Pressure Relief Valve Blowing Periodically


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Old 10-10-12, 03:30 PM
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Pressure Relief Valve Blowing Periodically

Periodically the pressure relief valve on my gas fired Burnham boiler is blowing. When I check on it everything is running fine. Any suggestions?
 
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Old 10-10-12, 03:32 PM
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Yes, read this first:

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

If you have the 'other' type of expansion tank, let us know and we'll instruct.
 
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Old 10-10-12, 03:32 PM
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Expansion tank issue most likely.

Can you take several clear pics of your boiler?
 
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Old 10-10-12, 06:22 PM
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I installed a new expansion tank last year. Pictures were inspected by NJ Trooper and the installation passed. Can you provide me with the instructions for setting the air pressure in the tank again, please. Whoops! I didn't see the link provided by NJ Trooper. Maybe I have a slow leak. I will drain it and re-set it.
 

Last edited by hhornig; 10-10-12 at 06:26 PM. Reason: Needed to add information
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Old 10-10-12, 06:32 PM
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Possible its you fill valve if you check the tank and all is good.

The relief valve could be faulty also.

But then again the aquastat can be in runaway mode and exceeding temp. Is the relief valve blowing water or steam?
 
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Old 10-10-12, 07:20 PM
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On the subject of relief valves..
Is there a standard line of though for replacement of these ? How old is 'too old' ? Do they get lazy or stuck after some time ? Best to just manually activate it once per season ? Mine is 12 yrs old and never been touched.
 
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Old 10-10-12, 07:35 PM
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Is there a standard line of though for replacement of these ?
Test once a year, and I believe replace every 5 years from what I remember.


 
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Old 10-11-12, 04:23 PM
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It appears to be mostly water, but there is some steam. The aqastat was put in new last year. The relief valve is original (1978).
 
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Old 10-11-12, 05:13 PM
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Yeah... even if it's NOT the cause of the spewing, just go ahead and replace it.

You STILL need to check the other things mentioned though.
 
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Old 10-12-12, 04:03 PM
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OK, I replaced the relief valve and checked the expansion tank. The expansion tank was at 5 psi. Could that have been the problem. I re-set it to 12 psi. It will probably get cold enough tonight to kick on the heat and we will see if the problem still exists. What else should I check?
 
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Old 10-12-12, 04:08 PM
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That probably is it. So you relieved the pressure to change the relief valve, and added air to the expansion tank, right?

What was the starting cold pressure when you refilled the boiler?

If 12-15 psi good. But now as the boiler heats up to the 180f high limit note the psi and post back. If it goes up to the 30 psi range shut her down. It should only rise 5-8 psi.
 
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Old 10-12-12, 05:05 PM
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Just to make sure you did it correctly, you check the pressure of the expansion tank when there is 0 pressure on the boiler side.
 
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Old 10-12-12, 05:42 PM
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FYI, this is H's tank install:



He took my advice (2 years ago) and added the drain and the ball valve to make easy the check/charge of the tank.

And see that? It was a brandy new tank what, two years ago? and already down to 5 PSI.
 

Last edited by NJT; 10-12-12 at 07:16 PM.
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Old 10-12-12, 06:06 PM
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His pumps on the return and the tank looks small to me.

I had that trouble with my boiler way back when.r. Since I was not changing the pump location I put a bigger tank on, even though mathematically it did not call for it.

Have not had an issue since.

Just my 2 cents on the issue. Don't leave no stone unturned.

Thinking about it I think water logged would be an issue. he still had 5 psi.... Plus his statement below leads me to believe this.
Periodically the pressure relief valve on my gas fired Burnham boiler is blowing. When I check on it everything is running fine. Any suggestions?

 
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Old 10-12-12, 07:15 PM
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I sorta recall that we had talked about the tank size back when he changed it... but not sure. I thought it looked like a ' 15 ' myself.

It seems that tank air charge problems don't become a problem until the tank is down to 5 PSI. Almost like a 'magic number' !
 
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Old 10-13-12, 05:07 AM
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What I did was shut off the power and let everything cool down until it was touchable, then turned of the make-up water and popped the old relief valve until nothing came out. For an added measure i opened the boiler drain and let out a little water. I changed the relief valve and opened the make-up water. I did not note the pressure on the system at this time.

I then close the valve between the expansion tank and the boiler. Then I opened the valve on the left and drained the water out of the top of the expansion tank. With the left valve still open I checked the pressure on the bottom of the expansion tank. It was 5 psi. After adding air to 12.5 psi with the top valve open, I closed the left valve and opened the valve between the expansion tank and boiler. Sure glad I took NJ Trooper's advice and added those two valves to my system. It made that adjustment simple.

No pressure relief blows last night, but it only got down to 52 outside last night. I will check the pressure on the entire system when cool and hot when I get an accurate gauge. Should I check anything else?
 
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Old 10-13-12, 05:19 AM
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Should I check anything else?


Not really. Just let us know what the pressure readings are.

Here is a good article.

Pumping Away
 
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Old 10-13-12, 07:43 AM
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Just for curiosity sake, what size is your expansion tank ?

Since you have the valves, check that tank at the start of every heating season.
 
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Old 10-13-12, 06:12 PM
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I checked the cold pressure with a 30 psi gauge and it was 15 psi. The temperature here was in the upper 70's today so the house is too warm to fire up the boiler. I will check tomorrow morning.

The expansion tank is a B&G HFT-15 which is rated at 2 gallons. It is the same size as the original expansion tank.

I will put a note with my pump oil can to check the expansion tank at the beginning of the season.
 
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Old 10-25-12, 07:31 PM
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It blew again and I was home to make some observations. The temperature finally dropped to kick on the heat. I suspect the heat was running most of the day, but the pressure relief blew this evening. After the steam cleared the air I noted the circulator was not running. I turned the power switch off and on a couple of times and it started to run again. Pressure was down to 15 psi. After the thermostat no longer called for heat everything shut down as normal.

I checked the expansion tank and it was at 12 psi. After opening up the valve between the expansion tank and the boiler, I check the boiler pressure and it was also at 12 psi. I then turned up the thermostat 3 degrees and when the zone valve called for heat the circulator relay hummed but did not turn on the pump. I had to cycle the power switch again to start pump. The pressure in the boiler climbed up to where it was between 21 (fire off) and 23.5 psi (boiler fired just before turning off).

Are the pressures while circulating in the "normal" range? The aquastat is less than a year old. I would think the aquastat should shut down the boiler if the circulator doesn't carry the heat away. Am I correct?

My guess is I have a bad relay or a dead spot in my pump motor. Any suggestions on where to go from here?
 
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Old 10-25-12, 07:55 PM
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Here's what to do next...

Shut off boiler and let cool. Check boiler pressure and if it's HIGHER than 12 PSI , close the make up water feed valve and LEAVE IT CLOSED.

Let some water out one of the drains to drop the boiler pressure to 12 PSI.

LEAVE THE WATER FEED CLOSED FOR NOW.

Turn a thermostat all the way up to force a heat call that will cause the boiler to go all the way up to 180

While the boiler is heating up, watch the pressure gauge. If the pressure approaches 25 PSI, shut the boiler down and note the pressure at that point. If you are able to get to 180 please note the pressure when the boiler is at 180 and let us know what it is.

If the pump isn't starting, that's a problem, and we'll get to that soon, but it shouldn't cause the relief valve to blow.

I think that tank is too small...

You said you have a 30 PSI gauge... is that what you used to measure the 21 and 23 PSI with?
 
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Old 10-25-12, 08:21 PM
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How cool do I need to get it? The inlet and outlet lines are warm to the touch, but not hot. The pressure is now at 17.5 psi. I am using a Watts 30 psi gauge for all measurements except for the shredder valve on the expansion tank where I used a tire gauge.

How do I know when I reach 180? I do not have a temperature gauge. Do I just assume the aquastat will turn off the boiler when it reaches that limit?
 

Last edited by hhornig; 10-25-12 at 08:27 PM. Reason: More questions.
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Old 10-25-12, 09:04 PM
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How cool do I need to get it?
Enough that you do not get scalded and introduce cold water in a hot boiler.

After the steam cleared the air
This leads me to believe a temp issue. Running well above 180f.

The boiler should have a temp and pressure gauge. Like I said in a previous post the aquastat may be faulty.

Let us know what the temp reading is when the boiler kicks off.


 
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Old 10-25-12, 09:26 PM
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The pipes going in and out are cool enough to touch with my face and the pressure gauge (0-30) on the drain reads 15 psi while the gauge on top of the boiler reads 140 degrees and about 23 psi so I don't really trust that gauge.

The cast iron fittings coming out of the boiler are too hot to hold on to so that 140 might be right. What temperature should I cool to in order to start the test. Since I am above 12 psi, I will probably shut off the make-up valve and should not be putting in any cold water.
 

Last edited by hhornig; 10-25-12 at 09:34 PM. Reason: More info
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Old 10-25-12, 09:35 PM
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Well first things first.

http://www.doityourself.com/forum/bo...ure-gauge.html

I have to read through this thread again to refresh my memory....
 
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Old 10-25-12, 10:57 PM
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OK, I did my test. The temperature on top of the boiler was about 130 and I could hold my hand on the cast iron outlet pipe. The pressure got down to 14 so I shut off the make up valve and lowered the boiler pressure to 12.5 psi measured with a 0-30 gauge on the boiler drain. After turning up the thermostat and toggling the power switch to start the pump I monitored the temperature and pressure. The pressure increased by 6.5 to a reading of 19 psi at 180 degrees and maintained that pressure to 220 degrees when the burner shut off. The limit switch on the aquastat appears to be set at 190.
 
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Old 10-25-12, 11:14 PM
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Turn the aquastat down to 160 and re-run the test. If the temperature climbs to 190 on the thermometer then either the thermometer or the aquastat is badly out of calibration. My bet is that the thermometer is reasonably accurate and the aquastat is out of calibration. No matter, just adjust the aquastat to whatever setting will allow the temperature to come to about 180-190.
 
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Old 10-26-12, 06:37 AM
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Blew Again

Went to bed after the last test and just got to sleep when it blew again. The pump was not running again. Turned it off and went back to bed.

This morning the boiler was cold and the boiler pressure was 15 psi. I turned it on and after the zone valve opened, the boiler fired, but the pump did not run. There was no voltage between C1 and C2 on the aquastat until I toggled the main switch a few times to get the pump running. The boiler pressure kept creeping up to about 25 psi before I shut everything down. I lowered the pressure in the boiler back down to 15 psi and fired up again. It is now running with the make up valve off at a pressure between 15-16 and the temperature is cycling between 180 and 190. I can hear the pump running from the floor above so I know there is some air in the system.

Is the relay in the aquastat replaceable or do I have to replace the entire aquastat? Since the temperature went up to 220 I am leaning towards replacing it.
 
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Old 10-26-12, 12:59 PM
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I just scanned this whole thread and I didn't see if you have a tankless coil in this boiler supplying domestic hot water. Do you have a tankless coil? Are you on city water or a well? Do you know your incoming water water pressure?

You MAY have an undersized expansion tank or it MAY be that the manual shut-off valve on your make-up water line is leaking along with either a leaking or maladjusted pressure reducing valve. It is also possible that your safety valve is discharging at a lower pressure than its rating although that is not likely.

No, the relay in the aquastat is not field replaceable. More likely is that the calibration of the aquastat is off. Did you try turning it down to around 160 and see if that shuts down the burner at the 180 to 190 temperature? If that does the trick then you can leave it that way but if it still climbs to over 220 then yes, replace the entire aquastat.
 
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Old 10-26-12, 03:52 PM
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H, as I recall, you had replaced the aquastat two years ago?

When you did so, were you absolutely certain that the sensing bulb went all the way to the bottom of the well and stayed there?

Was it you that also had to replace the well?
 
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Old 10-26-12, 06:40 PM
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Yes it was replaced along with the well. i am sure the sensing bulb went to the bottom. That would not have any impact on the functioning of the relay. It also seems strange that it went up to 220 that one time and normally runs between 180 and 190. Could it have been caused by air in the system? The new aquastat worked fine for two years. Now why should it all of a sudden act up?
 
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Old 10-26-12, 06:51 PM
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No, I don't think air in the system... but it's likely that with the relief spewing and adding fresh water after the fact that you do now have some air.

I'm thinking about the pump not running though... what if:

The boiler fired with the pump not running and with no circulation in the boiler it got hot enough in part of the boiler but not the part that the a'stat well is located in? This would cause slow reaction of the a'stat in shutting the burners down because it won't know that the bottom of the boiler is already overheated...

This coupled with an expansion tank that may be marginally sized...

Of course, not sure about anything, just theory, but if there is any question if the pump runs reliably or not, that should be fixed first.

The fact that there was no voltage at C1 C2 when there should have been points to a problem with the new aquastat. They just don't make them like they used to. Either the contacts are dirty, or there is a cracked solder connection on the board where the relay is soldered in.
 
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Old 10-27-12, 12:53 AM
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I can't get a new aquastat until Monday. Can I run the pump continuously and if so, do I remove a zone valve actuator so the system is open or can the pump just dead-head? The pump is a B&G 100, I believe.
 
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Old 10-27-12, 07:02 AM
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Could you also take pics of your system? We have not seen any yet.

We may see something you don't....
 
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Old 10-27-12, 09:55 AM
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lawrosa,

I am afraid I forgot how to send pictures. There is a photo provide by NJ Trooper which shows the expansion tank included in this thread. I took several pictures of my system at that time and posted them. They are still in photo bucket. The system has not changed except the new expansion tank and replacement of the aquastat with a new L8148E1299. Please provide me with a link to explain how to attach pictures or send me a private message and I can e-mail new picture from my iPhone.
 
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Old 10-27-12, 10:16 AM
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Go to photobucket then paste the link to those pics back here.
 
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Old 10-27-12, 10:39 AM
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Temporary Solution

Right now I am turning off the boiler so that it doesn't start up without running the circulation pump. When it gets chilly in the house I turn on the boiler main switch and wait for the B&G CT-24 zone valve to activate the aquastat which in turn fires the boiler. I then have to toggle the main switch or tap the relay in the aquastat to get the pump running and everything works as expected except for slightly higher pressure which I will discuss later. I then turn off the main after the thermostat is satisfied.

Proposal until I can get a new aquastat on Monday:
I can remove the two leads from the motor on C1 and C2 and tie them to the power leads going into the aquastat L1 and L2 so that the pump runs continuously. The pump would be dead-heading into closed zone valves if no heat was called for and I don't know if that would hurt the system. As an alternative I can remove a zone valve controller and suspend it with a zip strip so it would activate the contacts inside if the thermostat would call for heat. If no heat was called for the valve without the controller is open and will allow water to flow. Am I missing something?

High Pressure:
As I am controlling the system off and on I have notice that the pressure at the drain with a 0-30 psi gauge is registering 15 psi when cold. I think that is because the make-up regulator is set at that level. As the boiler heats up to to the 190 degree limit the pressure rises to 28 psi which is too close to the relief valve trip for my comfort and probably why the valve spews hot water and steam when the pump is not running. It seems to me that I can do three things:
1. Reduce the make up regulator pressure setting. I think that can be done but am not sure.
2. Add a larger expansion tank.
3. Lower the limit switch on the aquastat to 180.

Am I on the right track or is there something else to do. In which order should I do these steps or just do all of them?
 
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Old 10-27-12, 10:48 AM
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Sharing Pictures

I am sorry. It must be due to lack of sleep, but I can't paste pictures on this site.
 
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Old 10-27-12, 03:56 PM
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Here are some pictures in 2010 before and after I added new expansion tank and before replacing aquastat.

 
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Old 10-27-12, 08:12 PM
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The pump would be dead-heading into closed zone valves if no heat was called for and I don't know if that would hurt the system
It won't hurt the SYSTEM, and I'm not sure with a 3 piece pump (which you have) it will hurt the pump... I don't think it will, but not sure, so don't do it just yet. Doing this to a modern 'wet rotor' like the 007 WILL eventually hurt the pump since the water is also what cools and lubricates the pump and rotor in that design.

As an alternative I can remove a zone valve controller and suspend it with a zip strip so it would activate the contacts inside if the thermostat would call for heat
What is the make/model of those valves again?

Not sure if you can do this either... If those are electric motor type valves, without being attached to the valve body there will be nothing to stop the motor from spinning past the limit. It could easily damage the valve.

Those may be a different design though... if they are a HEAT MOTOR, you MAY be able to do that... again, not sure if something in the valve head will be damaged by 'over extension' without being connected to the valve itself.

pressure at the drain with a 0-30 psi gauge is registering 15 psi when cold. I think that is because the make-up regulator is set at that level.
Probably so.

[table="width: 600"]
[tr]
[td]1. Reduce the make up regulator pressure setting.[/td]
[td]I wouldn't mess with that, very limited benefit[/td]
[/tr]
[tr]
[td]2. Add a larger expansion tank.[/td]
[td]YES, you may need to. You can add a second 15 if you can find room for it.[/td]
[/tr]
[tr]
[td]3. Lower the limit switch on the aquastat to 180.[/td]
[td]Do this ANYWAY. Even 170. You surely don't need water any hotter than that in any case.[/td]
[/tr]
[/table]
 
 

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