak when boiler fires up and circulators turn on. 

I don’t understand how the psi can increase to 25 with the Autofill valve closed.  I’ve even made sure to first turn on the heat in all zones to ensure maximum expansion before letting water out to lower the psi to 20.

my only thought is the coils in the indirect water tank must be leaking.  However the plumber assured me that can’t be the problem because it’s only leaking when the boiler fires up.  He thinks it would be constantly leaking if that was true.

Any thoughts?  As I’m running out of ideas and so far nobody has been able to solve this mystery.    Is it possible there is air in the zones? But I’ve checked each zone when I call for heat and they all have hot water flowing out and back.

also this house is only 9 years old so everything is fairly new. 

many thanks

EBEBRATT-Ed

Your plumbers logic sound right to me. But the increase pressure is coming from some place.

If the auto fill is shut off with a good valve and they already changed the expansion tank what else could it be?

I would take the expansion tank off and recheck the pressure on the air side. It has to be isolated/drained on the water side with no water pressure on the bladder to do this. 12 psi

if it's not that the indirect is the next suspect

If you can do without HW for a day valve off the indirect and disconnect the indirect control so it will not call for the pump or boiler and then run the boiler and see how the pressure is.

ek99

Yes I can isolate the feed into the coils going in and out of the indirect water tank. 

To prevent the indirect water tank from calling for heat can I simply lower the temperature on the Aquastat to room temp?  

If pressure goes up after doing the above then I know for sure it’s not the coils.  

Will give it a try thanks!  

EBEBRATT-Ed

Yes but if you turn the indirect temp down and leave the tank off a longtime and the tank cools it might call the boiler on. You could disconnect a wire from the indirect control if your comfortable doing that. They are usually but not always 24 volt

ek99

By disconnect do you mean removing the electrical wires on the AQUASTAT?  Those behind the cardboard in the picture?  I assume as long as those two wires don’t touch there will be no call for heat.  

If I turn the dial on the AQUASTAT down to the lowest temp range (40 F) that should work as long as the temp in the house / water tank doesn’t go below 40 F.  

I suppose removing the wires would guarantee that the circulators turn on while the ball valves are closed to isolate the coil section of the system.  I also see a cap where I can screw on a pressure gauge on the isolated section.  This way I can monitor whether the pressure is increasing from the domestic water side of the indirect water tank. 

Will give this a try tomorrow 

ek99

Sorry typo - I meant to say 

I suppose removing the wires would guarantee that the circulators WON’T turn on while the ball valves are closed to isolate the coil section of the system. 

EBEBRATT-Ed

Yeah since your control goes down to 40 deg you should be fine turing it down

ek99

Okay it looks like there must be a leak in the coils. It’s a slow leak as the pressure in the section that I isolated increases by 2 psi every 30 mins or so. It went from 18 to about 23 over the hour. I also released pressure on the boiler side to ensure that the increase isn’t from the boiler side. Made boiler side pressure less than 18. So now that I’ve more or less determined where the pressure is coming from…what is the fix? I assume it’ll require that change out the entire indirect water tank.If I purchase the exact same model is it simply isolate all sources of water going in and out - domestic supply and boiler supply,unscrew the pipes and reattach?Any thoughts on whether this is something I can do myself or do I need a plumber? I attached a few pics of the setup and closeups of the fittings.

EBEBRATT-Ed

If you can solder copper tubing your good to go. I would not use the old T & P relief valve you should put a new one on. Manufacturers change things there is no gaurantee everything will line up. Sometimes you get surprised.

you'll have to bleed the boiler side of air when complete. Looks like you have valves there to isolate everything

catastrophy

Is that an expansion tank on the indirect also?

ek99

It’s is.  They installed it on the recirc outlet for some reason.  Not sure if does anything to be honest.

pretty sure the pressure in the expansion tank isn’t set to 80 psi which is what my waterpressure is…

TAG

80 psi is a lot .


I thought 60 was recommended max ... think my well is 50