Variable voltage to ignitor

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  #1  
Old 11-18-20, 01:26 PM
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Variable voltage to ignitor

Trane XV95 gas furnace. We had no heat this morning, tested and found the ignitor was fried. Problem is, we replaced the ignitor last year and they should last a couple years easy. Did some additional testing and found variable voltage coming to the ignitor (80v-93v). It has an 80v ignitor.

Update: Emerson control board 59-4628 Rev A

Is that voltage variance ok, or is that a likely cause for the repeat ignitor failure?
 

Last edited by Simon Rodgers; 11-18-20 at 01:44 PM.
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Old 11-18-20, 01:30 PM
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Welcome to the forums.

Can you post the part number off the control board.
 
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Old 11-18-20, 01:44 PM
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Yep, added to teh original post, thanks.
 
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Old 11-18-20, 02:35 PM
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That board uses an 80v igniter.
The voltage is changed/modulated to change it's operating temperature and attitude.
The igniter used is very important.

From Emerson:
This control has an adaptive algorithm that reduces the igniter temperature to slightly greater than the minimum temperature required to ignite gas in each particular application. The control temperature setting based on the measurement. After each successful ignition, the control lowers the igniter temperature slightly for the next ignition attempt. The control continues to lower the igniter temperature until ignition does not occur, and the control goes into retry mode. For the second attempt to ignite gas within the same call for heat, the control increases the igniter temperature to the value it was on the previous successful ignition. After ignition is successful, the control sets the ignition temperature at this value. The control is constantly making adjustments to the igniter modulation routine to compensate after power interruptions. The Silicon Nitride igniter manufactured by White-Rodgers must be used. These igniters are specially designed to operate with the adaptive ignition routine used by the control to ensure the most efficient igniter temperature.
 
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Old 11-18-20, 02:45 PM
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Thanks PJ. Last year the ignitor was replaced with one from a friend, this year we ordered the ignitor based on the control board model number. So it sounds like the ignitor last year was just not suited for this board, and this one should be fine.
I assume the variable voltage to the ignitor is the controllers attempt to lower/raise the ignitor temp and therefore is expected to be variable.
So If I am understanding everything, we should be in good shape now.
Thanks for your help!
 
  #6  
Old 11-18-20, 03:41 PM
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Yes.... that's their way of squeezing out every last bit of efficiency.
And as is typical.... the more you save in efficiency.... the more the repairs cost.
 
 

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