I'm stuck on boiler high pressure.

[TGhost]

I have a buderus logano boiler in my home. I do most the repairs myself and have some knowledge. The PRV has been releasing water constantly at a slow intermittent rate. Constant puddle. The PRV was bad, I replace it. Still kept relieving pressure so I figured the expansion tank was bad. I was right. Full of water and dead sound. I replaced with the same Amtrol Exotrol 30. Still did not solve the issue. So....I replaced the Watts fill valve. Still did not fix the problem. Could it be my Spirovent? Im worried it might be something less obvious because it appears to maintain proper pressure when the boiler is cool. I can hear my spirovent working at times. I would really appreciate some advice.

 

[Jadnashua]

WHen the boiler's pressure is relieved, the only time you can set the ET's pressure, it should be set to the normal operating pressure. Did you check the pressure on the tank before installation?

If the tank is not sized properly for the volume and temperatures you use in your boiler, that can allow the pressure to rise more than it should.

If you have an auto-fill valve, when they get older, they can sometimes leak, letting the pressure rise. IF you don't have any leaks, you shouldn't need to leave the auto-fill's supply open.

Another possible way the pressure can rise is if there is a leak between the potable water in the hot water supply and the boiler's closed heating water. If you have an indirect, it could be a problem in that. IF you have an internal coil, it could be in there.

 

[Sponsor]

 

[TGhost]

WHen the boiler's pressure is relieved, the only time you can set the ET's pressure, it should be set to the normal operating pressure. Did you check the pressure on the tank before installation?

If the tank is not sized properly for the volume and temperatures you use in your boiler, that can allow the pressure to rise more than it should.

If you have an auto-fill valve, when they get older, they can sometimes leak, letting the pressure rise. IF you don't have any leaks, you shouldn't need to leave the auto-fill's supply open.

Another possible way the pressure can rise is if there is a leak between the potable water in the hot water supply and the boiler's closed heating water. If you have an indirect, it could be a problem in that. IF you have an internal coil, it could be in there.

Ahhh. I just replaced the auto fill valve. I have no leaks. So, the water supply valve feeding the fill valve can/should be turned off? I did have a faulty EP but maybe I made a mistake of leaving the 1/4 turn supply open. What do you think?

 

[Jadnashua]

If you don't have any leaks in your boiler, once filled, you should never need to add water unless you need to drain it for repairs, so yes, you can shut off the supply to an auto-fill valve. But, if you do have a leak, eventually, the system will shut down (assuming the low-pressure cutoff works!). Leaving it's supply valve open could mask a slow or fast leak, if you weren't home when it happened.

 

[TGhost]

No leaks. I think I was being a moron. I do believe you nailed the issue. Man, thank you so much. I truly appreciate it. You are great with all your replies. I was hoping you'd chime in. Thanks again, brother.

 

[TGhost]

I think I still have issues. Also the expansion tank is at 15psi.

 

[TGhost]

I still have this issue. Somebody?

 

[Reach4]

Set the air precharge to a little above the cold water pressure. The tank should be empty of water when the water is cold.

So maybe your thermal expansion tank is too small. You did pick a 4.4 gallon tank, so that is bigger than some use. Your boiler system looks pretty impressive, so maybe the system capacity is big. http://apps.taco-hvac.com/wizard_exptanks.html is a calculator. When you let the water cool and watch the pressure gauge, how far does the pressure fall. Does it fall enough to where the autofill should be adding water? Or is it stopping significantly higher than that?

Maybe the new autofill leaks.

I am not a pro, and I don't have relevant experience.

 

[Dana]

It looks like the valve to the expansion tank is in the OFF position:

For the tank to do it's job the valve handle needs to be in the same orientation as the valve above it, parallel to the pipe. Open that valve! Without the tank there will be overpressure every time the system fires.

None of the pictures show the isolating valve between the potable supply and the auto-fill. Close that isolating valve (if it isn't already), and bleed the system down to 12-13 psi, then fire up the boiler (turn up a thermostat or something) and note where the pressure peaks during the cycle.

 

[Reach4]

For the tank to do it's job the valve handle needs to be in the same orientation as the valve above it, parallel to the pipe. Open that valve! Without the tank there will be overpressure every time the system fires.

Ding! Ding! Ding!!

 

[Dana]

Did I win the Powerball?

 

[TGhost]

It looks like the valve to the expansion tank is in the OFF position:

For the tank to do it's job the valve handle needs to be in the same orientation as the valve above it, parallel to the pipe. Open that valve! Without the tank there will be overpressure every time the system fires.

None of the pictures show the isolating valve between the potable supply and the auto-fill. Close that isolating valve (if it isn't already), and bleed the system down to 12-13 psi, then fire up the boiler (turn up a thermostat or something) and note where the pressure peaks during the cycle.

They are both parallel to the pipe.

 

[Reach4]

"They are both parallel to the pipe."

Did that solve the problem?

 

[TGhost]

"They are both parallel to the pipe."

Did that solve the problem?

Thats the way I've had them. Still rises. The supply valve is off too.i can hear water running through the hw storage tank even when the water is not being used.

 

[Dana]

Ah- it was the angle the picture was taken at that threw me off.

With the system filled and at the proper pressure, turn the one facing the auto-fill to off (the right-most one in this picture.) That would prevent water from being added by a seeping auto-fill (which you say is brand new, but just to rule it out...).

If there's a leak between the potable side and system side of the heat exchanger inside the water heater that would cause the pressure to rise too.

 

[TGhost]

Ah- it was the angle the picture was taken at that threw me off.

With the system filled and at the proper pressure, turn the one facing the auto-fill to off (the right-most one in this picture.) That would prevent water from being added by a seeping auto-fill (which you say is brand new, but just to rule it out...).

If there's a leak between the potable side and system side of the heat exchanger inside the water heater that would cause the pressure to rise too.

I shut off the 1/4 turn supply (top of photo) and the valve after the fill valve. I brought the pressure down to 13 psi and it slowly went right back up to 30psi.

I have experience with this stuff (obviously not as much as some of you). I'm stumped. No leaks anywhere that I can see or hear.

We burn pellets so the thermostats have been off. The boiler is only being used for hw.

 

[Dana]

Leave the top/left side valve open, so that the system water expand into the expansion tank.

If it's going back up to 30psi even with the valves closed, it's almost certainly a potable-to-system side leak inside the water heater. Hopefully there are isolating valves on both the boiler supply and boiler return to the water heater (?). If yes, isolate the water heater, repeat the experiment.

 

[TGhost]

Leave the top/left side valve open, so that the system water expand into the expansion tank.

If it's going back up to 30psi even with the valves closed, it's almost certainly a potable-to-system side leak inside the water heater. Hopefully there are isolating valves on both the boiler supply and boiler return to the water heater (?). If yes, isolate the water heater, repeat the experiment.

I shut these two ball valves off and no rise in psi. Its maintaining. I dont see any leaking though, or is it sucking in air somewhere?

 

[Dana]

It's not sucking in air- higher pressure water on the potable side is seeping into the heating system water through leaks in the internal heat exchanger.

The water heater is toast, done, gone.

If the only thing you're using the boiler for most the time is hot water you're probably better off putting the replacement money into a heat pump water heater. The average efficiency of the boiler when it's only heating hot water is pretty crummy- less than 60%. See the "Summer domestic hot water efficiency (%)" column in Table 2 of this document.

At an optimistic 60% efficiency the 138,500 BTU/gallon source fuel energy of heating oil is only putting (0.60 x 138,500=) 83,000 BTU/gallon into the water heater- the rest is standby & distribution loss. So per million BTU (MMBTU) that's taking 1,000,000/83,000= 12 gallons per MMBTU. At $3/gallon that's costing $36/MMBTU.

At the legal minimum EF 0.92 of a dumb electric tank every kwh is delivering (0.92 x 3412BTU/kwh=) 3139 BTU into the water- the rest is standby loss. So that's (1,000,000/3139=) 319 kwh/MMBTU. At 19 cents/kwh that's $60.61 / MMBTU. A typical EF 2.2 heat pump water heater would be costing ($60.61 x 0.92/2.2 =) $25.35/MMBTU. With a heat pump water heater with an EF of 3.0 the cost of heating water would be ($60.61 x 0.92/3.0=) $18.59/MMBTU, half the cost of heating it with the oil boiler.

If it normally takes a dehumidifier to keep the basement dry enough in summer, a heat pump water heater will be doing double-duty, taking signifant load off the dehumidifier, converting the latent heat of vaporization of the water retrieved into hot water in the tank rather than warming up the air in the basement.

The down sides to heat pump water heaters are the slow recovery rate, and they're a bit noisy (not usually a problem if installed in a basement boiler room), but some have gotten a lot quieter in the past couple of years. With more than a decade of product history, development & design tweaking for better reliability they are no longer a new-unproven technology to be avoided. A 50 gallon Rheem with an EF of 3.2 runs about $1300 at box stores, and would be adequate for most houses. There are others.

Have any big soaker tubs to fill? Do you feel a need for the "endless shower" experience? Those might be show-stoppers, but a typical 4 person mostly-showering family can usually do just fine without upsizing from there.

 

[Dana]

From the big picture view it looks like the ball valves you turned were isolating the potable side of the water heater. There's one ball, valve on the plumbing between the water heater and boiler, but is there another, obscured from view, perhaps above the red pump (at the top of the top center of the pic) driving that loop?