Gas and Oil Home Heating Furnaces - miller m1ma 077 furnace lights and goes right out
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peteheat
10-30-09, 09:07 PM
I've replaced ignitor wwhich doubles as flame sensor and I get glow, flame for two seconds and then power to valve opens and of course valve shuts down.
New furnace I did not install though.
1 1/4 line from meter to 20 feet of 3/4 " line to 3 feet of 1/2" (gas pipe black iron ) only other appliance is gas stove which works fine.
Stumped ... any ideas? Dont own manometer but old furnace worked.
New furnace I did not install though.
1 1/4 line from meter to 20 feet of 3/4 " line to 3 feet of 1/2" (gas pipe black iron ) only other appliance is gas stove which works fine.
Stumped ... any ideas? Dont own manometer but old furnace worked.
SeattlePioneer
10-30-09, 09:25 PM
The typical hot surface ignition system turns the main burner gas on, then detects that the main burner ignited electrically using the flame sensor usually found on the opposite side of the furnace from the HSI.
If the main burners don't light, you don't want the gas to remain on, so it's shut off if the flame isn't detected within 2-3 seconds.
So very likely the ignition control isn't detecting the fact that the burners are lighting.
Since you have a new furnace, I don't understand why you are doing repairs to it. You should be contacting the installer for repairs under whatever warrentee you have.
If the main burners don't light, you don't want the gas to remain on, so it's shut off if the flame isn't detected within 2-3 seconds.
So very likely the ignition control isn't detecting the fact that the burners are lighting.
Since you have a new furnace, I don't understand why you are doing repairs to it. You should be contacting the installer for repairs under whatever warrentee you have.
ecman51`
10-31-09, 11:23 AM
Did you buy the correct HSI so it's length and positioning is correct?
Does it have the correct mount, and it is in there square (not angled to the side some?), the same as the original?(And who knows if even the one you took out is the original one.) In the case this HSI doubles as the flame sensor, then I guess you could also check to make sure the burner slot or hole, by the HSI, is not plugged right there. Just because it fires off does not mean it can sense the flame, if the flame is not right there by the HSI.
I have dealt with furnaces with HSI flame detection, with no other single wire flame sensor in there. Also, 2 days ago I went to one of our several mechanical supply houses, and looked through their assortment of different looking HSI's to pick one to have on hand for weekend outages (Murphy, you know). Like I said, especially with an HSI that senses flame....you need the one the furnace calls for.
Most furnaces I'd say do not use that technique, so I just bought a typical looking one for $20. The furnace guy charges $115 to diagnose and install one. :eek:
Does it have the correct mount, and it is in there square (not angled to the side some?), the same as the original?(And who knows if even the one you took out is the original one.) In the case this HSI doubles as the flame sensor, then I guess you could also check to make sure the burner slot or hole, by the HSI, is not plugged right there. Just because it fires off does not mean it can sense the flame, if the flame is not right there by the HSI.
I have dealt with furnaces with HSI flame detection, with no other single wire flame sensor in there. Also, 2 days ago I went to one of our several mechanical supply houses, and looked through their assortment of different looking HSI's to pick one to have on hand for weekend outages (Murphy, you know). Like I said, especially with an HSI that senses flame....you need the one the furnace calls for.
Most furnaces I'd say do not use that technique, so I just bought a typical looking one for $20. The furnace guy charges $115 to diagnose and install one. :eek:
SeattlePioneer
10-31-09, 11:57 AM
Oh. I see I missed the fact that the furnace in question uses the HSI to detect the flame.
Ecman correctly notes that the burner flames need to strike the HSI for them to be detected.
The correct way to diagnose flame failure symptoms is to measure the DC microamps flowing through the flame sensing circuit. In systems with a flame sensor, this involves connecting a DC microammeter in series with the wire to the flame sensor and going back to the ignition control.
With systems using the HSI to detect flames, you can't do that because of the 120 VAC that is applied to the HSI. So in those cases you measure the microamps between the furnace chassis and the "G" terminal on the ignition control in most cases.
A reading of 3-5 microamps indicates that the flame should be detected. If it isn't replace the ignition control. If the read is in the 1-2 microamp range, look for a defect in the HSI or the wiring to it.
Keep in mind that we are talking microamps here ---- there are 1,000 microamps in 1 millamp. 1,000,000 microamps in an amp.
Ecman correctly notes that the burner flames need to strike the HSI for them to be detected.
The correct way to diagnose flame failure symptoms is to measure the DC microamps flowing through the flame sensing circuit. In systems with a flame sensor, this involves connecting a DC microammeter in series with the wire to the flame sensor and going back to the ignition control.
With systems using the HSI to detect flames, you can't do that because of the 120 VAC that is applied to the HSI. So in those cases you measure the microamps between the furnace chassis and the "G" terminal on the ignition control in most cases.
A reading of 3-5 microamps indicates that the flame should be detected. If it isn't replace the ignition control. If the read is in the 1-2 microamp range, look for a defect in the HSI or the wiring to it.
Keep in mind that we are talking microamps here ---- there are 1,000 microamps in 1 millamp. 1,000,000 microamps in an amp.