Very Frustrating Boiler System Problem
I have an oil burning boiler with a stainless steel indirect heater water tank.
This is the problem I am experiencing:
1) The boiler pressure rises slowly until the pressure relief valve on the boiler blows
2) I shut off the water supply at the reducer valve thinking was leaking. The pressure no longer builds, but now, I hear water rushing through the pipes, and the pipes are making very loud slamming noises, until I open the reducer valve again. At this time, the running water sounds and pipe slamming stops immediately.
I bled the air out of each zone many times, and so has the heating contractor.
I can't find any sign of a leak.
These are the parts the heating contractor have replaced so far:
1) Expansion tank
2) Pressure relief valve
3) Reducer valve
4) Back flow protection check valve
5) Boiler pressure and temperature gauge
I have attached a sketch of my heating system.
About 3 months ago, the pump failed and was replaced. Is it possible that the new pump is dropping the pressure at the reducer valve enough that the reducer (set at ~15) lets more water in even though the boiler pressure (~22) is well above the reducer setting? Note that the pump is on the boiler return. I assume that there is a pressure difference on each side of the pump. That is just a thought, I'm no heating expert.
Does anybody have any idea of what might be going on here?
Comments
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Because you are not "pumping away" from your expansion tank, it is likely that the pressure is dropping on the intake side of the circulator tricking the PRV.
What type of boiler is it?
What model Circulator?
Are the zones baseboard?"If you can't explain it simply, you don't understand it well enough"
Albert Einstein0 -
Boiler type: Not sure what that means. SorryZman said:Because you are not "pumping away" from your expansion tank, it is likely that the pressure is dropping on the intake side of the circulator tricking the PRV.
What type of boiler is it?
What model Circulator?
Are the zones baseboard?
Circulator: I'll find out when I get home
Baseboard: Yes
I attached and actual picture here if that helps.0 -
It looks like you have low resistance cast iron boiler and a Grundfos 15-58 circulator. The piping is not ideal but systems like that usually get rid of the air eventually.
I don't see the expansion tank in the picture. Where is it? Did you check the pressure before you installed it?
What can you tell us about the appendage on the air eliminating device? That is how the air is supposed to get out."If you can't explain it simply, you don't understand it well enough"
Albert Einstein0 -
The boiler shares a flue with a woodstove? Does that circulator say Alpha on it?0
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The expansion tank is right behind the boiler. It's on the diagram I sketched. The heating contractor checked the pressure before he installed it (I watched). The appendage is just a part of the troubleshooting, trying to determine if air was getting in through the eliminating valve. It will be taken off today.Zman said:It looks like you have low resistance cast iron boiler and a Grundfos 15-58 circulator. The piping is not ideal but systems like that usually get rid of the air eventually.
I don't see the expansion tank in the picture. Where is it? Did you check the pressure before you installed it?
What can you tell us about the appendage on the air eliminating device? That is how the air is supposed to get out.0 -
Paul48 said:
The boiler shares a flue with a woodstove? Does that circulator say Alpha on it?
I am not sure if it says Alpha on it. I can check when I get home.
Yes, the wood stove and the boiler share the same flue. The wood stove is only used when we lose power for days (or weeks). NH says that is a bad idea, but Massachusetts did a study on the practice and found that simultaneous use actually kept the chimney cleaner and didn't negatively affect the performance of either heat source. I don't know what to believe and really don't care, because I don't use them together.
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Do you get the same reaction with all the zones calling for heat, at the same time?0
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I got the same reaction when 2 out of the 3 were calling for heat. The third zone is the water heater. I can turn up the heat on that for testing, but didn't think about it. Are you thinking a valve is defective?Paul48 said:Do you get the same reaction with all the zones calling for heat, at the same time?
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Did this problem start after the circulator was replaced?0
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null
Is that piece of hose on the SpiroVent an attempt to close off its vent port? If so, it won't be able to remove air from the system.
Is your expansion tank a diaphragm type?Bob Boan
You can choose to do what you want, but you cannot choose the consequences.0 -
That hose is just part of the troubleshooting in the last couple days. It was to make sure air wasn't getting in through that. It will be taken off today.Ironman said:null
Is that piece of hose on the SpiroVent an attempt to close off its vent port? If so, it won't be able to remove air from the system.
Is your expansion tank a diaphragm type?
I don't know if it is a diaphragm type. I can find out.
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You have a puzzling one. The pressure rise problem acts like a bad or clogged pressure regulating valve as you where thinking.
The noise sounds like an air problem.
The orientation of the pump, reducing valve, and expansion tank are not helping but I don't think it explains all of it.
It might be time to start looking for a the odd stuff.
What does the pressure do when you isolate the regulating valve?
How much does the pressure move right when the circ turns on?
Is the boiler clogged with sediment (what does the water look like)?
Are the zone valves or air eliminator plugged?
Do you have an auto air vent somewhere high in the house?
How high is the house?
I think you have a 15-58 circulator. Under normal conditions it would have a pressure differential of around 2.5 psi. which should be pretty forgiving to your piping layout.
If something is obstructing, it could generate more like 6 psi. Not as forgiving...
"If you can't explain it simply, you don't understand it well enough"
Albert Einstein0 -
Which way is the arrow on the pump housing pointing?Bob Boan
You can choose to do what you want, but you cannot choose the consequences.0 -
Zman said:
You have a puzzling one. The pressure rise problem acts like a bad or clogged pressure regulating valve as you where thinking.
The noise sounds like an air problem.
The orientation of the pump, reducing valve, and expansion tank are not helping but I don't think it explains all of it.
It might be time to start looking for a the odd stuff.
What does the pressure do when you isolate the regulating valve?
When I turn the regulating valve off, the pressure stops building, but the pipes start pounding BAD....and this is whether I bled the air out of the system or not.
How much does the pressure move right when the circ turns on?
Just a few lbs.
Is the boiler clogged with sediment (what does the water look like)?
The water looks clean
Are the zone valves or air eliminator plugged?
I don't know
Do you have an auto air vent somewhere high in the house?
How high is the house?
The house is a normal cape. The highest pipe is probably no more that 20 ft from the bottom of the boiler.
I think you have a 15-58 circulator. Under normal conditions it would have a pressure differential of around 2.5 psi. which should be pretty forgiving to your piping layout.
I attached a picture of the pump.
If something is obstructing, it could generate more like 6 psi. Not as forgiving...
I fear that might be happening, but have no idea where.0 -
Take a picture of the expansion tank. In your schematic, you show the expansion tank after the Spirovent, however based on the photo, that is not where it is located.0
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I mention this because recently we had a call into tech with a similar issue. The problem ended up being an air pocket trapped in the pipe leading to the expansion tank. The pipe was sloped from the system pipe, upwards into the expansion tank.0
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That was my mistake. The Spirovent is actually on the other side of the expansion take. No idea why I did that. The rest is accurate.todd_ecr said:Take a picture of the expansion tank. In your schematic, you show the expansion tank after the Spirovent, however based on the photo, that is not where it is located.
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todd_ecr said:
I mention this because recently we had a call into tech with a similar issue. The problem ended up being an air pocket trapped in the pipe leading to the expansion tank. The pipe was sloped from the system pipe, upwards into the expansion tank.
That is interesting. At one point while the boiler tech was looking things over. He mentioned that this furnace was notorious for trapping air....and he pointed at the top of the boiler somewhere near the pressure relief valve. I should have questioned that more.
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I would re-install the circ, with new O-rings, taking care to tighten the flanges up evenly. My W.A.G. is that a tiny amount of air is being drawn in at the inlet flange of the pump, every time it starts. It's cheap and easy with the valves isolating the circ.0
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That makes complete sense. The last I talked to the boiler tech, we discussed moving the pump to the other side of the compression tank. I'll go ahead with that and make sure he replaces the O-rings. Thank you.Paul48 said:I would re-install the circ, with new O-rings, taking care to tighten the flanges up evenly. My W.A.G. is that a tiny amount of air is being drawn in at the inlet flange of the pump, every time it starts. It's cheap and easy with the valves isolating the circ.
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Is there any water under the boiler or any steam vapor coming out of the chimney?
Set the PRV to 25 psi, close the valve on the fill line and see if the system holds pressure with everything turned off.Bob Boan
You can choose to do what you want, but you cannot choose the consequences.0 -
No water under the boiler. I can look for steam vapor.Ironman said:Is there any water under the boiler or any steam vapor coming out of the chimney?
Set the PRV to 25 psi, close the valve on the fill line and see if the system holds pressure with everything turned off.
When i shut the fill off, air gets into the lines, and the pipes start pounding very loudly. That's the weird part.
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Are you sure the pressure gauge is reading correctly? Steve0
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Yes, suspecting a problem with the reading, I had it replaced. After that, I tested the pressure with a pressure gauge that I know to be accurate, at two different points in the system (with all the valves open and system off) and the reading was the same as the pressure gauge on the boiler.sdodder said:Are you sure the pressure gauge is reading correctly? Steve
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Do this and watch the pressure carefully.Ironman said:Is there any water under the boiler or any steam vapor coming out of the chimney?
Set the PRV to 25 psi, close the valve on the fill line and see if the system holds pressure with everything turned off."If you can't explain it simply, you don't understand it well enough"
Albert Einstein0 -
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Just to be clear. I am setting the Pressure Reducer Valve to 25psi to charge the system to 25psi, then shut off the city water supply, and watch the boiler pressure gauge, while the furnace is off and the zone valves manually open. Correct?Zman said:
Do this and watch the pressure carefully.Ironman said:Is there any water under the boiler or any steam vapor coming out of the chimney?
Set the PRV to 25 psi, close the valve on the fill line and see if the system holds pressure with everything turned off.
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CorrectBr. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England0 -
Did they leave the check valve in the 15-58 circ when it was replaced? I have seen that do some funky stuff when left in on a ZV set up...0
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kcopp said:
Did they leave the check valve in the 15-58 circ when it was replaced? I have seen that do some funky stuff when left in on a ZV set up...
Funny that you ask that. The boiler tech called me late yesterday and said he wanted to come over and try something. He came over this morning and took off the circulator and removed the check valve. Since then, the boiler has been cycling all day, 1) without gaining pressure, 2) No air in system aka. rushing water, and 3) No pipe pounding. It seems to be running perfect for the time being. I was going to monitor it until tomorrow before I got my hopes up. I'll post back tomorrow.
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Sorry to say, but that is not set up right. I have put in countless PFO boilers, and for one, you are most likely making steam here. I can't see if the relief valve is behind the smoke pipe, but you should have a Tee and a autovent on the top, relief on the branch. That is the highest point of that block. Second is that the control well should be closest to the boiler, and in the outlet flow. These controls are at least 20 degrees off when the well is coil mounted, let alone how it is installed here. I can't tell if it is a "T" model with a coil, but if it is, I would have the control well and capillary moved to behind that left side jacket. The Spirovent is not really needed here, but sounds like a good expansion tank and feed valve would be in order here0
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Looking at the first actual pic - The circulator looks to be in backwards. You sure all he did was remove a check? Take another pic of the circ now and post please. Inquiring minds want to know..
There was an error rendering this rich post.
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My boiler tech and I have discussed moving a bunch of things around. It was installed 22 years ago. I just took note of your recommendations. Thank you.billtwocase said:Sorry to say, but that is not set up right. I have put in countless PFO boilers, and for one, you are most likely making steam here. I can't see if the relief valve is behind the smoke pipe, but you should have a Tee and a autovent on the top, relief on the branch. That is the highest point of that block. Second is that the control well should be closest to the boiler, and in the outlet flow. These controls are at least 20 degrees off when the well is coil mounted, let alone how it is installed here. I can't tell if it is a "T" model with a coil, but if it is, I would have the control well and capillary moved to behind that left side jacket. The Spirovent is not really needed here, but sounds like a good expansion tank and feed valve would be in order here
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Chris said:
Looking at the first actual pic - The circulator looks to be in backwards. You sure all he did was remove a check? Take another pic of the circ now and post please. Inquiring minds want to know..
Here are the pics. I panned out so you can see the direction. It wasn't backwards.
It is fed by the return, which is not optimal.0 -
UPDATE:
It appears everything is working ok now. The check valve in the pump was removed, and seemed to make the difference. Pressure is no longer building.
Thank you (everybody) for the help. I learned an enormous amount of information.
Rick
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Glad it helped. Sorry I didn't look at this thread sooner.0
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