Oil burner water pressure too high.

armonkiwi

After dripping PRV that turned to more solid flow after releasing it for a moment (didn’t close off completely) and with pressure at 25psi and 165F temperature, I replaced both with new PRV and expansion tank. Both new PRV and new expansion tank were exact replacements.
Assumed failed PRV due to hard water/particles as it didn’t shut off completely at less than 30psi. However, expansion tank also full of water when removed.
Next morning water on the floor, pressure at 35+psi and temperature around 160F. PRV gushed water at slightest touch but shut off without dripping. Drained water to 20psi and shut off incoming water.
Incoming water is well water, not town supply, and goes through a pressure reducer to 12-15psi. Monitored throughout the day and ranged between 15psi at 148F and 22psi at 157F. Honeywell is set to HL of 175F.
After overnight, water again on floor, and morning pressure back to 34psi at 143F.
Boiler is only being used for heating hot water at the moment through an indirect water heater; no home heating required.
Water heater is a couple of years old and furnace and all plumbing was new in 2014.

What’s going on?! Why has the water pressure increased to over 30psi again? With the water intake still shut off, is water getting in elsewhere? The water heater piping?

Cheers

Jamie Hall

PRV -- is that pressure relief valve? I'll assume it is.

When you replaced the expansion tank, to what pressure did you set it before it was connected to the system? It must be set to the desired system cold pressure (typically around 15 psi) before it is connected.

When you say you are heating domestic hot water with the boiler, I assume that that is through an indirect hot water heater? If so, it is quite possible that there is a leak in the heat exchanger, allowing domestic water to leak into the heating system (I assume the pressure reducer is for the heating system, not the domestic). If so, try closing the valves isolating the heat exchanger from the boiler.

mattmia2

Coil in the indirect is probably leaking.

EBEBRATT-Ed

Or the new expansion tank is bad

SuperTech

I'm betting that you need a new indirect tank.  The heat exchanger coil inside the tank probably has a leak. Your water pressure is higher than the boiler pressure, typically between 30-60 PSI with a well pump. Its easy to imagine that if the coil in the indirect tank has a pinhole that it could raise the pressure in your boiler high enough to open the pressure relief valve. 

STEVEusaPA

Could simply be the water feed. Best to have someone who understands hydronics and knows how to check all the components properly before firing the 'parts' and 'components' cannons at it.

Zman

Do you have isolation valves on the domestic side of the indirect? If so, try isolating it overnight and see if the pressure still spikes.

dopey27177

Try this, after filling the system to the required water pressure and venting all the air out of the system (air is a compressible gas and when heated it will increase the pressure in the system) close the manual fill valve to the boiler and see if the water heating system pressurizes. If that happens you may have a leak in the coil that makes hot water.

Jake

armonkiwi

Thanks for all your comments! I see a thread but let me update you and see if it continues.

First of all, when I installed the new expansion tank I did not check the pressure which is meant to be 12 to 15 psi. I didn’t check because I was going away for a few days and took a gamble as I didn’t have time. So under-pressurized expansion tank might still be a cause.

However, I went away for a couple of days and shut the boiler off. Returned just now and water on the floor and the bucket under the PRV (yes, pressure relief valve) on the boiler (not the indirect water heater) was full of water. Temperature of course was down to 70F (lowest on the dial) given the boiler was off. But pressure was at 35+ psi!

Seems to me the indirect water heater has been leaking water into the boiler system the couple of days I was away. Anyone disagree? Could it still be the expansion tank? Tonight I am going to cut off the water heater from the boiler and see if it makes a difference.

One other thing. Upon return, there are rusty water stains on the Taco air scoop. And occasionally a spitting noise from its air vent. Thoughts? All appreciated!

Cheers.

Jamie Hall

At this point really the only two possibilities are the pressure reducing valve between your domestic water and the boiler fill -- if there is on (there may not be) or a leak in the indirect.

mattmia2

armonkiwi said:

One other thing. Upon return, there are rusty water stains on the Taco air scoop. And occasionally a spitting noise from its air vent. Thoughts? All appreciated!

Cheers.

Whichever thing is adding fresh water to the system, weather it is the indirect coil leaking or the pressure reducing/fill valve not holding, is adding dissolved air with the fresh water which is collecting in the air scoop. Not a cause but a symptom.

EdTheHeaterMan

Please get your acronyms right.
PRV = Pressure Reducing Valve , while
PRV = Pressure Relief Valve,
Don't confuse these two parts. You must use the correct Acronym!

Jamie Hall

EdTheHeaterMan said:

Please get your acronyms right.
PRV = Pressure Reducing Valve , while
PRV = Pressure Relief Valve,
Don't confuse these two parts. You must use the correct Acronym!

Quite. Which is why I, for one, am careful to write the whole thing out...

armonkiwi

And which acronym is which?

Jamie Hall

The other one...

JUGHNE

I have seen these labeled on prints as the "Pop Valve"

jedpo75

Hi everyone

I have been working with the same problem. I remplace my apollo release valve. I thought that was the problem. Valve still leaking because the water pressure is more than 30 psi.

What can be wrong?? See pictures attached.

jesmed1

@jedpo75 Most common reason for too-high system pressure is a waterlogged or failed expansion tank. Too much water in the tank leaves too little free volume for the hot water to expand into, resulting in excessive pressure.

What is system pressure when the water is cold? And post a pic of your expansion tank.

jedpo75

I guess the expansion tank is the one on top? When water is cold is between 10 and 20 psi.

jesmed1

@jedpo75 Yes, it's the gray tank.

Cold temp between 10 and 20 is fine. That points to the expansion tank being the problem. Unscrew the black pastic cap on the bottom of the tank to expose the Schrader (air fill) valve. Press the valve stem to release a bit of air. If water comes out, the tank diaphragm has failed, and the tank needs to be replaced. If only air comes out, that's good. Then the tank is OK but needs water drained out of it.

Try that test, then report back.

jedpo75

Jesmed1: Thank you for respond. I will try, and I will be in touch. Thanks

EBEBRATT-Ed

One of three things:

Expansion tank water logged and failed

PRV filling boiler and leaking by

Tankless coil has failed

To test these, shut the boiler down. Valve off the water make up to the prv. Drain the boiler down to 15 psi and leave it like that over night.

If the boiler fills overnight it would then be the tankless coil, so valve that off and leave it overnight

If the boiler has normal pressure when cold (15psi) and the pressure shoots up when heated to 30 psi the expansion tank has failed. Some pressure rise from 15-22 would be normal.

jedpo75

I checked the expansion tank, no water is leaking, but, I checked the psi and is only 10 psi.

10 psi is bad? Can we add more psi with a compressor ? Or definitely we have to remplace ir?

Thanks everyone

mattmia2

have to isolate it from the system and open the water side to the atmosphere and pump it up to the cold fill pressure of the system, usually 12psig

Jamie Hall

10 is a bit low, but could be acceptable. The question is now much air is left in the tank? And the only way to find out and get it right is to drain the tank completely (it may need to be disconnected from the piping, or you may have valves which can do that) and then charge it with air — like with a compressor — and then reconnect it to the system.

mattmia2

https://forum.heatinghelp.com/discussion/comment/1851604#Comment_1851604

i don't think the laws of physics allow it to be less than the system pressure without the water side of the bladder being completely full.

EdTheHeaterMan

There may be only 4 or 6 PSI air pressure when that tank is disconnected from the boiler pressure.  Having 10 PSI in the boiler will automatically compress the air in the tank to 10 PSI on the air side.   What you want to do is lower the boiler pressure to 4 or 6 PSI and see if the air pressure is also 4 or 6 PSI.  

You want the air pressure in the tank to be 12 PSI when it is not connected to the boiler.  The only way to do that is to make sure the boiler pressure is well below the desired air pressure in the tank  4 or 6 PSI for example.   See this illustration I used in my one day seminar that explains the relationship of the air pressure when disconnected and that same amount of air when connected to the boiler.

See how the tank that starts out with low pressure has less room for expansion when it is later connected to the boiler pressure?

Jamie Hall

Perhaps I misunderstood, @mattmia2 — or made a faluty assumption. I assumed that the OP read 10 psig air pressure — and 10 psig system pressure. That can easily happen even when the tank is almost totally full of water. Indeed, some bladder tanks have the bladder slightly smaller than the actual air space, and it can happen that the bladder is stretched as far as it can be and the small amount of air remaining above and around it can be less than the system pressure. (in fact, many years ago Jacuzzi made a pressure bladder system which depended on the elasticity of the bladder to control the system pressure on expansion, rather than air pressure. It did work, but it had a very small acceptance volume and was really meant only for shallow well jet pumps or jet booster pumps.)

mattmia2

https://forum.heatinghelp.com/discussion/comment/1851624#Comment_1851624

i assumed the prv was keeping it at 12 psig or so cold but since there is a 4 year old post and new posts mixed together it is very hard to tell.

jesmed1

Sorry, I confused things by reading the 4-year-old post at the top. The current poster says his water pressure is between 10 and 20 psi cold. And his (presumably cold) air pressure is 10 psi. Both can be true, given that those water pressure gauges can be several psi off.

Then the rise to 30+ psi when hot points to the expansion tank having too much water in it.

mattmia2

https://forum.heatinghelp.com/discussion/comment/1851680#Comment_1851680

or the bladder is completely full on the system side.

jesmed1

@mattmia2 said:

"or the bladder is completely full on the system side."

Yes, that's what I meant by the tank probably having too much water in it (on the system side of the diaphragm).

We know from OP's report that he found no water on the air side, so at least the diaphragm is still intact.