Boiler ignition cutoff

jim lockard

would be willing to bet flame sensor needs cleaned or replaced

Warren J. Mateychak

Boiler cutoff

I'm having a problem with a relatively new Dunkirk gas fired steam boiler. I just moved into a house with this system and I've noticed that the boiler doesn't always fire on the 1st, or sometimes 2nd and 3rd attempts. After removing the front panel and watching it fire I'm seeing, on the failed attempts, that the gas is flowing, is being ignited, the burners are lit but after 2 seconds or so something is cutting them off. After 5 minutes, the regular refresh cycle, it'll attempt again. Eventually it'll fire. This is an intermittent problem and seems worse when the boiler has been cold for several hours. I suspect a problem with one of the fault sensors, either the flame roll-out or the damper obstruction. Given the fact that the system eventually overcomes the problem I tend to think it's more electronic than mechanical. I should note also that the damper control is mounted close to the top of the boiler. Could this have anything to do with it?

Thanks

Warren

Warren J. Mateychak

where would you typically find the flame sensor?

thanks

w.

Gary_17

Flame sensor

There are a couple of ways to sense flame. 1 is to sense it thru the ignitor itself. 2 is a separate flame rod usually located at the last burner that lights. It is just a simple metal rod with a pocelain base. Not much can go wrong with it besides getting a dirt film on it or a cracked porcelain (I haven't seen that yet). Just remove it and clean it up with sandpaper.

Unknown

Sounds like you are having

a sensing problem. The system needs 2 to 10 microamps to get back to the electronic control in order for it to stay on. This is accomplished through the flame itself rectifying an AC signal to a DC microamp signal which the electronics sees as a safe light off. As others have mentioned it may only be a matter of cleaning a flame rod. The fact that you have the five minute shut down tells me it is not a hot surface igniter but a intermittent pilot system. The pilot probably needs cleaned and when it is out and being cleaned the sensing rod can also be cleaned.

The test then is to put the meter in series with the output from the rod to the electronic control with the meter set for microamps. As I said 2 to 10 is the range, normal is 3 to 5.

I would suggest you hire a professional to do this.