replaced all parts still has over 30psi burnham V8 boiler

RickeyB · January 22

2005 install in single floor family home. Don't remember exactly when it started to blow open high pressure relief valve. I know enough to be dangerous.replaced valve and adjusted high cutoff down. limped along until 2020 and had a local contractor look at it. He replace High pressure relief valve, fill valve,backflow valve, and expansion tank. ran 3 or 4 cycles and the pressure was still 29/29 and said i should replace aquastat with a digital one . said all was good and left. it was still limping until last week when i entered the cellar and floor had a lot of water, fill valve or backflow was leaking. then the burner did not shut off until it went over 37 psi and relief opened. temp was around 215 maybe making steam ? I had shut of the boiler off 3 years ago and returned 3 weeks later to find water leaking from the coil flange gasket. after the boiler came up to temp there was no more leaking ???. So I guess when the system is pressured the force keeps water from leaking and no tank pressure allows leaking ?? not sure iof this is true. with all the parts new ( I also replace the temp gauge ) why does it still go to 29/30 psi ? I did adjust the high limit down a little and it stays around 30 , but cycle more than once ina row and bam over 30. expansion tank has air no water, still dripping from backflow/fill valve. Do i have to drain the boiler to change out the fill valve ?I heat primarily with a wood stove and this is why it doesn"t cycle more than once, use the water for laundry, showers and sink. The tech also this burner was over kill for my size home 1300 Sqft.. Thanks and hope I didn't bore anyone

MaxMercy · January 22

You have to drain to replace the fill valve but you can also add a ball valve before it while you're at it. If you shut off the ball valve and it keeps building pressure... >>>

Has the DHW coil ever been replaced?

MikeAmann · January 23

The diaphragm inside your new expansion tank could be stuck up against the nipple, in which case it would be like there was no expansion tank there at all. And it's pressure must be set while the tank is disconnected.

EBEBRATT-Ed · January 23

If you have a tankless coil it could be leaking water into the boiler water. it's either that or the PRV water feeder or the expansion tank. Those are the only 3 things that would affect the pressure,

If you can shut off the water to the tankless coil and see if the boiler runs ok and the pressure hold you will know if it is the coil

RickeyB · January 23

Hello, thanks for help...No the coil has not been replaced.. what i don't understand is . In 2020 all parts were replaced with a local HVAC tech. temp gauge,expansion tank,relief valve,fill valve,backflow valve and it still had 29 Psi. tech said aquastat is unreliable and should be replaced with a digital one . would a bad aquastat cause over pressure ? Maybe time for a new furnace or boiler.. maybe in spring put in a new coil.but the cost being so high i would like to get a few more years out of this one.

Jamie Hall · January 23

EBEBRATT-Ed said:
If you have a tankless coil it could be leaking water into the boiler water. it's either that or the PRV water feeder or the expansion tank. Those are the only 3 things that would affect the pressure,

If you can shut off the water to the tankless coil and see if the boiler runs ok and the pressure hold you will know if it is the coil

Please read, There are only three things which can cause the pressure to rise. Either you are getting more water in than the expansion tank can cope with (the coil or the PRV) or the expansion tank isn't working.

NOTHING ELSE. Not the aquastat. Not something in the boiler.

It's easy to test, too. Shut off the water supply to the tankless coil (yes, no hot water for a bit) and drain enough water from the system to get to 15 psi. Watch the pressure with the boiler off. If it goes up, it's not the tankless coil. If it doesn't go up, it might be -- so turn the water to the tankless coil back on. Does it go up now? It's the coil. Otherwise, coil is good. Now turn off the feed from the domestic water to the boiler and watch the pressure. Stable? It's the PRV, but to double check, turn the feed back on. Does it go up? If you've cleared the tankless coil and the PRV, your next check is the expansion tank. To do that, you will have to disconnect and drain the tank, then check its air pressure. Should be at whatever you run cold -- probably around 15. If not, try adjusting the pressure (just the same as a tire). Does it hold pressure? If not, it's done.

pedmec · January 23

if the boiler water is allowed to cool down does the pressure in the system go down? if it does you have either a defective expansion tank, it could be undersized, or never pressurized to match the system fill pressure.

the other option i'm leaning on is a leaking tankless coil. this would cause the relief valve to discharge continuously.

ethicalpaul · January 23

But @Jamie Hall he said in his first post the temp was 215

Couldn't a bad aquastat be causing his boiler to…boil?

fueloilrich631 · January 23

RickeyB said:
Hello, thanks for help...No the coil has not been replaced.. what i don't understand is . In 2020 all parts were replaced with a local HVAC tech. temp gauge,expansion tank,relief valve,fill valve,backflow valve and it still had 29 Psi. tech said aquastat is unreliable and should be replaced with a digital one . would a bad aquastat cause over pressure ? Maybe time for a new furnace or boiler.. maybe in spring put in a new coil.but the cost being so high i would like to get a few more years out of this one.

That was three years ago, parts can fail.... Do you have a coil or an indirect water heater? If so, one of those could have a hole in the coil....
While i won't argue with the aquastat suggestion, i wouldn't be so inclined to guess that's what the problem is.

RickeyB · January 23

thanks for support, i will try this afternoon what Jamie has suggested. when I shut off the boiler eventually the water pressure goes to "0". cycling the boiler it starts it"s normal cycly to bring water temp up at around 25/28 then climbs to over 30 .

SuperTech · January 23

Those are classic signs that your expansion tank has failed

EBEBRATT-Ed · January 23

I agree with @SuperTech

Wide swings in pressure when the water is heated or cooled point to one thing and that is the expansion tank.

be happy. They are fairly cheap and easy to replace.

RickeyB · January 23

all my hoses are frozen as I live in NH and we are starting to get above 32 degrees. I will buy one at Homedepot tomorrow and continue with testing. The local tech changed all the parts (2020) including the tank and it was still hovering around 30 psi, he ran the boiler a couple of times and said it was fixed. I pushed on the valve under the tank and air came out, no water. Heres a question..should the pressure maintain if the system is shut down for a a day or 2 ? what should the real pressure be 15 to 20 psi ? right now it is cycling when low limit is reached and as in the picture from this morning the pressure goes up to 32/34 and relief valve does not open. it did the other day at around 38 psi and i lowered the high limit a little. not really using it to heat the house , in the morning its around 58 degrees and i fire up the wood stove.

RickeyB · January 24

ok, per Jamie's instructions
1. turned burner off

shut off water supply to coil
3. drain enougfh water to lower psi to 15
4. psi went basck up to 26 then slowly to 28 psi, drained about 7 gallons of water to get to 15psi
5. DO I HAVE TO MANUALLY ENGAGE THE FILL VALVE OR WILL IT AUTOMATICALLY FILL BACK WHAT I REMOVED ???
6. is the PRV the fill valve ? yes it is still dripping. how much water do i have to drain in order to replace the fill and backflow valve ? should there be water in the expansion tank, I push up on valve and some air came out .. no water.

RickeyB · January 24

I think the mechanical relay in the Aquastat may have stuck when it went up to 220 psi. has no down it again

RickeyB · January 24

one more question when the system is operating , should i be able to add water from the fill valve? I lifted the arm on it yesterday and i could hear water entering.

Jamie Hall · January 24

OK. We have two valves here which both use the abbreviation "PRV". The pressure relief valve, which opens to let excess water pressure out -- usually onto the basement floor, or at least that's where it is supposed to go. And then the pressure reducing valve, which connects between the domestic water supply and the boiler, and should operate to maintain a constant minimum pressure in the boiler -- usually around 15 psi.
.
If you closed the feed valve to the hot water coil and drained enough water to get down to 15 psi -- and then the pressure started going back up again, that pressure reducing valve is leaking. It is that valve to which I think you are referring when you say "fill valve". It is not repairable -- it may need to be replaced.

On the expansion tank. Getting air out is good; at least the bladder hasn't failed. The trick is to have the right amount of air in there, and the only way to do that is to isolate the tank from the system and drain all the water out, then adjust the air pressure to the desired minimum boiler pressure (a bicycle pump will do, but will take time). Then hook it back up.

RickeyB · January 24

Thanks for the explanation on PRV. since i see the psi rise to lets say 28psi, do i keep draing water until there is no more coming out in order to change the Pressure reducing valve ? after i replace the valve will it automatically fill the boiler to the correct amount ? I don't have to raise the lever on top of the PRV .

psb75 · January 24

The PRV valve (reducing) may not be working right. It may have failed at being able to maintain the set pressure at a constant 12 to 15 psi. You may need a new one. Or this one needs cleaning inside. Extra pressure--in the form of additional water--may be leaking through the vallve. When you drain out excess water/pressure, the failed valve seems to be letting the same extra pressure back into the system. You are supposed to be able to empty the system down to "correct" pressure and that pressure should stay almost constant. It may rise a bit upon heating up but it should not get above 20.

EdTheHeaterMan · January 24

ethicalpaul said:
But @Jamie Hall he said in his first post the temp was 215

Couldn't a bad aquastat be causing his boiler to…boil?

not likely... Water at 15 PSI will not boil until the temperature is about 250°F. I believe the "Replace Aquastat" advise was not from an experienced technician, but a parts cannon operator.

EdTheHeaterMan · January 24

I wonder if this illustration might help.

The gray area indicates the city water pressure that is inside the water pipes. Both the hot and the cold water pipes should have 40 PSI or more water pressure inside them. Where the green line separates the city water pressure from the lower boiler water pressure all the light green area indicates that the water pressure inside the boiler and the heating pipes should be between 12 PSI and 18 PSI under normal operation.

If that makes sense then we can move on to the 3 reasons that the boiler pressure might be higher that 18 PSI during operation.

At the auto feed valve PRV (Reducing) the pressure changes from city water pressure to boiler cold pressure. to test to see if that valve is allowing higher water pressure than yopu desire, close off the manual feed valve and remove water from the boiler to get the pressure to drop to 15 PSI

With that valve manual valve closed the water pressure should not go up at all. Do this test for 30 minutes or until the pressure rises above 25 PSI which ever comes first.

If the pressure rises then you have a bad DHW coil. If the pressure does not rise then turn the manual valve open. If the water pressure increases the then Auto Feed PRV is passing. and it should be adjusted lower, or replaced if adjusting will not stop the flow.

I think this is now as clear as MUD

mattmia2 · January 24

It is also possible that the manual valve before the PRV or the tankless coil is not holding in which case the test results will not be correct. You can test if the valve for the tankless coil is holding by keeping a hot water faucet open while you test. If you get water continuously coming out then either the valve isn't holding or boiler water is leaking in to the coil. You could have water from the pipes in the domestic hot water system dribbling and trickling out for quite a while so the pressure gauge on the boiler will tell you more about what is happening than water coming out of the hot water faucet.

EdTheHeaterMan · January 24

OOPSSssss!

I forgot the third reason, The expansion tank:
Here is what I told someone in a private message about why you need an expansion tank:

As far as the expansion tank is concerned. Not as simple to explain…
In short… when water is cold it takes up less space
when that same water gets hot, it expands and takes up more space
Since this is a closed system, when the water expands it needs a place to go. Otherwise it will get bigger than the container it is in (the boiler and radiators and the connecting pipes is the container). When it gets bigger, Hydraulic pressure pushes on the inside of the container. Eventually the container can not resist the pressure so there is an explosion of water pressure and the metal container ruptures with lots of force. sometimes deadly force.

FACT: 100 gallons of water at 70°F will become 104 gallons of water at 211°F. We need to have a place for that 4 extra gallons

Since we know this about water, we need to provide a place for that expanded water to go. Since water will not compress we use a tank full of air or a tank with enough air space in it for that extra 4 gallons because air will compress. For example if you have a 20 gallon tank with nothing in it except 20 gallons of air. When you add water but don’t let the air out, the air will take up less space but it will have a higher pressure. For this to happen, the water might have to fill up the tank with maybe 11 gallons of water in order to compress that air to 12 PSI.

When the boiler water gets hotter and the water expands, there is maybe 9 gallons of air space left in the tank to compress. When the 4 gallons goes into that tank it will compress that air even more and the pressure may rise to 15 PSI or 18 PSI and there will only be about 5 gallons of empty tank left with compressed air at the top of the tank. After the thermostat is satisfied, the burner stops heating the water. All the radiators and the boiler water will cool off and eventually that 4 gallons of extra water will shrink back to only 100 gallons again. The compressed air in the tank will push the 4 gallons of water out of the tank and back into the system and the tank will be filled to 11 gallons again.

The number of gallons and the actual pressure in your system may vary, the numbers were chosen for illustration purposes only.

For more details, I would need to know what brand and model boiler you have and how many thermostats (zones) you have and how many circulator pumps you have and if you have any zone valves. What kind of radiators do you have? Old cast iron radiators or baseboard radiators, or something else? Do you have an expansion tank or a compression tank? The difference being that the expansion tank is smaller because it comes with air pressure already in the dry side of the tank with a membrane that separates the water from the air. A compression tank is larger because there is no membrane to separate the air and water so, as the water fills the system up to the top floor, that water is also going into the tank compressing the air as the tank gets to be 1/2 to 2/3 of the way full while the rest of the tank has compressed air at the top.

Sometimes a picture of the radiators, the boiler and the pipes that connect the boiler to the radiators. That will make explaining YOUR system to you much easier, because I won’t need to tell you about stuff you don’t have.

Now if your expansion tank does not have the proper charge of air pressure in it before it is connected, then your tank may not accept the expanding water as the system heats up.

I do not believe this is your problem based on your explanation of what is happening. The first two reasons in my previous post are more likely. There is one thing that you said earlier that concerns me. that test you do to make sure that the expansion tank os good is actually making the expansion tank "not so good". This is the wrong way to test a tank.

I pushed on the valve under the tank and air came out, no water.

All that does is let out the factory charged air and gives you no useful information.

The proper Expansion tank test is to disconnect the tank form the boiler water pressure and use a tire pressure gauge to see what the air pressure is in the tank when there is no other pressure on the other side of the tank. That is the only correct way to test a pre charged tank. To make a comparison, How many times do you check the air pressure on your car tire by letting a little air out of the tire valve? ... Same thing. You know you have some air but that is all you know. You have no useful information!

Alan (California Radiant) Forbes · January 24

Also, check the pipe and fittings between where your expansion tank connects and your system piping. It could have some rust or debris which might prevent proper operation of the expansion tank.

RickeyB · January 24

ok, my head is spinning. replacing backflow and PVR ( if i can get the fittingf off ) looks like a 1/2" or metric allen is needed. also replacing expansion tank. first i have to remnove the fitting . I really suck at this comment post as i tried to remove a picture and couldn't figure out how to and now I'm haveing a problem adding one. From this afternoon I thought we had said the coil is good .

RickeyB · January 24

finally i left a picture of the connector to PRV valve i need top remove

RickeyB · January 24

Ok so which is true. shut off HWC water and drain tank to 15 psi and see if the psi raises or With that valve manual valve closed the water pressure should not go up at all. Do this test for 30 minutes or until the pressure rises above 25 PSI which ever comes first. I did the first and it went up to 28 psi, and as i read the ifo means the HWC is good , is this true?

RickeyB · January 24

Pretty sure i understand the workings involving pressure in the system. still didn't like the local tech that said it was fixed and the pressure was around 30psi, his comment was to replace Aqustat with a digital as they are more accurate. thanks to all and still working the problem. will let you know my results , but first need the large allen key

mattmia2 · January 24

RickeyB said:
Ok so which is true. shut off HWC water and drain tank to 15 psi and see if the psi raises or With that valve manual valve closed the water pressure should not go up at all. Do this test for 30 minutes or until the pressure rises above 25 PSI which ever comes first. I did the first and it went up to 28 psi, and as i read the ifo means the HWC is good , is this true?

This is true if the valve from the cold water supply to the tankless coil is holding. Open a faucet to make sure the valve isn't leaking and re-pressurizing the domestic water side of the tankless coil. If you repeat and the pressure in the boiler still goes up with the hot water faucet open then the PRV isn't holding.

(This assumes by "drain the tank" you mean the boiler and that the boiler is turned off, it is not firing during this test.)

That fitting that has the internal hex is part of the valve, you remove the other half of that union from the system plumbing and the new valve should have a new union with it that you connect to the system plumbing.

realliveplumber · January 24

RickeyB said:
Pretty sure i understand the workings involving pressure in the system. still didn't like the local tech that said it was fixed and the pressure was around 30psi, his comment was to replace Aqustat with a digital as they are more accurate. thanks to all and still working the problem. will let you know my results , but first need the large allen key

No, you don't. That nipple and captive nut comes with a new reducing valve.

RickeyB · January 25

the fitting in the picture is threaded into the valve. went to homedepot where i boughjt it and they don't sell that part and a new valve has a solder on connection. looking for correct allen key. As for the test I have already removed all water and the backflow and PRV. Yes I drained the boiler and also washed the floor ( hose fell out of bucket , thought no more water was in tank ). my terminology is not always correct.

delcrossv · January 25

Try supplyhouse.com Is that a Taco valve? If so put taco pressure reducing valve in the search bar and pick the model that matches yours. They do come with one union.

EdTheHeaterMan · January 25

RickeyB said:
Ok so which is true. shut off HWC water and drain tank to 15 psi and see if the psi raises or With that valve manual valve closed the water pressure should not go up at all. Do this test for 30 minutes or until the pressure rises above 25 PSI which ever comes first. I did the first and it went up to 28 psi, and as i read the ifo means the HWC is good , is this true?

If you got the water pressure in the boiler (on the gauge) to 15 PSI and the pressure went to 28 PSI, that means that you have NOT ruled anything out yet. You still have more pressure entering the boiler. That is the problem you want to stop. When you find the sequence of turning off valves that allows the boiler pressure to stay at 15 PSI then you can start to turn valves back on to see what makes the boiler pressure go back up.

What if you happen to have all three problems.
Bad expansion tank
Leaking DHW tankless coil
Water feed valve passing.

To find out what problem(s) you have, you first must gat to a situation where you have 15 PSI of water pressure in the boiler and the pressure does not change more than 1 PSI in 30 minutes. Get to that place then we can do more tests.

This is getting Tedious. I am going to PM you.

RickeyB · January 25

The parts are “Watts” and can’t do a thing until i find a tool to remove the connector. I can order from Amazon a tool but it won’t be here until Monday and i need it fixed now or back to the way it was. I may have to make one .

SuperTech · January 25

That connector doesn't get removed. You brought the wrong part. They make a version of that valve with a union that has solder connections and another one with threaded connections.

dko · January 25

He might have purchased only the feed valve and not the combination backflow PRV.
Might be wanting to reuse the backflow preventer.

https://www.supplyhouse.com/Watts-0386423-B1156F-1-2-Bronze-High-Capacity-Feed-Water-Pressure-Regulators-12825000-p
https://www.supplyhouse.com/Watts-0386462-B911S-1-2-Bronze-Combination-Fill-Valve-Backflow-Preventer-Sweat-x-NPT

Makes sense if there is nothing wrong with backflow preventer.

Or he could have bought something else entirely. That was just my interpretation of his writing + guess.

EdTheHeaterMan · January 26

You are not going to believe what was wrong with this system.....

@RickeyB will have an update soon I hope!

RickeyB · January 27

did all the testing and found out the temp gauge was inaccurate and stayed at 10psi. replaced it and readjusted the PRV and pressure now stays around 20psi.
thank you to all who contributed to help fix my dilemma. I guess the local tech was either interested in selling parts ( He was getting a kick back or all on the cost of parts as he double what i could have bought them for ) or wht I don"t know.
what a great site with so many knowlegable helpful tech's you all get an A+ in my book
Rickey

RickeyB · January 27

so

sorry the wrong phot got loaded and don't know how to remove. this photo shows 10psi on temp gauge when deinstalled

EBEBRATT-Ed · January 27

That's why shooting the parts cannon is expensive$$$$

Although its not impossible to have multiple parts fail all at the same time it usually does not happen that way. Look for the simple things first.

replaced all parts still has over 30psi burnham V8 boiler

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