Agree with acman3 and ghosthouse. The service factor on startup may be causing a temporary drop in voltage. Logic circuits usually use a 5VDC supply. You may be able to get as low as 4.5VDC and still be safe. 115VAC through a step down transformer to yield 4.5VAC is a 25x reduction in voltage. If the line voltage dips to 100VAC, the voltage on the secondary side will drop to 4VAC. Rectification has little to no affect on voltage. At 4VDC the logic circuit would likely freeze and not function until a complete reset of the logic circuit is performed.
220VAC supplied circuits will use both legs of the service being supplied. Startup will affect all service since the 220 breaker uses both supplied phases. You said when the air kicks on. Not sure where you are located but here in TN we haven’t used the air in months. Is this a heat pump in heat mode?
You may be able to prove this by testing using a uninterruptible power supply/battery backup unit like used on computers. This should keep the line voltage stable.
Just a thought.
220VAC supplied circuits will use both legs of the service being supplied. Startup will affect all service since the 220 breaker uses both supplied phases. You said when the air kicks on. Not sure where you are located but here in TN we haven’t used the air in months. Is this a heat pump in heat mode?
You may be able to prove this by testing using a uninterruptible power supply/battery backup unit like used on computers. This should keep the line voltage stable.
Just a thought.