boiler not heating radiators, bad vapostat settings?

rhodebump

Thermostat is calling for heat, boiler turns on, but it shuts off after 30 seconds. It does turn on intermittently for short periods, but not enough to heat the building.

I have called the pros on multiple occasions but I have not been successful with getting a running system and trying to understand things myself at this point.

My vaporstat (diff subtractive) main is set for 1 PSI with a diff of 12 OZ. Picture is below. Is this a reasonable setting? The main setting seems to be too low to me. What would be good settings to start with? I think I want to raise the main to 2 PSI

Thank you!!!

Jamie Hall

Nothing wrong with the vapourstat settings -- assuming that it is accurate, which isn't always the case. However, the fact that the boiler turns on, runs for 30 seconds, and turns off, then turns on again intermittently tells me that it probably isn't the vapourstat.

And DON'T set it to 2 psi. 1 psi is ample for most buildings. However, just to check, you might set the differential to 6 ounces instead of 12. If the vapourstat is messing with things, the boiler should turn back on sooner that way.

The only really reliable way to check the vapourstat is with a low pressure gauge on the same pigtail (0 to 3 psi) -- not a bad investment.

Where is your water level in relation to your low water cutoff?

rhodebump

I will check the water level, but I have not had to hit the LWC switch in a long time. When I get that condition (LW), the boiler is down for good until I reset the LWC switch. That is not occurring now.

Jamie Hall

You only have one low water cutoff, and that one manual reset? Unusual.

Hap_Hazzard

What kind of LWC? What you're describing sounds almost like normal operation for a CycleGard.

mikeg2015

I could see normal surging at initial steaming triggering a LWCO. Maybe probe needs cleaned.

In order to determine which device is shutting down the burners, you need a voltmeter and/or a jumper wire. But before using a jumper on any safety device, you need ot be sure the other safety devices are working and you have a reliable pressure gauge.

This type of issue is one reason I wish they made an inexpensive monitoring board for boilers with a terminal strip for all the safety devices and indicator lights for their status. Would make things easier for homeowners with simple issues... similar to what modern gas furnaces have. Intermittent pilot controls have some of this with a status LED.

ratio

I've had luck wiring a fuse with a minuscule rating in parallel across the contacts that I suspect to be opening. IIRC I've used 600mA (see below) successfully in the past, but basically as small as possible. When/if the contacts open, the fuse will blow. It's not effective on contacts that are expected to open during normal operation unless you're there to see it happen.

EDIT Dec07: This's been coming to mind ever since I posted it, I finally figured out what's wrong. The fuse I used was 6 mA, NOT 600 mA. Big difference. Since the fuse goes in parallel across the contacts, it is imperative that the fuse be unable to carry the current at any condition, else the contacts will be unable to open the circuit. With modern electronics, even that size of fuse may be too big to open when the contacts open, best to check with an ammeter.

Jamie Hall

ratio said:

I've had luck wiring a fuse with a minuscule rating in parallel across the contacts that I suspect to be opening. IIRC I've used 600mA successfully in the past, but basically as small as possible. When/if the contacts open, the fuse will blow. It's not effective on contacts that are expected to open during normal operation unless you're there to see it happen.

Brilliant.

rhodebump

Today i changed the thermostat (no change). I also released some water from the sight glass (what is that called?) and the automatically water kicked in and filled it back up. I double checked and i only see one LWC switch.

Here are some more pics:

Fred

Is the thermostat set/programmed for Steam at one or two cph? They come from the factory preset for forced air at 5 CPH.

rhodebump

I do not see a way to program this thermostat for steam. It's a honeywell rthl221b1008

I will read up on CPH

rhodebump

Problem solved!!! UGH!! Frustration.

After changing thermostats, resetting thermostats, changing various settings, cycling power multiple times, the solution was.
drum roll please...
..
...

Turn off all power to the boiler for 30 seconds.

I power-cycled the boiler a few times but i would just do it for a few seconds (impatience hurt me here).

Working just as it should at this point.

Thanks everyone for your advice.

rhodebump

Just to wrap it up. The next day, the same issue. Shutting off the system for several minutes did not cure it.

The root cause of the issue was the flame detector that was mounted on the burner assembly. We removed it, sanded it with a dollar bill and put it back. Boiler is running like a champ for several days now.

The flame detector had become oxidized and could not detect that the burner had been lit and because of this, it would do a shut off to prevent gas-build up (and explosive conditions).