Boiler blow off / High pressure


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Old 03-09-17, 06:40 AM
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Boiler blow off / High pressure

I recently noticed that my boiler was letting out hot water via the high pressure safety valve. So i have replaced said valve and the old one did seem to be full of stuff which i thought was why it was leaking. My entire boiler was replaced about 7-8 years ago so its not exactly old. Its a 3 zone oil fired hot water system 1 circulator pump 3 zone valves.
I still have issues with high pressure in the boiler and it occasionally opening to release pressure. From what i understand if this is operating properly i should not see more than 30 psi on the guage being the water inlet pressure should only be 15 or so and a bit of pressure because of expanding water from being heated.
My water expansion tank on the side of the boiler seems to generally be about half full, this is just a guesstimate from me tapping on it but i assume that is about right. So what else should i check out in hunting down this issue?
 
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Old 03-09-17, 07:33 AM
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Tdiguy-

I’m no expert, just the warm-up act till the experts come along. But I’m pretty sure any kind of tap or sound test for the expansion tank is not considered valid by the pros here and is frowned upon. I think it’s fairly common for the diaphragm tanks to lose pressure over time and cause pressure problems in the system.

I’ve seen the experts time after time refer people to the sticky “Service your bladder type expansion tank” in the list of stickys for this forum.
 
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Old 03-09-17, 07:35 AM
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Tapping on the tank isn't a good way to find out if your expansion tank is waterlogged. There is a sticky at the top of this forum that provides info on the required depressurization of the water side of the tank to check the pressure.

There are a couple of other things that could cause your problem, but check the expansion tank first.
 
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Old 03-09-17, 08:23 AM
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Thank you guys. I will have to take a look at that. I am not looking forward to trying to service the expansion tank. While i was replacing the pressure valve i tried to take the tank off. Dam thing is on there wicked tight. I have an adjustable wrench i was using but i couldn't get it to budge. i think i need to find me a cheater bar and maybe have a backup tank in case i break it trying to remove it.
 
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Old 03-09-17, 08:56 AM
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I would like to offer my thoughts on tank tapping if I could. I know from past posts that some people frown on tapping the tank and see it as a waste of time but not to stir the pot I respectfully disagree.

The expansion tank comes precharged with air which adds resistance so the heating water which expands will not completely fill the tank causing excessive pressure to build in the boiler and the relief valve to expel water at 30 psi. This a fairly common knowledge.

When investigating a pressure problem the first thing I do is tap the tank. This to me is a good and painless starting point but in all fairness to those who think it's meaningless, only a starting point.

First, we know that the tank because of the air charged bladder only fills the top portion with water.

What the tap test tells me is that if the top is solid and the bottom is hollow you still have air in the bladder. It may not be a full charge but still, a charge so the tank may just have to charged but is possibly still useable.

If the tank is solid both top and bottom then you immediately know what the problem is. Although it could be just deflated chances are the tank has to be replaced.

This is just a first step in diagnosing the problem. It takes no time and labor to do this and in my opinion anything that saves time, money and work is not a waste of time.

One other quick method to try is remove the cap from the shredder valve at the bottom of the tank and push the valve stem slightly. Being that is a one piece sealed rubber bladder if any water comes out, your bladder has a leak and must be replaced.

These are quick and painless tests that can be done without isolating or removing the tank and how much time is being wasted with what they get just for labor charges today.

On a side note I know the thoughts of others on here and we have all had different experiences but I can say that my personal experience with my own original tank which has been in since 1984 has never been serviced or even checked because I've never had the need to and everything is working perfectly but on the other side of the coin I've installed tanks that haven't even made the warranty period. You just never know.

These are just my thoughts and may not apply to everyone.
 
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Old 03-13-17, 07:27 AM
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Well i am still having a small issue. The situation has gotten a lot better than when i first started with this. After adjusting the temp settings and the pressure inside the expansion tank it blows off much less hot water than what it was, its now just a bit of a drip after the boiler runs for a while. I will be home wednesday and will shut down the boiler and re-check pressures but i tend to think there might be another issue.
 
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Old 04-23-17, 06:03 AM
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OK I am still experiencing this issue.
One other observation on this, it seems like air is somehow getting into the system or maybe my burner flame is too aggressive? and creating steam? I say that because i expect if there was a way for air to get into the system anywhere that i would have a water leak since all the pipes are under pressure.
 
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Old 04-23-17, 06:11 AM
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Something else to note, The pressure buildup seems to only happen after the burner has been running / heating up the boiler.
The fill valve seems to operate properly i can hear it filling with water when i open a purge valve and it sounds like it closes after a few seconds with the purge valve closed.
 
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Old 04-23-17, 06:46 AM
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Excessive pressure is either

1. Your expansion tank needs servicing. ( Need 12-15 psi of air in it) This air needs to be added and tested off the boiler or with 0 psi on the boiler to be accurate

2. the fill valve is faulty. Fill the boiler to 12-15 psi cold and then turn off water feed valve. This will stop the boiler from being slowly over filled if fill valve is faulty.

3. Leak in tankless coil. If you heat your domestic water with a coil it may have a leak. Domestic side pressure may be raising the boiler pressure. Pressure can rise only when the boiler gets hot due to thermal expansion. Meaning the crack in the coil opens up when hot..
 
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Old 04-23-17, 02:03 PM
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T,
You mentioned that your pressure problem only arises when your boiler is heated which is telling me the water, when heated, expands, has no place to go creating a pressure problem which causes your relief valve to leak.

If you had a coil leak or feed valve leak the fresh water would feed into your boiler continuously causing high pressure whether the boiler was hot or cold.

If your boiler maintains proper pressure when cold, to me, that would eliminate the coil and feed valve but if you want to double check those components you can just close off the manual valves to isolate the boiler from any potential fresh water entering the system.

After doing this if you still have the problem I would either service or replace your expansion tank as this would be the last cause of your problem.

As far as your boiler making steam, your boiler temp would have to be up around 240 deg. at 12 psi to make steam. The higher the pressure the higher the temp needs to be to make steam and unless your aquastat is faulty and not shutting off the boiler your control most likely can not even be set that high, even by accident.

As far air getting into the system, this can be done by bad air vents or bad pump gaskets sucking air in when the pump comes on. They can be bad enough to let air in but not bad enough to leak water.

This is just the way I would go about servicing your problem but we all work differently and as you know by now anything can happen, so as long the problem gets solved who's to say what is the right or wrong way to go about finding your solution.

Hope this helps a little.
 
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Old 04-26-17, 08:20 AM
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Thank you guys very much for the advice on this.
So it seems my next steps testing wise will be simply to empty the bucket ( so i can tell if its still happening ) and shut off the boiler fill valve and see if this keeps happening. I should also look around for a guage that is easy to read at low levels, probably a digital guage thats accurate down to 2psi if i can find one for cheap. The analog guages i have seen are wicked hard to read the differance between 10 psi and 20 psi.
 
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Old 04-26-17, 10:28 AM
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Let us know the outcome .
 
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Old 04-27-17, 07:39 AM
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Once again thank you everyone for the advice. I think i finally have this figured out. The fill valve seems to have gone south. I don't have the money to replace it right now ( 80$ seems to be the average price for a replacement! yeash is this made out of brass or gold?! ) but after having the water to the fill valve off for a day or so there was no added water in the bucket. So i took the fill valve apart and there was tons of corrosion / buildup inside it. The plunger in the middle was not moving freely like i expect is normal when there is no pressure on it. So i did the best i could with a wire brush and a cloth to remove grime and buildup. the punger moves much easier now but i think i screwed something up because after re-assembly the metal tab that i think manually opens the valve doesnt seem to do anything. I will check on it again tonight and see how its doing pressure wise.

Man its a good thing boilers have multiple systems for pressure regulation. I imagine without that blow off valve this could have caused some expensive repairs.
 
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Old 04-27-17, 08:37 AM
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Also change out the relief valve when you tune up the boiler. Change fill valve, check exp tank, and replace the pressure temp gauge on the boiler..

Its good practice...
 
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Old 04-27-17, 10:38 AM
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T,
If you go to SupplyHouse.com - Plumbing, Heating & HVAC Supplies and enter Watts feed water pressure regulator into the search bar you will see different options for feed valves to accommodate what you have.

I don't know what you were pricing but this is all you need. My guess is you were pricing whole house mainline pressure reducing valves.

The upside is, you can shut off your feed valve and still run your system until you get it fixed.

Hope this helps a little.
 
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Old 05-05-17, 04:38 PM
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Excellent - Seems to be fixed.

Well this issue really seems to be fixed for me at least for now. After cleaning out the auto fill valve i have had the water supply turned on to the boiler to see if this issue was coming up still. Well it has been a few days now and not only is the boiler not blowing off water it seems to be maintaining pressure to the point where without taking measurements i dont know that it has changed.
So for now i will leave it be but i am going to try putting some money aside to get this valve and maybe a couple other things to make servicing this easier in the future, the plumber that put this all in did a good job and all but it is not what i would call service friendly.
 
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Old 05-05-17, 05:43 PM
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Thanks for the update.
 
 

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