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Old 08-19-2011, 04:04 PM   #16
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dishwasher, disposal and OTR Micro circuits


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Originally Posted by rasz View Post
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


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.
My interpretation is based on NEC requirements not a gut feeling. Obviosly you have read my other posts. Good for you. But did you notice that not one person proved me wrong. As for your installation, look at the DW installation instructions. The manufacturer will either recommend or require a seperate circuit. Which way you choose to wire this project is not my concern, but you will be the person constantly walking to the panelboard to reset the breaker cursing yourself for not doing it right the first time. Good luck!

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Old 08-19-2011, 04:05 PM   #17
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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.
Didn't state that they were. I only state what the NEC requires. You should try it sometime.
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Old 08-19-2011, 04:07 PM   #18
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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.
Motors are motors. That is why Article 422 - Appliances requires that Article 430 has to be followed also.
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Old 08-19-2011, 05:01 PM   #19
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Originally Posted by electures View Post
Didn't state that they were. I only state what the NEC requires. You should try it sometime.
That is for continuous loads. Dishwashers and disposals are not continuous. That would mean that they would have to run for eight hours or more.
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Old 08-19-2011, 05:15 PM   #20
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Motors are motors. That is why Article 422 - Appliances requires that Article 430 has to be followed also.
Different type of motors. They do not fall into those two articles. Only way they could possibly, would be if they were commercial grade appliances, which are used for longer periods. The only article that I can see them fitting under is 430.53, and yes 422, and 210.23. It is just that you are stating it in a broad aspect, not that the way that the NEC is stating. That is why manufacturers state in their paperwork the proper size wire & breaker/fuse, because homeowners are not going to have a copy of the NEC handy, nor are they going to take the time to question.

If anything, most will hire an electrician, and have them wire it, because some get that feeling that they are over their head, when they feel that people start to doubt their abilities. As for the over current protection, I am like you, two separate circuits, because you never know when one may trip the breaker, when the other is being used, due to initial surge current when starting up the item. That is why I have still not decided how I am going to do both the portable dishwasher & countertop microwave that sits on top of it, due to they both use the same gfci outlet, which is right next to the sink base, and that I may move the microwave over the stove, but have not decided, until I figure out cabinets.

Even redoing the wiring in my house gave me a headache, because it was only four original circuits, and had a circuit for the dryer added some time later, and a outlet for the washer, and one breaker for the garage. I still have to go back over it and redo some circuits, because I am not happy at this moment with some circuits that were done before we moved in, but everything is protected as it should be, and not overloaded.
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Old 08-19-2011, 06:24 PM   #21
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That is for continuous loads. Dishwashers and disposals are not continuous. That would mean that they would have to run for eight hours or more.
You sure about that?
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Old 08-19-2011, 06:43 PM   #22
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You sure about that?
The great thing about appliances and the such, manufacturers have already done the calculations for the equipment, so you do not have to figure run time, load, etc. As for dishwashers, microwaves, disposalls, dryers, clothes washers, refrigerators, etc. is they do not run for long periods of time, unlike a furnace or air conditioner unit. Window units are one that I would look at run time, because that equipment can run for very long periods, just like attic fans, so yes you have to take run & load into consideration when installing those, but again, the manufacturer has already figured everything up for you, so you do not need to do it.
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Old 08-19-2011, 06:55 PM   #23
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dishwasher, disposal and OTR Micro circuits


NEC 2008

422.10(A) 2nd paragraph
430.6(A)(1) Exception 3

both deal with motor operated appliances

If it's labeled with voltage and amperage that is what you use, not 430 tables and calcs.
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Old 08-19-2011, 07:33 PM   #24
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You sure about that?
Oh, this from Article 100: "Continuous Load. A load where the maximum current is expected to continue for 3 hours or more." So, I was off by five hours. Shoot me. I do believe that the appliances we are talking about (DW, MW, GD) do not fit under this description. That would also be refrigerators, stoves, range hoods, clothes washers, clothes dryer, furnaces, sump pumps. I would though place air conditioners under this description, but as brric has stated, the manufacturer has taken the pleasure of not doing the math, due to the place a label on the device to tell you the proper sizing for the breaker.
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Old 08-20-2011, 06:15 AM   #25
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OK. here is my plan:
a) circuit "a" 20amps: dishwasher and disposal on existing ded. dishwasher 20 amp, wired as follows: http://forums.mikeholt.com/showthrea...890#post857890
b) circuit "b" 15 amps: use former 15 amp disposal for microwave. Install 15 amp receptacle on cabinet. The microwave/hood I am planning on installation instructions say "15 or 20 amp dedicated."

Likelihood of breakers tripping on either: none

Code compliance on listing unit for sale in 5 to 10 years:
a: remove disposal. 20 minutes work, $5 in plumbing parts, $5 electrical parts. Full code compliance
b: swap microwave/hood for hood. hardwire hood. 100% code compliant. Labor 1 hour. parts (hood and paint) $100.


Circuit loads:
a) 20 amp circuit dishwasher + disposal
- 23 hours per day - a couple of mA dishwasher standby
- 1 hour per day - 1.8 amps for dishwasher pump
- 8 minutes per day - 8.1 amps dishwasher heater dry cycle (motor does not run)
- 2 minutes per day - 9.9 amps (dishwasher pump and heat element the motor and heater on currently on water heat cycle)
- ten seconds per day: 6.8 amps disposal.

assuming worse and most unlikely case of concurrent usage (disposal pulsed during two minutes/day of DW water heating) one gets 16.7amps on a 20Amp circuit for ten seconds out of the day.

b) 15 amp microwave/hood circuit loads
- off for 23 hours per day
- 30 minutes per day @ about one amp for fan
- 30 minute per day @7.5 to 9 amps with microwave on high and hood fan running.
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Old 08-20-2011, 06:35 AM   #26
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My interpretation is based on NEC requirements not a gut feeling. Obviously you have read my other posts. Good for you. But did you notice that not one person proved me wrong.
yes you have said the 99.999% of inspectors and jurisdictions are wrong, the engineers who rate the disposals, as well as the US government agencies that oversee appliance ratings, and for that matter UL are wrong. did it occur to you why they didn't bother to "prove" you wrong ?


Quote:
Originally Posted by electures View Post
Which way you choose to wire this project is not my concern, but you will be the person constantly walking to the panelboard to reset the breaker cursing yourself for not doing it right the first time. Good luck!
so a 16.7 am load for ten seconds a day on a 20 amp circuit is going to have me "constantly walking" to the panelboard? No, it wont have me walking to the panelboard ever.
my entire second floor is one one 15 amp circuit. That is thanks to "code", wired by a licensed electrician, and approved by inspectors at the time. That has me walking to the panelbox twice per year, and proably has that 15 amp circuit aging prematurely from heat from it being used at vbery high load/cacpity for hours on end. that would cost a couple hundred bucks to change with a licensed electrician because one bedroom is above the panel board.

That is the irony. something I do not need to change to be complaint, adding a new circuit upstairs, and which would cost only about $300 to $400, would add a lot of convenience and safety. yet spending $1,600 to wire a dedicated microwave circuit, when the existing power to kitchen allows it, would be something I would need to do to pass an inspection.

Last edited by rasz; 08-20-2011 at 06:40 AM.
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Old 08-20-2011, 07:08 AM   #27
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dishwasher, disposal and OTR Micro circuits


Quote:
Originally Posted by brric View Post
NEC 2008

422.10(A) 2nd paragraph
430.6(A)(1) Exception 3

both deal with motor operated appliances

If it's labeled with voltage and amperage that is what you use, not 430 tables and calcs.
That is correct.

At a recent inspector ceo class, I was speaking with another inspector.
We know that only 1 20 amp laundry circuit is required.
He went to inspect the job and the appliances were in place. The combined rating of washer and dryer was about 22 amps. He had to fail it, until a 2nd circuit was installed.
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Old 08-20-2011, 07:22 AM   #28
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dishwasher, disposal and OTR Micro circuits


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Originally Posted by rasz View Post

Code compliance on listing unit for sale in 5 to 10 years:
a: remove disposal. 20 minutes work, $5 in plumbing parts, $5 electrical parts. Full code compliance
b: swap microwave/hood for hood. hardwire hood. 100% code compliant. Labor 1 hour. parts (hood and paint) $100.
I would not do any of this in preparation for resale. The chances of any of this being an issue is "slim & none". Probably closer to none than slim.
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Old 08-24-2011, 04:59 PM   #29
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thanks for everyone's help. all done working fine. no breakers tripping. dishwasher disposal 20amp circuit not tripping even when I use test disposal during the ten minutes/day while dishwasher is using both pump motor and its heater element.

Checked a few more identical units in my condo, every single one of many that have retrofitted over-the-range microwave/hood, the electricians have either used counter circuit (which I would not do) or did what I did: combining dishwasher and disposal and used the 15 amp disposal as a dedicated for microwave/hood circuit.

Again I understand why the code is there . But loading a 20 amp circuit 23 hours at zero, 50 minutes of the 24th hour at less than two amps (motor only dishwasher cycle), and 10 amps for 9 minutes (motor and heater) seconds, and for ten seconds a day maximum at 17 amps, does not seem worth $1600 in running a new circuit.
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Old 08-24-2011, 07:47 PM   #30
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Thanks for the update Rasz. Glad it's working out. I doubt you'll have any problems.

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