Last winter my gas-fired boiler refused to fire, even after replacing the
low-water cutoff switch, the pilot generator, and eventually the gas valve.
After poking and prodding everything that seemed to move, I lifted the indicator
on the steam pressure cutoff box and the burners finally lit off. When I took
my fingers off the indicator, the burners went out. "Hmmm", thought I. "Another
adjustment that probably went awry."
I turned the screw at the top of the switch box until the burners lit and stayed
lit and congratulated myself on my brilliant deduction.
I awoke the next morning to a great whooshing noise emanating from the basement,
and discovered the room full of steam. The relief valve on the boiler was open
and gushing steam "everwhar". Ot was so damp down there, the flourescent lights
wouldn't go on. After filling the boiler with cold water to bring the pressure
down, and exhaustiing the steam outdoors with a fan, I turned the cutoff switch
screw back to where I thought it was originally. Of course, the boiler wouldn't
fire again, and I finally discovered that that curly pipe going to the bottom of
the switch box was plugged with rust. I replaced the pipe, and the furnace has
been working dependably since then.
However, one thing concerns me:
The pressure gauge on the boiler reads around 4-7 lbs when it's really
humming since we've had this cold spell, and I think the cutoff switch isn't
adjusted correctly. The boiler never exceeded 2 lbs. back in the days before
things started wearing out on the unit.
Can anyone enlighten me as to the proper adjustment procedure for the steam
you might search for the manuals online thru www,google.com for not
just the main boiler but the individual controls. read them. name them
with a sharpie marker and name the pipes and arrow them for direction
of flow. if you post some nice picture links here at alt.home.repair
somebody may recognize the general operation of your system. but you
should hire a local boiler old-timer because the balancing and setting
of the devices in your system varies with the design for your home's
layout. take notes. make signs on the devices, and develop an annual
checklist for your system. also dumping cold water into some systems
under some conditions can damage your boiler.
Most boilers operate in the range you have it, or a little lower. Maximum
is usually 10 pounds, the safety low off is usually set at 15 pounds
pressure. Higher pressure means more heat is being carries to the
radiators. If 2 lbs. worked, set it back to that range.
I don't know the specifics of your boiler. Some have a high fire and low
fire range. That means the unit starts out on high fire, reaches a set
pressure, then goes down to low fire and stays there until a drop send it
back to the high fire position. You may or may not have that.
One caution here. The overpressure you had may have been a PITA, but did
not do any damage to the boiler. However, letting in a lot of cold water
can cause problems, such as cracking cast iron from stress. Then you'd have
a very expensive mess on your hands. Never put cold water into a hot
Ouch! The PressureTrol on Most steam boilers should be set per another
reply with 0.5 psi cut-in and 1 psi rising differential cut-out (or if it
does not go down to 0.5 it may be a control that you set to 2 psi cut-out
and 1 psi decreasing differential cut-in). In other words it should
operate between 0.5 and 1.5 psi (not more than about 2 psi). Systems with
a Vaporstat run even lower (in ounces of pressure).
Most steam radiator air vents only work well up to 1.5 to 2 psi. Any
pressure higher than that just makes the steam heavier, slower, and less
efficient (costs more money).
If your pigtail was plugged, your pressure gauge might be too. When I
bought my home, the steam pressure was cranked way up (causing loud
hissing of air vents), a snubber on the pressure gauge was blocked, but
the gauge itself was stuck (would not go to zero when removed). Since I
replaced the gauge and set the pressure as low as it goes, it has worked
Depends on the system. I have a low pressure setup that runs between 5#
and 9# with a cutout at 11#. I also operate two boilers at 110# with
cutout at 120#. They modulate depending on load. We use about 8 to 10,000
gallons of water a day to make steam.
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