RE Smith GV-100 lockout

Steve Ebels

I posted about this boiler the first of this week. (thanks for the info Bill at Honeywell). The problem is intermittent lockout. As the weather is becoming colder the lockouts are becoming more frequent so the HO is having to reset it 2-4 times a day.

I watched this boiler cycle for about 2 hours yesterday afternoon and this is what I observed. It (the burner) would start and run normally up to about 5 degrees from aquastat set point. It makes no difference what the setpoint is at. Could be 150, could be 200. Anyhow, when it hits setpoint minus 5 degrees the flame will extinguish itself. As this happens there is no variation in flame sensor output. It only drops after the falme is gone. In the brief period from when the flame just goes out to when the falme sensor shuts down the gas valve, there is still gas flow. It makes no difference whether the boiler had to run for 30 seconds or for 15 minutes to reach that temperature, It still locks out at setpoint minus 5 degrees. There is adequate combustion air, gas pressure is right on, the boiler is clean. I have never seen anything like this in my life and I'm out of answers and ideas of what to try now.

Any suggestions or theories as to what could cause this???

Unknown

Wierd

Give me some control info and is the aquastat you are talking about the hi-limit? I just got back into the office after being away for a week so I did not see your prvious post. What kind of module, gas valve is there a relay etc.?

tim from Reed Wright

shut down

? have you had your meter on the pressure switch when it shuts down, could be that the pressure switch is opening up? Is this a Weil Mclain boiler??