October 16-17, 2024

    Once the days got a bit cooler and we had the electrostatic precipitator fixed and in place again, we noticed that we were icing up the evaporator coils, which is not a good thing! Our HVAC guy cut in another inlet to the master return air duct, fairly close to the inlet side of the electrostatic precipitator. This helped some, but not quite enough. We’re studying the situation and it looks like we almost have added enough return air to the system.

    This study was complicated by a couple of equipment failures. The electrostatic precip failed, so we just removed its front panel and removed a cell to experiment with adding 100 square inches of return air as close as possible to the air handler’s blower. This wasn’t quite enough. Then our recording thermometer failed and we had to replace it.

You’ll have to stretch out your window and hit the magnifying glass icon to see what’s happening. 

At the left, is the now very gradual ice up. It ran from about 7:30 (before the replacement thermometer went online at 10/16/2024 8:48 AM) until sometime around 11:34 AM before the outlet air temp started increasing, indicating a freeze-up condition was starting. Then you can see 2 cycles of the compressor somehow detecting the condition and shutting itself down for about 2 hours at a time. 

Then at 5:24 PM the thermostat shut the HVAC down and several commanded cycles were run. The extremely short cycles on the right were the thermostat calling for 10 - 15 minute runs with about the same amount of time between them. This is what we’d expect overnight.

Here’s a bit of the X-300 thermostats log for the time of interest. A lot of rows during the day were deleted, since they were pretty much the same.