Reduce Boiler Water Pressure


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Old 02-13-07, 06:11 AM
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Reduce Boiler Water Pressure

I have a Utica propane fired hot water boiler. There is a feed line from my hot water heater to the boiler. Recently, the bronze pressure reducing valve on the feed line began leaking from the top and needed to be replaced. It was replaced with a Watts. According to the metal tag on the replacement valve, the set range is 12 - 15 lbs. The operating range is 10 - 25 lbs. Now, when the water temperature on the boiler is at 185 degrees, the water pressure reads about 24 lbs. My concern is the pressure is too high. Should I be concerned? I have a two zone system with a taco circulator pump for each zone with a boiler drain just below each pump. If the pressure should be reduced, can I open one of the drains until the pressure drops to the 12 -15 lb. range. Will it stay there? Is there any other way to reduce the pressure? Thanks for your help.
 
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Old 02-13-07, 03:54 PM
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You may need to take a look at your expansion tank.

The pressure in your system will increase from cold to hot, because the water expands as it is heated. The job of the expansion tank is to take up the expansion by compressing a cushion of air trapped inside that tank.

If you have the old style tank (big, steel, above the boiler), it may be waterlogged and need to be drained.

If you have the newer style diaphragm tank, it may need a charge of air, or the internal rubber bladder may have a hole in it.
 
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Old 02-13-07, 06:19 PM
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24# hot is a bit high. You can reduce the pressure by letting out a little bit of water through one of the drains. It won't take much.

For a typical 2-story residential system, 12-16# cold to about 16-20# hot is about right and within the precision of most gauges.

Assuming your autofill valve was left at the factory setting, everything should settle out ok. Possibly whoever did the valve replacement did a fast fill and didn't check the pressure once the system got cranked up. Most likely no biggie.
 
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Old 02-13-07, 06:50 PM
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24 psi is okay and won't hurt anything. That puts you at 80% of the maximum allowable working pressure (MAWP) of your boiler. Anything less than 90% of the MAWP is acceptable.

If you wish to lower the pressure you may follow the advice of of NJ and Xiphias.
 
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Old 02-16-07, 08:49 AM
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Smile Thanks.

Thanks to the three (3) of you for taking the time to reply. Your expert advice is much appreciated. Have a Good Weekend.
 
 

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