Electrical Question

watercrawl

watercrawl

Joined
Jun 2, 2006
Messages
422
I know this may not be the best place to ask this question, but I figure some one here might know and it's knife related....so:

My grinder motor is currently wired directly into a 30 amp disconnect that I use as a switch per the direction of the electrician that hooked it up for me. It works great with no complaints.

However, with the delivery of a 220 volt kiln, I want to add an outlet in this set up so I don't have to run another 220 volt circuit.

The kiln that's coming uses a NEMA 6-20P, 20 amp plug.

The grinder is currently wired directly into the disconnect which is mounted on the wall. The wire is some 3/8" diameter black stuff that's rated to be left exposed with no conduit....I'll look for the type of the wire tonight when I get home if that matters.

The circuit is 30 amps....obvious given the disconnect, but making sure the info is out there for review.

Question is this....can I cut the wire run between the grinder motor and the disconnect and put a Nema 6-20P outlet on the wire coming out of the disconnect and a Nema 6-20P plug on the wire coming out the grinder? This way I can use the one outlet for either the kiln or the grinder motor.

I'm assuming I can. The grinder motor is rated at 9.5 FLA at 220 volts and the kiln at 11 amps, so my assumption is that if the 6-20P plug will work for the kiln, so will it work on the motor.

Assumptions correct? Anything I'm missing?
 
You could run a cord out of the bottom of the disconnect with a 6-20R on the end of of it from the line side of the disconnect to plug the kiln into . This wouldn't meet code but would work ..
 
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You don't really want a 20 amp plug in a 30 amp circuit. The "weak link" has to be the breaker, nothing else is really safe.
 
The breaker would need to be changed to a 20 amp, but the 9.5 FLA grinder may draw up to 250% of the current (amps) to start. That may trip the 20 amp breaker. Then you would need a dedicated circuit for the kiln.

You could also have an electrician change the 30 amp disconnect to a sub panel. That way you can tie both loads into the panel, but still only use one at a time.
 
Personally, I'd just wire that 20A plug right into the 30A circuit. It should work fine. The kiln obviously isn't using more than 20A of power, I see a 30A breaker as a green light to wire anything less into it, as long as phase/voltage are within spec.

Are you kidding me? I run 10A loads with 10A plugs off 15-20A breakers all the time. It's known as "standard household electrical wiring."

I know that the above recommendations are perhaps the "by the book" way to go, but...
I'm going to be the dissenting, get-r-done mentality here.

Take it for what it's worth.
 
Okay, it seems by doing a little research NEC doesn't allow an outlet with a lower amperage than the circuit....never would have thunk that.

Need to look into this a bit more now.
 
Alright, to close this out, I called the electrician and asked what I could do. Here's what he said:

a. Put in a 30 amp outlet, put a 30 amp plug on the grinder, and buy an adapter to go from the Nema 6-20P to the 30 amp outlet.

b. Put in a 20 amp NEMA 6-20P outlet, use the plug that comes on the kiln, put a Nema 6-20P plug on the grinder and then put 20 amp fuses in the disconnect and that would make it legal.

I think I'm going to go with option a. but the adapter is effing expensive. However, I like that option better.
 
The circuits in your house are 15 - 20 amp 120 volt. ( they make them small enough to trip when needed.)
We are talking about a 30 amp 240 volt circuit. If the kiln is required by the manufacturer, to be on a 20 amp 240 volt circuit, and you hook it to a 30 amp 240 volt circuit, you are taking a chance, that if there is a problem, you may ruin the kiln wiring. Possibly causing a fire.
If you accidentally run both at the same time, on the 30 amp circuit, you may burn up the motor windings also.

It may work, but just because it works electrically, does not mean it is safe.

Check the name plate on the motor, and the specs on the kiln. And Never forget your grounds.

Al


Salem Straub said:
Personally, I'd just wire that 20A plug right into the 30A circuit. It should work fine. The kiln obviously isn't using more than 20A of power, I see a 30A breaker as a green light to wire anything less into it, as long as phase/voltage are within spec.

Are you kidding me? I run 10A loads with 10A plugs off 15-20A breakers all the time. It's known as "standard household electrical wiring."

I know that the above recommendations are perhaps the "by the book" way to go, but...
I'm going to be the dissenting, get-r-done mentality here.

Take it for what it's worth.
Click to expand...
 
watercrawl said:
Alright, to close this out, I called the electrician and asked what I could do. Here's what he said:

a. Put in a 30 amp outlet, put a 30 amp plug on the grinder, and buy an adapter to go from the Nema 6-20P to the 30 amp outlet.

b. Put in a 20 amp NEMA 6-20P outlet, use the plug that comes on the kiln, put a Nema 6-20P plug on the grinder and then put 20 amp fuses in the disconnect and that would make it legal.

I think I'm going to go with option a. but the adapter is effing expensive. However, I like that option better.
Click to expand...

I'm curious, as per option A.- merely using an adapter to plug the 20A plug into the 30A outlet doesn't really seem like it's an improvement. Unless that adapter had fuses in it? The couple that I looked at a minute ago did not. So, that seems like it's still a "weaker link" than the breaker.

That does seem nicely simple, however. By expensive, did you mean $64? That was the lowest price I saw.
 
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I found an adapter for $49 locally. That's a good point about the fuses though. Electrician didn't say anything about that though....although I was only asking what met code.

Might have to go back to option b. If the grinder kicks the fuses, I'll have to run another line or change the disconnect to a subpanel.
 
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