Can’t figure this out leaking PRV rising pressure

[mrm143]

Good morning everyone and thanks in advance.
I am a di’yer who can pretty much fix anything but I’m coming to the end of the line with this problem and need some help.

Well McLain cg-6-spdn
The PRV is dripping/purging every few days

I have already replaced the #30 tank
Turned off the makeup water fill valve totally off so no extra water can get to the system at all
Circulator is only a few years old I replaced it already
Verified pressure in expansion is 12 PSI even experimented with different pressures to see the reaction.
Bled all the radiators and even turned off one of the 3 zones because it’s a Basement with no bleeders with PEX so I need to install one. But again this zone is out of the loop right now.

I originally replaced the expansion tank 2 weeks ago due to this issue and it did have water coming out of the fill valve so I knew it was bad

Still every few days the pressure hits 29/30 and the valve dumps.

I’m pretty handy but can’t figure out what else it could be

 

[Reach4]

Turned off the makeup water fill valve totally off so no extra water can get to the system at all

Sounds like that valve could be leaking water coming in. If you keep losing water, and the cold pressure is not dropping, the incoming valve leaking makes sense.

What is the water pressure when cold?

I have already replaced the #30 tank

What is a #30 tank? You may need a bigger expansion tank.

I am not proficient at boiler stuff. I am looking for details of the description.

 

[Sponsor]

 

[mrm143]

Sounds like that valve could be leaking water coming in. If you keep losing water, and the cold pressure is not dropping, the incoming valve leaking makes sense.

What is the water pressure when cold?


What is a #30 tank? You may need a bigger expansion tank.

I am not proficient at boiler stuff. I am looking for details of the description.

As far as leaking past, I turned off the autofill valve, as well as the actual ball valve to that pipe, so unless its leaking past both I dont think thats an issue

As far as the #30, its a size, so i believe its 4.4 gallon... Thats what has been on it for the past 5 years since i replaced it last time, I could go bigger and its an easy swap but dont want to throw out more money if it was working fine all these years with the last one...

 

[mrm143]

Could it be the circulator is going bad? I replaced it about 5 years ago, but i can hear and feel it running which is why I didnt think about it... Also when it didnt run I wouldnt get heat to all the baseboards...

 

[Dana]

Is there a tankless coil or indirect water heater on this boiler? When pinhole leaks develop in the heat exchangers of the domestic hot water heaters runing off the boiler it'll add unintended water to the heating system.

When you replaced the expansion tank did you verify the pre-charged pressure before putting it on the system?

The CG-6 is a pretty gia-normous boiler- ridiculously oversized for the heat loads of most homes in RI (but maybe not crasy oversized for fairly large uninsulated houses.) It's probably worth running a fuel-use based load calculation to figure out the approximate oversize factor. If the oversize factor greater than 3x it's worth retrofitting a heat purging economizer control. If greater than 5x it might be time to consider retiring it early, and installing a right sized modulating condensing boiler.

 

[mrm143]

Is there a tankless coil or indirect water heater on this boiler? When pinhole leaks develop in the heat exchangers of the domestic hot water heaters runing off the boiler it'll add unintended water to the heating system.

When you replaced the expansion tank did you verify the pre-charged pressure?

The CG-6 is a pretty gia-normous boiler- ridiculously oversized for the heat loads of most homes in RI (but maybe not crasy oversized for fairly large uninsulated houses.) It's probably worth running a fuel-use based load calculation to figure out the approximate oversize factor. If the oversize factor greater than 3x it's worth retrofitting a heat purging economizer control. If greater than 5x it might be time to consider retiring it early, and installing a right sized modulating condensing boiler.

I checked and rechecked the precharge and even experimented with different psi's to check result
It is a huge boiler, and not sure how old, I need to check with the serial number later tonight..

What is an indirect water heater, I know their is no tank less coil

Its a larger house, about 2500 sq ft, but as of right now, the basement loop is off until I can purge it later tonight...

There is no unatended water coming in as the first thing i did after reading the forums was to turn off all water coming into the boiler, i shut off the autofill and also the ball valve to the boiler

 

[mrm143]

I checked and rechecked the precharge and even experimented with different psi's to check result
It is a huge boiler, and not sure how old, I need to check with the serial number later tonight..

What is an indirect water heater, I know their is no tank less coil

Its a larger house, about 2500 sq ft, but as of right now, the basement loop is off until I can purge it later tonight...

There is no unatended water coming in as the first thing i did after reading the forums was to turn off all water coming into the boiler, i shut off the autofill and also the ball valve to the boiler

I have a separate hot water heater, with its own heat source if thats what you mean

 

[Dana]

An indirect is a tank with an internal heat exchanger that is heated by the boiler. If your domestic hot water is from a standalone water heater with it's own burner this isn't the problem.

It's possible than both the isolating valve and auto-fill are seeping. (Seen that more than once, especially when the isolating valve is an old gate valve rather than a ball valve.)

An insulated 2x4 framed 2500' house over an uninsulated basement in RI will typically come in with a design heat load of 45-55,000 BTU/hr. The CG-6 has three times that much- about 140-145,000 BTU/hr. If the basement walls are air sealed and insulated it'll be under 40,000 BTU/hr. If the heat emitters are fin-tube baseboard it takes about 250-300 linear feet of baseboard to even emit the full output of the CG-6. If you don't have enough heat emitter it's going to force the thing into cycling on/off during continuous calls for heat which cuts into efficiency .

If you DO have that much heat emitter and the fuel use calc indicates a load in the 50K range or less it means a condensing boiler would be able to deliver 95% efficiency running ~120F water even on the coldest day of the year. There are some decent, easy to retrofit stainless fire tube mod cons out there.

For the CG 6 to be "right sized" (per ASHRAE recommendations) for the house the 99% heat load would have to be 100,000 BTU/hr, which for a 2500 square foot house would be a ratio of 40 BTU/foot-hr. The only way to get there at ~9-10F design temps for RI is with all LEAKY single pane windows (no storm windows) and no insulation in the walls or attic. If your load is really that high there is a lot of low hanging fruit left on the building envelope upgrade possibilities. I've seen essentially un-insulated houses in Worcester County MA significantly larger than yours that come in well under 100KBTU/hr @ 0-5F design temps.

 

[mrm143]

An indirect is a tank with an internal heat exchanger that is heated by the boiler. If your domestic hot water is from a standalone water heater with it's own burner this isn't the problem.

It's possible than both the isolating valve and auto-fill are seeping. (Seen that more than once, especially when the isolating valve is an old gate valve rather than a ball valve.)

An insulated 2x4 framed 2500' house over an uninsulated basement in RI will typically come in with a design heat load of 45-55,000 BTU/hr. The CG-6 has three times that much- about 140-145,000 BTU/hr. If the basement walls are air sealed and insulated it'll be under 40,000 BTU/hr. If the heat emitters are fin-tube baseboard it takes about 250-300 linear feet of baseboard to even emit the full output of the CG-6. If you don't have enough heat emitter it's going to force the thing into cycling on/off during continuous calls for heat which cuts into efficiency .

If you DO have that much heat emitter and the fuel use calc indicates a load in the 50K range or less it means a condensing boiler would be able to deliver 95% efficiency running ~120F water even on the coldest day of the year. There are some decent, easy to retrofit stainless fire tube mod cons out there.

For the CG 6 to be "right sized" (per ASHRAE recommendations) for the house the 99% heat load would have to be 100,000 BTU/hr, which for a 2500 square foot house would be a ratio of 40 BTU/foot-hr. The only way to get there at ~9-10F design temps for RI is with all LEAKY single pane windows (no storm windows) and no insulation in the walls or attic. If your load is really that high there is a lot of low hanging fruit left on the building envelope upgrade possibilities. I've seen essentially un-insulated houses in Worcester County MA significantly larger than yours that come in well under 100KBTU/hr @ 0-5F design temps.

Well their is one way to test the valves, Ill turn off the main to the house, that should rule it out pretty quick hopefully....
The house is older, from the 50's with a couple additions, I am sure its definitely oversized but i cant get another unit until the summer as far as finances go, so getting this one ok till then is my top priority...

Its an older style auto fill with just the screw, I tightened it down all the way as well as turning off the valve right before it, but who knows, could be bad.. I was going to install a newer valve with a purge override on it to make this easier, but for now turning the screw is ok for now....

Could it be an undersized expansion tank, I mean thats my "cheapest" option

 

[mrm143]

Could trapped air do this as well?

 

[Dana]

Trapped air won't increase the water pressure or cause the PRV to spit.

If you have high volume radiators a 4.4 gallon expansion tank could be undersized, but if it's the same size as what went before and it had been working OK (before the bladder failure) that shouldn't be an issue. You could just do the math on the total water volume and the anticipated temperature swing, or use an easy online calculator to at least ball-park it.

If the boiler is in good shape it could go for quite awhile- replacing a functioning boiler isn't usually the next-most-cost-effective solution to lowering utility costs. Replacing the boiler isn't going to fix the problem if it's a valve leak or an expansion tank sizing problem. Installing a brand new ball valve between the auto-fill/pressure reducer and the potable supply would guarantee that even if the valve seats on auto fill are seeping no new water is added. That's a pretty cheap fix if there's no other possible way for water to be entering the system.


A heat purging boiler control could recover most of the oversize factor efficiency hit for less than USD$200 (as opposed to several thousand for a new boiler.) But running the math to know your approximate heat load you'll be better able to size the replacement correctly when the time comes. Only if it's 5x oversized or larger for your existing load (or even the existing radiation) would it make it onto the "A" list of things that should be rectified. If fin tube baseboard, add up the lengths of all baseboard in a zone, multiply by 500, and that's about how many BTU/hr the zone will emit with an entering water temperature of 180F from the boiler. Add up the emittances of all the zones- it if it's not anywhere near 140,000 BTU/hr some "bigger is better" idiot took it to the nth degree installing that boiler. If the total radiation on all zones together can only emit 30,000 BTU/hr, it's time to start saving up for a new boiler. Ideally the radiation would be somewhat oversized relative to the boiler output, not undersized. But if the radiation is oversized for the load by 2-3x a right sized condensing boiler can do a lot for comfort & efficiency. (There are usually rebate incentives for replacing a functioning older cast iron beast with a condensing boiler in RI, depending on which gas utility you're on.)

If you think do eventually want to replace it with a modulating condensing calculator it's worth grinding through a bit of napkin-math on the zone radiation to verify that it can be operated in condensing mode without short cycling on zone calls.

 

[mrm143]

Trapped air won't increase the water pressure or cause the PRV to spit.

If you have high volume radiators a 4.4 gallon expansion tank could be undersized, but if it's the same size as what went before and it had been working OK (before the bladder failure) that shouldn't be an issue. You could just do the math on the total water volume and the anticipated temperature swing, or use an easy online calculator to at least ball-park it.

If the boiler is in good shape it could go for quite awhile- replacing a functioning boiler isn't usually the next-most-cost-effective solution to lowering utility costs. Replacing the boiler isn't going to fix the problem if it's a valve leak or an expansion tank sizing problem. Installing a brand new ball valve between the auto-fill/pressure reducer and the potable supply would guarantee that even if the valve seats on auto fill are seeping no new water is added. That's a pretty cheap fix if there's no other possible way for water to be entering the system.


A heat purging boiler control could recover most of the oversize factor efficiency hit for less than USD$200 (as opposed to several thousand for a new boiler.) But running the math to know your approximate heat load you'll be better able to size the replacement correctly when the time comes. Only if it's 5x oversized or larger for your existing load (or even the existing radiation) would it make it onto the "A" list of things that should be rectified. If fin tube baseboard, add up the lengths of all baseboard in a zone, multiply by 500, and that's about how many BTU/hr the zone will emit with an entering water temperature of 180F from the boiler. Add up the emittances of all the zones- it if it's not anywhere near 140,000 BTU/hr some "bigger is better" idiot took it to the nth degree installing that boiler. If the total radiation on all zones together can only emit 30,000 BTU/hr, it's time to start saving up for a new boiler. Ideally the radiation would be somewhat oversized relative to the boiler output, not undersized. But if the radiation is oversized for the load by 2-3x a right sized condensing boiler can do a lot for comfort & efficiency. (There are usually rebate incentives for replacing a functioning older cast iron beast with a condensing boiler in RI, depending on which gas utility you're on.)

If you think do eventually want to replace it with a modulating condensing calculator it's worth grinding through a bit of napkin-math on the zone radiation to verify that it can be operated in condensing mode without short cycling on zone calls.

Thanks for the response, Let me first isolate any water coming in, easiest way is turn off the main and see if the pressure rises... I will report back with the results... Doesn't make sense, how would pressure rise with no water coming in... Even if their was a leak, and the valve was off, no water should be coming in, so the pressure shouldnt rise and the emergency shut off kicks in due to low water

 

[Dana]

The pressure rises and falls with the system water volume as it heats up and cools off, but that pressure change is moderated to reasonable limits by the expansion tank. The only way for the system to be incrementally increasing in pressure over time is to add water. Seepage leaks are usually pretty slow- I'm not sure you really want to be out of water for a day or two just to diagnose this.

In rare instances there is enough obstruction in the system that the circulation pump can add 10 psi or more to the boiler when running, if the pump is pumping toward the boiler. That jump would be obvious to see on the gauge as soon as the pump started up. A 1-2 psi jump would be pretty normal on a cast iron boiler as soon as the pump starts, but not 5-10 psi.

 

[mrm143]

Even if it were seepage, wouldnt it drop down to 12psi regardless once it hits the Regulator, which is set around 12?
It happens pretty quick, so for example cold pressure is around 10-12, it jumps up to 25 probably within an hour or so

 

[mrm143]

Is their anyway to tighten a Globe Type Valve, thats what is on it currently

 

[Dana]

If both the shutoff valve and autofill (it's not really a "regulator", it's a pressure reducer with an adjustable output pressure) are seeping, the pressure will continue to rise. The autofill is a convenience for filling the system, but cause more issues than they solve (this being one of those issues.) The auto fill on my system at home has failed- doesn't really open or fill the system without manually using the lever on top, but I have no interest in replacing it. If the system starts leaking I'll know about it by the sizzle & bang on on the heat exchangers long before it damages anything.

Globe valves are designed for adjusting flow rates, not for turning things off, and with flow the plug and seat faces wear a bit. If that is what is being used as the shutoff between the auto-fill and the potable supply, replace it with a ball valve, which are designed to quickly and reliably turn things off with 1/4 of a turn.

^^globe valve^^

^^ball valve^^

 

[mrm143]

If both the shutoff valve and autofill (it's not really a "regulator", it's a pressure reducer with an adjustable output pressure) are seeping, the pressure will continue to rise. The autofill is a convenience for filling the system, but cause more issues than they solve (this being one of those issues.) The auto fill on my system at home has failed- doesn't really open or fill the system without manually using the lever on top, but I have no interest in replacing it. If the system starts leaking I'll know about it by the sizzle & bang on on the heat exchangers long before it damages anything.

Globe valves are designed for adjusting flow rates, not for turning things off, and with flow the plug and seat faces wear a bit. If that is what is being used as the shutoff between the auto-fill and the potable supply, replace it with a ball valve, which are designed to quickly and reliably turn things off with 1/4 of a turn.

^^globe valve^^

^^ball valve^^

Thanks for ALL the help, let me first replace with a ball valve, ill cut the other one out, its probably been their for 50 years.... Its not leaking from inside thank god as I dont hear any sizzling....

Ill try this weekend and report back....

 

[mrm143]

Is their a specific ball valve i should get apart from the pipe size?
Also as far as the basement loop goes there are no bleeders anywhere, its 90% pex, can i install an auto bleeder somewhere on the copper in the boiler room, or will that not be enough?

 

[mrm143]

Can I put the new ball valve where the red circle is? I’m going to leave the old gate valve due to access issues it would be easier to install on the other pipe. Would that be ok?

The yellow are the existing gate valve and fill valve

 

[Dana]

The ball valve that's easiest to install is the right one. The flow rates when filling a residential system are low- half inch is fine if that's what you have.

Isn't there vent on the boiler somewhere?

When the radiation is below the boiler it doesn't tend to pick up air. Any amount of flow is enough to purge it.