Replacing old hood with over-the-range microwave

Nathan0115 · 08-04-2011, 01:47 AM

So I just bought a nice new over the range microwave and installed it myself with some help.

Everything went relatively smoothly except for when I wired the outlet.

The old hood was hardwired so when I took it down I shut off the breaker, drilled a hole in the cabinet above, and ran the wires up. I figured when I was done installing the microwave, I'd simply mount a box inside the cabinet and hook the wires up to an outlet so that I could plug in the new microwave.

I did all this, plugged the microwave in and went downstairs to turn on the breaker. My wife said that when I flipped it back on, a shower of sparks came from the outlet and the microwave did not turn on. If I run an extension cord to power the microwave elsewhere it works fine. Based on what shut off when I turned off the breaker, this ciruit is shared with one outlet in the kitchen plus (off all things) the washing machine in the basement. Neither of these things was being used at the time, nor did the breaker re-trip. Just sparks and no power.

I'm at a loss. What did I do wrong?

dSilanskas · 08-04-2011, 05:44 AM

Take the outlet box apart that you made up. Make sure you don't have the hot touching the sides of the metal box.

Just Bill · 08-04-2011, 07:28 AM

What he said. I suspect hot was touching the box, neutral, or ground and made sparks. It should be obvious when you open the box. Did it trip the breaker??

Nathan0115 · 08-04-2011, 09:37 AM

Well that's the weird part. It did not trip the breaker.

What's more, I only get the spark shower if something is plugged into the outlet I rigged when I turn the power on.

If there was a short circuit in the box, I would be seeing the big pop regardless of what's plugged in there, yes?

seansy59 · 08-04-2011, 10:01 AM

Keep the breaker off for now.
I am Not an electrician

When you have sparks like that, it's not very likely that something is overloaded. That means theres a dead short in contact with metal/ground. When something is overloaded, your breaker will trip which is overcurrent.

First, I take it that your gang box is metal?
Check that there is NO bare wiring or screws touching the box. Bare wire to green screw (Ground), black to brass screw (Hot), white to silver screw(neutral)

- If that still causes a problem, then your outlet may be faulty. Try a new outlet?

- Maybe there is a knick in the wires touching something, that may have
happened when you moved the wire/fan.

md2lgyk · 08-04-2011, 11:44 AM

If I were you, I'd run a separate circuit for the microwave. The way the circuit you tied into is shared, I guarantee the breaker will trip if you try to nuke something while the washer is running.

gregzoll · 08-04-2011, 12:14 PM

Quote:

Originally Posted by md2lgyk

If I were you, I'd run a separate circuit for the microwave. The way the circuit you tied into is shared, I guarantee the breaker will trip if you try to nuke something while the washer is running.

Also sharing with the washer is not code compliant.

electures · 08-04-2011, 12:27 PM

Quote:

Originally Posted by seansy59

Keep the breaker off for now.
I am Not an electrician

When you have sparks like that, it's not very likely that something is overloaded. That means theres a dead short in contact with metal/ground. When something is overloaded, your breaker will trip which is overcurrent.

First, I take it that your gang box is metal?
Check that there is NO bare wiring or screws touching the box. Bare wire to green screw (Ground), black to brass screw (Hot), white to silver screw(neutral)

- If that still causes a problem, then your outlet may be faulty. Try a new outlet?

- Maybe there is a knick in the wires touching something, that may have happened when you moved the wire/fan.

WHen you take the box apart look for any indication of the short such as blackened areas around the connector or terminals.

electures · 08-04-2011, 12:29 PM

Quote:

Originally Posted by md2lgyk

If I were you, I'd run a separate circuit for the microwave. The way the circuit you tied into is shared, I guarantee the breaker will trip if you try to nuke something while the washer is running.

Check the manufactures installation instructions and see if they require or recommend a seperate circuit. Now may be the time to install one.

HouseHelper · 08-04-2011, 02:53 PM

Since an over the range microwave is also a hood, and it is cord and plug connected, then the circuit supplying it should be an individual i.e., dedicated, branch circuit. (see 422.16(4))

Dwillems · 08-04-2011, 06:32 PM

Sounds like it may be wired wrong if it only happens with something plugged in. I'm no electrician so I look it up every time. The hot and neutral go on opposite sides of the outlet on a specific side. And the ground has it's own separate green colored screw

gregzoll · 08-04-2011, 06:41 PM

Quote:

Originally Posted by Dwillems

Sounds like it may be wired wrong if it only happens with something plugged in. I'm no electrician so I look it up every time. The hot and neutral go on opposite sides of the outlet on a specific side. And the ground has it's own separate green colored screw

Yes, it is Black to Brass, White to Silver.

electures · 08-04-2011, 07:35 PM

Try plugging something else in. Maybe there is a short in the appliance.

Missouri Bound · 08-04-2011, 11:46 PM

The appliance is (at least it was) fine. You have a hot wire touching to ground. Could be another wire, could be the box. Inspect the box for any blackened areas. Did you use stranded wire, by chance?

jbfan · 08-05-2011, 07:21 AM

Where did the power come from?
If it sparks only when something is plugged in, you could have pulled from a switch leg!