New boiler, pressure too high

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Old 09-29-15, 06:54 PM
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New boiler, pressure too high

I had a new Buderus 115 boiler and indirect water heater installed, and 1 week after I did the contractor went under....
Now every time there is a call for heat from the indirect at the end of the firing cycle the pressure creeps to 30 psi and drips from the relief valve. Everything is new, nothing was reused from the old system. I was able to get one of the guys that installed the boiler to come out and he changed the water feed valve, he had thought that would take care of the problem, it did not. The expansion tank is also brand new. It is a cold start boiler and when its cold the pressure sits at 13-15 psi. Not really sure what else to check.
The expansion tank is located after the circulator pump, which is a grundolf 3 speed with a check valve, 3 zones, with zone valves on the returns. Would the pump when not circulating the water not allow the water to pass threw it so the expansion tank could not absorb the pressure from the boiler?
 
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Old 09-29-15, 07:10 PM
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I would call the manufacturer, Buderus, for help. Was it installed by a Buderus authorized installer? Meanwhile, file a legal claim against the contractor - get in line with other creditors.
 
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Old 09-29-15, 07:35 PM
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Not sure if they were an authorized installer or not, it was the system they recommended, at this point I just want to fix it and move on. I would think its just a matter of something not setup right, I may just buy a new expansion tank and try that first before I have to hire someone else to come fix it.
 
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Old 09-29-15, 08:32 PM
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What was the static charge pressure of the expansion tank? What does its pressure read at the Schrader when the boiler's at 30psi?

If the cold pressure is good, the feed water valve is probably working (and it was changed anyway).

The systems I've had all had the expansion tank on the return side. I don't think I've seen one after the circulator.
 
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Old 09-29-15, 09:12 PM
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The expansion was also new, 12 psi when installed, when I was looking at it earlier tonight the boiler and the expansion were both at 28 psi after it finished running when the indirect called for heat.
 
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Old 09-30-15, 11:18 AM
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You can't check the expansion tank pressure on the air side when there is water pressure on the boiler side. You will NOT get a correct reading.

It sounds to me as if either the new tank was not checked before installation for correct pressure and it had lost it's charge somehow, OR , the tank is undersized for the application.

One place that new tanks sometimes lose pressure is at the Schrader air valve. Remove the plastic cap and put some soapy solution over the air valve to check for bubbles. If you see any you may just need to tighten that valve a touch.

Here's how to check the tank pressure the RIGHT way:

Do this first...

http://www.doityourself.com/forum/bo...sion-tank.html


Tell us what type of radiation is in the home (meaning fin-tube baseboards, cast iron radiators, etc). This information along with the SIZE OF THE TANK will help us determine if it is correctly sized.
 
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Old 09-30-15, 11:24 AM
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The expansion tank is located after the circulator pump, which is a grundolf 3 speed with a check valve, 3 zones, with zone valves on the returns. Would the pump when not circulating the water not allow the water to pass threw it so the expansion tank could not absorb the pressure from the boiler?
After re-reading this...

It sounds to me more as if the tank is incorrectly located.

If the pump is effectively isolated from the boiler by the check valve in the pump, and the zone valves on the other end, then that's a problem.

Can you post some pictures of the piping please?
 
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Old 09-30-15, 12:32 PM
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NJT: He said the initial charge pressure was 12 psi. I asked him to check it while the boiler was at 30 psi to see if the tank was being isolated by the check valves or the circulator. Since the boiler and the tank were both at 30psi it would seem the tank is not isolated and that's not causing the problem. I agree this is not proper way to determine the pre-charge, but that wasn't the point. I think your suspicions of too-small tank seem likely.
 
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Old 09-30-15, 04:28 PM
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After looking again today, out of the corner of my eye I saw the pressure gauge next to the reducing valve on the water main where it enters the house, it read just over 70 psi, I ran the water and backed off the adjuster till it was under 60 while running. As soon as I shut the water off it climbed to over 70 again. So I will be having that replaced also, my new guy I have scheduled to come out says that may be the whole problem if the boiler is seeing street pressure, that the auto feed can only handle up to 75psi.
Last year the city installed sewers threw the neighborhood and when digging they hit the main in the road and I had to have a plumber go to the house remove all the screens on the faucets and run the water for about an hour before it stopped spitting rust and scale out before it ran clear. Hes thinking there may be trash in the diaphragm of the main reducing valve. Either way going to have it replaced when he goes.

The expansion was checked when the new auto feed was installed, boiler cold and drained 13psi. That was my first thought was that the tank was isolated but I dont believe so with the pressure rising the same as the boiler.

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Old 09-30-15, 04:57 PM
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70 psi from the street is excessive, I think. You should call the water department. I wonder if your gauge is accurate.

Usually, the city water pressure is determined by the elevation of water storage tanks around town. Roughly, figure 1/2 psi per foot of elevation - so, for example, a 120' tank could only produce about 60 psi when full.
 
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Old 10-01-15, 07:05 AM
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70 psi from the street is excessive
Not really I don't think... at least not here on the EC where most water systems are pumped. It's pretty rare to see a water tower around here... (maybe in CT?)

But no, I doubt that the water pressure to the valve has anything to do with the problem.

The pics are too small to see much of anything.
 
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Old 10-01-15, 04:22 PM
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Yes its all pumped here, no water towers. I replaced the pressure gauge on the main water line today, when water is running 58psi after it shuts off 68-70psi almost instantly. I'm at the point if the whole system has to be taken apart and re-piped that's whats going to happen. After talking with a few local people about the problem I have been told the expansion tank should be before the pump, not after like it is now. This is why I hired someone to install it in the first place, because I knew this was beyond my knowledge, and has turned out to be a nightmare. I was told by one of the local guys that tank could be moved easily just add a tee under the pressure relief valve and install the tank there and plug the old location under the air scoop.
Its a small 1500 foot home, 3 zones, 2 for fin tube base base board and the 3rd for the indirect.
The expansion tank is a #30
 
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Old 10-01-15, 04:34 PM
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Thumbs up

OK, I learned something. In the Midwest, where I live, every little berg has a water tower and the water pressure runs continuously at about 50 psi throughout the town. Otherwise, I suppose pump(s) need to run continuously to keep the system charged. Factories, prisons, and large hospitals often have their own water towers for added fire protection.

Plus, without a water tower, what would a town paint its name, logo, and motto on? And, all the cellular companies pay rent to mount their antennas up on 100'+ water towers - which gives them coverage for many miles out into the surrounding prairie.

At 70 psi, I'd worry about my cheapo plastic garden hoses bursting. But fire hoses could reach higher elevations even without a pumper truck
 
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Old 10-01-15, 04:43 PM
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when water is running 58psi after it shuts off 68-70psi almost instantly
Yeah, that regulator is shot, but it' not the problem with the boiler pressure.

I have been told the expansion tank should be before the pump, not after like it is now.
This is true in general, but it is not likely the reason that your system is going high in pressure. There are OTHER reasons for placing the expansion tank on the suction side of the pump.

The expansion tank is a #30
That should certainly be enough tank for a system that size with fin-tube.


I STILL SAY to re-check the expansion tank charge! There might be a leaky schrader valve and it has lost it's charge.

Were YOU the one that checked the charge on the tank BEFORE IT WAS INSTALLED? Or was it the installers that checked it AFTER the system was pressurized?

CHECK THE TANK AIR CHARGE THE RIGHT WAY!

AFTER you do that, here's another possible scenario...

Where is the feed valve piped into the system in relation to the tank and the pump? Is it on the suction side of the pump by any chance?
 
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Old 10-01-15, 04:45 PM
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I'd really like to see more and bigger pictures.

I can't follow the piping in those to get a mental picture of how the system is piped exactly.

Can you draw and post a diagram perhaps?
 
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Old 10-01-15, 06:34 PM
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Hope this makes sense. Trying to enlarge it.

 
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Old 10-02-15, 07:52 AM
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Perfect...

I think I have an idea of what's happening.

At initial fill of the system, everything is fine. As the pressure in the boiler increases THE FIRST FIRING, everything is fine.

NOW, the call for heat is completed, and the boiler starts to cool, which means that the pressure in the boiler begins to fall.

BUT

Because the tank is 'divorced' from the boiler at this point, the pump check valve and the zone valves prevent flow from the tank back to the boiler, the TANK AND REST OF THE SYSTEM REMAIN AT A HIGHER PRESSURE, and the boiler cools to a lower pressure, less than the 12 PSI setpoint of the fill valve... which responds by feeding more water into the boiler.

Now, there's too much water in the system... and this cycle would repeat until the system eventually hits the limit of the relief valve.


There's also the issue of the water feeding into the boiler which is on the suction side of the pump.

Because when the pump runs, it's 'differential pressure' is SUBTRACTED from the pressure in the boiler (because the pump is pumping TOWARD the tank which is also the point of no pressure change), the feed valve senses this drop in pressure and feeds water into the system. Now when the pump stops and the system cools, there is too much water in the system and the cold pressure will be higher... and may continue to slowly creep up every time the pump runs and drops the pressure in the boiler.


So, you've got TWO things going on...

1. Your tank is somewhat divorced from the system when the boiler is cooling down because of the check valve and the zone valves.

2. Your water feed should not be entering the system on the suction side of the pump. This is tricking the feed valve into feeding more water.

My advice is to reverse the position of the pump and the air scoop / tank, and pipe the water feed into the system between the air scoop and the tank.

Then all will be well in Whoville.

By the way, supercharged Chevelles are awesome!
 

Last edited by NJT; 10-02-15 at 04:48 PM.
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Old 10-02-15, 10:58 AM
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I agree with NJT. Correct the improper piping arrangement and all will be fine. To add, the air separator should ALWAYS be on the suction side of the pump because the lower the pressure (caused by the pump suction) the easier the air comes out of solution (water) to be expelled via the air vent.
 
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Old 10-02-15, 04:54 PM
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Thank you very much for taking the time to help and explain it very clearly for me, I was able to get in touch with the person who installed it and is the one who thought the high water pressure was the cause. I will give him a call and tell him I want it re-piped, as I also found the piping diagram that came with the boiler which shows the piping is incorrect. Thank you again, I will hopefully post back again with the issue resolved.
 
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Old 10-02-15, 05:03 PM
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By the way, supercharged Chevelles are awesome!
I agree, I ended up trading that 67 for a 24 foot fishing boat, which I traded for a custom chopper and then sold that and bought another 67..... Like a giant circle. Did just build a 70 camaro for the wife though.... Hopefully getting a turbo over the winter, well as long as I can get the piping fixed without having to hire someone else
 
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Old 10-04-15, 01:52 PM
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I remember being told that Massachusetts plumbing code (not sure about Maine) for *new* construction required a pressure reducing valve just beyond the water meter (customer side/responsibility) to reduce whatever the city pressure was down to some defined level.

Remember that you aren't going to have the same pressure throughout the town, even if all the houses are at the same elevation (which they aren't in New England) -- the further away you get from either the tower or pumps, the less pressure you will have, even if people upstream of you aren't using any water. Most places that pump also have standpipes in an attempt to balance this out and hence they aren't as high (or as visible) but you really have to have them as a buffer as your usage is never going to be constant.
 
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Old 10-07-15, 05:56 PM
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All the piping issues have been corrected, also replaced the relief valve again as it was just steadily dripping even at 15 psi, and the expansion tank just to safe, I also added a ball valve between the air scoop and expansion tank to make life easier in the future. Now that is running fine I do have one more question. The boiler has a Beckett Aqua smart control, and a Taco 3 zone controller, the Aqua smart has the ability to extend the run time of the circulator pump after the call for heat has been satisfied, to make use of the hot water remaining in the boiler. But as soon the call for heat has been satisfied the Taco zone controller closes the zone valve immediately, its there a way to also delay the closing of the zone valve also?
 
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Old 10-07-15, 06:47 PM
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...its there a way to also delay the closing of the zone valve also?
I can think of a work-around but it is somewhat involved. Maybe NJT knows of a simple way.
 
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Old 11-21-16, 09:06 AM
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Buderus GC 124 high pressure

About 4 years ago, I had a Buderus GC124-32/5 boiler and a Buderus indirect hot water heater installed. The installer also put in one Extrol 30 expansion tank. We have an older home with two stories and large cast iron radiators.. After the installation, the pressure when the system was providing heat was going up to 27psi. I contacted the installer, and he put in a second Extrol 30 expansion tank which brought the pressure down to 23psi. Now, I noticed that the pressure is going back up to 27psi. The expansion tanks don't appear to be filling up, and the second one hardly seems to be getting warm.
I'd appreciate any thoughts on what could be causing the problem before I call the installer back again. I've attached 2 pictures of the system. Thanks for your help!Name:  IMG_0536.jpg
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