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-   -   split receptacle for fridge & microwave? (http://www.diychatroom.com/f18/split-receptacle-fridge-microwave-10165/)

Beren 07-25-2007 08:29 PM

split receptacle for fridge & microwave?
 
How do you professionals feel about a split receptacle on a two-pole 20A breaker for the fridge and microwave? (Older house, not enough counter space to put the microwave on the counter and use an existing appliance circuit. Has to go along the other wall by the fridge.)

The microwave draws 12A by itself, and the fridge 5-6A. Too much for one 15A circuit and iirc too much to put on a shared 20A circuit!

Stubbie 07-26-2007 12:28 AM

I see no reason why you cant have both on a 20 amp circuit. I guess I'm not following the reasoning behind your split receptacle idea for these two appliances. There are three codes that you must be concerned with NEC 210.21(B)(2), 210.23(A)(1), 210.23(A)(2), if the microwave is cord and plug then 23(A)(2) is not applicable. However if you put the microwave on a counter top then if it shares the duplex receptacale with the fridge it will have to be a gfci type receptacle or gfi breaker in the panel.

roger

Beren 07-26-2007 06:33 AM

The fridge is an inductive load, isn't it? Won't it draw more than the listed 5-6 amps when the compressor starts?

DCK 07-26-2007 08:09 AM

You are correct.:yes:

The standard rule of thumb for motor devices, when sizing an emergency power generator, is that all such electrical circuits be considered to draw 3 times their normal current on start up.

Example: Your 5 amp fridge would draw @ 15 amps. So were the microwave on the circuit total is 27 amps, which is not good.

So unless you want to constantly manage the operation of the fridge it would be best to keep the m/w off any motorized outlet

Good luck with it.

Dave

Beren 07-26-2007 08:20 AM

DCK:

So my original thought to use a split-wire receptacle
is rational in this context (as it would provide 20A dedicated to each outlet) , but I need to make sure the microwave is not on what can be classified as "kitchen coutertop" or I need a GFI on its circuit?

DCK 07-26-2007 09:40 AM

First “google” Stubbie’s cited NEC codes & read such.

I built my house & wired it back in 1977 to NEC code. Since my book is 30 years old it obviously would not be ethical for me to give you precise instructions from it.

And with @ 40 years in telecommunications I have power wired equipment that the wire size ranged from #18awg, for data circuits, to 750 mcm (a cable with @ a 5” copper circumference) for central office power boards so you can take my following recommendation as general instruction.

Knowing little of your particular circumstance it is my opinion that you would be wise to dedicate a receptacle for the m/w even though a split receptacle may meet 2007 NEC code.

Good luck with it.

Stubbie 07-26-2007 12:04 PM

It is quite common to catch the fridge and a countertop microwave on one 20 amp circuit. Start up currents for a refrigerator last around .4 seconds before falling back to running amps of 5 or 6. This will not trip the breaker if the microwave is running at the same time or vice versa. You are not creating a locked rotor condition where the breaker will trip if the start current is sustained long enough to trip the breaker whether or not the circuit is shared by another appliance. If you dedicate a 20 amp circuit to the fridge and a 20 amp to a portable microwave using a multiwire your wasting a heck of a lot of power usage.

A split receptacle is very common for a cord and plug dishwasher and waste disposal where each appliances sum currents can exceed 20 amps running .

If what you are worried about were an issue then you would have trouble plugging your 12 - 15 amp vacumm sweeper into the general receptacles in the rest of your house.

Remember code requires that the kitchen be served with at least two small appliance 20 amp circuits. These circuits are also required to serve the refrigeration equipment. So unless you dedicate the fridge to 20 amps your going to be sharing it with the countertop or other appliances for kitchen use anyway.

You are over-thinking the inductive load of a refrigerator.

This is of course your house and a split receptacle will certainly work I just think your wasting a lot of power dedicating 20 amps to each appliance.

And you have an issue with gfci for the microwave how will you do that with a split duplex receptacle?

I would only add if you do this multiwire make the microwave a self protected gfci receptacle by making it your end of run and the fridge on a non-gfci receptacle.....two duplexes instead of one split.

Stubbie

Beren 07-26-2007 01:01 PM

This issue came to the front when our first microwave died. The fridge kicked on; the microwave gasped and died.

The house we're renting is strange, and the more I learn about code the more I find is not up to current standards. Then again, the house was built in the 1950's.

There is currently a single 15A circuit supplying the fridge, basement washing machine, and some other basement outlets. (I believe current code requires that laundry circuits be dedicated to the laundry area.)

The kitchen only has one 20A appliance circuit, iirc, but I will double-check. The other circuit (which also feeds other outlets and some lights, I need to refer back to the panel diagram) has receptacles at floor level and is not GFI protected. Also, actually using them would block foot traffic through the kitchen. Putting the microwave on the 20A appliance circuit would take up most of the countertop. That space is currently needed for food preparation!

I asked the landlord the cost for a split-wire recep so I could get the fridge/mw off the shared laundry circuit. I should have mentioned that bit from the start.

Are landlords required to keep rental properties up to current code?

DCK 07-26-2007 03:28 PM

About 10 years ago I was shown a refrigerator plug that had partly melted.
The 20 amp breaker served both refrigerator & the m/w.
So I ran a dedicated line to the m/w.
But the owner bought another refrigerator & put the old refrigerator in the garage fearing the plug & age of the refrigerator.
Today his new refrigerator plug looks the same as when he bought it.
And the that 30 year old refrigerator, it is still trucking.

Beren,

Usually, but not always, any code compliance update is left up to the seller/buyer when there is a transfer of property. Check with your city/county people for more information about your situation.

Stubbie 07-26-2007 04:31 PM

Dck...I respectfully submit that you are not correctly pin pointing the fault of that fridge plug melting. It is not due to sharing a 20 amp circuit with a fridge and microwave. Plugs melt because of loose connections and the build up of heat not because of shared loads. The breaker or fuse protects the wiring before it gets too hot, of course things have to be properly protected with the correct ocpd.

DCK...If I had a microwave (12 amps) and and a electric skillet (12 amps) on a properly installed and 20 amp protected branch circuit would the plug melt because of this? BTW this is going to produce way more heat at the plug than the situation we are discussing here.


Beren:

A microwave doesn't fail/go bad because a fridge starts while on the same circuit.

There is no obligation for the land lord to update the electrical to 2005 code standards. If you are having difficulties with appliances failing and/or breakers/fuses opening then the landlord should have an electrician take a look at the electrical and the loads connected to the problem branch circuits.


Your current wiring is typical of that era. To this I would agree that a 15 amp breaker may be pushing its limit to operate a fridge and a washing machine at the same time. The running amps would exceed the branch circuit rating in that screnario.

stubbie

Beren 07-26-2007 06:17 PM

Thanks. I got home and rechecked my notes. It's a 20A breaker, but it also supplies something for the furnace.

terryfitz 08-22-2008 02:10 PM

Sorry to correct you Stubbie, but the refrigerator can, and I think should be on a separate circuit. NEC 210.52B1x2 Personally, I have always done it this way since a GFCI tripping a refridge wouldn't be known until someone opened the door or started to smell something. Unfortunately, the 2008 is now requiring that even those receptacles that are not readily accessible in the garage and basement where you might have a freezer plugged in are now to be GFCI.

Speedy Petey 08-22-2008 02:56 PM

Quote:

Originally Posted by terryfitz (Post 150874)
Sorry to correct you Stubbie, but the refrigerator can, and I think should be on a separate circuit. NEC 210.52B1x2

True, but there is nothing non-compliant about have the fridge on with a counter micro.

Of course it's not the best setup, but definitely IS legal.

210.52(B)(1) specifically allows the refer on one of the S-A circuits.
210.52(B)(1) Exc.2 specifically allows the refer on a dedicated 15 or 20A circuit if the installer desires.

terryfitz 08-22-2008 03:06 PM

Thanks Pete. I agree with you. If I read Stubbie correctly, he said that the fridge HAD to be on the GFCI circuit which it doesn't. If I misread, I'm sorry.

SD515 08-22-2008 06:29 PM

One thing I haven't seen discussed that I'll add is that if you are going to use a split duplex receptacle (on the same yoke) your 20A 2 pole breaker you mentioned will have to have a listed handle tie so both poles are shut off at the same time. Just FYI.


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