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Old 08-19-2011, 09:12 AM   #1
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dishwasher, disposal and OTR Micro circuits


Guys, I have a early 1970's construction, with what was looks like kitchen renovation in the mid/late 1980's.

coutner outlets are wired fined, refrigerator is on a 20 shared with dining room, lighting and room outlets on a 15, a dedicated 15 for disposal, a dedicated 20 for dishwasher, and 220 for the stove. There is no gas service.

At the 1980's renovation they used a 220v range with microwave attached.

I have nursed the range. the microwave blew, repair was an insane amount, and we stopped using it. at about 8 years old the oven handle broke (a GE with plastic handle mounts) and it has a dowel for a handle now. One burner is is out and two on their way out. So it has to be replaced and this type of integrated 220v range/microwave is no longer made.

Got three local electrician for pulling a new 20amp from my service panel, which is on same floor but diagonal opposite from OTR microwave in my very long shotgun style TH
1) $1150 no repair of 30 or so holes planned, hole repair estimate $400 to 500.
2) $1600 with repair of holes
3) 1300 no repair of holes

OK, so I check four of my neighbors in same association ith same type TH. One has old range still. Two have updated panel legend with DW/GD on 20 and OTR micro on what was the GD 15. One looks almost certain to have pulled a leg from one of the two 20a counter circuits. While visiting half a dozen friends homes in the past few weeks I have checked and noticed that pretty much all pre 80's has DW and disposal on the same circuit.

Dishwasher: 1.8 (motor/pump)+ 8.1 heating/dry element=9.9amps net max.
Disposal: largest that will fit in their: 6.8amps
OTR micro I am looking at: 850 watts/7.0 amps on label. others I have looked at in the range are 1000 to 1100 watts (8 to 9 amps)

Frankly I am sorley tempted to also combine dishwasher and disposal on the 20 and put the OTR micro on the 15. I have $900 for a decent range and micro, but do not have an additional $1600 to run through 20 joists for a new microwave.

It seems to me that combining the dishwasher and disposal is safe. the dishwasher only uses the heat for two 5 minute segments during its one hour run. Even if the disposal were used during those ten minutes per day that is less than 16.7 on the 20 and only for a few seconds.

The microwave would draw 7 to 8 out of the 15 depending on what model.

Frankly that is safe enough for me. I do understand the code leaving extreme tolerances in case someone installs some super high powered appliances, but franly I have seen much MUCH worse on counter appliances (coffee makers, toasters and counter micros on the same circuit.)

I can figure a junction box to extend the 15amp to the cabinet over range fine, but would like some advice on how precisely the wiring of the always hot d/w + switched disposer on a shared 20 amp is done.

Thanks in advance


Last edited by rasz; 08-19-2011 at 09:14 AM.
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Old 08-19-2011, 09:21 AM   #2
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dishwasher, disposal and OTR Micro circuits


Dishwasher & Disposal can be on the same 20 amp circuit, If putting back in a microwave rangehood, it will need its own 20 amp circuit. As for the small appliance circuits along the counter, those need to be at a minimum 2 20 amp protected circuits with a GFCI outlet either at the first on the string, or can use a gfci breaker. Outlets along the base board for kitchen & Dining have to also be 20 amp protected. The dining/kitchen outlets can not serve any other spaces/rooms in the house. Lighting can stay on the 15 amp, unless you plan on adding more than already in the kitchen/dining, can go with a 20 amp circuit, no restriction on what else the lighting can serve for other rooms (ie hall & living room/family room).

If you are planning a total kitchen remodel, it is easier to do the rewire with no gypsum board on the walls.


Last edited by gregzoll; 08-19-2011 at 09:53 AM.
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Old 08-19-2011, 09:30 AM   #3
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I can figure a junction box to extend the 15amp to the cabinet over range fine, but would like some advice on how precisely the wiring of the always hot d/w + switched disposer on a shared 20 amp is done.
No comment on the code compliance of your plan. Also, are you allowed to do wiring as a home owner in your jurisdiction?

Wiring: Install a receptacle under the sink using the 20 amp DW circuit. Split the receptacle with half hot (for the DW) and half controlled by the disposer wall switch. You will need appliance cords for the DW and disposer that will reach the new receptacle.
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Old 08-19-2011, 09:34 AM   #4
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dishwasher, disposal and OTR Micro circuits


This post is a perfect example of when not to put the dw and gd on the same circuit. While the NEC does not prohibit it, it dies require that the circuit be sized to handle it. The branch circuit supplying a motor and othr loads has to be sized at 125% of the motor load plus the other loads.
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Old 08-19-2011, 09:42 AM   #5
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dishwasher, disposal and OTR Micro circuits


The dw and gd are required to be on separate circuits for your installation. If the gd is a 1/3 hp motor then the current is based on 7.2 amps. 7.2 x 125% = 8.95amps. Add that to the 9.9amps for the dw and you have a total of 18.9 amps. A 20amp circuit is overloaded. Some posters here make blanket statements that the gd an dw are permitted on the same circuit. They are correct as long as the circuit is sized to handle it. In this case it is a code violation.
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Old 08-19-2011, 09:45 AM   #6
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Just a clarification…In a residential kitchen, only the receptacles that serve the countertops have to be GFCI protected. Dining room receptacles don’t have to be GFI’d, unless they’re within 6 ft of the sink edge and 2011 code. 2008 code doesn’t require GFI for dining rooms, but both ’08 & ’11 require AFCI for dining rms, unless local amendments supersede the requirement.
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Old 08-19-2011, 09:55 AM   #7
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dishwasher, disposal and OTR Micro circuits


Quote:
Originally Posted by electures View Post
This post is a perfect example of when not to put the dw and gd on the same circuit. While the NEC does not prohibit it, it dies require that the circuit be sized to handle it. The branch circuit supplying a motor and othr loads has to be sized at 125% of the motor load plus the other loads.
The garbage disposl and dishwasher are not continuous loads. The 125% applies to motors that have to run all the time, not something that only runs for a few seconds like a garbage disposal, or a dishwasher that at the most would run an hour at a time.
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Old 08-19-2011, 09:57 AM   #8
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dishwasher, disposal and OTR Micro circuits


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Originally Posted by electures View Post
The dw and gd are required to be on separate circuits for your installation. If the gd is a 1/3 hp motor then the current is based on 7.2 amps. 7.2 x 125% = 8.95amps. Add that to the 9.9amps for the dw and you have a total of 18.9 amps. A 20amp circuit is overloaded. Some posters here make blanket statements that the gd an dw are permitted on the same circuit. They are correct as long as the circuit is sized to handle it. In this case it is a code violation.
You are talking about motors such as pump risers, fan motors to move air into spaces like on board a ship, or irrigation motors, not a garbage disposal or dishwasher.
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Old 08-19-2011, 10:20 AM   #9
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dishwasher, disposal and OTR Micro circuits


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Originally Posted by gregzoll View Post
If you are planning a total kitchen remodel, it is easier to do the rewire with no gypsum board on the walls.
greg, thanks if I was planning a remodel this would all be different. It is just replacement of a range with otr 220 micro feed by the range's 220 (a type no longer made) with a seperate 220 range and 120 otr micro.
Everything else in the kitchen is in compliance: four 20 amp circuits; two 15 amp circuits an a 220. specifically: 2x20 amp circuits on counters; 1 20x serving refrigerator and d/r outlets; 15 dedicated direct wire on disposal; 20 dedicated direct wired on d/washer; 220 direct wired to range; and lights and floor outlets on separate 15amp.

$1600 in additional wiring to simply place an OTR circuit in a small two person home so I can be well under capacity except for being at 80% of capacity instead of 77% of capacity for ten seconds a day, if I happen to run disposal when dishwasher is in heat cycle is not something I will lose sleep over.

If I am worried at selling time or if home inspector raises an issue, I can just remove the disposal at that point

Quote:
Originally Posted by electures View Post
This post is a perfect example of when not to put the dw and gd on the same circuit. While the NEC does not prohibit it, it dies require that the circuit be sized to handle it. The branch circuit supplying a motor and othr loads has to be sized at 125% of the motor load plus the other loads.
And respectfully, your post shows why people take codes with a grain of salt because with your interpretation of the code, with motor load calculations that would mean requiring 30 amp for plenty of >1/2 hp consumer disposals, putting 99% of 15 and 20 amp circuit disposals out of compliance.
For my installation I am talking abut the rated plate amps by the maker, not the motor calculation based on horsepower

Also this circuit would be following assuming one hour per day for the dishwasher and 30 seconds per day for the disposal:
96% of time: no load whatever.
3.9% of the day: 1.8 amps
.5% of the day: 9.9 amps
.03% of the day (assuming the very unlikely case of disposal used while dishwasher is in heat cycle: 16.7 amps/20 ie circuit only being 120% tolerance instead of 125, for 1/3000th of the day.
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Old 08-19-2011, 10:27 AM   #10
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dishwasher, disposal and OTR Micro circuits


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Just a clarification…In a residential kitchen, only the receptacles that serve the countertops have to be GFCI protected. Dining room receptacles don’t have to be GFI’d, unless they’re within 6 ft of the sink edge and 2011 code. 2008 code doesn’t require GFI for dining rooms, but both ’08 & ’11 require AFCI for dining rms, unless local amendments supersede the requirement.
thanks. I am not touching the two 20 amp kitchen counter circuits which serve a total of three outlets. So even though I have a single 20 amp circuit serving only one counter outlet, and another serving two coutner outlets , I feel pulling from their would be much more risky due to the fact that a coffee maker, toaster oven or some other high demend device might be plugged in there. Although as I said one of the three of my nieghbors units where the range was prelced, the installer wired teh new outlet to a counter 20amp, and two did what I am considering doing.

the only thing I may do on those counter circuits is replace two that are not GFI, one being 18" from the sink and one 24" from it, which apparently was not required for code when installed by builder, but seems sensible to upgrade do while I do the other work.
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Old 08-19-2011, 10:42 AM   #11
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the only thing I may do on those counter circuits is replace two that are not GFI, one being 18" from the sink and one 24" from it, which apparently was not required for code when installed by builder, but seems sensible to upgrade do while I do the other work.
You do not have to replace the receptacles if they are already GFCI protected. The requirement for kitchen countertop receptacles to be GFCI protected has been in place for many code cycles, so check if they are already first.
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Old 08-19-2011, 11:08 AM   #12
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You do not have to replace the receptacles if they are already GFCI protected. The requirement for kitchen countertop receptacles to be GFCI protected has been in place for many code cycles, so check if they are already first.
Interesting. this is a early 1970s construction (40 yrs old), with a mid 1980s (25yrs or so) remodel. l the outlet that is actually over the sink has what I commonly understated as GFI (test and reset buttons on face as in my bathrooms), but the outlet 18" to the right and 24" to the left look to be standard outlets. Is there some GFI setup I would not see on the outlets?

Now on running dedicated 15 amp vs dedicated 20 amps for the microwave. I know there are higher rated microwaves, but I am looking at 20 right now that are 850 to 1100. that is not the microwave power but 7 to 9.1 on the makers plate, meaning they are taking full power microwave, fan and light into account to label that max 7 to 9 amps. My current plan is to go with a 900 watt/7.5amp max unit which is exactly 50% of of the dedicated 15 I would have from taking the dedicated disposal circuit, while pairing the disposal on the d/washer 20 amp. The only worry is the if a future owner would but a monster in there. But I do not intend to falsify the breaker box label, nor put a 20 breaker on a 15, nor even put a 20 amp receptacle for the m/w, or do anything that would be different from the older 15 amp otr mw code,and a buyer could not assume it was 20 amp since prior codes allowed 15 amps according to all of my local electricians.

So my preferment is to go pairing the dw and disposal on the dedicated 20, and running the 15 dedicated to the otr mw.

One other quesiton. my stove 220, the dw and the disposal are all direct wired. no pugs or receptacles. My thought was to place a junction box and direct wire from there (Disp would have to go to switch). the only receptacle added would be for mw in cabinet. my local code seems to say direct wired and I'd rather keep it that way.

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Old 08-19-2011, 11:26 AM   #13
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dishwasher, disposal and OTR Micro circuits


I will play the Devil's advocate. Since an OTR microwave is a portable device (plugs in the same way a counter top MW does), why can not it plug into a SABC?

BTW, we have been round and round on ameracity and over-current devices on dishwashers and disposers. Consensus seems to be that NEC motor sizing requirements are not applied to these devices in a residential setting.
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Old 08-19-2011, 01:08 PM   #14
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Before you buy a new microwave/vent hood double check the specs. Some can be installed on a 15 amp circuit. If the manufacturer specs a 20 amp dedicated circuit and you don't follow those instructions your not in compliance.

A 1000 watt microwave is 1000 watts cooking, not input, power. A typical 1000 watt GE microhood is listed at drawing 1585 watts or 13.2 amps.

Good luck.
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Old 08-19-2011, 01:12 PM   #15
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I do understand the intent of the codes for new construction major remodels etc..

I know they have to take into account is even on green appliances there is not really a reduction peak/spike load. EG when you replace your incandescents with fluorescents your start-up draw may in fact be more even if you have reduced the average draw by 1/2 or more. Same is true with refrigerators,where efficiencies may mean the motor works less hours but when running it is not using less current. On top of that counter-top tasters become toaster ovens and then become toaster convection ovens. I am sure some makers of OTC microwaves might not worry about having four incandescent for lighting, a high power cfm fan and for that matter high draw heater elements to create a "multi purpose microwave/convection/hood.

If I were doing a remodel, I would run plenty into the kitchen, and if I didn't add over the code, I would run a conduit (my 1600 estimate for the circuit alone would be 1/5 that if there head been conduit). I would run a couple of cat6 for that matter.

But I keep coming fact to the fact with 15 amp dedicated for otr microwave I am:
a) looking at several OTR labeled 7.5 to 8 amps
b) that is well withing specs intent for that microwave ~ 50% on a 15 amp dedicated
c) the breaker box will say 15 amps
d) there are lots and lots of 15 amp dedicated otr range supply from prior codes.

Seriosuly, if I was writing that there was a 15 amp up there in the cabinet over the m/w slot, and I had determined it was dedicated, ie fully up to old code. and I was writing here saying I intended to put a labeled 7.5 to 8 watt otr microwave on an existing unused 15amp dedicated otr mw outlet , would you guys say I was creating a danger?

I am trying to balance that against multiple quotes over $1600 soley to run a single 20 amp from my breaker box to my range -- which I cant do and would mean I would have to put a microwave on a counter and share circuit with a toaster and espresso machine!

Quote:
Originally Posted by AandPDan View Post
Before you buy a new microwave/vent hood double check the specs. Some can be installed on a 15 amp circuit. If the manufacturer specs a 20 amp dedicated circuit and you don't follow those instructions your not in compliance.

A 1000 watt microwave is 1000 watts cooking, not input, power. A typical 1000 watt GE microhood is listed at drawing 1585 watts or 13.2 amps.

Good luck.
thanks I know that. that is why I am stating the labeled amps of the ones I am looking at and not the advertised 'microwaving power'. the labeled amps, unless I have a very poor understanding, would be for mw on and exhaust and any lamps on.


Last edited by rasz; 08-19-2011 at 01:17 PM.
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