Ease of replacing boiler pressure/temp gauge?


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Old 02-22-17, 11:23 AM
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Ease of replacing boiler pressure/temp gauge?

After rigging up a pressure gauge to test on some of my return lines of the boiler, I can see that my actual boiler pressure gauge is off quite a bit. Is it easy to replace? From what I understand, I just need to turn off the system, let it cool, and pressure down then just unscrew the old and screw in the new? Anything I'm missing? Obviously some air purging may be needed once it fills back up.

For the rest of this winter I just plan on leaving the rigged up gauge on, and opening the valve to check it when needed. Then once the heating season is over replace the boiler gauge just so I know I have an accurate reading on there.
 
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Old 02-22-17, 11:36 AM
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Unless the boiler can be directly valved off, any water above the location of the gauge, both in the boiler and associated piping, will drain out of the opening as well as suck air in.
 
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Old 02-22-17, 12:38 PM
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I do have shutoff valves for the supply and return side of each zone, plus a shutoff right before the incoming water near the pressure reducing valve, so I should be able to isolate the boiler a bit before depressurizing.
 
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Old 02-23-17, 07:39 PM
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If you do not have one already this would be a good time to put a shut off valve on the expansion tank 1/2” NPT fitting. Especially if there is a leak somewhere, closing it, the water feed valve and letting out as little water is instant depressurization.
 
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Old 02-24-17, 07:54 AM
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If you are going to add a valve for your expansion tank, use one of these:

40612 - Webstone 40612 - 1/2" Threaded Pro-Pal Ball Valve w/ Hose Drain.

Not expensive and makes checking tank pressure or draining simple without draining the system.
 
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Old 02-24-17, 05:20 PM
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I
just plan on leaving the rigged up gauge on, and opening the valve to check it when needed.
I would prefer to leave the valve open. Shutting it, and isolating the gauge, may expose the gauge to over or under pressure due to thermal expansion or contraction of the trapped water.

If you cool down the system, valve out the expansion tank, isolate the boiler as much as you can, and depressurize it down to, say, 5 psi or so, you should be able to change the gauge without draining. First, get the replacement gauge's threaded male connector coated with pipe dope. Remove the old gauge, plug the female hole with your thumb, and then quickly screw in the new gauge.
 
 

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