STIHLY DAN
Minister of Fire
My news from the HPWH front.
I am past the fifth anniversary of putting mine in and scrapping my 'old unfaithful, tried to kill my kids' oil fired boiler. Only problem I had years ago was I had the AO Smith unit 'brick' when its controller board died (a couple months after an epic power surge), and I replaced it myself after the maker fedexed me a replacement board for free.
I have found that the intake air filter (looks like the screens on window ACs) never gets dirty. Thinking that it might restrict the airflow (the AOSmith unit has a bigger fan than most) I took it off and found that the unit got much quieter...can't hear the low 'warp engine' thrum in my living space when its running. Happy.
But at the same time my dehumidifier started working a lot harder (both are in a power ventilated, semi-conditioned attached garage). I figure that at much higher airflow, the air coil is running a lot closer to the air temp, and perhaps above the dew temp...limiting dehumidification. So I put the filter back on.
However, I plan to run without the filter in the cold weather (it gets down to the low 50s in there in Jan-Feb) and should get a little boost to COP and recovery, in addition to getting quieter warp engines.
That is a short term fix unless you have the ability to clean the evap coil yourself. I cleaned mine this spring and it was very easy to do.