MegaSteam short cycling on pressuretrol

donaldmc

Burnham boiler installed In a 80 year old house 4 months ago. When it calls for heat in the am after a 3 degree night setback, the burner runs for about 20 - 30 minutes. The system fills with steam (about 10 cast iron radiators) the burner shuts off on the 2 lb on the pressuretrol and in 60 seconds the pressure drops and the burner runs for 3 minutes and the cycle repeats until the thermostat is satisfied. 513 sq steam oil burner, sized correctly, on a one pipe steam system. Dropped header, new main vents, insulated mains, everything seems ok except for this! Any ideas would be greatly appreciated.

Dave in QCA

This is Normal

When the boiler runs an extended time and the radiators become fully heated and the pressure builds up, the pressuretrol shuts the boiler off until the pressure drops, which will occur quite quickly, as you have reported. This is completely normal. In most normal cycles, except when it is extremely cold, this will not occur.

nicholas bonham-carter

Short-cycling boiler

You could always have your heating tech reduce the firing rate of the boiler, and see if that would more closely match the load.

Nirvana for us steam users is a system whose firing rate is so closely matched to the load, that no excess pressure will be developed, and the boiler will run for as long as the thermostat calls for heat, without any cutoff from the pressuretrol.--NBC

donaldmc

Can the short syscle be changed

Is it possible there is a small steam leak making it cycle this short? It's 1 minute off, 3 minutes on. If the system can hold the pressure longer (Stop small leak ) wouldn't that lenghen the off cycle? The opposite is true, if I remove a steam vent off a radiator (large leak) it doesn't cycle because the steam can't build up to 2 lbs.

Jamie Hall

It isn't cycling in one minute

because it's leaking, it's cycling in one minute because the steam is condensing.  Which is what it is supposed to do.



The opposite certainly is true -- if it has a leak it won't build pressure.  But you really truly don't want a leak, I wouldn't think.



The boiler will do that recovering from a setback; it's the nature of the beast.  Read Dave's answer again.

fixitguy

Setbacks?

I am still doing research on whether it pays to setback a steam system. My inclination is that it doesn't. Takes so long to heat the cold soaked building that it uses the same energy that it would use maintaining a steady temperature [which is more comfortable]. As for the short cycling, have you tried running your water level higher? That may do the trick. Remember, the normal water line is wherever you make it.