Steam boiler turns on for awhile then turns off

deyrup

My steam boiler will turn on for about half an hour then turn off for hours without reaching the settings on the thermostat.

Check thermostat:
I checked the thermostat and when I increase the temperature above room temperature I hear the thermostat click and if I am downstairs I hear the boiler click. The thermostat is set to 70, but the temperature reads 60 without any response from the boiler.

Check power:
I double checked that there was power to the unit. I have circled the two places I checked for power on the boiler in the attached image; I see 120v with my multimeter. One spot is out of frame, but is the box leading into the unit

Check pilot light:
Pilot light is on all the time and stays lit.

Check sight glass:
I thought the sight glass might be off and that the low level water cutoff might have been triggered, but when I emptied water from the boiler the sight glass went down to zero as the boiler emptied and filled back up when I manually refilled the boiler.

Check low level cutoff:
I have checked this function has worked in the last month or so when the heater turned off due to low water (it was at about 1/4 full at the time) and then seeing the furnace turn back on when I refilled the boiler, but I haven't been able to check it by manually removing water to see if the furnace turns off. I know the level it is filled to currently is above the low water level cutoff (about half full is greater than the previous low water level cutoff I previously observed when it turned back on when it was >1/4 full). When I turn the valve marked empty boiler in the water level test picture in either direction I am unable to empty the boiler, except for once last night and I am not sure what steps I did to get that to happen. I thought the ball valve on the side was the blow off valve for the low water level cut off so I opened that valve and a bit of black sludge came out and then nothing more, so I am uncertain what the valve is for (see water level test picture). I do notice a very slight bouncing during the heat cycle (~1-2mm) and after the heating cycling ends the water level does go back up more significantly ~2in, but the water level never goes below the cutoff as far as I can tell from the sight glass.

Check pressure:
I checked the pressure levels throughout the heating cycle and it goes up to 15psi during the heating cycle and stays there until the boiler shuts off.

Anything else I should be checking? I did have a plumber out to check it, but he kind of scratched his head and said a bunch of things could be wrong with it, and didn't do anything. To be fair to him it was one of those random times where it was working.

nicholas bonham-carter

If that is a mercury pressuretrol, it will only function properly when it is level.
Take the cover off, and take a picture of the interior.--NBC

acwagner

Also, remove the pigtail for the pressuretrol and check if it is clogged.

Does your pressure gauge go back to zero when the boiler is off?

Jamie Hall

15 psi?!??! That's way way too high. Like about 10 times what it should go up to.

While it's possible that the pressure gauge is inaccurate -- those gauges aren't known for accuracy -- it's doubtful that it's that inaccurate.

However, while the pressuretrol (the blue box on the pigtail) is set too high, it's also not set that much too high, and therefore either it isn't seeing the boiler pressure or it's defective (or flat out broken). It's also well off level, and if it's an older unit they are very sensitive to level -- but it's not that far off level.

The curly pipe -- pigtail -- which connects the pressuretrol to the boiler may be plugged up. I can't really tell, of course, but you may have enough clearance to disconnect the wiring from the pressuretrol (turn off the power first!) and then unscrew it from the top of the pigtail. Then you can unscrew the pigtail from the boiler and see if it -- or the opening into the boiler -- is plugged.

The item labelled "no idea what this is" in the WaterLevelTest picture is the safety relief valve. Judging from the pictures -- a little hard to tell -- the valve marked "sludge came out" is most likely for skimming the boiler; the tapping into the boiler looks as though it is above the water level, so it's not surprising that nothing came out. The valve marked "empty boiler" should do that; if nothing comes out, the chances are that it is solidly plugged with sludge.

On the whole, it looks as though the boiler was installed moderately well, which is a good thing. I suspect that it may not have had the maintenance it needs, however, and probably should be thoroughly cleaned -- both water side and fire side -- and the controls checked and the burners properly adjusted. That really is a job for a competent steam man (not a plumber!), and I would suggest you arrange to have it done as soon as possible.

Where are you located? Its possible we know someone in your area whom we could recommend.

deyrup

The pressure gauge currently reads 2psi. The heat went off about an hour ago and there is still a bit of heat left in the system, so I am not sure how long it will take for it to go back to zero. I have attached pictures of the pressuretrol. I thought that residential boilers are supposed to be between 15-25psi? You can see where I read the pressure levels on the sight glass test picture. I haven't changed any of the pressure settings and just left them at the default lowest. I guess that contradicts what the pressure troll says in that it is set to .2 psi. I am located just north of Boston. We recently bought the house so we don't know what kind of maintenance was done, but judging from the state of other things I am doubtful that much if any maintenance has been done.

neilc

thinking / pretty sure that pigtail is clogged,
shut the power off,
take the wires from the Ptrol,
take the Ptrol from the pigtail,
you can try blowing thru the pigtail back into the boiler,
if you can't blow,
take the pigtail from the boiler,
check that nothing is blocking the hole into the boiler,
and clear the pigtail, or replace it,
when you reassemble, add a little water to pigtail before reattaching Ptrol,

JUGHNE

There may be heat left, but the steam pressure is certainly down to zero.....and the gauge should be as well.
Water boilers might be between 15-25 PSI......not your steam boiler it should not exceed 2 PSI.
That pressure relief valve ("no idea") should open at 15 PSI as it should say on the little tag attached to it. You do not want that to open, 15 PSI of steam will fill the room and be a memorable event.

If that pigtail is plugged the pressure control will not sense the actual pressure inside the boiler and do it's on/off job.
Sludge in the pigtail can "capture" a slug of pressure and fool the control that it should stay off.

The low water cut off relies upon a conductive probe into the water. It can be fooled by sludge.

Your boiler drain valve must be sludged up and not draining.

Any one who showed up for repairs/service should have checked the pigtail and low water cut off probe.....then scratch his head.

Pictures of your thermostat, side shot of the boiler piping on the left and clear shot of the boiler drain, please.

Jamie Hall

If you are looking for a good contractor in your area, I recommend Ryan at @New England SteamWorks . Busy busy, but one of the best. And it seems to me you need him...

deyrup

The pig tail is definitely clogged. I couldn't pour water through it. I have attached images of the thermostat, drain boiler piping and the boiler drain.

JUGHNE

If you get the pigtail open and also the port where it is screwed into the boiler, prime the pigtail with some water, then you should see a difference in operation.
If you remove the gauge, again check the boiler port and the inside back port of the gauge for sludge.

If your water fill is connected at the tee of the boiler drain, you may be able to open the drain and by operating the fill valve open and shut you might blow out the drain valve.
If you get it open drain out sludge as possible.
Then rocking the fill valve again you may loosen more sludge in the bottom of the boiler.
Do not add water when the boiler is hot.....only cooled down to where you can put your hand on the inlet pipe on the other side of the boiler.

deyrup

Update:
Unclogging the pig tail seemed to have fixed the problem. If anyone else ever needs to unclog a pig tail I recommend just buying a new one; it isn't worth unclogging them; it looks like they are ~$20 on Amazon. It took over an hour to unclog it.

One thing I don't understand though is that shouldn't unclogging the pigtail have caused the pressuretrol to trip if it wasn't tripping before? Either it was a complete jam in which case no pressure would have been read by the pressuretrol, or there was a narrowing of the tube causing the pressure to read as lower due to Bernouilli's principle. I would think that unclogging the pigtail would make it more likely that the heat cycle would shutoff if there were pressure issues, which didn't seem to be the case. Am I misunderstanding something here?

The pressure gauge on the side of the boiler now reads 10 PSI which is also confusing. I am assuming that the pressure gauge is malfunctioning and the pressuretrol is working, but hopefully when the pros come to service it they can explain why the pressuretrol doesn't cut off whenever the gauge says .5 PSI which is what the pressuretrol is supposed to cutoff at.

I asked @New England SteamWorks too come out and do some maintenance (it is New Year's so they haven't gotten back to me yet, but hopefully will hear back from them) I will do another update after maintenance.

Jamie Hall

Bernoulli's principle only applies to moving fluids -- and the fluid (steam) in the pigtail isn't going much of anywhere. So what the clog does do is keep the pressure change on one side from being sensed on the other side once it is really clogged -- and the change from pretty horrible to fully clogged is abrupt and takes only a little more junk -- so something can appear OK one day, and be hopeless the next.

What does that pressure gauge read when the boiler is cool?

deyrup

The pressure gauge read zero when cool, which suggests that the pressure gauge is at least somewhat accurate, but the pressure safety valve isn't spewing water all over my floor either. I looked for a tag on the pressure safety valve to see what PSI it would trigger at and didn't see one.

I think I understand what happened with pressure; if we increase the resistance by narrowing the tube then the overall pressure will go up, just not in the space where the narrowed tube happened.

EzzyT

That near boiler piping needs some serious attention. It’s gotta be redone.

Fred

@deyrup , the .5 PSI on the Pressuretrol scale is the "Cut-IN" pressure not the Cut-Out pressure. When the Pressure shuts the boiler down, that Cut-in is when the Pressuretrol will allow the boiler to fire up again.
On the inside of the Pressuretrol, there is a white wheel. It should be set to "1". That is an additive Pressuretrol so the Cut out pressure is the Cut-in setting plus the Cut-Out setting or 1.5 PSI. Those pressuretrols are not terribly accurate so if it allows the pressure to build past about 2PSI, it needs to be re-calibrated. If that's the case, post back and we will provide the calibration procedure.

deyrup

@Fred the cut out differential is set to 1. @EzzyT Are you talking about the suspect duct tape that someone used on the pipe?

EzzyT

@deyrup No I’m referring to piping layout itself. That’s where I would start first.

neilc

did you poke the pigtail's nipple clear back into the boiler ?
and was the pigtail loaded up to the top under the Ptrol?
maybe smutz is also clogging the bottom of Ptrol(?)
if so, poke and wipe carefully, there's a diaphragm there that you don't want to compromise.

deyrup

@neilc The pigtail didn't connect directly back into the boiler, there was a secondary connection from the boiler to the pig tail. The connection had sludge which I cleaned out. The top of the pigtail was clean going into the pressuretrol

neilc

surprised you're still hitting 10 psi , , ,

neilc

you were able to run water thru the pigtail, or blow thru it, right?

deyrup

yes the pigtail was initially completely clogged, but after about an hour of scrubbing with a zip tie and water I was able to get water to flow through it without any issue

Fred

I doubt the pressure is at 10PSI. Those 0-30 PSI gauges are worthless, especially if they are old. Also, that gauge is on a separate tapping and not on the same pigtail as the Pressuretrol. That tapping or the orifice on the gauge may be gunked up with crud and holding pressure as well.
You need a 0-3 PSI gauge on that boiler, on a Tee off of the pigtail. Here is a good one:
https://www.pressureworx.com/product/low-pressure-gauge-25-0-3-psi
And, when you get a new gauge, here is the procedure to re-Calibrate the Pressuretrol:
Inside the Pressuretrol, right below the micro switch, there is a pivot arm. At the end of that arm you will see a screw pin that is activated by the diaphragm at the bottom of the Pressuretrol. If you look very carefully at that screw pin, you will see it actually has a tiny (I mean tiny) hex head on it. It takes a .050 hex wrench and you can turn it clockwise (Towards the bottom of the Pressuretrol to decrease the Cut-out pressure or counter clockwise to increase the cut-out pressure (which none of us want to do but who knows, your Pressuretrol may be really screwed up!). Turn the power to the unit off first. You may find the first attempt to turn that screw a little bit stubborn (relatively speaking) because it has some Locktite on it but it does turn. Don't turn too much, a fraction of a turn goes a long way towards getting it adjusted where you want it (maybe 1/32 inch turn to start with). You may need to play with it to get it exactly where you want cut out to be.

If you can't turn the little allen screw because of the Locktite, use a small soldering iron to melt the Locktite.

neilc

how stiff is that ring of grease on the Ptrol pivot arm?
poke or scrape most of that clean,
a little shot of WD40, or ??
it's on both sides,
then gently exercise that pivot arm, just to hear it click each way a few times