Trane XL control draft blower turned off purposely ?

Old 11-02-10, 02:56 PM
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Trane XL control draft blower turned off purposely ?

I am not a handy person so we had a technican came to change our broken thermostat for a 2-stage furnace (Trane XL80 or 90) and AC system. I found out later that he replaced our 2-stage thermostat with a single stage one (I am not too excited about that to start with). In addition, he took a short wire and jumpered something inside the furnace which he said would be good for the longevity of the furnace.

Before he "fixed" our system, the draft blower used to blow for about half a minute before the ignitor turned on (and after the gas was lit, the indoor blower would be turned on fully after another minute passed). However, after the "fix", the draft blower will turn on for only 2 to 3 seconds and then stop, another half a minute will pass before the ignitor is on (and the blower will be full on after another minute, as usual). Here is my question:

1. Why did the fix turn off the the draft blower after 2 or 3 seconds? I thought the draft blower would clean the air around the ignitor for better ignition and it was a good thing (except for the cold air coming out the exchange for the 1st minute).

2. Will turning off the draft blower after only 2 or 3 seconds shorten the life of the blower or the circuit board? I am no Ph.D. but I remember from physics that turning circuit on and off quickly induce quite a bit of current in the system which is not necessarily good for the electronics or the fan. Is this an accepted practice in Trane furnace?

3. If this does not sound right, should I fix it (how?)

Old 11-02-10, 04:21 PM
Join Date: Mar 2006
Location: Wet side of Washington state.
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It is absolutely wrong, the induced draft blower needs to run the entire time the burner is operating. It starts before the ignitor is energized to "prepurge" the combustion chamber of any unburnt gases that may be present and it continues to run for a few seconds after the burner stops to "postpurge" any unburnt gases.

Replacing the previous two-stage thermostat with a single stage model was also wrong.

I suggest that you call the company and demand to speak with the service manager or owner telling him/her what this so-called technician did. Also send a letter to the owner (get his/her name, do not use "To whom it may concern") with a copy to your local Better Business Bureau and also any local or state consumer affairs office.

I have a feeling that the so-called "technician" may have damaged the control board of your furnace with his so-called "fix for longevity" and if so you are entitled to a new board from his company installed at no charge. In fact, it is possible that the heat exchanger in the furnace has been damaged so that also needs to be thoroughly inspected.

Please keep us informed.

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