Pressure relief valve leak

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  #1  
Old 02-16-06, 11:36 AM
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Pressure relief valve leak

I noticed that the relief valve discharged about 4 ounces of water. This only happens following a period (4-5+ hours) of warm weather when there is no call for heat. Once it gets cold and the the boiler cycles on and off two or three times thats when it happens. After that everything is fine. Is this somthing I should be concerned about?
 
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Old 02-16-06, 12:04 PM
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Relief Valve

It;s rare that the relief valve itself is the cause of the problem; it usually is just doing its job of relieving excess water when the pressure exceeds 30 pounds per square inch, at which time it opens automatically as a safety measure to relieve the pressure.

First check the indicator dial on the boiler for its two readings; one reading is for boiler water temperature, the other is for BOILER WATER PRESSURE.

The pressure reading should be around 12-15 psi; when the boiler is running, the pressure may gradually rise to ~20 psi; if it rises to 30 psi or more, something else is going on in the system.

One possibllity is the expansion tank is either waterlogged or the bladder (on newer tanks) has ruptured internally & the system can no longer absorb the added water pressure; regardless of which type of these tanks you have, its job is to provide an internal air cushion so that the heated water, as it expands, is kept within safe bounds.

Another possibility is the pressure reducing valve is shot & is letting more water than needed into the boiler; PRVs are designed to allow only ~12psi of pressure into the boiler.

Another possibliity is a rupture of a domestic coil inside the boiler, allowing high pressure tap water into the boiler system.

If the pressure gauge reads high, shut off the water inlet valve that allows house tap water into the boiler system to see if that makes a change.

Please repost as to what kind of expansion tank you have; if it's the older type, has it been drained in recent months.
 

Last edited by Chimney Cricket; 02-16-06 at 12:19 PM.
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Old 02-16-06, 12:33 PM
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Thanks for all the possible causes. I am at my office now so all can add is that the boiler is a Burnham revolution, water temp is set at 210 (as specified by manufacturer) I thought the pressure was about 15. I guess since the system is only two years old that the expansion tank must be the newer design.
 
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Old 02-16-06, 01:31 PM
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Relief Valve

Check the Burnham specs at their website or any manuals you may have; 210 degrees seems much too high; the standard temp for hot water systems is 180 degrees (high limit).

There is a little gray box on the front of the boiler (aquastat); removing the cover will reveal high limit and low limit settings on adjustable plastic dials; (160 low, 180 high).

Check your expansion tank by hitting the bottom with your knuckle to see if you get a "hollow ping", or a "dull thud"; then push in the "tire valve" pin JUST FOR A SECOND; if you get water, the tank is shot; if you get air it may need further testing; often a bad tank will feel hot or warm to the touch around its bottom, & it will make a dull, thud sound.
 
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Old 02-17-06, 04:31 AM
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I too thought 210 was on the high side but when I had the unit serviced in the Fall the technician said this boiler is supposed to be set at 210. He even wrote that on the aquastat cover, so I emailed Burnham and they too said that unit should be set at 210. I will check on the tank when I get home this evening. Thanks.
 
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