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Boiler adjustment & service questions from newbie

I have a one-pipe steam radiator system in an 80-year-old 2,500 ft/sq two-story house. The boiler is a 6-year-old Peerless, installed by the prior owner. The steam pipes and radiators throughout the house are all original to the house and have not been replaced or disturbed. Air vents on the radiators seem to be functioning properly. Some look ancient and some look like recently installed Varivalve vents, all set to the minimum position. I have checked radiators with a level and shimmed a few that need a degree or two slope back toward the inlet pipe. Regardless, there is still a wee bit of water hammer on two radiators. Some idiot removed all the insulation on the steam supply pipes that run from the basement and into and through a crawlspace to supply three radiators in a first-floor, one-story bedroom at the back of the house above that crawlspace, probably in a misguided effort to warm up the air in the crawlspace. I wrapped those steam supply pipes in heavy fiberglass insulation, and that seemed to lessen the water hammer in that room. I also sealed off all the foundation vents into that crawlspace and encapsulated the entire dirt-floor crawlspace, following proper crawlspace encapsulation procedures. Wow. No more musty crawlspace air entering the full basement and infiltrating the house. The house has a full basement, and the boiler is in the full basement, I should note. The crawlspace is under a one-story first-floor bedroom at the back of the house. This is my first winter, and I have questions about system maintenance and steam pressure.

After reading this forum quite a bit, I looked at the pressure gauge that sticks direction out the right side of the boiler, near the pressuretrol and sight tube, and near a pipe that comes out of the boiler mid-height, with a ball valve for flushing out water. When the boiler would run for a while, I noticed that the pressure gauge was reading about 12 to 13 psi. I observed this on many occasions.

After reading on this forum that steam pressure should be 1 to 2 psi, and that the safety valve is designed to blow at 15 psi, I read further, and saw instructions for setting the pressuretrol. When I opened the cover (Honeywell), I saw that the white adjustment wheel inside was set at about 1.5 (there is no 1.5 marking, but the wheel was set between the 1 and the 2 markings). The little slider adjusted by the screw mechanism was set to about 1 or slightly higher.

Following suggestions on this forum, I re-set the white plastic wheel to 1 and the slider indicator to 0.5.

Now, after the boiler has been running a few minutes, I see a reading on the pressure gauge of about 6 to 7 psi. When the thermostat tells the boiler to turn on, the flame burns about 3 or 4 minutes, and the pressure on the gauge goes from 0 up to about 6 psi or sometimes a wee bit closer to 7. After running at that pressure for a bit, the boiler shuts down and stays off for four minutes or so. During the time that the flame is not running between cycles, the needle on the gauge stays at about 6. Then the boiler comes back on and runs again for four or five minutes. In those on/off boiler cycles, the pressure gauge needle stays at about 6. In milder temperatures, after the room temperature reaches the setting on the electronic thermostat upstairs, the boiler might stay off for a good while, until the room temperature drops enough to require the boiler to make more heat.

The furnace has a sticker indicating that the prior owner had professional service about 15 months ago. I do now know what the technician did, or if the technician was proficient in old steam radiator systems.

Anyhow, as far as maintenance, once a month or so, when the boiler is off and there is either no heat or just a tiny bit of warmth on the steam outlet pipes of the boiler, I have flushed out several five-gallon buckets of water, using the flush ball valve near the sight tube and pressuretrol. The first few times I did that, the water coming out was murky brown. I would flush until clear water came out. Subsequent monthly flushings now produce mostly clear water with some brownish discoloration. The water in the sight tube is nearly clear, although it has a wee bit of brown coloration.
The boiler has an automated water feed system on the left side of the boiler. When I have flushed out a good bit of water from the boiler, that water feed system has turned on to let new water into the boiler. However, it does not fill the sight tube to the recommended fill mark that is marked on the side of the furnace. So I have pressed the manual feed button on the water feed auto-valve to let in more water until the water in the sight tube is perfectly level with the proper water level indicator marking on the side of the furnace.

I have read about the need to sometimes clean the copper pipe loop that the pressuretrol is attached to, but I have hesitated to remove the pressuretrol to clean that pipe, until I educate myself a bit more.

On the left side of the boiler, toward the back, where the return pipes drop down to the floor to return condensate to the furnace, there is a garden-hose-type spigot. I assume this is to be opened periodically to flush out debris and corruption that has trickled back down as condensate returns to the boiler. I have not flushed this yet, because I need to educate myself more on how to properly flush that return line.

So, to sum it all up, my questions include the following:
1. If my pressuretrol is set to 1 on the white knurled wheel inside the housing and the slider indicator controlled by a screw adjuster is set to 0.5, is it OK that the pressure gauge that sticks directly out of the boiler on the pressuretrol side of the boiler shows about 6 psi when the boiler has been running for a few minutes? That pressure gauge returns to zero pressure when the system has been off a while, so at least I know that the needle is not stuck, but I am not sure of the accuracy on the reading of 6 psi. From everything I have read, it would be best to see a reading of 1 to 2 psi on this type of one-pipe system.
2. Why does my automatic water feed system not refill the boiler enough so that the water in the sight tube is level with the proper water feed level as marked on the side of the boiler? Can I adjust the water auto-feed unit so that it always raises the level to that mark, or is it better for me to just manually add water to the proper level by pressing the button on that auto-water-feed unit to let in enough additional water to raise the water to the proper level?
3. On a six-year-old Peerless boiler, is it time to remove the pressuretrol from the looped coper pipe to clean out that pipe? If so, what is the procedure? Is this better left to a pro? (I have extensive auto and motorcycle repair and restoration experience, formerly had my own hobbyist metal lathe and mill, and have very good electrical and plumbing skills at the highly advanced amateur level. My mechanical skill level is very high, but I also know when I should stop, read, educate myself, and move forward only when I know the precise procedures to follow).
4. What is the procedure for flushing the condensate return line at the floor level, through the hose spigot valve?

Meanwhile, I will order a copy of The Lost Art of Steam Heating.


  • BobC
    BobC Member Posts: 5,471
    The pigtail between the presuretrol and the boiler can fill up with crud, it should be checked once a year to make sure it isn't plugged. When the boiler is cool or just warm you can do this yourself if your willing and able.

    Shut the power to the boiler off, open up the pressuretrol cover and remove the wires from the terminals (make note of what goes where), remove the wire harness from the pressuretrol. Using a wrench n the brass fitting of the pressuretrol twist itCCW and remove it. Check the base of the pressuretrol and make sure the little hole at the base is clear.

    Now remove the pigtail from the boiler and run some water through it to make sure it is clear, you can boil it in some vinegar and water to help clean it out, flush it with clean water when you are done.

    Put everything back together using teflon tape on the threads and wire it back up, set the dial to 1 and adjust the tab as low as it will go with the screw on top of the case.

    Run the boiler and see if the pressure is more reasonable. Be warned that pressuretrols are all over the lot at the low end and 0-30 PSI gauges really are not very good at the low end of the scale. You may have to go through a calibration procedure to get that pressuretrol working right.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • stevieg
    stevieg Member Posts: 19
    Agree with Bob, I think you have a pigtail that's mostly plugged. This can be very dangerous. Follow what Bob said and Be very careful to relieve the pressure from the boiler before starting the repair. While the boiler is down and the pressure is off line, I would change out the pressure gauge as well. They are pretty cheap and will be well worth the money. Remember Cut in + differential equals cut out. A residential steam system running at the pressure you have described can be dangerous, 3 lbs will usually do the trick. The higher the pressure the slower the head. Good luck.
  • Fred
    Fred Member Posts: 8,542
    A Pressuretrol is, in fact, as safety device. Ideally you want the boiler to turn off because the thermostat (room temp) has been satisfied. Not because the Pressuretrol shut the burner down on pressure. Do as @BobC instructed you, above and add a 0-3 PSI gauge to the boiler. You can add that, using a "Tee" fitting onto the same pigtail the Pressuretrol is mounted on. Below is a link to a gauge many of us use. While the Cut-In (scale on front of the Pressuretrol) should be set to .5 PSI and the white wheel set to "1", anything over 2 PSI is not helping you heat your house. actually it is counter productive. If, after cleaning the pigtail and installing the new gauge, the pressure is still over 2 PSI, the Pressuretrol needs to be re-calibrated. If you are comfortable doing that, we can give you the procedure. If you are not comfortable, let a steam Pro schedule maintenance for you and ask him/her to re-calibrate the Pressuretrol.