Kind of lost repairing dehumidifer

Thread Starter

electronis whiz

Joined Jul 29, 2010
512
I got a dehumidifier to try and fix from a friend supposedly it was "tripping breaker" (unsure they meant GFCI or fuse/breaker in panel).

I didn't really want to trip a breaker so I rigged up a 14AWG cord from a junk power strip (cord is fine), I Connected the ground of the cord to the ground on an outlet. The neutral side of the outlet had the sockets in a bridge setup, the hot side was not so I put the hot from the cord to one screw, the neutral to the other hot screw. I then plugged a hair dryer in the one receptacle which was linked in series via the bridged neutral side on the outlet to the dehumidifier.

Soon as I plugged the entire setup in to my bench the GFCI on my bench and another one down the circuit in the house both tripped.
I see no reason looking at the dehumidifier for this to happen no shorts, all seems fairly normal. Although when testing for shorts on the dehumidifier plug I was getting like 100 ohms between neutral and ground (which seemed odd as usually they are either isolated or connected with caps or MOVs in the appliance). There is a fuse in the unit rated 3A (which was not blown) which protects the digital control circuit and blower fan, compressor was just liked to a relay then out to the line in.

I can't see issue in the dehumidifier unless the compressor is bad or a relay is arcing, but tested all relay contacts with ohm meter and they seemed fairly normal. Or something is going on with having the blow dryer in series to try and absorb the surge that caused it to trip breaker.

I' inclined to say it's the dehumidifier as that was why I was asked to fix The date code if I read right said 2002 it's a Westpointe brand which I don't recall ever hearing about before had UL sticker though so expect is not a real junk brand.

Any ideas? Should I maybe try and bypass GFCI and see what happens, or should I try and find a fairly unused non GFCI circuit and plug in direct and see what happens? Or should I just stop now and tell them I think it's over 10 yrs old I think it may be time to just replace it.
 

dl324

Joined Mar 30, 2015
11,000
A GFCI will trip with mA level fault current. Does the dehumidifier have a 3 prong power cord? If not, it sounds like you have a fault from line to neutral.

High "normal" current will not trip a GFCI; that's what circuit breakers are for.

Since you don't know what you're doing, it would be safest to discard and buy a new one.
 

Thread Starter

electronis whiz

Joined Jul 29, 2010
512
It has 3 prong cord I got a fairly reasonably high resistance line to neutral. Line to gnd was nothing gnd to neutral I saw like 100 or so ohms.
 

JohnInTX

Joined Jun 26, 2012
4,114
Kind of agree with @dl324 here, toss it.
If you really want to mess with it, disconnect the compressor and any other subsystems (insulate the bare wires left over) and plug it into the GFCI outlet until you get to a point that doesn't trip the GFCI. Reconnect one at a time until you identify the culprit. The compressor could have an internal fault or maybe water has gotten into a switch or something like that to cause excessive leakage. Inspect the wiring to see if any are pinched through the insulation or skinned.
If its not something simple like that, ditch it.
And NEVER plug it into a non-GCFI protected outlet. Its trying to tell you that it is NOT SAFE. Don't ignore the warnings.
 

dl324

Joined Mar 30, 2015
11,000
It has 3 prong cord I got a fairly reasonably high resistance line to neutral. Line to gnd was nothing gnd to neutral I saw like 100 or so ohms.
Does nothing from line to ground mean 0 ohms or infinite?

This forum has restrictions on mains connected stuff without isolation transformers for safety reasons. Working directly with line voltage should probably restricted because of the safety issue.

That being said. 100 ohms neutral to ground is a red flag. A GFCI compares the current in the hot wire against neutral. Any difference is unsafe because US electrical code only allows neutral to be connected to earth ground in one place - at the power panel. GFCIs offer no protection against hot to neutral faults; e.g. you touching both and getting shocked or killed.
 

Thread Starter

electronis whiz

Joined Jul 29, 2010
512
I had infinite ohm line to ground.

Yes I did forget about the mains rule. I wa thinking perhaps my dummy load setup was the culprit, but I think i'll test that by plugging in my 3 prong variac to it and seeing if it still trips. Variac isn't really a motor, but both inductors so it should be somewhat similar and draw enough to verify the blow dryer comes on.

I looked it over wires seem fine, motor capacitors seem fine I see nothing fried in the logic part, near as I can tell the relays are fine. If it did trip a breaker then the only item not fused is the compressor so that would be my suspect even though it does show 135 ohms resistance. The fan seems to have 2 speeds as has 3 wires 2 hot and neutral. One registered 95 ohm the other 75 ohms (both to neutral).
 

BR-549

Joined Sep 22, 2013
4,938
"The neutral side of the outlet had the sockets in a bridge setup, the hot side was not so I put the hot from the cord to one screw, the neutral to the other hot screw. I then plugged a hair dryer in the one receptacle which was linked in series via the bridged neutral side on the outlet to the dehumidifier."

Could you draw that? Maybe some pictures?
 

Thread Starter

electronis whiz

Joined Jul 29, 2010
512
I figured it out or atleast as far as i'm going to. I decided to test my dummy load setup I tried a variac on it no issue, space heater fan only fan ran, turn heater to low the hair dryer ran. I did confirm it was tripping breaker in the breaker box. It kept tripping GFCI even with all the hot except the line in to the control board disconnected. I disconnected the neutral on the compressor and no more tripping. I'm guessing there is some sort of a winding short or similar in the compressor. I told the person it was not worth fixing and they said okay just drop it off and i'll throw it out.

I said okay, but i'm going to cut the cord on it first so no one tries to use it or dig it out of trash.
 

Thread Starter

electronis whiz

Joined Jul 29, 2010
512
I looked at this one odd brand, near all of it was plastic it looked fairly new, but date sticker said 0902 which i'm guessing means it's from late 2002. I saw a sears or kenmore unit I think lasted something like 20 years, i want to say was early 90s model and my mom ended up with it when my parents split in the late 90s, last I saw it was 2012 before my mom moved and it was still going although the case was getting a bit rusty. I think it's also you get what you pay for as i'd expect a sears or kenmore to be a good bit more than a westpointe (which i had never heard of before).
 
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