Boiler Pressure High, Please Help!

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Old 02-12-17, 08:22 AM
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Boiler Pressure High, Please Help!

Weil-McLain WGO-4 Oil Boiler.

I've been having issues with my boiler pressure, relief has popped twice and I don't know what else to do. Changed the expansion tank (for no reason lol but now I have a backup ). Here is some information that may help.

Cold Fill Pressure - 12 psi.
Expansion Tank Pressure (With cold boiler) - 12 psi.
High Limit Pressure - 28+ psi.

All of these pressures have been double checked with the boiler pressure gauges and digital pressure gauges.

Boiler is 3 zones, two heating and one for the indirect. Heat is done off zone valves with one main circulator on the return and the indirect uses a flo-chek with a circulator on the return.

The expansion tank is a watts #30 (Which online calculators say is adequate for the boiler) which comes off an air scoop which has a hy-vent off the top on the supply side.

I also have the water feed shut off to the boiler, to stop any water from being sucked in from the circulators..

Please point me in the right direction, this is driving me mad.
 
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Old 02-12-17, 08:34 AM
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The expansion tank needs to be set with 0 psi in the system.
If the system has 12psi in it..... then the tank will show that.
 
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Old 02-12-17, 09:26 AM
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When I bought the tank I checked the pressure before installing it and it was at 12 psi. This was not more than a month ago. I do not think that is the issue?
 
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Old 02-12-17, 09:38 AM
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What temperature is your high limit operating at ?

And do you have any air cavities in your system, especially with the water feed shut off, these bubbles may now be filled with steam; which is periodically breaching the 30 PSI limit on the Pressure Relief Valve as it passes by.

I believe I experienced the same symptoms until I thoroughly purged the system of air during the time periods when the thermostat was satisfied, and air could accumulate for bleeding at the vent.

And I kept the Automatic Feed Valve open thereafter.
 
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Old 02-12-17, 09:41 AM
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180 degree high limit.

This has been an ongoing issue for months. The boiler should not be running anywhere near that threshold to begin with.. I know to expect slight expansion, but this is crazy. it's increasing 12-15 psi at high limit...

The zones and boiler were properly purged, if I two months from now and let the boiler get cold, the pressure will more than likely still be at 12 psi.
 
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Old 02-12-17, 10:54 AM
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O,
With your description it sounds like everything is normal except when the water gets heated it sounds as if there's no place or not enough space for the water to expand.

I know you mentioned the tank was large enough for the system but what do you have for equipment and do you have any cast iron radiation.
 
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Old 02-12-17, 03:02 PM
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Your boiler is rated at 126,000 Btu output. I think your #30 tank is very borderline, particularly if you have any cast iron heat emitters and depending upon the system volume. I think it should have been a #60.
 
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Old 02-12-17, 03:45 PM
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No cast iron, just baseboard radiators throughout the house
 
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Old 02-12-17, 03:50 PM
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No cast iron, all 3/4 baseboard radiators... I know the boiler is way way oversized. 1100 sq ft house. But most online calculators will go up to 175,000 before calling for a #60.

Is it possible that I'm not moving enough water and that is causing the increase in pressure?
 
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Old 02-12-17, 03:56 PM
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Can you heat your house with, say, 165 deg water? Try that. If it solves the immediate problem, you will also benefit with higher efficiency.
 
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Old 02-12-17, 04:00 PM
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I know the boiler is way way oversized. 1100 sq ft house.
OMG. For 126,000 Btu output? That's your problem. Dial down the boiler temp.
 
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Old 02-12-17, 04:01 PM
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I have a bucket under the relief, it has only blown off twice and now with the water feed shut off it hasn't blown off in a while, it just runs at 28 psi... I have no idea whether or not that truly matters but I know the pressure should be nowhere near there and I would really like to figure it out.
 
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Old 02-12-17, 04:04 PM
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Yup. can you explain why lowering the boiler temperature will help me? Won't that just lead to a slower heat rise in the home?
 
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Old 02-12-17, 04:06 PM
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with the water feed shut off it hasn't blown off in a while, it just runs at 28 psi
Totally too high!...................
 
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Old 02-12-17, 04:10 PM
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Regardless of what any "on-line calculator" may state your expansion tank simply is not large enough. You can either add another #30 tank in parallel with the existing or you can replace it with the #60 tank.
 
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Old 02-12-17, 04:10 PM
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What should I lower my high limit to? Can you explain why the boiler size is affecting the pressure?

Thank you

What effect does running at high pressure have on the system?
 
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Old 02-12-17, 04:10 PM
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Try it and get back to us.
 
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Old 02-12-17, 04:21 PM
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Boiler pressure seems to start rising once the boiler gets above 120 degrees.
 
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Old 02-12-17, 04:34 PM
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O,
With all due respect to the other posts your boiler size should have nothing to do with your high pressure. It will just reach limit faster and shut down. You may get short cycling but not excessive pressure.

If you're not getting high pressure since you shut your feed valve off bring your boiler pressure down to 20 psi and if all is well you shouldn't vary more than a couple of pounds. If all goes well turn on your feed valve on again and watch it. If pressure starts to rise shut it down and change it.

As far as lowering your boiler temp if you can do it and have enough radiation to comfortably heat your house that's fine but just because your boiler may be oversized it doesn't mean you have enough baseboard to run lower temps. All that will happen with lower temps is a longer time to heat the house. The boiler will still be oversized and will still be short cycling and your current temp is know where near high enough to cause you any kind of pressure problems at 180 or 190.

As far as water not moving fast enough it would just make the boiler shut off that much faster. You must remember that before we had pumps, systems were gravity and nothing moves slower than gravity except maybe cold molasses.

Hope this helps a little.
 
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Old 02-12-17, 04:35 PM
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Can you explain why the boiler size is affecting the pressure?
It is not so much the size of the boiler as it is the total water volume of the system. Water is, for all practical purposes, non-compressible. When it is heated it expands and THAT causes the pressure to rise. The total change of temperature from ambient to maximum operating temperature AND the volume of the expansion space versus the total volume of water work hand-in-hand to control the pressure rise. You need more expansion space.
 
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Old 02-12-17, 05:23 PM
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Is there any negative consequences to it running at higher pressure besides the possibility of the relief blowing off?
 
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Old 02-12-17, 05:45 PM
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Look on your boiler plate and see what your max pressure rating is. Most are 50 psi so you would be well within limits but if your is 30 psi you will put undo pressure on the boiler sections. Why would you want to run higher pressure than you have to.

For every 1 psi of pressure you get 2.31 ft of lift, so if your highest point of radiation is on a 2nd floor and every floor is figured at 10 ft. 15 psi will give you over 30 ft. I personally run 20 psi on my jobs which Taco recommends for there wet rotor pumps to alleviate possible cavitation. The amount of pressure that your running is needless and not helping the situation.
 
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Old 02-12-17, 06:17 PM
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I understand, I just hate to have to buy another expansion tank to get the pressure down. I may try to twin the two 30's together and see if that gets the pressure down before I invest in a new #60. I guess the problem I have is that the boiler is too big and the amount of radiators I do have along with the #30 expansion tank is not enough to offset the pressure that is built up by expansion. Makes sense I guess.
 
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Old 02-27-17, 12:54 PM
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High Pressure

I'm assuming this setup has been working fine for some time (years?) and just started causing issues? A number of suggestions below would apply to a new setup with excessive BTU output but i don't think would apply here (sorry, no offense everyone)

You mentioned a 12PSI expansion tank (about $40). Do you have a 40lb hot water tank (about $100) in line with the hot water system?

- If yes, drain the pressure from the line and test the pressure on that tank. It should be around 40 PSI.
- If that's normal, check or have the High Pressure valve to the boiler checked, on the supply side from the water main
- If that checks out, shut off the supply and return to the indirect hot water tank over night, see if the pressure stops rising. if that solves it, it's likely you have a pinhole leak in the hot water tank coil and need to have that replaced.
 
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Old 02-27-17, 01:30 PM
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GB,
If you go to his first post you will see he is having trouble with his boiler pressure and his boiler expansion tank and not his domestic water or an extrol on his potable water.

The tank and pressure you are talking about is for domestic cold water pressure and your pressures would be right if that was the case but this being a boiler pressure issue the tank is factory precharged at 12 and not 40 and his relief valve does discharge at 30 psi and is not a temp & pressure relief valve as on a hot water tank.

No offense taken.
 
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Old 02-27-17, 01:59 PM
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Spott,

I did see that he replaced the 12PSI tank but i'm speaking from experience, having had the same issues 3 months ago. Having a leak in the hot water tank has exactly same symptoms as OP described - increased pressure in the boiler, popping the high pressure valve. Replacing the 12 PSI tank didn't help and after multiple checks, the hot water heater tank was the issue. I did see he has 3 zones, one of them being an indirect hot water heater.
 
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Old 02-27-17, 02:38 PM
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GB,
I understand what you are saying and that certainly could be a cause of this problem except for the fact that that the pressure only rises when the boiler temp goes up most likely making it an expansion problem.

If it was a coil leaking into the boiler it would constantly be releasing pressure from the relief valve as the water continued to enter the boiler with nothing to shut it off. The same as putting the feed valve on manual.

In this case, unlike yours it is not feeding constantly from a leak or defective feed valve but the pressure only rises when the water is heated.
 
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Old 02-28-17, 01:03 PM
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Hi,I have a wm wtgo4 w/126 btu like yours.I have about a dozen castiron radiators and extrol30 exp tank,which handles the pressure ok.my hi is 180.when it's really cranking ,pressure gets to 20 maybe 21heat soak gets to 190.
 
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Old 02-28-17, 02:43 PM
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K,
What is your cold pressure, out of curiosity. Next, you are extremely lucky being able to get away with a #30 extrol. Even the manufacturers do not recommend anything under a #60 with any cast iron emitters in the system. This comes from their tank sizing tables.
 
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Old 02-28-17, 05:14 PM
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I think the larger expansion tanks are recommended for use with cast-iron radiators is because of their added volume (compared to fin-tube units). Otherwise, most expansion tank manufactures' sizing tables just go by the Btu rating of the boiler (which is a gross simplicity).

I think a pressure increase from cold to hot to 21 psi is borderline. Gives reduced margin as a bladder-type expansion tank loses its air charge, which it inevitably will due to diffusion of air through the membrane.
 
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Old 03-01-17, 12:26 PM
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Spot,It stays 140 and press about 14.{not precise}when it runs for heat,I get concerned it'll blow,when its near 0.Press.holds at 20 maybe 21.Tank is goin on3yrs.Before replacement,I had problems.
 
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Old 03-01-17, 12:51 PM
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What do you mean when it's near zero? What will blow.
 
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Old 03-01-17, 01:05 PM
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Spot I wasnt clear w/that,sorry.when the outside temp gets near zero,the boiler runs about every 45mins w/boler temp 180,I get worried the safety relief valve will blow.
 
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Old 03-01-17, 06:24 PM
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K, the relief valve is good to 30 psi. If you are only going to 21 at high limit you're safe. Although a 7 lb swing is a little high you are still within a safe range. That's the difference between a 30 and 60 with a cast iron rad, high water content system.
 
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Old 03-02-17, 07:16 AM
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I get worried the safety relief valve will blow.
I can't add anything to spot's reply (that you aren't close to the relief valve's setpoint). However, your speaking of the relief valve "blowing," makes we wonder if there may be misunderstanding.

A relief valve on a hot-water boiler doesn't "blow" when it reaches its setpoint - it lifts and drains some water out of the boiler to reduce the pressure, and then automatically resets. The water drains into a floor drain (if the valve is properly piped). It's not anything like an explosion - there may be water vapor, but not steam if the boiler temperature is below 212 deg. If the relief valve lifts, the boiler needs attention, but it's not a dramatic event.

Once each heating season, it's recommended that you manually lift the relief valve to make sure it is clear - that will also give you an idea of what happens if the valve lifts due to overpressure. It's also recommended that the relief valve be replaced about every five years or so.
 
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Old 03-09-17, 06:33 PM
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Any updates on this? What was the issue?
 
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Old 03-10-17, 06:27 AM
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I recently had this issue. I am still working on it sort of. I first replaced the pressure relieve valve because it seemed like the obvious answer. Next thing i found was that my boiler was running WAY too hot. Heating up it was set to 180 as a high shut off, however the temp guage on my boiler was reading 220 when it finally shut off. So there was a pretty large difference between what the control was reading for temp and what the water temp was reaching. Not really sure if the boiler was generating steam but it would explain things because pressure was also building inside the boiler and it was purging out air / steam.
Needless to say i am glad that i found that, easily corrected by dropping my high point down to 150 which leads to readings of about 170 in water temp. Not what i consider idea for a fix because i really like having accurate readings but it works well for now.
Next thing i did was following the sticky here about the expansion tank. I did that just yesterday and i am out of free time to check on it so i will check on it again monday but for right now i am pretty sure most of the important issues with the boiler have been corrected.
 
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Old 03-11-17, 07:52 AM
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Last edited by doughess; 03-11-17 at 08:39 AM.
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