Steam Boiler Pressure ???

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  #1  
Old 11-20-09, 07:02 AM
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Steam Boiler Pressure ???

Hello, i'm hoping someone can help me out with this .....
my question is in regards to pressure in my steam boiler
i have a weil mclain steam boiler rated 15psi now i've been
told that the pressure inside the boiler should be no more then 1/2 lb but i've knoticed it has been running between 1 1/2 to 2 lbs ....i've just replaced the pressure switch and pigtail ...is it a problem that the boiler is running higher then suggested ???? if so ...what should i look for to correct this problem ???? any help would greatly appreciated
 

Last edited by gptrow; 11-20-09 at 07:49 AM.
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Old 11-20-09, 12:33 PM
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Sounds right to me. The boiler should shut down around 2 psi and come back on around 1/2 psi. If it is operating that way leave it alone.
 
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Old 11-22-09, 08:53 AM
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You have settings in your control that are adjustable, depending on what brand you have. If you have the instructions it will tell you what the formular is. For example is it a McDonald Miller or a Safeguard.
 
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Old 11-27-09, 05:17 AM
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Thanks for all of the advice .......i did call well mclain
i do believe the cut in and the cut out ......needs a little tweaking ,they told me that the settings should be cut in .5lbs
cut out 1lb but i can adjust the cut out up to a 1 1/2 lbs
whats happening now is the pressure switch is kicking off the boiler .....while the thermo is still calling for heat ...so i'm hoping raising the settings will help ........once again thanks to all for the advice
 
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Old 11-27-09, 07:19 AM
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The higher-than-needed pressures you are experiencing are because they are limited to the settings of a typical pressure control device that is supplied with most every boiler sold in the US.
A better and more sensitive regulating device is called a vaporstat which will allow the boiler to run in ounces of steam pressure rather than pounds.
 
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Old 11-27-09, 09:11 AM
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the pressure switch is kicking off the boiler .....while the thermo is still calling for heat
This might not be abnormal operation.

I will add that you might want to ensure that the piping is properly insulated, the main vents are all working, as well as the vents on the radiators.
 
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Old 11-27-09, 09:36 AM
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You didn't say if this is a new boiler. If it is they may have oversized it. If the boiler is making steam faster then it can deliver it, it will go off on pressure as a safety just like a water boiler goes off on high limit but will come back on when the limits go down. You really don't want to raise the pressure too much.
 
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Old 11-27-09, 09:44 AM
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The longest run cycle will be when the thermostat first calls. When it hits pressure the boiler will shut down. The cycles from that point on will be shorter than the original.
As Trooper stated make sure the mains are insulated, good operating vents. This will also affect the cycle rate. How long is the boiler off before it comes back on after it shuts off on pressure?
Never exceed 2 psi on the pressure control.
 
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Old 11-28-09, 10:02 AM
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thanks to all for the advice ....i really do appreciate it ......well last night ...when the thermo called for heat ....which we set it at 70degrees on cold days ....the boiler kicked on .....ran great checked all rad. valves put new main vent valves in ....
i did tweak the cut out alittle ......is was at 1lb turned it up to
about 1 1/4 lb ....now instead of the pressure switch kicking off the boiler .....the thermostat does ...which is the way it's been doing for the past 10 years .....my problem before was
if i set the thermo at 70 the boiler would kick on ,,,,,ok great ...then when the thermo would read say 71degrees it would reach it set point and stop calling for heat .....
in this instance it wouldn't the thermo would still be calling for heat .....now i know there is a delay ....before the thermo kicks off ....but this is not the case ....the boiler would keep running because the thermo was still calling for heat i would have to manually go over to the thermo and kick it down a couple of degrees so the boiler would kick off ....if not the boiler would kick out through the pressure switch ....so i was starting to think that maybe the thermosat is out of calibration called honeywell they did sometroubleshooting they couldn't figure it out soooo now they are sending me a new thermostat .....i hope this makes sense ...THANKS TO ALL THAT HAVE OFFERED THEIR HELP .......oh the boiler is about 30years old had a new gun installed about 2 years ago plus a new pressure switch ,pigtail ....low cut off cleaned in perfect condition boiler is blown down every other week .....
 
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