Ignition Lockout, near 0 degrees, Interesting problem found.

[Wedgeman55]

Any of you who live in the tundra like myself,   here is something to think about if your having problems with furnace when the temp drops to near 0 temperatures.     
 
Went out to repair a unit today at customer's home.   Temp was 12 degrees daytime,  near 3 at night.    Unit was locked out when I got there,  Ignition lockout according to code.  I reset computer,   fired it up and it attemped to start 4 times.    Would fire,  then go right out.      Forced vent motor,  fine.   Pressure switch,  OK.    Flame was lighting up on 2 of the flame tube orifices.   
 
I suspected either bad gas valve or low gas pressure.   Turns out,  very low gas pressure.   Upon talking to someone,   they said moisture in gas lines which ends up in the meters causes the meters to freeze,  and deliver low pressure.    Furnace was fine once gas company came out and put on new meter for customer.    Something for you guys to think about when servicing in these cold temperatures.     May not be the unit itself. 

[RegUS_PatOff]

is that the only gas appliance in the house ?
(does it affect the Gas wter heater / range / etc)
 
(Milwaukee, Wisconsin) 
 

[Wedgeman55]

Wierd enough,  Reg,  she had an electric oven and electric hot water heater but gas furnace.    Otherwise,  might have told me no hot water either I would have figured it out easier.

[Wedgeman55]

It would affect the dryer also,  flame would not be as large,  maybe take longer to dry or kick out the hi limit thermo on the tube.   

[videobruce]

Also, water in the underground supply main that collect in a low spot will cause furnaces to pulsate the flame due to bursts of gas getting by the water pocket.

This happened to a neighbor three doors away. The utility replaced the line.

[jumptrout51]

It will also happen at the gas valve if a gas supply drip leg is not installed.