Rising flame rectification reading

Hi all,

Wondering if anyone has experienced this. I was working on a Commercial RTU (Lennox)

Heating was locking out on Flame failure.

I checked board was correctly grounded-ok,  clean flame rod, and flame rod wire had good continuity.

When I checked the uA I found at first 3.5 to 4uA and within a minute it would rise up to 9uA and then would shut off. Same thing would happen several times and then would lock out.

I ended up changing ignition control  board and works well (4uA)

Explained to owner and they told me that in the past 3 years the ICB has been has been changed.

Have you experienced this before? Why would this happen? Never seen a runaway flame rectification.


Rookie Asked on January 22, 2019 in Commercial HVAC.
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