Trane ignitor voltage

[sciencefreak614]

I have a customer with a Trane gas furnace model# TUY100R9V4W5. I believe it was installed in 2005. They have had to have the ignitor replaced 3 times already. The first time I talked to Trane tech support I could not get a lot of information out of them other than they have changed the part number for the ignitor three times. I take that he was implying that they are just defective ignitors. The guy at our Trane supplier said that the boards on these particular models step down the voltage to the ignitor to 80VAC, and they have found some boards that fail to do this and thus send too much voltage to the ignitor, causing premature failure. I recently checked this out for the customer (I am not the one who did any of the repairs previously, just following up for them to try and resolve this issue) and found that the voltage to the ignitor fluctuates between 86VAC and 121VAC. I have a Fieldpiece multimeter that updates about every second, and the readings look like 86...94...121...86...94...121...etc, the entire time the ignitor is energized. At this point I am definitely leaning towards replacing the board (they have 10 year parts). I can't imagine these readings would be normal. I will be talking to tech support again on Monday morning but I wanted to throw this out here to see what any of you Trane experts think. I work for a Carrier and Lennox dealer and I just don't see a lot of Trane furnaces, and have never run into this problem.

[tinmantu]

Not familiar with your meter, but if it isn't an analog, I'd recommend trying one before you condemn the board.

[sciencefreak614]

It's a digital meter model HS36. I have used it for 3.5 years and have never had an AC voltage reading that fluctuated more than a couple tenths of a volt. I guess I could try an analog meter (after I dust it off hehe) but I am not sure it would give me any better info.

[tinmantu]

I've just found reading voltages off of boards are totally different from putting them on two wires to see if you have high voltage. I see fluctuation with a digital that I don't see with the analog. I carry both. Might not be the problem, but when you don't see a constant voltage, eliminate the guessing with an analog, IMO.

[Twilly]

Twilly has solution.

[Adnshel]

Tell us about your solution Twilly!

[sciencefreak614]

Yes, I'm all ears Twilly!

[Ghostrider67]

I've had readings like that when the igniter is not plugged into the circuit. I use the Fluke 87 meter. Are these readings with the igniter unplugged? It should read 80 volts with the igniter in the circuit. Anything over 80 volts will kill the igniter sooner.

[bill_irwin32]

From what I remember from a Trane training class a year or so ago, The more recent boards with nitride ignitors "learn" what minimum voltage needs to be applied to the ignitor to get proper ignition to not wear the ignitor out prematurely. I think the boards may also be "chopping" the power to achive these voltages which would show up better on an analog meter. This may be normal. You may want to also check the quality of the incoming 115 VAC as well as the ground.

[sciencefreak614]

I've had readings like that when the igniter is not plugged into the circuit. I use the Fluke 87 meter. Are these readings with the igniter unplugged? It should read 80 volts with the igniter in the circuit. Anything over 80 volts will kill the igniter sooner.

Ya, the ignitor was plugged in. I just pushed my meter leads into the back of the plug to the board. So, you have measured the voltage in this situation before, and it should be reading a constant 80VAC?

[sciencefreak614]

From what I remember from a Trane training class a year or so ago, The more recent boards with nitride ignitors "learn" what minimum voltage needs to be applied to the ignitor to get proper ignition to not wear the ignitor out prematurely. I think the boards may also be "chopping" the power to achive these voltages which would show up better on an analog meter. This may be normal. You may want to also check the quality of the incoming 115 VAC as well as the ground.

It does not have one of the new boards. I remember now Trane tech support telling me that the unit did have the older type board, and mentioned something about a replacement kit.

[bill_irwin32]

Then the new board may have more ignitor "friendly" circuitry... Funny how nowadays, you seldom see recalls or even "programs" for fixing known issues with things... They know they have problems but they make you pay for the fixes.

[esker3]

If the voltage to the ignitor doesnt end up being the problem go to the basics. Remember that furnace short cycling will cause a unit to keep blowing ignitors also. Are you sure that the furnace is not oversized causing it to have too many on and off cycles? Also check things like plugged evap coil and dirty filters or squirrel cages causing the unit to go off on limit. Just trying some alternative solutions. Post what you find out

[ClimateCntlJohn]

How about after ignition occurs, does that board still send power to that igniter? Not had a problem on a Trane furnace but I've worked on a couple Lennox furnaces that had issues with premature igniter failure because it would energize that bad boy the entire heat cycle.

[sinsee]

From what I remember from a Trane training class a year or so ago, The more recent boards with nitride ignitors "learn" what minimum voltage needs to be applied to the ignitor to get proper ignition to not wear the ignitor out prematurely. I think the boards may also be "chopping" the power to achive these voltages which would show up better on an analog meter. This may be normal. You may want to also check the quality of the incoming 115 VAC as well as the ground.

If I remember correctly. You may not be able to read the voltage correctly with all meters. They do not actually drop the voltage but do somethiing with the hz. The chop the hz frequency which in effect cuts the applied voltage

[sciencefreak614]

According to Trane, those boards will have a fluctuation in voltage to the ignitor. It can start out in say the 90-120 range. Then for each successive energizing of the ignitor, the voltage will drop so it will eventually get down to say 30-60 VAC. It keeps doing this until it fails to light, then ups the voltage a little. It will then hold this voltage for something like 294 cycles, or until power to the unit is interrupted. Then it starts over.