Burner cutting out prematurely on new steam boiler

Mark Oppedahl

Looks like it was an itermittent connection in the thermostat circuit. Bypassing the thermostat at the boiler fixed the cycling. Got a new stat & tightened the connections, voila, heat. In retrospect, should have checked it sooner. Thanks for the comments.

Mark Oppedahl

Burner cutting out prematurely on new steam boiler

Hi,

We just installed a new HydroTherem VGA400 steam boiler and are having problems with the burner cutting out way before it reaches pressure. I'm thinking we just need to clean it again but don't want to miss something.

When we first fired it up, we followed Hydrotherm's cleaning instructions to add cleaner and boil the gunk out the pressure relief tap for an hour, making up the lost water with the boiler feed. Then drain, rinse with hot water, drain again, and fill. The LWCO seemed to work fine during cleaning, and when we first fired it up after we were done cleaning, all was well and we made 3 psi.

But pretty soon the water line started moving around more than I'd like, and just when things start cooking (and the water line is still way up in the glass), the system shuts down. Even though it looks like the water's no where near the low point, I'm thinking the LWCO is what's cutting the circuit.

LWCO is a Honeywell RW700A Guard Ring. It says right on it, "if the burner shuts off with a normal water level, clean the probe or check the water treatment."

I'm thinking I don't have to pull and clean the probe since it's brand new. I've tried two pressuretrols, which worked fine initially, so I'm pretty sure they're not the problem. There's no flame rollout or spill sensor. The sight glass is a bit dirty, so once again, I'm thinking cleaning is the solution.

Comments, gentlemen? Any other diagnostics?

Thanks,

Mark O, Dubuque,IA (where it's pretty cold out right now)

Mark Oppedahl

S8600 cuts out burner

OK, it's not the LWCO -- we bypassed that and the burner still cuts out. Turns out the flame is being cut by a relay in the honeywell s8600 control unit. Checked the ground & ignition cables, they're tight. Pilot assembly looks OK. Again, boiler fires fine & burns about a minute, then cuts out. Two or three more minutes, and the cycle repeats. Same whether the boiler is hot or cold. Could it be problems with venting -- backdraft from the flue for example? The looks like flue is shorter than specs call for.

tim smith

s8600

make sure you have a good ground to the unit and check that pilot gas is good during main firing. Good luck.

Blackoakbob

S8000

I agree with Tim, Mark. It's very possible that the ground is loosening up with the initial heating. Also, check the black and white lines all the way back to the power source to make sure they haven't been switched around. This can cause cycling in some boards. Best Regards.