Pressuretrol and standing pilot

Alex265

Hi, I have a relatively old (~15 years) Burnham gas boiler with standing pilot light and a thermopile. Pressuretrol shut off the pilot when it cuts out on pressure - is this the designed behavior? There is also another pressuretrol on a pigtail coming out of an old float-type low water cut off - I am not sure what this one does.

Charlie from wmass

if this is a big boiler

one is a safety manual shut down and the other is the controlling pressuretrol. Call a pro if the pilot goes out when pressure is reached as that is not a properly working unit.

Alex265

just one clarification

Charlie, thanks for your reply. I'm sorry, it's not clear for me - which one you think is the safety manual shut down? Can the controlling pressuretrol be the one on the low water cut off?

JStar

Could be...

...that the main gas valve is closing too fast, and pulling the pilot flame out. What make and model is the gas valve?

Alex265

Not sure right now about the model

but it's an older Robertshaw. But doesn't it make sense that the safety manual reset shut down control would shut down the pilot?

JStar

Depends.

Do you light the pilot by hand or is it lit by spark? If you have to light the pilot by hand, how could a pressuretrol turn it off?



Robertshaw had some gas valves on water heaters that were fast-acting and causing the same problem when the water reached temperature. I would gather some boiler and valve numbers, and track down any recalls.

Alex265

JStar, thanks for the information!

The pressuretrol which I now think is the emergency shut off control is wired in the same circuit with the thermopile, so it might shut off the pilot when it breaks the circuit. As I understand, this one should be set to a high cut off (4-5 psi) and should never break under normal conditions. The other one is the burner controlling pressuretrol, in the same circuit with thermostat, it does not shut off the pilot, and can be set to 1.5 psi cut off (or lower).

Tim McElwain

Alex 265 that is correct

the second pressuretrol was to continue to allow a single seated powerpile gas valves to be used on heating and it is called an auxiliary high limit pressuretrol.



It can be set to knock off at 14 lbs and back on at 9 lbs ( set cut in to 9 and differential to 5) this will prevent nuisance pilot outage. The pop safety on the steam boiler opens at 15 lbs.



The other pressuretrol is the normal one for boiler operation set to 2lbs off 1/2 lb on.

JStar

Ahhhh.

ThermoPILE. Not ThermoCOUPLE. Now it makes sense doesn't it?

Alex265

Yes, it does now!

Thank you very much for the information, Tim, JStar and Charlie.