Boiler pressure help!

[jackthepug]

New to the boiler game and looking for some feedback. Pressure relief valve blew. Had new prv and reducing valve replaced which is a 12 psi. Since then, my pressure is reading at 9-10psi and I have no water at upstairs boilers. I’ve been bleeding rads. Upstairs and getting air but it has been over a week of doing this and still no water, just air at upstairs radiators. The guy who installed said to keep bleeding air but I don’t think it should take over a week.

The pressure reducing valve has a screw on top but no lever to add water. Could the lever have been removed? Is it universal to where I can get a lever to add water? Do I need to turn the screw on top to increase pressure?

I turned it on today and the pressure only went up to about 10-11psi and bottom radiators we’re heating fine. This thing looks ancient and is a Weil-McLain. Will try to post pics. Thanks for any feedback.

 

[Dana]

The spitting pressure relieve valve more likely to be from an expansion tank failure than a seeping pressure reducing valve (aka "auto fill valve") or a faulty pressure relief, though either is possible. The expansion tank needs to be sized and pre-charged to the system pressure to accomodate the higher volume of the water when it's hot vs. when it's cool. When the tank has insufficient air volume to expand into, the system pressures go very high when the system is hot, causing the relief valve to open to keep it from hitting system damaging pressure levels.

The reducing valve is adjustable with the screw on top- you can raise the system pressure to 12-15 psi if it's reading low. Read the model # and look up the manual online. Quick-fill levers are not universal, but model-specific. But where/how are you measuring the pressure?

Unless the "upstairs" more than 3 floors above the point where the pressure is being measured 10 psi is enough to get water up there. You get 0.433 psi per foot of elevation, so 10 psi will push water 43' higher than where the pressure is measured, but it's customary to add a couple or three psi to the absolute minimum in order to compensate for pressure differentials induced while the system is pumping. Boilers will also run into flash-boil issues if the pressure at the boiler is much less than 10psi. (You'd be hearing it if that were happening.)

Air will tend to migrate to the highest level in the system. (Air is lighter than water- who knew? ), so it's common to run into vapor-lock on the upper levels even if the lower levels are pumping fine. Keep bleeding air out of the top radiators it'll eventually get there. It's not unusual to see air vents installed on the higher levels of the system for purging air, but it's not absolutely necessary.

 

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[Dana]

BTW: That antique boiler is probably ridiculously-woefully oversized for your actual space heating loads. The nameplate indicates either 1.9 gph if oil, 266 MBH if gas. (Which fuel is it? Can't tell from any of the pictures.)

The average 2x4 framed 2500' house in IL with reasonable efficiency updates (better windows, or at least storm windows, some amount of air-sealing and some improved attic &/or wall insulation) will come in under 50 MBH for a design heat load, which means you probably have enough burner to keep the place warm (with margin) even if you moved your house as-is to the south pole. Being 4-5x oversized is bad for both efficiency and comfort- it never met it's AFUE numbers, and after 50+ years there's no way it's even meeting it's original steady state efficiency. Rather than wait until it flat-out dies, start planning the replacement equipment now rather than having to make a mid-winter panic decision under pressure. That starts with an accurate heat load estimate.

If you have a heating history on it from last winter (don't use shoulder season data) you can run a fuel-use heat load calculation based on the nameplate efficiency (BTU;hr or MBH-out divided by it's BTU or MBH-in. If it's an oil burner jetted at 1.9gph that's 262 MBH , or 262,000 BTU/hr for the input), and how much fuel was used to cover a particular number of heating degree-days. With an old and oversized boiler like this the fuel-use calculation will hit higher than reality- it's an upper-bound. The last thing you want to do is just replace it with another 250MBH+ boiler!

It's also useful to measure up the radiation (zone by zone, if multi-zoned) to get a handle on the peak water temperature required to meet the design condition load. Many old high volume radiator system really shine on both comfort and efficiency with a modulating condensing boiler running it.

 

[jackthepug]

Dana, thanks for the replies. Quick update - the time I had today to work on the issues was depleted due to a bird that I had to take out with a dust broom.

Gas boiler. Pressure tank is 3 years old and that checked out ok during the “repair”. Reading 9psi pressure on the boiler gauge.

In any event, I loosened the nut and turn the screw on pressure reducing valve clockwise 1/2 turn, no pressure change. Waited and turned clockwise another 1/2 turn and still no change on pressure gauge. I left it like that, one full turn clockwise. Turned power on, boiler is running but still no water at second floor. Did get some gurgling noise upstairs which was a new noise but only at one radiator. Other radiators are still bleeding air for about 10-15 seconds before I close bleed valves. I through breaker back to off when I left.

I feel like I need to “add water” but have no idea how to do that or ensure I have the appropriate amount of water. The reducing valve doesn’t have a fill lever.

The pressure relief valve did more of a exploding than seeping from what I was told. This led to replacement of psi reducing valve and the pressure relief valve. The boiler was supposedly off when the pressure relief valve exploded. Now I can’t get pressure up over 10 psi.

Thanks for any feedback or suggestions.

 

[jackthepug]

Forgot to mention:

I did tap on the expansion tank and it sounds different when tapping the top vs. bottom. Changed in sound takes place about halfway up the expansion tank.

Maybe I don’t need to add water because the pressuring reducing valve/auto fill valve does this automatically(??). Thanks.

 

[Dana]

The auto-fill adds water whenever the system pressure drops below pressure to which the valve is set. There has to be a valve between the auto-fill and the potable water supply (it's a bit hard to fully discern the plumbing in the picturses.) That valve needs to be open for the auto-fill to be able to add water while you are purging air. From the pictures it looks like you MAY have a gate valve between the auto-fill and the heating system. If so, that valve has to be open too.

I wouldn't trust a boiler gauge that looks like it was installed during the Truman administration to deliver a precision measurement, but 10psi is enough to push water 43' in elevation above the gauge. How many feet is there between the boiler gauge and the very top of the top-most radiator?

When you open the air bleeder on a top floor radiator does water eventually come out? It can (and should) be bled with the system off, no pumps running. If there is sufficient water pressure there should eventually be a steady stream of water coming out of the bleeder, no spitting and hissing, just piddling a steady stream. If you turn the bleeder off before then there's no telling how much air was left in the radiators & plumbing. If you got some gurgling there may be some flow, or it could still be burping on a large volume of un-purged air, and can't establish a full loop flow.

Once the system seems fully purged of air and has been running well for a week or two you can turn off the valve between the auto-fill and potable supply, or just leave it.

Most systems have at least one air vent that automatically removes bubbles once flow has been established. None of your pictures show it however. Often it's on an "air scoop" component directly opposite the expansion tank:

(The bronze thing screwed into the top of the air scoop is a vent.)

But it can be elsewhere, often installed on a short riser off a tee other times in seemingly random locations.

 

[Dana]

With the help of PumpMd I've become aware of some disinformation in the past couple of posts:

"You get 0.433 psi per foot of elevation, so 10 psi will push water 43' higher than where the pressure is measured..."

Uh, that's some creatively bad arithmetic on my part, eh?.

10 psi/0.433= 23.1 feet (and not 43)

(why was I instead multiplying 10 x 0.43 and coming up with 43' instead of dividing is beyond me- it didn't quite seem right- even the order of magnitude was wrong, yet I repeated it in my followup post no less!?!

So if gauge on the boiler is 5' below the first floor, and you have 10' per floor for 2 floors, and the top of the upper floor radiation is 3' off the floor you have 28 feet of elevation gain, and would need a minimum of 28 x 0.433= 12.1 psi at the gauge to get water to the top of the system...

...and 14- 15 psi to ensure that while pumping no part of the system under negative pressure relative to local room air.

So, have you measured the elevation yet?

If you open a bleeder on a top floor radiator, does water EVER come out?

If not it would be an indication that you need to give the adjustment screw on the B & G B7-12 another full turn or two clockwise.

 

[jackthepug]

Dana, thanks for the follow up. I think were slowly making progress as we are getting some gurgling and new noises upstairs. No water at all yet from upstairs radiators, just air. I close off after air stops as I was told it may suck air back in if I just leave open (??). Any thoughts regarding just leaving open the bleed valves?

I have not measured elevation but would indicate that the elevation would be approximately 5-10 feet higher than standard as the first floor has five or six steps up to that level in addition to basement. Further, the ceilings are quite high compared to standard height so I think I need to be in the 15psi range to get water all the way through.

I agree that the gauge looks questionable but I did see it near 30psi before the relief valve let go so it does move.

I did not go today to see if pressure had changed. I will go over tomorrow to bleed again and give the adjustment screw another full turn. Will report back ASAP. Thank you again for your time and feedback.

 

[Jadnashua]

A typical 2-story house won't need more than 15psi. Many boilers come with a 30psi relief valve, and most boilers can handle a maximum of about 50psi with a different relief valve. You may need some momentary increases in pressure to flush the air out of the system. The pump usually needs the lines full to circulate the fluid, or, it will likely be excessively large for the application. When the lines are full, the falling water on the return helps the water rise though the supply side, and the actual pump size doesn't need to be huge. But, to purge it of air, it can be tougher. If you actually have purge valves at the top, then it should work, but many radiators, the purge valve is at the bottom of the thing, not the top, so a bit more pressure may be required. I'd leave the supply valve open until you get water out of the purge valve. If you never do, then increase the pressure slightly. Eventually, if you have an air scoop or air eliminator device, it will remove the remaining air, but it has to be moving for it to work effectively.

 

[jackthepug]

Thank you for the replies. I’m going nowhere fast. I’ve turned the pressure reducing valve screw adjustment clockwise two complete turns and pressure gauge did not change.

My upstairs radiators have valves at the bottom which are all open and air bleeder valves at the top that I use the little key to open and close.

Still bleeding air out of upstairs radiators but we’re going on like 2-3 weeks now. Could it possibly take that long?

 

[Jadnashua]

WIth valves at the top of the radiators, you should get air and as the autofill opens, eventually water. It could be that the autofill is not operating, and isn't adding water. Usually, you can hear when it opens from the flow of the water into the line. You should get air coming out of the bleed valves under the same pressure as the system's water pressure. If you do not, either a valve is stuck or something else we don't understand is going on. The autofill valve will have a manual override lever on the top...do you get any water going in when you press on that lever? Does that autofill valve have a shutoff before it? Is it open? When you open the autofill manually, you should see the pressure in the system rise. If you let it rise too far, the pressure relief valve should open when it gets to 30-ish. At that pressure, if you were to open the bleed valves, it should quickly purge the air.

 

[Dana]

Jim: His auto-fill is a B & G B7-12 pressure reducing valve, which is built without a quick-fill lever, as seen in his picture​

It's the same bell housing as some of B & G's other auto-fills, but whether internally things would line up to allow retrofitting a lever on that model is a question for B & G.

Jack: Seriously, are you bleeding air until water comes out or not?

If there isn't steady stream of water out of your bleeder valves there is still copious amounts of air in the system.

If water never comes out of the air bleeder, there isn't enough system pressure. Did the PRV get installed in the correct orientation, with the flow indicator arrow pointing at the heating system? (It looks like it's probably right inferring from the pictures, but verify.)

Do you hear ANY water flowing through the auto-fill when you turn the screw? You'd hear at least something, perhaps as quiet as the last 2 seconds of a toilet fill valve turning off, but something. If not, perhaps I read the manual up-side down, and it needs to be turned the other way. The valve that isolates the auto-fill valve from the potable supply also has to be open for it to work.

If there's enough pressure to push water out the air bleeders it shouldn't take weeks to resolve to where at least some flow is possible- we're talking minutes, an hour at most of screwing around purging air from every radiator on that floor that has a bleeder. There are systems where once flow is established enough migrating air collects over a day or two to vapor-lock the zone again, but the re-purging to resume flow should go even quicker.

 

[jackthepug]

Thanks for the replies. Here’s where I’m at. I fired the boiler up today and let everything run for a couple hours. Not much change in my pressure gauge but I’m not thinking it’s wirking too well

Regardless, 1st floor radiators are all greAt and putting out good heat. All first floors put out water from bleed valves so I’ve left those alone for a couple weeks.

2nd floor radiators are hot on the bottom 15% of the radiators so I have to be getting close. I got a lot more air (heavier flow and longer time) when bleeding the radiators after it Ran a couple hours. I thought someone said not to bleed the air with the system on but thats the only way I make any progress. I would say today I got a strong 30-45 seconds of air from most of the upstairs radiators. Before today, I’d only get about 15 seconds of air before I heard it stop and closed the valve.

Also, I’ve only been bleeding the 2nd floor radiators until I hear the air stop flowing, then I close the valve. So no, I’m not leaving open until water bc the water never comes. I wish it would. I left the main radiator upstairs open for about 5 minutes during my last attempt and did not get water.

Should I just leave a valve open for awhile to see if I get water?

I thought if I left bleed valve open it may suck air back into the radiator.

Finally, I am now only one clockwise turn on the pressure reducing valve adjustment. At one point, I had made two full turns on the adjustment screw but turned back to one full turn because my pressure gauge did not change at all.

Thanks for any feedback. If I can just get the upstairs to fill, it seems everything else is operating well.

 

[jackthepug]

Trying to post some pics so you guys can help me see what’s going on

This pic with the line that has a bucket under it is my waterline in. Above the bucket there’s a really old valve that I was told to shut off if I ever have problems because it will kill water to the radiator. That valve is wide open and drip about every two minutes.

Now if you follow that water line to the back of the boiler (left of the bucket), the line 90s and you immediately hit my new pressure reducing valve. Past that, there is another valve that you can see in the pic just after the pressure valve. That valve is also open.

Then there are two pumps and a release valve that drains into the sump. We opened the release during the repair and it is now closed.

When I turn on, I throw the big breaker to the right and I hear those two other boxes labeled “circulator 1” and “circulator 2” turn in and the gas for the boiler starts burning.

Thanks again. Hope pics help a little.

 

[Dana]

If water never comes out of the top floor bleeders and you can only bleed them with the pumps running the system it means the system pressure isn't high enough.

The facts that turning the auto-fill adjustment never changes the system pressure, and that you never hear water running through the auto fill seems to indicate either a valve in line with it being closed, or it's installed backwards. With the system off (so you can hear water flowing) crank ALL of the gate valves in the system counter-clockwise to ensure they're all open.