Trane XE 70 Furnace Ignition Problems

Old 01-30-01, 05:51 AM
Visiting Guest
Posts: n/a
Model TDN090A948A1 will respond to call for heat by successfully igniting pilot, but when main burner starts to come on unit will shut down (no pilot, no main burner). Unit repeats this until successful ignition (sometimes 3 or 4
times before success). Gas pressures were recently adjusted higher for more heat output, and pilot assembly cleaned.

The owners manual says this unit has a gas fired heat exchanger. What does this mean? There are three main burners in the bottom of the unit, and heat output seems low. There are three cavities in the upper portion of the unit (heat
exchanger area) but no flames visible. This is a Downflow furnace.
Old 01-30-01, 09:29 AM
lynn comstock
Visiting Guest
Posts: n/a
By "starts to come on", I presume that the burner fires briefly (less than a second). Then after several tries you at least sometimes get a normal heating cycle (following the "successful ignition".

If this is correctly understood, it appears that the flame is not being proven to the ignition control and the gas is shut off as a safety matter (to keep the furnace from filling with an explosive mixture of gas and air).

Most systems have a sensor rod or prong that is in the flame during a normal burn. It may be dirty or not positioned quite right. Sometimes the flame may lift or pull away from the sensor. Watch it, clean it with a very fine sandpaper and let me know the results.
Old 01-30-01, 03:14 PM
Visiting Guest
Posts: n/a
Did unit ignite correctly before you adjusted gas pressure? Never heard of raising gas pressure to get more heat out of a unit. Your furnace was engineered to operate at a specific gas pressure. Too high or too low will cause ignition problems.
Old 01-30-01, 06:20 PM
lynn comstock
Visiting Guest
Posts: n/a
I think that fjrachel is right. CHECKING the pressure is OK (it should be 3.5 inches WC) More than that could make the flame overblow and lift of of the burner.

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: