Boiler pressure continually increasing?

hwb221227

Recently I purged all the zones (4 heating and one indirect tank) off of my boiler. After doing this I noticed that the boiler pressure was continually increasing and crossed 25 PSI. I closed the flow from street water (disabling auto-feed) and drained water to bring it back down to normal operating pressure of 15PSI. The boiler operated as expected but I noticed what sounded like air in the indirect zone when the it would call for heat. I checked the Taco auto air-vents in the system and sure enough, the open on top of the indirect tank was seized shut. I replaced all the vents and re-purged the system. I'm having the same issue when I leave the street pressure to the refill valve on. Any help would be greatly appreciated.

The indirect hot water tank has a Taco check valve on the supply and it's own circulator on the return.

Jamie Hall

Your sure it stops when you turn off the water to the refill line? In which case it's the refill valve -- either defective or stuck slightly open.

hwb221227

Yeah, it stops when I turn off the refill valve (upstream). What's strange is I had no issues with the auto-refill prior to purging. Could air in the system be causing any periodic issues that would cause the valve to temporarily fill?

Jamie Hall

No -- much more likely that the valve hung up on something when it opened to bring the system back up to pressure. You might be able to free it up by manually lifting it to fast fill and letting it snap close. Sometimes you get lucky and that works. Sometimes not.

hwb221227

Jamie, that makes sense. I can isolate the auto-fill valve on both sides. Is it better to try to get it unstuck isolated or with water pressure (i.e. filling the system)?

Jamie Hall

hwb221227 said:

Jamie, that makes sense. I can isolate the auto-fill valve on both sides. Is it better to try to get it unstuck isolated or with water pressure (i.e. filling the system)?

with water pressure. That way when you open it if something is caught on the seat it might get flushed out. It sometimes works. Sometimes...

hwb221227

Jamie Hall said:

hwb221227 said:

Jamie, that makes sense. I can isolate the auto-fill valve on both sides. Is it better to try to get it unstuck isolated or with water pressure (i.e. filling the system)?

with water pressure. That way when you open it if something is caught on the seat it might get flushed out. It sometimes works. Sometimes...

Just gave it a go, hopefully that does the trick. One last thing... if I do have to replace it, do I need to drain the whole system if it's isolated on both sides?

mattmia2

hwb221227 said:

Jamie Hall said:

hwb221227 said:

Jamie, that makes sense. I can isolate the auto-fill valve on both sides. Is it better to try to get it unstuck isolated or with water pressure (i.e. filling the system)?

with water pressure. That way when you open it if something is caught on the seat it might get flushed out. It sometimes works. Sometimes...

Just gave it a go, hopefully that does the trick. One last thing... if I do have to replace it, do I need to drain the whole system if it's isolated on both sides?

No. I like the caleffi valve that does auto fast fill.

EBEBRATT-Ed

@hwb221227

Unfortunately, it's common for the feeders to get plugged with rust and gunk if they sit for a long time without being used. If your system is leak free and it never adds water it sits and get gunked up. Sometimes you can clean or flush them and that may work or maybe not. You can get repair kits but in most cases it's more cost effective to just replace.

If your isolated on both sides then no reason to drain.

hwb221227

Didn't end up fixing it. Going to replace it tomorrow. Thanks for all the help!

EdTheHeaterMan

If that doesn't work, you have a more expensive problem. That is why Jamie wanted to know if the increasing pressure issue stopped, when you manually shut off the feed line.

Best of luck with this repair. Let us know how you make out. Use this same thread for context.

hwb221227

EdTheHeaterMan said:

If that doesn't work, you have a more expensive problem. That is why Jamie wanted to know if the increasing pressure issue stopped, when you manually shut off the feed line.

Best of luck with this repair. Let us know how you make out. Use this same thread for context.

As in a leak in the indirect tank coil? I assume this would cause the house water pressure to leak into the coil and raise the pressure?

mattmia2

hwb221227 said:

EdTheHeaterMan said:

If that doesn't work, you have a more expensive problem. That is why Jamie wanted to know if the increasing pressure issue stopped, when you manually shut off the feed line.

Best of luck with this repair. Let us know how you make out. Use this same thread for context.

As in a leak in the indirect tank coil? I assume this would cause the house water pressure to leak into the coil and raise the pressure?

Yes

hwb221227

Replaced the auto-feed today without any issue (thank you all!). Noticed the set point for the new Watts unit was 15PSI but my expansion tank is 12PSI. When I do out the calculation in the Watts manual, I get ~11.5PSI so that makes sense. I drained the system and took a measurement with a tire gage and noticed the expansion tank was at ~8PSI. The tank was manufactured in 2015 so It's not new so I pumped it back up to 12 PSI and refilled the system. Does this mean I should replace the tank? I assume I should adjust the auto-fill to match the expansion tank?

mattmia2

Might check the expansion tank again in the spring or if you see pressure problems but the schrader can leak a little and air can diffuse through the bladder so it is probably fine.

EdTheHeaterMan

The membrane in those tanks can lose up to a pound of air pressure a year. It happens on the molecular level thru the membrane and dissolved into the water. like osmosis. Just pump the expansion tank air side up to 15 PSI (with no water pressure on the other side) and place it in commission again. You should be good to go!

hwb221227

I'll drain it down and pump it up to 15PSI. Before this my system was at 12PSI when cold, any issue keeping it at 15PSI instead?

SuperTech

hwb221227 said:

I'll drain it down and pump it up to 15PSI. Before this my system was at 12PSI when cold, any issue keeping it at 15PSI instead?

I don't have any problems with it.  I always set them up for 15 PSI. 

hwb221227

I drained the boiler and pumped the expansion tank up to 15PSI. I then purged the zones again and noticed some odd behavior. With the drain valve open and the pressure regulator on automatic (15PSI setting) as the pressure dropped it would hit a point and then drop rapidly. Sounded like air or something in the expansion tank. When I finished the pressure in the cold boiler was correct so I turned it back on. 15 minutes later I checked the pressure and it was 21PSI. I let some water out and that same thing happened where it dropped very quickly as if there was air releasing. Any ideas?

hot_rod

The tank had water pressure pushed against the 12 psi or lower charge, so after the tank released that amount of water, the flow will slow. Think of it as a spring. Pull the spring out all the way and it retracts quickly, once’s it reaches its end the force dissipates.

hwb221227

hot_rod said:

The tank had water pressure pushed against the 12 psi or lower charge, so after the tank released that amount of water, the flow will slow. Think of it as a spring. Pull the spring out all the way and it retracts quickly, once’s it reaches its end the force dissipates.

This happened once I had pumped the tank up to 15PSI. So the bladder is compressed and once it crosses the 15PSI level it expands back to it's normal size pretty quickly pushing the remaining water out?