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Posted by HeatPro on February 18, 2006 at 14:03:11:
In Reply to: Why two pressuretrols? posted by Paul Williams on February 18, 2006 at 12:38:25:
Two pressuretrols are better than one. When one fails you have the other. A commercial boiler HAS TO have two pressuretrols, one manual reset, so you are better off.
As to the reason for a pressure control, you have your hat on backwards. The thermostat SHOULD turn the burner on and off in a properly operating steam system as a thermostat IS an operating control to turn the burner on and off, not a safety control as is a pressuretrol.
A finely-tuned steam system will have the pressure slowly come up to 1 psig, giving time for the air to leave through the vents, then maintain the pressure by balancing the fuel input with the radiation output; hopefuly, never reaching the pressuretrol cutoff setting.
For some reason, some people think that they should have a heating system run like a runaway car with the gas pedal all the way to the floor and have to turn the key on and off to regulate the average speed. The cruise control puts in just enough fuel to make the car stay at speed, so the fuel input in a steam system - a steam system has only one speed.
In another issue: Check off the days that the steam system DOESN'T become a sprinkler system when the auto water feeder solenoid gets a bit of dirt in the seat and feeds the water out of the air vents. An annual service to check the condition, flush the lines, clean the filter before the solenoid valve seat, or change a solenoid can give some security about the floor condition. Some people as in getting up the highway, like to take many chances so they don't have to notice the details until it is too late.