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Troubleshoot Trane furnaces
When troubleshooting, understand you are working with potentially lethal voltages and a highly flammable gas. If you do not have the ability to do these operations safely, do not attempt them.
Trane model BLU
Below is an overview of the BLU model gas furnace. All the parts and a quick explanation of their operation are covered.
Sequence of operation
On a call for heat, power is applied to the "W" terminal which energizes the inducer relay located on the inducer control board through the rollout switch, the limit switch and the vent high temp switch.
The inducer motor is then energized in high speed.
The top pressure switch is there to allow the inducer to reduce its speed to low If the vent is moving the right amount of air through the heat exchanger. The unit will start if the top pressure switch does not close, but the inducer will stay in high speed. The lower pressure switch senses pressure at the outlet of the heat exchanger and if this switch does not make, the sequence stops here. If it closes, power passes to the ignition control. The control starts its sequence. The HSI warms, then after warmup timing, the gas valve is energized for a trial for ignition. If the flame lights and proves through the flame rod, the burner stays on.
The heat exchanger warms and after a preset temperature is reached, the circulating fan comes on and sends heat throughout the structure.
The video below covers the sequencing.
The inducer motor is then energized in high speed.
The top pressure switch is there to allow the inducer to reduce its speed to low If the vent is moving the right amount of air through the heat exchanger. The unit will start if the top pressure switch does not close, but the inducer will stay in high speed. The lower pressure switch senses pressure at the outlet of the heat exchanger and if this switch does not make, the sequence stops here. If it closes, power passes to the ignition control. The control starts its sequence. The HSI warms, then after warmup timing, the gas valve is energized for a trial for ignition. If the flame lights and proves through the flame rod, the burner stays on.
The heat exchanger warms and after a preset temperature is reached, the circulating fan comes on and sends heat throughout the structure.
The video below covers the sequencing.
Troubleshoot of the Trane BLU model
Below is the beginning of the troubleshoot of this furnace. The video below is part 1 and covers a no heat call with nothing happening when there is a call for heat.
Trane also had a BLU model 80% efficient furnace. The videos below are related to this furnace. The below video will be available 2-4-15.
The sequence of this furnace is essentially the same as the 90% efficient model. The video below covers this sequence. This video will be available 2-18-15.
The video below describes the burners used in the BLU 80% efficient furnace. This video will be available 2-18-15.
The videos below relate to diagnosing and repairing problems with this furnace
A common problem with any furnace that uses an inducer is the inducer will not rotate. If the inducer won't start, the pressure switch does not close and the ignition sequence will not continue. Reasons for this could be simply an obstruction, such as a bird in the housing or bearing failure of the motor. The video below covers how to diagnose and repair this failure. This video will be available on 2-8-15.
This one covers the symptoms and diagnosis of a failure of the HSI.
This video will be available 2-10-15.
This video will be available 2-10-15.
This video shows testing the flame rod and what the flame rod should read on the meter. This video will be available on 2-12-15.
The video below covers symptoms and diagnosis for a no heat condition that gives no light at all on the ignition control. This video below will be available on 2-14-15.
This one shows the pressure switch not closing and some of the reasons the switch would not make. This video below will be available on 2-16-15.