Replacing a pressure relief valve


Old 09-25-18, 10:27 PM
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Replacing a pressure relief valve

Older furnace needs to have its pressure relief valve replaced.

The existing valve is rated for 550,000 BTU/Hr but all the ones I have found online seem to cap at 510,000. I assume since the furnace output 90,000 BTU/Hr that the ones rated 510k are fine?

Is there a preferred brand I should look for based on quality?

Lastly, the expansion tank looks original so its gotta be 40 or so years old. Is it wise to replace that as well while we're at it.

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Old 09-25-18, 10:45 PM
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Thread moved to the boiler forum. A furnace is hot air.
Old 09-26-18, 07:16 AM
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Anything over the boiler input rating will be OK. It's 112,500 Btu/hr, not 90,000. The most common brand is Watts, but I wouldn't worry too much.

Is it a bladder-type expansion tank or a conventional, horizontal tank? A bladder-type tank looks like a propane cylinder for a BBQ grill. A conventional tank will last indefinitely, a bladder tank will eventually fail and will require checking and replenishing the air periodically. There is a sticky on this forum that tells how.

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