Boiler Short Cycling - Troubleshooted but still happening

BobbyC

Gas fired burnham steam boiler keep short cycling frequently.  I removed and unclogged the pig tail and still happening.  Jumped out the tstat.  Water level is fine so shouldnt be LWCO.

Thinking gas valve by the noise it's making.   Any suggestions or additional troubleshooting ideas?

thanks

Long Beach Ed

Noise?

If the gas valve's making noise, something's wrong with either the valve, transformer or something in the circuit.  

Tim McElwain

Is this a 24 volt system

or is it a powerpile self generating system? If 24 volts what is your voltage load and no load?

BobbyC

its a 24 volt system.

not sure on the load or no load..  gonna go over tomorrow and put some meters on it.  would that be next step to make sure i'm getting 24 volts to the valve?  

gerry gill

what kind of low water cut off is it?

is it a cycle guard?

BobbyC

mconnell miller feeder.. I think the cut off was ITT....

it was installed last year so not old at all.  boiler used alot of water last year which prompted us to install it....

STEAM DOCTOR

pressure

Might be a pressure issue. Do you have any condition that might cause pressure build up (bullhead T leading to steam mains, no main air vents etc). Try setting the pressurestrol to a higher setting just for troubleshooting purposes.

gerry gill

maybe

failed vents...or overfired...or boiler oversized..

BobbyC

I jumped out the pressuretrol and it still was short cycling.

Also put it at a higher setting.  I did check and have 24 volts going to the gas valve so by process of elimination should I replace gas valve? 

Does have a main vent.  Figured if it was pressure buildup from piping configuration this would of happened before.   She has ran with no issues until this.  Slight loss of boiler water from time to time, hence we installed the water feeder to prevent from going over all the time.

thanks in advance.  

Tim McElwain

Do you have

24 volts at the valve when the short cycling takes place? If so then it may be the gas valve, if not then one of the controls is causing this to happen, check the pressuretrol and make sure pigtail is clean and that control is working at correct set pressures. It could also be the low water cut off, do you have a float type or sensing probe?

nicholas bonham-carter

short-cycling

don't suspect the gas valve unless you have tested each part of the fire control system.

you said you jumped the pressuretrol, and it still short-cycled. next would be to jump out all the parts of that circuit [pressuretrol, lwco, and the thermostat] if it short-cycles, then the valve is unable to stay open.

if it runs normally, then remove the jumper from the lwco, and see if it behaves. at the end of the line, is the thermostat which may also be faulty.

it would cost the manufacturers very little to put led's on the various parts of the 24 volt control circuit so you could see which part was doing what!--nbc

BobbyC

Hey Tim

so went over there last night and put my meters on it.  When it short cycles it reads like 24-25volts.  When the boiler is running the volts dip to like 23.7 - 24.  So it is getting power even when it short cycles. 

The number on the valve that needs replacing is VR800C1513.   Can't seem to find that number but the exact same boiler next to it that feeds another floor has a different gas valve and that number is V800A1088.  Looks like these are more readily available and must of been replaced in the past too.   Seeing everything (btu, mfg etc) is the same on the boiler I should just be able to replace with V800A1088 valve?