Microwave wiring requirements

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  #1  
Old 02-12-02, 08:39 AM
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Microwave wiring requirements

I have just installed a Sears 1000 watt microwave and range hood combo.

It worked fine for a week or so, but now it runs for 20-30 seconds and the error message F7 appears in the clock area of the display panel and the unit shuts off. The breaker does not trip.

The install manual says I need a 15 or 20 amp 120V 60Hz supply to the microwave.

My previous countertop microwave was 600 watts and on a dedicated circuit. I tapped off of this outlet for the power for the new model and I am not using the old plug for and other item in conjunction with the new microwave/range hood.

The old plug had 12/2 w/ a ground wire to it and I tapped off with 14/2 with a ground.

Could this be the problem. Should I have tapped off with a 12/2 wire? Should I just run a new 12/2 with ground straight to the breaker box?

Total run length from the breaker box to the old outlet was 80 feet with my tap off running 25 feet to the new microwave.

Is my wiring the cause or did I just get a lemon with this microwave?

Sears can tell me nothing about what the F7 error code means.

Does anybody know of an on-line site which has a calculator to figure what size of wire to use based on power consumption of the appliance and run length from the breaker to the appliance?

Thanks for any and all help.
 
  #2  
Old 02-12-02, 08:54 AM
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What size is the circuit breaker feeding the dedicated outlet that is now feeding the new microwave? Is the new microwave cord and plug connected or is it hardwired (not cord and plug)? Is there any other load on the dedicated outlet besides the new microwave?
 
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Old 02-12-02, 09:06 AM
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It is a 15 amp breaker on the dedicated outlet that now feeds the new miocrowave. The microwave is plugged into an outlet (new) that was installed in the cabinet above the microwave. This new outlet gets its power from the old dedicated microwave plug. There was no option to hardwire the microwave. It comes with a 3 prong cord and that is what was used.
 
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Old 02-12-02, 09:08 AM
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Thinman,

Forgot to indicate that there is nothing else (other than the new microwave) plugged into or using any "juice" from the old dedicated circuit.
 
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Old 02-12-02, 09:09 AM
snack
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Have yu rechecked to make sure all the connections are good and tight. A poor connection will heat up especially under a heavy load.
 
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Old 02-12-02, 09:11 AM
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I haven't rechecked connections but can and will. This was why I was wondering about the wire size, 12/2 vs. 14/2.
 
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Old 02-12-02, 09:20 AM
rhhjr
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SOMEBODY at Sears and/or the manufacturer can tell you what "error F7" means.
 
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Old 02-12-02, 11:09 AM
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rhhjr,

I wish there was somebody at Sears that could answer my question about the F7 error message. The repair line is nothing more than a scheduling service for repair techs and the scheduler told me that there is no longer a technical advice line for Sears. The owners manual is no help either as it does not address any error codes, it just tells you to contact the repair line---Sounds like a vicious cycle to me and unfortunately I'm caught in it. I'm holding off on calling for a tech, because I don't feel like wasting 1/2 day waiting around for the tech to arrive.
 
  #9  
Old 02-12-02, 01:13 PM
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There is a recall in effect for certain Whirlpool/Kenmore microwave/rangehood combinations. You might want to check http://www.repair.whirlpool.com/MWR/welcome.jsp to see if your unit is affected.
 
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Old 02-12-02, 01:46 PM
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You may use either 14-gauge or 12-gauge wire, or both, on a circuit protected by a 15-amp breaker. This has nothing to do with your problem, although I'd venture that almost everyone here would have continued the circuit with 12-gauge.

If the unit is new, see if the warranty includes in-home service.
 
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Old 02-12-02, 02:12 PM
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You could use an extension cord to plug the microwave into a different receptacle and see if it still displays the "F7" error".
 
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Old 02-12-02, 02:22 PM
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mikewu99 and John Nelson,

Thanks for your replies. Mike, I checked the web site and my microwave may fit into the recall. I have to check for a "green sticker" near the serial # to tell me whether or not the unit is okay. Apparently, even if the serial # starts with XC(signifying a recalled unit) as long as there is a green sticker it is supposed to be okay. I'll do that when I get home tonight.

John, I'm probably going to pull out the 14/2 and run 12/2. Just too lazy to run out and get 12/2 when I did the initial install.

If my unit was one of the recalled ones, I'll probably rip the whole unit out and take it back to Sears just to show how disgusted I am that they would sell recalled items.

I'll send out a post after this saga concludes.

Thanks again.
 
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Old 02-14-02, 12:55 PM
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Well the Sears Tech showed up today and he had to spend 15 minutes on the phone with his office to get the lowdown on the F7 error message.

It appears the microwave has a rather sophisticated "brain" which tells it when it is putting out too much power for the amount of food that is being heated. To avoid damaging the magnetron, the unit turns itself off and displays the F7 error.

The solution is to utilize a lower power level, (not level 10 as I was doing) and let the food heat a little longer.

I guess I had that Tim Allen syndrome of "More Power" which as he showed time and again ain't necessarily so.

Thanks to everybody for their input and I'm hoping that my problem will be solved--if not I'll post again.
 
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Old 02-14-02, 06:39 PM
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Don't know if anybody else feels this way, but I think the tech's explanation sounds pretty fishy.
 
  #15  
Old 02-14-02, 06:41 PM
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It sounds like you have this solved but for future reference, you have plenty of power assuming the circuit is wired correctly. You should always use the same wire guage in a circuit run so I would definitly replace the 14/2 with 12/2.

You can determine the maximum amperage draw on the appliance with the following formula: Amps=Watts/Volts. Your microwave is rated at 1000 maximum Watts power (this is peak power). Divide that by 120V and you have 8.3 Amps. A dedicated 15 AMP circuit would easily handle this. Good luck.
 
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Old 02-18-02, 07:53 AM
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The saga continues. It was two days after the tech left and the first time I needed to reheat something in the "repaired" micowave. It lasted about 1 1/2 minutes of a 3 minute low power cycle before the F7 error message returned.

Today I return to Sears with a hardly used, out of box microwave for a refund.
 
  #17  
Old 02-19-02, 08:53 AM
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Well, John Nelson called it. The "repaired" microwave lasted about 1 1/2 minutes out of a 3 minute low power reheat cycle before I got the F7 error message again.

I have returned the microwave to Sears and I think it is in sporting goods to be used as a boat anchor!!!!!!!!

I have a different model on order and should have that one installed by Sunday.

Thanks to those who have replied and offered suggestions--I have enjoyed and appreciated your expertise and comments.
 
 

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