exhaust fan wiring


Old 12-11-00, 01:33 AM
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I'm about to install an over-the-range microwave. The existing exhaust fan has been there about 20 years. Is the wiring for that okay to use for a receptacle for the new microwave? I am clueless when it comes to electrical subjects. If not, how can you tell which wiring is for receptacles? THank you. Heidi
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Old 12-11-00, 04:02 AM
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current electrical code requires that a microwave have it's own dedicated circuit. Although the wire that's already there will probably work, it may trip the breaker when used if there are other loads on that circuit.
Old 12-11-00, 03:15 PM
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Don't even try using the existing wiring for supplying the built-in microwave unit. Terminate the existing wiring in a juction box (which must be accessable from th eexterior of the wall, use an old work box with ears, and use a blank cover. If you can trace this particular cable back to a further location, disconnect and remove it there.), and install a new 120V 20A circuit with nothing other than the dedicated single receptacle. The receptacle must have a NEME 5-20R face.

Old 12-11-00, 05:00 PM
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Both these guys are right, I just did the same thing last Sat to a house that was 20+ yrs old. I have a post on it title Kitchen appl 12/4 it was answered by WG you may want to read it. Best advice upgrade the amp to 20 and make sure its a dedicated line....
Old 12-11-00, 11:57 PM
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Smile relating to a microwave/vent combo

I hope I'm not breaking the rules by asking a question in the middle of a thread, but it relates to what I plan on doing. I want to but can't afford to at this time, get a new microwave/vent to go over the stove. The electrical would not be a problem as I would install a new dedicated line to it. I'm wondering where the placement of the electrical box would go. I haven't even looked at a microwave yet. The microwave unit would be installed under the cabinets of course. Do you think I should just place the box about 5" under the cabinet on wall or are all microwave units are different and would have different placement, thus I cannot wire unless I have the microwave unit at hand. Note; there is no existing exhaust vent. Above the stove cabinets is a soffet whereby I can exhaust out the side wall of house. I assume there are ventless microwave/vent combos. I'll have to weigh the pros and cons of vent or ventless.
Old 12-12-00, 09:54 AM
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Vent vs ventless. The vented exhaust fan comes in handy if you burn your pancakes. The vented exhaust fan would help to vacate the kitchen of smoke. With the ventless exhaust hood you could filter some smoke coming off of meat browning but will do little good helping out your hiding the fact that you burnt the pancakes. The ventless will not filter smoke in heavy quantities.

A microwave hood combo uses up enough amps in order for it to run that there is little left for anything else to be on that circuit. The hood combo should be powered by a 20 amp breaker and be dedicated to that appliance only. There is a piece in the NEC that limits the maximum load size of any one fixed in place appliance to only 50% of that ciruit's ampacity. This would mean that you can only install a fixed in place appliance on a circuit with other loads on that circuit if that appliance is not over 10 amps in amp rating during use. The microwave would exceed that maximum of the 10 amps.

You could pre install you circuit for your microwave before you purchase the microwave hood combo. The hood combo usually has a cord and plug connection. When you install your new hood combo you would drill a hole in the bottom of the cabinet above the hood in order to pass the hood combo cord and plug through that hole into the cabinet above so that you can just plug in that hood combo into a new receptacle mounted in that cabinet above the mounting of the hood. This receptacle would be where you new 20 amp circuit should be terminated and located in that cabinet above where the hood is to be mounted.

Good Luck

Old 12-12-00, 10:37 AM
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Smile Thanks Wgoodrich

Thank You Wgoodrich, that information was what I needed. I will install an outlet in the cabinet once I get the top cabinets in. That seems so simple. I thought the microwave/vent would have to be hard wired. I never thought about it coming with a plug!!! Thank You very much. It's information like this that makes me glad I finally got a computer. Now if I can just remodel this kitchen before I turn 30.

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