Join Early Retirement Today
Reply
 
Thread Tools Search this Thread Display Modes
Possible NEC Violation?
Old 05-23-2014, 07:59 AM   #1
Thinks s/he gets paid by the post
DFW_M5's Avatar
 
Join Date: Sep 2003
Posts: 4,980
Possible NEC Violation?

Recently discovered that our builder has our builtin microwave and our gas range hood wired together on a single 20a breaker. I believe per NEC, the maximum recommend amps for a 20a circuit is 16a.

That said, my GE microwave shows 1.65 kw on the sticker inside the microwave, but their spec sheet claims 1200 microwave watts.

Since the hood is rated at 4.1a @120, if I use 1.65kw on the microwave, this would push these two appliance over 16a vs using 1200W which would not.

Wondering if any of our EEs knowledgeable in residential wiring can advise?
__________________

__________________
Doing things today that others won't, to do things tomorrow that others can't. Of course I'm referring to workouts, not robbing banks.
DFW_M5 is offline   Reply With Quote
Join the #1 Early Retirement and Financial Independence Forum Today - It's Totally Free!

Are you planning to be financially independent as early as possible so you can live life on your own terms? Discuss successful investing strategies, asset allocation models, tax strategies and other related topics in our online forum community. Our members range from young folks just starting their journey to financial independence, military retirees and even multimillionaires. No matter where you fit in you'll find that Early-Retirement.org is a great community to join. Best of all it's totally FREE!

You are currently viewing our boards as a guest so you have limited access to our community. Please take the time to register and you will gain a lot of great new features including; the ability to participate in discussions, network with our members, see fewer ads, upload photographs, create a retirement blog, send private messages and so much, much more!

Old 05-23-2014, 08:12 AM   #2
Full time employment: Posting here.
 
Join Date: Jan 2011
Location: Just North of Boston
Posts: 517
I am an amateur, so take with a grain of salt...

I believe per NEC, the maximum recommend amps for a 20a circuit is 16a continuous or 20a non-continuous..

amps = 1000 kilowatts / volts
So, the microwave amps = 1000 * 1.65 / 115v = 14.34amps

For a total 4.1 + 14.34 = 18.44a

It is non-continuous, so I would think it is ok.
__________________

__________________
ChiliPepr is offline   Reply With Quote
Old 05-23-2014, 08:16 AM   #3
Dryer sheet wannabe
 
Join Date: Jan 2011
Posts: 16
The NEC is pretty clear on this topic but people still debate it. The first thing to do is to check what the installation instructions for the microwave and hood say. If either says that it must be on an individual (or dedicated) branch circuit, there is no argument - the installation instructions rule in that case.

Here's what the 2005 NEC says:

422.16(B)(4)Range Hoods.
Range hoods shall be permitted to be cord-and-plug connected with a flexible cord identified as suitable for use on range hoods in the installation instructions of the appliance manufacturer, where all of the following conditions are met:
(1) The flexible cord is terminated with a grounding- type attachment plug.
Exception: A listed range hood distinctly marked to identify it as protected by a system of double insulation, or its equivalent, shall not be required to be terminated with a grounding-type attachment plug.
(2) The length of the cord is not less than 18 in. and not over 36 in..
(3) Receptacles are located to avoid physical damage to the flexible cord.
(4) The receptacle is accessible.
(5) the receptacle is supplied by an individual branch circuit.

If your hood will be plugged into an outlet, the outlet must be on its own circuit. Again, I think this is very clear but people argue that the installation instructions overrule this - if the instructions don't say that you need to use an individual circuit then (5) doesn't apply. That makes no sense. You have to install things in accordance with both the NEC and the installation instructions. The instructions only overrule the NEC when they are more restrictive, not when they are less restrictive. Otherwise the instructions would have to include every applicable section of the NEC.
__________________
Gus. is offline   Reply With Quote
Old 05-23-2014, 08:23 AM   #4
Thinks s/he gets paid by the post
DFW_M5's Avatar
 
Join Date: Sep 2003
Posts: 4,980
Do you know how much run time separates continuous from non-continuous?

Its certainly possible both appliances could run simultaneously several minutes, but I don't know really know how long these appliances might be full on as that is DWs specialty.

Also, I was using 120v in my calculations, P=VI. We had the combination tripping the breaker recently and thats what lead me to believe there might be too much draw on one breaker. Replaced breaker and tightened lugs in panel and now everything is fine.
__________________
Doing things today that others won't, to do things tomorrow that others can't. Of course I'm referring to workouts, not robbing banks.
DFW_M5 is offline   Reply With Quote
Old 05-23-2014, 08:26 AM   #5
Thinks s/he gets paid by the post
DFW_M5's Avatar
 
Join Date: Sep 2003
Posts: 4,980
Quote:
Originally Posted by Gus. View Post
The NEC is pretty clear on this topic but people still debate it. The first thing to do is to check what the installation instructions for the microwave and hood say. If either says that it must be on an individual (or dedicated) branch circuit, there is no argument - the installation instructions rule in that case.

Here's what the 2005 NEC says:

422.16(B)(4)Range Hoods.
Range hoods shall be permitted to be cord-and-plug connected with a flexible cord identified as suitable for use on range hoods in the installation instructions of the appliance manufacturer, where all of the following conditions are met:
(1) The flexible cord is terminated with a grounding- type attachment plug.
Exception: A listed range hood distinctly marked to identify it as protected by a system of double insulation, or its equivalent, shall not be required to be terminated with a grounding-type attachment plug.
(2) The length of the cord is not less than 18 in. and not over 36 in..
(3) Receptacles are located to avoid physical damage to the flexible cord.
(4) The receptacle is accessible.
(5) the receptacle is supplied by an individual branch circuit.

If your hood will be plugged into an outlet, the outlet must be on its own circuit. Again, I think this is very clear but people argue that the installation instructions overrule this - if the instructions don't say that you need to use an individual circuit then (5) doesn't apply. That makes no sense. You have to install things in accordance with both the NEC and the installation instructions. The instructions only overrule the NEC when they are more restrictive, not when they are less restrictive. Otherwise the instructions would have to include every applicable section of the NEC.
Neither the hood or microwave installation instructions say anything about electrical requirements
__________________
Doing things today that others won't, to do things tomorrow that others can't. Of course I'm referring to workouts, not robbing banks.
DFW_M5 is offline   Reply With Quote
Old 05-23-2014, 08:31 AM   #6
Dryer sheet wannabe
 
Join Date: Jan 2011
Posts: 16
A continuous load is one that is expected to run at maximum capacity for three hours or more. An electric heater is one such load.

If the breaker tripped a lot it may have worn out. If that's the case I would expect the replacement to wear out eventually too.
__________________
Gus. is offline   Reply With Quote
Old 05-23-2014, 08:36 AM   #7
Give me a museum and I'll fill it. (Picasso)
Give me a forum ...
travelover's Avatar
 
Join Date: Mar 2007
Posts: 9,874
I sure wouldn't worry about it. Microwave ovens only run for minutes at a time.
__________________
Yes, I have achieved work / life balance.
travelover is offline   Reply With Quote
Old 05-23-2014, 09:15 AM   #8
Give me a museum and I'll fill it. (Picasso)
Give me a forum ...
 
Join Date: Sep 2005
Location: Northern IL
Posts: 18,261
I installed a built in combo microwave oven with built in fan, so I can't comment on the separate units. But is sure seems odd to me to require that a fan would need to be on it's own circuit, when it is only ~ 4 amps?

As I recall, the NEC does specify a separate circuit for a built in microwave (but not a counter-top unit that could be the same power rating!). I may have overlooked this when I installed mine, but the other outlets on that circuit would not normally have a high current appliance plugged in, they are a bit difficult to reach we hardly use them at all. At any rate, we have never tripped a breaker in the kitchen. Though using a toaster on that outlet might trip it if both were on.

I think code also requires a separate circuit for a dish washer, ours shared the circuit with two counter-top outlets and a light. Never tripped those either (all 20A).

-ERD50
__________________
ERD50 is online now   Reply With Quote
Old 05-23-2014, 11:07 AM   #9
Thinks s/he gets paid by the post
DFW_M5's Avatar
 
Join Date: Sep 2003
Posts: 4,980
Quote:
Originally Posted by ERD50 View Post
I installed a built in combo microwave oven with built in fan, so I can't comment on the separate units. But is sure seems odd to me to require that a fan would need to be on it's own circuit, when it is only ~ 4 amps?

As I recall, the NEC does specify a separate circuit for a built in microwave (but not a counter-top unit that could be the same power rating!). I may have overlooked this when I installed mine, but the other outlets on that circuit would not normally have a high current appliance plugged in, they are a bit difficult to reach we hardly use them at all. At any rate, we have never tripped a breaker in the kitchen. Though using a toaster on that outlet might trip it if both were on.

I think code also requires a separate circuit for a dish washer, ours shared the circuit with two counter-top outlets and a light. Never tripped those either (all 20A).

-ERD50
Although microwave is built in, I am pretty sure there would be a normal receptacle behind it, so no real difference from a countertop model. I also thought NEC 2011 required a standalone circuit for a microwave, but if not, the combined draw needed to be 16a or less. I was not aware of the continuous vs non-continuous use in terms of what is acceptable load on a 20a circuit, so as others suggested, it may be OK.

Some of the hot lugs in my panel needed tightening. I suspect since they were a little loose, that may have caused heating and premature breaker ware on the problem breaker.
__________________

__________________
Doing things today that others won't, to do things tomorrow that others can't. Of course I'm referring to workouts, not robbing banks.
DFW_M5 is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
What is the maximum *possible tax rate on SS benef amt FIRE and Money 12 10-18-2004 09:02 AM
Is it possible? Wonderboy Young Dreamers 5 09-16-2004 12:09 PM
possible stupid question zbwmy FIRE and Money 10 06-16-2004 04:22 AM
Possible Deflation Scenario Cut-Throat FIRE and Money 13 08-30-2003 02:59 AM

 

 
All times are GMT -6. The time now is 08:23 AM.
 
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.