Sears 70 pint dehumidifier

[GaryP]

Has anyone else had problems with the humidistat on the Sears 70 pint dehumidifier being grossly inaccurate and cycling the unit off and on frequently? I'm on my third unit from two different stores over a period of two months (Sears is second to none in no-hassle exchanges) and they have all worked this way. If I set the electronic humidistat to 70%, the unit will run and rather quickly bring the humidity down as low as 45-55% RH or so, then start cycling off and on in about two minute intervals (off about two minutes, on about two minutes). If I set it to 65%, the unit will run for a while to bring the humidity level a bit lower, then start cycling again. Setting it lower continues to have the same effect.

When I first turn the unit on and it's humid, it will run for quite a while brining the humidity down like it's suppose to do without cycling, indicating it functions well and isn't icing up, etc. It's just the frequent cycling (literally off and on, off and on, almost every two minutes) as though it needs to sample the air to determine if it should continue to run that is annoying and can't be good for the compressor (both the fan and compressor are cycling).

[m Ransley]

There is a 3 or 6 hr cycle setting, try it. I bought a new sears 55 pt Mine doesnt cycle its freakin broke, 5 mo old its going back. If it pulls humidty down fast it may be to big a unit or it is stuck in a corner not getting air circulation.

[nicksanspam]

Maybe it's working as designed.

Can you find the humidity sensor and wrap it in an inch of cotton or direct the output airstream away from the sensor or move the sensor assembly to the other side of the room and wire in an extension cord to power the fan and compressor, under sensor control?

Or set the box to "always on" and power the whole thing with a Herbach and Rademan [phone]

$4.95 Navy surplus humidistat, their item number TM89HVC5203, with a 20-80% range, a 3-6% differential, and a 7.5A 125V switch that can be wired to open or close on humidity rise...

Nick

[GaryP]

These were good suggestions. The sensor is clipped to the evaporator coils on the input side of the unit. Attaching a cotton ball changes the 2-3 minute on/off cycle to more like 5-10 minute cycles, so that helped. What appears to be most successful is relocating that sensor completely outside of the unit and out of the forced airflow. I was able to do this by permanently removing the water reservoir, taping the reservoir switch full switch, then hanging the sensor outside the unit below where it normally mounts. My weather is currently such that the humidity is down in general, so I can't get a real sense on how well this sensor will work this way, but initial observations suggest that this might be the way to go. The unit brought the humidity down to within 5%-7% of two electronic hygrometers that I have, then shut off and didn't cycle on and off very often. Even though I'm using a hose and not the water reservoir, it's almost as though when the unit stops, humidity may build up inside the unit quickly and fool the sensor into believing it must run again. Once going, dry air is sucked in again and it stops. The cycle repeats.

Also good suggestions. The 3/6 hour cycle settings will give the dehumidifier some off time, but this solution still won't accurately control the humidity. Given my observations, the unit would run literally 50% of the time every 3-6 hours, whether it's needed or not. Not very energy efficient. The basement is 1700+ square feet, for which this unit should not be significantly oversized. And I've been placing it in the middle of a room near the floor drain, so it has gotten good air flow around the unit.

I may not be able to tell until next spring when things get humid again just how effective moving the humidity sensor out of the airflow has been, but it looks promising what I've observed so far. My ultimate plan is to have this dehumidifier managed under an X10 home automation system and not have it operate much during the day when my electric rates are higher (time-of-day metering).

Thanks for the suggestions!