We have a two-stage 5-ton FHP (AP061) with slinky ground loop. We live in a heating-dominated climate; our system is nicely sized for heating but (unavoidably) oversized for cooling by a good 1.0 to 1.5 tons. I posted here last year asking about strategies for increasing dehumidification when the unit is running during cooling mode and got some excellent feedback.
Other than tweaks to the TSTAT to promote longer Stage 1 run times (which I have done), several folks here also suggested trying to lower the unit's blower speed setting. Our unit's ECM board has an adjustment jumper pin which can reduce CFM by 15%. With cooling season approaching, I was going to try this, but I wanted to ask about a warning I read in the FHP install manual:
NOTE: Do not set the ADJ jumper to the (-) setting when electric heaters are installed. Doing so may cause the heaters to cycle on their thermal overload switches, potentially shortening the life of the switches.We have strip heating for Emergency Heat on our system. Am I safe to assume the above warning is nothing to worry about if I adjust the blower speed only for cooling mode, then reset it to regular speed next fall before heating season begins?
I read the above warning to mean that reduced CFM could cause the emergency heat to cycle on and off more frequently than normal CFM; hence, possibly burning out the strips faster. Nevertheless, I wasn't sure about the "switches" language or whether there would be something inherent in lower CFM that would be bad for switches. For instance, if CFM is reduced across the coil, would the reduced temperature of air blowing through the unit still mess up the switches even if the unit is in cooling, not heating, mode?