Electrical Contactor Help

I'm trying to setup a humidistat to control a dehumidifier rated at 8.9 amps.

Using a Honeywell humidstat H46C1166/U
Electrical Ratings
120 Vac, Full Load: 7.5A; 120 Vac, Locked Rotor: 30.0A; 120 Vac, Resistive: 12.0A; 240 Vac, Full Load: 3.8A; 240 Vac, Locked Rotor: 15.0A; 240 Vac, Resistive: 6.0A
I used an old crappy lighting controller for a box housing the receptacle, and used a Eaton 20A definite purpose contactor. Eaton C25BNB220A

I wasn't thinking and plugged it into an old ungrounded outlet. I touched the outside of the plastic case near a recaptacle and got a slight tingling feeling. (the receptacles are riveted in place on the outside and this is ground.) I tested ground on my multimeter and measured 39 volts. I then tried plugging it into a grounded outlet and there was no voltage on ground. Is this normal?

- Jiji

Bump. Where's all the good electricians!

I'm thinking this is normal, but I want to be 100 percent sure.

Also the original ungrounded outlet is actually a gfci outlet, but the gfci did not trip.

- Jiji

If the GFCI didn't let go and you feel confident the the GFCI is working properly, I'm positive that it isn't a grounding issue.

39 V to ground? How did you take the measurement, if you don't mind me asking?

I tested it with a multi meter. red probe on hot side of contactor (feed side coming in from power wire), black probe touching metal ground plate and got 39V. Also putting the red probe on the neutral connector of the contactor(feed side coming in from power wire) and black on the ground plate it measures about the same 39V.

I only get the 39V when the coil is energized. Otherwise it is less than 3V


- Jiji

It's not uncommon to pick up an induced voltage when you measure in a way that doesn't provide a true path to ground or neutral to ground. I can't tell you the exact process, but I've seen it happen plenty over the years. Try measuring from the ground on the box to something that you know for sure has a good ground and I think you will see no voltage. If there is still something there get back to me and we'll go through it systematically and get it figured out for you.

ok. I plugged the contactor box into an ungrounded outlet. With the contactor energized, red probe on the ground plate in the contactor box, and black probe on a known grounded outlet ground, I still read 37 volts.

- Jiji

jijiandfarmgang said:

ok. I plugged the contactor box into an ungrounded outlet. With the contactor energized, red probe on the ground plate in the contactor box, and black probe on a known grounded outlet ground, I still read 37 volts.

- Jiji

Click to expand...

Intriguing. I assume you have looked closely at all the connections in the contactor box? Most likely the wire is stranded rather than solid? If so, look closely, Do you see any single strands that managed to come out of the crimp connectors? Look especially close on the ground and neutral. I have seen a whisker pop out like that and cause trouble hot to ground. That's not exactly what you've got going here and now but we are looking for an oddball issue so we need to think outside the box here. An inadvertent neutral to ground could somehow set up feed back that your meter is picking up. Not likely at all but just to eliminate the possibility.

I'm feeling like your meter is most likely just seeing induced voltage in the ground from the coil on the relay. The relay coil is what you most likely felt in the plastic when you touched it. The coil will produce a vibration at 60 hertz when energized. The coil is just an electromagnet which is similar to a transformer and can create induction under the right circumstances. I work with industrial electric and I can attest to the coil vibration feeling like shock when a big contactor kicks in. I've done this kind of work for years and I still yank a hand back now and then!

Hello again,

All connections are fine, and its stranded. I tested for continuity between ground and hot and neutral and there was none. I think I was shocked though. I actually touched a rivet on the plastic outside of case that is confirmed ground but it was just a slight tingle so not 100 percent.

I also tried swapping contactors and the same thing happened.

Then I tried unwiring the load side, and I didn't get any voltage on ground. Then I looked at that stupid 2 dollar open ground tester that is plugged into the receptacle.

I wired everything back up the way it was originally and removed that yellow tester from the receptacle and measured less than .4 volts when coil was energized.

thanks for the help, a friend who is an electrician is going to double check it later.

- Jiji

HA! That's the kind of shit I pull on myself now and then. Hey at least it turned out to be something easy!