21V51U-843 / 50V51-843 Control board setting?

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21V51U-843 / 50V51-843 Control board setting?

Postby gsaik1 » Tue Jan 31, 2012 4:36 pm

Hi. Just got a replacement kit/board for a Lennox G60UHV furnace replacing the 18M99 controller. The White-Rodgers-Emerson 21V51U-843 / 50V51-843 control board has pretty bad explanations relating to dip switch S3 and S4 Motor Optimization. Can anyone tell me what - No Signal, Positive Half Wave, Negative Half Wave and Full Wave ??
Thanks!
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- 21V51U-843 / 50V51-843 Control board setting?

Postby Freon » Wed Feb 01, 2012 5:34 pm

What the Controller instructions do tell you is to make sure you match those switch settings to how the old board switches were set. Since we don't have the old board it's hard to tell you exactly what to do. See if you can find the furnace installation manual and see how the switches were set. I assume this is a newer furnace with a newer, non PSC motor.
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- 21V51U-843 / 50V51-843 Control board setting?

Postby gsaik1 » Thu Feb 02, 2012 12:07 am

Thanks. I was able to map-out most of the settings to the new board. However, the one that I am not sure about is dip switch S4 -1 and S4 -2. On the new Emerson board, it refers to "Delay". On the original Lennox board, it refers to "Blower Ramping profile". How do they relate?
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