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Dehumidifier Hack Schematic

Dehumidifier Hack

What does one do when the electronic control of a modern dehumidifier goes south? Simple; gut the electronics and replace the intelligent control with a simple, old style, reliable humidistat –not as simple a task as it may seem, but a rewarding exercise.

Dehumidifier Hack Schematic

Dehumidifier Hack Schematic

original schematic

original schematic

Background

One of my money-making sidelines is repairing and refurbishing of old dehumidifiers. Since they are relatively inexpensive as a household appliance, they are often discarded. A friend who is involved in scrap metal recycling picks them up along the street(s) and sells them to me for $5 each. I then determine which ones are functional (some just need cleaned up) and whick are suitable for repair –the remaining fallout, I strip and use for parts and /or sell on eBay.

Three basic failure modes

Refrigeration failure (includes refrigerant leak) –these, I discard –simply too hard to fix.
Fan or blower motor failure –replace motor with used unit
Electronic control and /or sensor failure –replace control if available

Actually any other component may fail such as the humidistat, motor capacitor etc., but these are quite rare.

Electronic controls

Up to a few years ago, only the first two failure modes existed, but progress dictated the addition of “bells and whistles” that required imbedded microcontroller intelligence. Unfortunately, this became the least reliable component. New and even used controls usually carry a prohibitively high price tag, so if I do not have a used one available, I generally look no further.

The solution

Gut the electronics and replace with a simple old-fashioned humidistat. Fabricate a new control panel out of a discarded dehumidifier plastic case. Rewire the unit. The tiny tank level shut-off micro switch has a current rating that accommodates most compressors and the normally closed pole connects to a simple LED circuit that functions as a tank full indicator. If a fuse was provided to protect against fan failure, it must also be included.

The best humidistat

Obtain a humidistat out of another older, dead dehumidifier –I have run across numerous candidates that have the same physical dimensions –some have a metal frame while others have a plastic body. The best is the glass-filled plastic body version –this can be seen in the photos.

Humidistat location

The humidistat should be located on the air inlet side –it was a struggle determining the best fit and location.

What is lost in the process –not much…

The electronic controls have the ability to manage the dehumidifier under marginally low temperatures where the old-fashioned units tend to freeze up and build a block of ice on the evaporator coils. However, this is rarely a problem in heated basements where they are usually located. Then, there is the digital humidity and temperature readout that is really unnecessary. Also, some have a timer feature that also seems unnecessary.

Photo gallery

Undocumented words and idioms for our ESL friends

go south –idiom –fail (failure)

bells and whistles –idiom –advanced, generally unnecessary features

2 Comments

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  • T.K.Hareendran

    Nice attempt, and good article (as usual) by Mr.Jim Keith. Thanks!

  • Jim Keith

    I’ll bet that some would like to do this and hack their late model cars –especially if they have been troublesome.
    I’m all for it, but in this neck of the woods all cars must pass an emission inspection that requires that all emission control hardware be stock and in place –this has kept even hot rod enthusiasts off the road.

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