Should the microwave be on a dedicated circuit?

I typed up everything below in hopes that you guys would come up with an answer that allowed me to NOT go crawling around in my attic but I think I already know the answer. To be short, should the microwave be on it's own circuit?

Preserved for context:

It was supposed to be separated during my kitchen remodel. I was going to put my disposal and dishwasher on the same circuit and then steal the power for the microwave. That was before I realized the dishwasher/disposal was on 4/3 Romex (I think that's what it's called) and I couldn't exactly split them up. Since we were in demo mode I instead put the microwave on the same circuit as the countertop outlets.  

The problem is those counter top outlets power an espresso machine, toaster oven and also my plasma TV. As long as we're not using all 4 at the same time the breaker doesn't trip. Unfortunately, sometimes we find a way to use all at the same time. Previously the microwave shared power with my guest bath, outdoor lights and all kinds of overhead lights.

Current Panel Setup:

W ould it be best to have the microwave on

I have zero regrets putting our over-the-stove microwave on its own breaker. It is a beast but with our ancient wiring it is nice to know I don't have a random wire in the wall glowing like an Edison bulb when we are reheating leftovers.

what is the amperage needs of the Microwave?

So, you can regularly overload the circuit?

I think you know the answer. 

Even if you have a small microwave and can get by without burning the house down, it’s too easy to buy a bigger one when you later replace the unit. 

Yes, The wiring should be upgraded. 

BTW, the dishwasher and disposal were not a large electrical load. All that countertop stuff you now have married to the microwave are. 

SVreX said:

Even if you have a small microwave and can get by without burning the house down, it’s too easy to buy a bigger one when you later replace the unit. 

Yes, The wiring should be upgraded. 

BTW, the dishwasher and disposal were not a large electrical load. All that countertop stuff you now have married to the microwave are. 

 

The microwave was never on the same circuit as the dishwasher and disposal. I was hoping to combine the dishwasher and disposal so that there would be a free circuit right there for the microwave. But since the dishwasher/disposal were part of the 4/3 romex with the common ground or whatever I couldn't split them up. So the dishwasher and disposal are still on their own separate circuits. The micro went from guest bath, outdoor outlets, kitchen lights, and hallway lights to the kitchen countertops / entertainment closet. Both would regularly overload.

I'll have to learn how to add a breaker. The wiring in the attic is easy to access, just a bit warm up there right now.

You've got open spots in the panel and access to run the wire?  Heck ya it should be on a separate breaker.

In reply to Enyar :

You still went backwards. 

Lighting circuit load doesn’t generally change much.  A guest bath load would likely only be impacted by a blow dryer. 

Every appliance you named on the kitchen counter has a large draw. 

Add a circuit. 

I need to do this. Our microwave is on the same circuit as the dishwasher and whole-house attic fan. We can run one of those things at a time, sometimes two, though that's risking it. Any more than that and we pop the circuit breaker.

In reply to mad_machine :

My microwave draws 15 amps.  (This is a BIG microwave by the way)

I plug it into a 20 amp  stand alone circuit.  

While I was remodeling I had it plugged into a 15 amp circuit.  We could not run it and the coffee maker at the same time without tripping the breaker  but it worked fine running alone.

I think you did answer your own question.  In this case a tripped breaker means the circuit is overloaded.

Putting the microwave on its own circuit isn’t the only solution, but it will work.

that is a big microwave.

Some day I will rewire my house.  Loads and codes have changed since 1961.  Fridge, microwave, living room lights and TV/entertainment center are all on one circuit.  Some days it blows...

And my breaker box is full.

Yes add a circuit if you can. It sounds like you should think about the layout of your kitchen and shifting loads can give you better balanced circuits. The microwave can live on a circuit alone. But I would over do the microwave circuit so there is extra capacity on this one. That way the use of some big mixer or other big kitchen tool can use the microwave circuit. 

You guys have lights on the same circuts as power outlets? That seems so strange to me. 

Over here it's standard practice for lighting to have it's own circut.

What amperage are the dishwasher and garbage disposal circuts, piggybacking the microwave onto one of them may be the easy answer? I also don't get why they have their own circuts given neither are high load applications.

daeman said:

You guys have lights on the same circuts as power outlets? That seems so strange to me. 

Over here it's standard practice for lighting to have it's own circut.

What amperage are the dishwasher and garbage disposal circuts, piggybacking the microwave onto one of them may be the easy answer? I also don't get why they have their own circuts given neither are high load applications.

The problem is the dishwasher and disposal is all 4/3 so at least at the time I couldn't wrap my head around how to split it up. I guess I could just cut it in the attic, add a box and then tap into it there?

In reply to Enyar :

Ok, please explain. You’ve send that several times. 

So you mean wire gauge?  There is no way your dishwasher and disposal are 4/3 wire.  I’m not even sure such a thing exists. 

Do you mean 14/3?  Are you talking about something other than wire gauge?

SVreX said:

In reply to Enyar :

Ok, please explain. You’ve send that several times. 

So you mean wire gauge?  There is no way your dishwasher and disposal are 4/3 wire.  I’m not even sure such a thing exists. 

Do you mean 14/3?  Are you talking about something other than wire gauge?

what he said.  it's fairly straightforward.  14ga wire (thickness), 3 conductors (red black white) and a ground (that's implied).  red and black are hots, i think you need a switch in there and imagine there's probably an outlet under the sink that powers them both?

Well, that didn’t make it any clearer. 

14 gauge wire is not sufficient for a 20A circuit. A microwave can be 1500 watts,  which would require a 20A circuit. 

14/3 COULD be 2 hot legs, but if it is 220V that would be weird. It would only be legal if it was a 15A 220V line, which doesn’t really exist.   If it’s 2 separate 110V circuits, that is not safe nor legal because they would be sharing a neutral. 

14/3 is generally used for 3 way switches in lighting circuits only, not kitchen recep circuits. 

And he didn’t say 14/3. He said 4/3 (which is much too large to be ganged together in a 3 conductor wire). 

I don’t see anything straightforward at all. 

My kitchen has a dedicated 20A circuit for the microwave. The outlet is accessible via the counter top, two or three studs away from where the microwave is actually mounted above the stovetop. The PO decided to wire it into an existing upstairs lighting/wall outlet circuit instead of moving the dedicated circuit. Sigh. It's on my to-do list but I'll have to open up the drywall so maybe when I renovate the kitchen. In the meantime, don't vacuum in that room upstairs while running the microwave :/

Forgive me for being blunt, but it seems you are halfway to burning down your house. If you don't know electrical, find somebody who does.

The NEC (section 210) requires a dedicated 20A circuit for a "permanently mounted" microwave, whether plug-in or hardwired. If it's a countertop model, it can plug into one of the (2 required) branch circuits that should feed the kitchen outlets, but it can't consume more than half the available power on that circuit. Either case requires GFCI.

I too, like SVreX, suspect you mean 14/3 wire for the dishwasher/disposal. If so, it's likely a multi-wire circuit with a shared neutral and a split outlet, and you DO NOT want to mess with that. They are not uncommon for this situation, but not recommended either.

Personally, I ran a dedicated 20A circuit for the entertainment center. Looks like you have that option. 

Good luck, and have fun pulling your new circuit. 

In reply to llysgennad :

Right, but a microwave will almost always consume more than half of the available power on a 20A branch circuit, therefore even a countertop model should have a dedicated circuit. 

I agree with your bluntness. 

stylngle2003 said:

SVreX said:

In reply to Enyar :

Ok, please explain. You’ve send that several times. 

So you mean wire gauge?  There is no way your dishwasher and disposal are 4/3 wire.  I’m not even sure such a thing exists. 

Do you mean 14/3?  Are you talking about something other than wire gauge?

what he said.  it's fairly straightforward.  14ga wire (thickness), 3 conductors (red black white) and a ground (that's implied).  red and black are hots, i think you need a switch in there and imagine there's probably an outlet under the sink that powers them both?

Sorry I meant 14/3. Both the dishwasher and disposal are hardwired off the 14/3 wire coming from the panel on 2 separate breakers.

llysgennad said:

Forgive me for being blunt, but it seems you are halfway to burning down your house. If you don't know electrical, find somebody who does.

The NEC (section 210) requires a dedicated 20A circuit for a "permanently mounted" microwave, whether plug-in or hardwired. If it's a countertop model, it can plug into one of the (2 required) branch circuits that should feed the kitchen outlets, but it can't consume more than half the available power on that circuit. Either case requires GFCI.

I too, like SVreX, suspect you mean 14/3 wire for the dishwasher/disposal. If so, it's likely a multi-wire circuit with a shared neutral and a split outlet, and you DO NOT want to mess with that. They are not uncommon for this situation, but not recommended either.

Personally, I ran a dedicated 20A circuit for the entertainment center. Looks like you have that option. 

Good luck, and have fun pulling your new circuit. 

I will run a new 20a circuit with 12 gauge wire for the microwave.

SVreX said:

Well, that didn’t make it any clearer. 

14 gauge wire is not sufficient for a 20A circuit. A microwave can be 1500 watts,  which would require a 20A circuit. 

14/3 COULD be 2 hot legs, but if it is 220V that would be weird. It would only be legal if it was a 15A 220V line, which doesn’t really exist.   If it’s 2 separate 110V circuits, that is not safe nor legal because they would be sharing a neutral. 

14/3 is generally used for 3 way switches in lighting circuits only, not kitchen recep circuits. 

And he didn’t say 14/3. He said 4/3 (which is much too large to be ganged together in a 3 conductor wire). 

I don’t see anything straightforward at all. 

The plan to steal the disposal circuit for the microwave was before I realized it was part of the 14/3 wire which was run.

In reply to Enyar :

New 20A 12/2 circuit is a good plan. 

While you are pulling wire, pull another one for the dishwasher, and abandon 1 hot leg in that 14/3. It’s got a shared neutral, and that’s dangerous. 

14/2 would be fine for the dishwasher, but 12/2 is better.