Hi,
I have noticed my AC blower will sometimes “hunt” through its variable speeds. It will ramp up and down repetitively for minutes. It’s not always exactly the same but I’d say on average it switches speeds every 5-10 seconds or so and will do that for ~5-10 minutes and eventually it settles out to a mostly constant speed. When it’s hunting it does seem to oscillate between a relatively higher speed and a lower speed but I can’t manually set the speeds so I’m not 100% on that. It’s hard to say how often it hunts but with the blower set to ON I’d estimate it hunts once per hour.
It occurs whether the fan is set to AUTO or ON but is more noticeable when ON because the fan speed is lower when the compressor is on. I can hear the fan ramp up slightly after the compressor turns off.
Should the fan speed be constant when set to ON or is it expected for the system to modulate fan speed anytime it’s on?
The unit is 18 months old and has always done this. I looked into it early on and discovered my unit has an ECM 5-tap variable speed blower motor and chalked it up as part of the “efficient” design but I’m looking into it again for whatever reason and I’m wondering. So I’m here asking, what do y’all think? Is this expected behavior or is there an issue?
The unit is a 2.5 Ton Carrier FB4C Base Series Fan Coil (FB4CNP030L00) and I am using a single 20×30 MERV 11 filter in an 1850 sqft home. It hunts even with a brand new filter but I have considered backing down to a lesser MERV filter to see if that changes anything. It’s worth noting the system works great and has since day 1. The hunting isn’t loud or annoying, airflow is great, and cooling is quick and efficient as far as I know. I’m mostly just curious if this sounds normal or potentially problematic. If it’s problematic, I’d like to fix it sooner rather than later and hopefully under warranty.
Thanks,
John