Boiler pressure keeps increasing


  #1  
Old 12-07-09, 08:56 AM
B
Member
Thread Starter
Join Date: Dec 2009
Location: South Dakota
Posts: 9
Received 0 Votes on 0 Posts
Boiler pressure keeps increasing

I have a low pressure, low temp. (140 degrees max) in floor radiant heating system (Wirsbo) - coal fired. I have read the forums on draining the expansion tank, which I have done. I reset the pressure at 15 pounds. The pressure stayed low for one cycle - then on each subsequent firing the pressure increased so that now the pressure relief valve is once again opening to drain off pressure. The expansion tank has a Bell and Gossett Airtrol Fitting ATF 12. This was added about 5 years ago to purge air (I think?). Is it possible that this device is not allowing the water back into the system from the expansion tank? The expansion tank does not have a bladder. In reading your posted info - it sounds like the expansion tank has a leak. Help!!! It's really cold here (5 degrees). I keep bleeding off the pressure, but am afraid that I will end up with no water in the system.
 
  #2  
Old 12-07-09, 09:22 AM
M
Member
Join Date: Sep 2009
Location: U.S. Midwest
Posts: 1,339
Received 0 Votes on 0 Posts
Your automatic fill valve is likely leaking past its seat. You should have a shutoff valve between the city water supply and the fill valve. Shut that valve and drain the system back down to 12 psi (cold, room temp) or 15 psi (hot). Leave the shutoff valve closed, and see if this fixes your problem. Check back here with your results.

I wouldn't expect a conventional steel expansion tank to develop an air leak, but I suppose anything is possible.

Coal-fired, huhh? Stoker? What make and model is your boiler? Can you post some photos - we would be very interested! What do you pay per ton of coal? Are you burning bituminous or sub-bituminous?
 
  #3  
Old 12-07-09, 11:25 AM
B
Member
Thread Starter
Join Date: Dec 2009
Location: South Dakota
Posts: 9
Received 0 Votes on 0 Posts
I guess I did that wrong - HA! The stoker is a Viking Eagle BMS175 - no longer manufactured. We live near the Wyoming coal fields so coal is plentiful and not terribly expensive. Most of the coal is too soft for my stoker - but I order stoker coal and hope for the best. I don't know which type it is. Cost is $500 for 6T which will last one heating system - almost. 3500 sq ft in the house in western SD. Often quite cold - but often moderate temps. Very economical - but I cannot get help from manufacturer. I will post pics if you're still interested.
Back to the problem at hand - I shut off the water supply to the fill valve so no leakage into the system is possible. Is it possible that the Airtrol Fitting is corroded and not letting adequate water flow between the expansion tank and boiler??? I agree that it is unlikely that the expansion tank has a hole but maybe it corroded thru and I can't see it. I would like to trouble shoot is steps to try to defray cost. THANKS for your quick reply - I'll get a handle on how to use the forum.
 
  #4  
Old 12-07-09, 11:38 AM
O
Member
Join Date: Dec 2007
Location: A Galaxy From Afar
Posts: 421
Received 0 Votes on 0 Posts
baddusey's thread got hijacked.

As far as the pressure creeping up with each cycle, this can be caused by having the wrong circulator and/or having the fill plumbed in at the wrong location.

What happens is when the circulator kicks on it lowers the pressure at the fill valve. Which then adds water. Once the water in the system is moving the pressure at the fill valve goes back up and it stops filling the system.

But as this happens on each cycle more & more water is added to the system until it over-pressures and the relief valve does it's job.

Now, with closing the feed shutoff valve correcting the issue, I would just leave it closed. If worried about dry firing then just install a LWCO and be done with it.

Al.
 
  #5  
Old 12-07-09, 02:29 PM
M
Member
Join Date: Sep 2009
Location: U.S. Midwest
Posts: 1,339
Received 0 Votes on 0 Posts
Originally Posted by baddusey View Post
I would like to trouble shoot is steps to try to defray cost.
If after closing the shutoff valve ahead of the automatic fill valve, and draining the system to normal pressure (12 psi cold, 15-18 - psi hot), and pressure remains under control - you are finished with the troubleshooting. Your fill valve is leaking through.

Tagpats thread is moved...
 

Last edited by NJT; 12-07-09 at 06:08 PM.
  #6  
Old 12-07-09, 06:01 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,538
Received 7 Votes on 5 Posts
Yes, very confusing... so much so that I can't sort it out into two separate threads.

badusey, you did OK, tagpat, you 'hijacked'...

I'd like to get these into two threads, but I can't figure out whose answers are for who. I'm gonna try, so look for a new thread for tagpats dialogue...
 
  #7  
Old 12-07-09, 06:59 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,538
Received 7 Votes on 5 Posts
I see where bad said he shut the manual valve, but didn't see where he returned and said that it fixed the problem?
 
  #8  
Old 12-07-09, 10:11 PM
B
Member
Thread Starter
Join Date: Dec 2009
Location: South Dakota
Posts: 9
Received 0 Votes on 0 Posts
Sorry for the lapse in time - No - turning off the shut off valve ahead of the fill valve did not solve the problem. "Old Boiler" talks of things being backwards. I don't think that is it - though at this point I'm certainly open to suggestions. This boiler and all operating components (minus the Airtrol Fitting ATF 12 - which was added about 5 years ago by a serviceman) have been in operation for 20+ years without a hitch. When I fired this boiler this year is when I first started experiencing trouble. Interesting thing. I had to go to doctor and fearful of leaving the boiler unattended, I shut it off. When I returned home, the water temp was down to about 100 degrees, but the boiler pressure still showed over 30 pounds and water was coming from the pressure relief valve. In the morning, I plan to remove the Airtrol Fitting ATF 12 and replumb the expansion tank without an air purger. I can do that manually. Does it make sense to remove this piece of hardware and see if anything changes? With the boiler off, the circulating pump off, the only two items in play are the boiler and the expansion tank - right??? Shouldn't the expansion tank "absorb" the expanding water from the boiler??? I have removed so much water from the system that it is impossible that there is too much fluid. THANKS for your help.
 
  #9  
Old 12-07-09, 11:56 PM
K
Member
Join Date: Nov 2009
Location: Fairbanks, Alaska
Posts: 40
Received 0 Votes on 0 Posts
Do you have a side arm heater on the boiler?
 
  #10  
Old 12-08-09, 06:10 AM
O
Member
Join Date: Dec 2007
Location: A Galaxy From Afar
Posts: 421
Received 0 Votes on 0 Posts
What kwgrant said... Or a coil set up for DHW.

I misunderstood that closing the shutoff valve did not correct the issue. With it closed and the burner is off, then water must be coming in other then the shutoff/fill valve set. Unless the shutoff valve is also leaking (along with the fill valve).

Now, if the pressure increases as the boiler heats up, yes, the compression tank should take that up. The pressure will rise some, but usually not more then 5 - 6 psi (dependent upon compressions tank volume, system water volume, and temperature increase).

If with the burner running and the pressure spikes high enough to open the relief, this is usually caused by the compression tank being filled with water. IOW, the air cushion is gone.

But first look into why when the burner is off and the water is cooing off, the pressure continues to increase.

Al.
 
  #11  
Old 12-08-09, 08:11 AM
B
Member
Thread Starter
Join Date: Dec 2009
Location: South Dakota
Posts: 9
Received 0 Votes on 0 Posts
The boiler is coal fired - two heat exchangers contained in the"box" that makes up the unit. I do not know what a side arm heater is. When I shut the system off, the coal was still lit - thereby creating heat. With the circulating pump off - the water that is in the boiler will continue to heat until the fire goes out. With the circulating pump off, no water will flow. I know that is why the pressure continued to increase. I have drained the expansion tank - more than once. ??? Why doesn't the excess pressure go to the expansion tank. Is it possible that the Airtrol Fitting ATF 12 is not allowing water exchange between the expansion tank and the boiler? That is the only thing between the two. Just a quick weather report :>))) 4 Degrees and snowing and no boiler. It is amazing what you can do with a heatalator fire place and a few electric space heaters. THANKS for your help.
 
  #12  
Old 12-08-09, 09:40 AM
O
Member
Join Date: Dec 2007
Location: A Galaxy From Afar
Posts: 421
Received 0 Votes on 0 Posts
When you drained the compression tank did a lot of water come out? Or just a few gallons? It may be that it wasn't completely drained. Many times you can push up on the end of the tank to feel the weight.

An empty tank is quite light, and feel like an empty steel tank. While a full tank is rather on the heavy side (100 - 200 pounds+).

As the boiler is cooling off does the pressure drop off? If so then it points to a water logged compression tank. If not, then it points to ingress of water into the system (under pressure).

A side arm heater is along the lines of a coil or indirect tank for DHW. A pin hole in one of these units will cause the boiler to be pressurized from the DHW side.

You may want to kick the circ on to further cool the boiler, and get some heat into the pipes. The issue being that you want to keep them from freezing (if no glycol in the system).

Al.
 
  #13  
Old 12-08-09, 11:51 AM
B
Member
Thread Starter
Join Date: Dec 2009
Location: South Dakota
Posts: 9
Received 0 Votes on 0 Posts
The am letting the expansion tank drain right now - valve open into a bucket. The expansion tank holds 15 gallons and I have drained off about 12 gallons. The boiler pressure did not drop as the boiler cooled. It also did not increase. I would think with 70 pounds pressure on the household side of things, the pressure would continue to increase. The only place that water is added to the system is at the fill valve. There is a shut off ahead of the fill valve and the pipe is NOT cold on the boiler side of the valve. The isolating valves that we have are one each of the four pipes (2 each) for 2 manifolds that have the zone valves. We are going to add another isolating valve just below the expansion tank. When we open that line to plumb in another valve we will be able to tell if we have a water leak at the fill valves into the system. I'll let you know how that comes out. What are your thoughts on the B&G Airtrol Fitting that was added 5 years ago between the boiler and the expansion tank. We have glycol in the system. I am able to keep the house tolerable with the air circulating fireplace and space heaters. 66 degrees. THANKS.
 
  #14  
Old 12-08-09, 11:58 AM
B
Member
Thread Starter
Join Date: Dec 2009
Location: South Dakota
Posts: 9
Received 0 Votes on 0 Posts
Could you tell me what DHW is? No coil on this boiler. I'm having some trouble getting my message to post - browser times out before it goes. I typed a longer message in response to your message typed at 10:40 am. I'll wait a few minutes to see if you got that one in addition to this one. Could you tell me if two messages posted at about the same time? Thanks.
 
  #15  
Old 12-08-09, 12:38 PM
O
Member
Join Date: Dec 2007
Location: A Galaxy From Afar
Posts: 421
Received 0 Votes on 0 Posts
Originally Posted by baddusey View Post
Could you tell me what DHW is? No coil on this boiler. I'm having some trouble getting my message to post - browser times out before it goes. I typed a longer message in response to your message typed at 10:40 am. I'll wait a few minutes to see if you got that one in addition to this one. Could you tell me if two messages posted at about the same time? Thanks.
DHW is domestic hot water. Can be from a coil or from an indirect. An indirect is a separate tank with a heat exchanger to isolate the two systems.

With getting 12 gallons from a 15 gallon compression tank, I'd say it is empty or close to it. Can push up on the end of the tank to check. They usually have a little room between them and the ceiling.

With the system work with the valves and such it can't hurt to pull the AirTrol is see if it is clogged. It shouldn't be, but one never knows.

Also, be careful of what type of valve is in the line to the compression tank. It should be a gate or ball valve to allow a continuous path for the air. The path through a globe valve has an air trap in it. I found out the hard way that it will prevent the proper flow of air back to the tank.

I'm not subscribed to the thread so the only posts I see are the ones in this thread.

Al.
 
  #16  
Old 12-08-09, 01:10 PM
M
Member
Join Date: Sep 2009
Location: U.S. Midwest
Posts: 1,339
Received 0 Votes on 0 Posts
Originally Posted by baddusey View Post
When I shut the system off, the coal was still lit - thereby creating heat. With the circulating pump off - the water that is in the boiler will continue to heat until the fire goes out. With the circulating pump off, no water will flow. I know that is why the pressure continued to increase. I have drained the expansion tank - more than once. ??? Why doesn't the excess pressure go to the expansion tank.
Do you have a thermometer on the boiler? If so, please tell us how hot it gets.

With a closed system, as the water continues to heat, the pressure will keep rising, expansion tank or not.

Consider redoing the aquastat so that the circulator runs whenever the water temp is above, say 180 deg - whether heat is called for or not. Of course, this may sometimes cause your house to be warmer than you would prefer.

Unlike your coal stoker, gas and oil can be turned off instantaniously.
 
  #17  
Old 12-08-09, 01:54 PM
B
Member
Thread Starter
Join Date: Dec 2009
Location: South Dakota
Posts: 9
Received 0 Votes on 0 Posts
High end on water temp is 140 degrees. Boiler shuts down that is. Still heats somewhat. Boiler kicks back on at 125 degrees. On warm days when we get a lot of solar gain, the boiler will just idle, i.e. the stoker runs for 2 minutes every 30 minutes. This is necessary to keep the coal lit. On those days the water temp does increase to about 160 degrees max. There is a temp shut off on the water line so that if the pipe carrying the water reaches 180 degrees, power is shut off to the unit. When the temp decreases the unit resets and power is restored. Low water temp is needed as the Wirsbo in floor water lines are damaged above 180 degrees. At this point, the water pump runs as long as there is power. I did that to dissipate heat off the boiler. Water temp has not been the problem - yet. As it turns out "Old Boiler" was correct! With the boiler off and the expansion tank with a hose on it for 2 hours - water is still dripping out of the drain hose. When I shut the second gate valve, which is there so that the fill valve can be isolated, the water quits dripping. Not much water but over time it is, and it doesn't take much water when the system is a temperature to increase the pressure. We are going to replace the gate valves with ball valves. They do a better job of being off when in the off position. Like I said, I can add water manually, at least for now until we get our problem figured out. Now it is 1 degree. Off to the store to get some ball valves. THANKS! I'll provide a progress report a little later.
 
  #18  
Old 12-08-09, 02:00 PM
M
Member
Join Date: Sep 2009
Location: U.S. Midwest
Posts: 1,339
Received 0 Votes on 0 Posts
QUOTE: "We live near the Wyoming coal fields so coal is plentiful and not terribly expensive. Most of the coal is too soft for my stoker - but I order stoker coal and hope for the best. I don't know which type it is. Cost is $500 for 6T which will last one heating system - almost."

Your coal probably is sub-bituminous, which typcially has an energy content of 8,000 Btu/lb. That works out to $5.21 per MBtu.

For comparison purposes, my natural gas price is $5.50/MBtu for December '09 (but the current price of gas is lower than it was in recent years past).

The next time you order coal, ask the supplier what the heat content is, Btu/lb. And where it comes from.
 
  #19  
Old 12-09-09, 08:42 AM
B
Member
Thread Starter
Join Date: Dec 2009
Location: South Dakota
Posts: 9
Received 0 Votes on 0 Posts
My problem is fixed. The diagnosis was that water is leaking into the system. You were exactly correct. Fill valve AND shutoff were leaking. However, when you talked of a leak, I was thinking it would be something that was one that could be detected by listening or touch. NOT! When I drained the expansion tank yesterday, in noticed that the hose was still dripping (one drop per second). I let it drip into a separate pan and in an hour, had 16 ounces. I shut off the isolating valve on the other side of the fill valve and the dripping stopped. With that slow addition, that is why the pressure increased with each cycle. (Of course, with the system hot, it may have been dripping faster.) We replaced the gate valve with a ball valve. I set the pressure at 10 pounds, cold. Now that the system is up to temp. (boiler fires at 125 and shuts off at 140) the pressure is at 14 pounds. YEAH! We live in the country where natural gas is not an option. Our propane runs $2+ per gallon. Heating fuel is $2.80 per gallon. The coal, at about $500 per heating season is a fration of the cost of the other fuels. Temp is AM is -3 - sure am glad we were able to get it fixed. THANKS for your help - we can now be warm.
 
  #20  
Old 12-09-09, 09:35 AM
M
Member
Join Date: Sep 2009
Location: U.S. Midwest
Posts: 1,339
Received 0 Votes on 0 Posts
Originally Posted by baddusey View Post
My problem is fixed. The diagnosis was that water is leaking into the system. Fill valve AND shutoff were leaking. We replaced the gate valve with a ball valve.
Congratulations - you done dooed it.

The shutoff valve ahead of the fill valve was a gate valve? Gate valves often aren't as leak-tight as ball or globe valves.

Still strange that a brand-new fill valve was leaking. But stranger things have happened.
 
  #21  
Old 12-09-09, 10:44 AM
B
Member
Thread Starter
Join Date: Dec 2009
Location: South Dakota
Posts: 9
Received 0 Votes on 0 Posts
THANKS again for your help to you and Old Boiler.
 
  #22  
Old 12-09-09, 11:07 AM
O
Member
Join Date: Dec 2007
Location: A Galaxy From Afar
Posts: 421
Received 0 Votes on 0 Posts
Originally Posted by baddusey View Post
THANKS again for your help to you and Old Boiler.
You're welcome, good to hear that the heat is back on.

Al.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: