Pressure relief discharge

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  #1  
Old 10-21-08, 08:28 PM
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Boiler relief valve

Hi there,

I'm a fairly new home owner and I was down in my basement today and noticed that my boiler relief valve was shooting out say 6 ounces of water after the boiler was on only for a few minutes. It releases the water once the boiler turns off. They never hooked up the relief valve to a drain. Is that normal? Also the PSI in the boiler is only about 7-8 PSI. What do you think the issue is here? Any help would be appreciated.

Thanks,
Josh
 

Last edited by NJT; 10-22-08 at 08:48 PM.
  #2  
Old 10-22-08, 01:29 AM
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Pendo, your problem is with the expansion tank. It is either too small or else the diaphragm has ruptured or at the least, lost its air charge. Please post some pictures of the system so we can offer some more advice.

To post pictures you need to first upload the pictures to a photo hosting site such as photobucket.com or villagephotos.com. and then post the public URLs for the pictures (or album) here. More pictures are always better than fewer. Please have CLEAR pictures and have both close up pictures and ones from a far enough distance that we can see how the various parts are interconnected.
 

Last edited by NJT; 10-22-08 at 04:15 PM.
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Old 10-22-08, 06:32 AM
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low PSI for boiler

Thanks Furd. Iíll get those pics posted ASAP. Do you believe the relief valve is OK? Iím wondering how the relief valve is allowing water to come out if the boiler is only at 8 PSI. The relief valves are usual preset for 30 PSI, right? Last off, the cold weather is starting to arrive and was wondering if it would cause a problem to turn the heat on with the boiler in this condition. Will even more water get discharged?

Pendo
 
  #4  
Old 10-22-08, 07:53 PM
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Relief valve and Expansion tank issue?

I just found out my wife's digital camera is broken now. I'm going to get her mother's within the next couple of days. The PSI in the boiler is all over the map. I was down there just now and it was reading 20 PSI. Before that it was always only registering between 5 and 10 PSI. We just turned the heat on for the first time today so would that have anything to do with the boiler all of a sudden registering higher PSI? We do run the hot water off the boiler so would that have the boiler only run at a lower PSI if it doesn't have to work for the heating?

I tapped the expansion tank it doesn't seem hollow at the bottom. I believe it is suppose to be, right? I tested the pressure and I didn't get a reading, but I hadn't dropped the pressure in the boiler to zero, how do I do that? Last off, do you think the discharge valve could be OK even though it has been discharging a lot of water each day? Just wondering if the expansion take is trash or if it may just need more pressure inflated. Does a bad expansion tank cause the relief valve to discharge a lot of water? FYI, it is a Amtrol model 30 extrol expansion tank.

Thanks again, Pendo
 

Last edited by Pendokid747; 10-22-08 at 08:21 PM.
  #5  
Old 10-22-08, 08:44 PM
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Pendo, here's what's happening. Your pressure reducing valve (PRV), also called the auto fill valve, is allowing cold water to enter the system to a certain pressure. That part is as it should be but what happens next is classic. The boiler fires and the water in the system expands. Because your expansion tank is for all intents and purposes non-existent the pressure skyrockets until the safety valve opens releasing the water and allowing the pressure to drop. As soon as the pressure drops below the "set point" of the PRV more water is added to the system. This vicious cycle continues as long as the defective expansion tank is not replaced.

You can ONLY measure the pressure in the "air side" of the expansion tank when the boiler/heating system pressure is at zero OR the expansion tank is removed from the system. You won't positively know the existing expansion tank is trash until you try to add air through the tire valve fitting and it either spits water or the pressure dissipates through the heating system.

Expansion tanks need to be sized to the total amount of water contained in the system and the temperature extremes at which the system may operate.

As for the safety valve...it may be okay or it may be toast. Safety valves are cheap enough that it makes no sense to play around with them. Since you have to dump at least a portion of the water in the system to change the expansion tank it just makes sense to change that safety valve at the same time. Safety valves should be changes routinely every five years and they should be tested at least once every year.

You may also have a problem with your PRV. And, if your domestic water is heated by a coil inside the boiler that could also be a contributing factor in your problem. How old is the boiler?
 
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Old 10-23-08, 05:15 PM
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Photos of boiler

http://i405.photobucket.com/albums/p...7/P1010550.jpg

http://i405.photobucket.com/albums/p...7/P1010556.jpg

http://i405.photobucket.com/albums/p...7/P1010559.jpg

http://i405.photobucket.com/albums/p...7/P1010565.jpg

http://i405.photobucket.com/albums/p...7/P1010567.jpg

http://i405.photobucket.com/albums/p...7/P1010568.jpg

Hi,

Here are the photos. I was just downstairs and watched the process again. Yes, once the boiler goes on and passed 30 psi the relief valve starts dripping a fairly steady stream of water out. How do I go about reducing the boiler's psi to zero? I'm new to boilers, but am willing to give it a shot. Should I reduce the pressure to zero and then test the expansion tank's psi first? If the tanks psi is dead and has water I'm assuming I need to buy a new one. Do you think it would be OK if I put it in myself if you coached me through it? If the tank can be repressurized by pumping it up to 12 psi should I just try that first? Do you think the tank is most likely dead/ruptured?

Where is the PRV in my photos? Is it next to the relief valve? Is it the "Taco"? I'm guessing my first step is to bring the boiler to zero psi and then test the tank. Do I not need to take the tank off to try and pump it up? Let me know what to do next coach. I appreciate all your help.

Pendo
 
  #7  
Old 10-23-08, 11:27 PM
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Sorry to be so late getting back to you.

I see that your boiler has a "tankless coil" for heating your domestic hot water. Sometimes these will develop leaks inside the boiler and will cause the boiler pressure to rise until the safety valve releases. I don't think that is the case here because it would be a continuous relieving of pressure, not the cyclic problem you are having.

Looking at the second picture, directly above the expansion tank is a cast iron fitting that has American Air Purger cast into it. To the left is this device:
[photo courtesy PexSupply.com]
The part on the left is the PRV and the handle on top is the quick fill lever. The part on the left is a "backflow preventer" and it is to keep boiler water from contaminating the domestic water supply. If you follow the piping from the backflow preventer back towards the camera you will come to a valve that connects to the domestic water system. This is your "make-up water" shut off valve.

To drop the pressure to zero first turn off the make-up water valve and power to the system then let it cool to about 120 degrees or lower to lessen the chance of serious burns. Close the valves in the piping above the three circulating pumps and then drain some water from the valve on the end of the pipe where the circulating pumps are connected. Use a hose if you have a floor drain or use a bucket (with a short hose if necessary) and drain only enough water to have the pressure gauge drop to zero. You may find that it only drains a small amount and this would be indicative of an expansion tank with no air cushion.

Once the pressure is to zero use a tire gauge that has a fairly low maximum reading (in other words don't use a gauge for truck tires that reads to 140 psi) and check the pressure in the expansion tank bladder, the tank has a tire valve under the blue cap on the bottom. If you get water out of the expansion tank then you know it is toast and needs to be replaced. If the air pressure is between 12 and 15 psi the tank is fine. Most likely you will find the pressure to be either non-existent or maybe only a few psi. If you do have a few psi of pressure then you can try to pump the bladder back up to 12 psi. You can do this with a bicycle tire pump (a fair amount of work) or a small home shop air compressor. If you use the air compressor set the pressure regulator to no more than 20 psi and add the air is short spurts, checking frequently until you get the 12 psi. This is assuming that you have two floors above the basement that are heated. If you have three floors then bring the pressure to 15 psi. Note that while you are doing this the pressure in the boiler may also come up and if it does you will need to drain some more water to drop it back to zero.

If you can't raise the pressure in the expansion tank AND keep the boiler pressure at zero then the expansion tank is toast and you need to replace it. If you do replace the tank I strongly advise installing a 1/2 inch nipple, ball valve, nipple, and tee in the bottom of the air purger device and then another nipple, ball valve and plug in the side of the tee before installing the new tank. This will allow you to isolate the tank from the rest of the system for testing and replacement if necessary. I notice your tank has a date of '04 on it so most likely it is not the originally installed tank.

If you get the bladder to hold air AND the boiler pressure to stay at zero, go make yourself a sandwich and relax for an hour. After that rest take another pressure reading on the bladder and check the boiler pressure. If the bladder hasn't lost pressure nor the boiler gained pressure your expansion tank should be okay for the time being. (No guarantees it will last even another week but it should.) If this is all okay then open the make-up water valve and the three valves above the circulating pumps you previously closed. (At this point you can no longer check the air pressure in the expansion tank so put the blue cap back in place.) You should hear the water entering the system and to speed it up a bit you can lift the lever on the PRV but be sure to lower the lever when the boiler pressure gets near to what you set the expansion tank bladder pressure. Once you lower the quick fill lever allow the system to settle for an hour or two to see if the pressure balances out at the 12 to 15 psi range.

If the pressure is lower than 12 psi (or the pressure of the expansion tank bladder, whichever is higher) you will need to adjust the PRV. To do so you need to unscrew the cap with the lever and loosen the locknut. Remove the little pin in the hollow threaded tube (don't lose it) and using a stubby screwdriver or a dime turn the hollow tube a half revolution at a time until you can just hear the water flowing. Wait until the water stops flowing and check the boiler pressure. Keep doing this until you get that 12 to 15 psi setting that equals the expansion tank pressure. Then, while holding the hollow tube to prevent it from moving, tighten the lock nut snugly, replace the pin and replace the cap.

Now you can restore power to the system and fore it up. This should make it all better. If you need to install a new tank be sure to check the bladder pressure before installing it.

If you have more questions just ask.
 
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Old 10-26-08, 03:19 PM
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OK Furd, I have shut off the make-up water valve and power to the boiler. I'm assuming the best way to shut of the power to the boiler is the red emergency switch. Should the pilot stay light even when that is turn off? Just curious. I'll keep you posted on the condistion of the expansioin tank. I'll probably just edit this post in a little while when I'm done today.
 
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Old 10-26-08, 06:17 PM
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OK, the pressure in the boiler dropped to zero PSI shortly after I closed the "make up water" valve and turned off power. I waited for the water to cool to around 120, but then since the pressure was already at zero I didn't really need to drain any water. I did drain just a bit after closing the three valves. I then looked to test the pressure in the expansion tank and got no reading. I tried to pump it up, but was unable to. After trying and no air going in I just checked the reading for the heck of it and it was still at zero. I tried this several times, but got no pressure reading, but no water came out also. Is it possible for it still to be toast even with no water coming out of the tank? Why would I not be able to pump it up? The tank sounds rather hollow.

If the tank is toast, how do I got about replacing the tank? I know you spoke of installing a 1/2 inch nipple, ball valve, nipple, and tee in the bottom of the air purger device then another nipple, ball valve and plug in the side of the tee before installing the new tank. Can you explain to me more about this. I don't know what a 1/2 inch nipple, ball valve, tee and plug are. Could you let me know those part names?

I'm assuming if I'm going to replace the tank to turn off the power to the boiler and shut the make up water valve like last time? Anything else I should know before attempting this? I'll probably think of something else before I attempt it, but if you could get me started that would be great. Can I buy a tank at Lowe's or Home Depot? Do you think the size and model I have now are adequate for my house? My house is one and 1/2 floors.

Thanks,
Pendo
 
 

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