The Electrical Contractor Network

ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Books, Tools and Test Equipment for Electrical and Construction Trades

Register Now!

Register Now!

We want your input!

Featured:
   

2017 NEC and Related
2017 NEC
Now Available!

   
Recent Posts
Calling all Non-US members!! (Non-US only)
by aussie240
Yesterday at 02:39 AM
Photo Upload Tutorial
by DanK
12/06/16 11:35 PM
Sprinklered equipment 26-008
by bigpapa
12/02/16 04:24 PM
On Delay Relay with Auto Reset
by Potseal
12/01/16 09:59 AM
Wow, that was close!
by jraef
11/28/16 07:06 PM
New in the Gallery:
12.5A through 0.75mm˛ flex (just out of curiosity)
Shout Box

Top Posters (30 Days)
gfretwell 13
HotLine1 9
Texas_Ranger 8
sparkyinak 7
Trumpy 6
Who's Online
0 registered (), 170 Guests and 4 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#211297 - 10/03/13 09:43 AM Can I use a 600W Toggle dimmer in a 20A circuit?
Hormel1144 Offline
New Member

Registered: 10/02/13
Posts: 1
Loc: NYC
Hello: I'd like to install a GE toggle-style dimmer in a 20A circuit. My concern is that the maximum load the dimmer is rated for in a single gang setup is 600W (it is downrated for multiple gang setups). This works out to a load capacity of 5A or less, in a circuit where the overcurrent protection will happily pass 20A before tripping; or enough to fry the device at least 4 times over. I understand that the code allows fixture pigtails to be sized to the max wattage of the fixture, regardless of the ampacity of the supply, because the maximum load on the pigtail will never be more than the fixture's maximum wattage. The issue here, however, is that the dimmer feeds into 12ga house wiring, and it is possible that in the future multiple fixtures could be attached to the leg, drawing as much as 2400w! We would then have a circuit which was not fully sized to handle the load permitted by the overcurrent protection. Wouldn't this violate the code?

Top
2014 / 2011 NEC & Related Books and Study Guides
#211309 - 10/03/13 07:38 PM Re: Can I use a 600W Toggle dimmer in a 20A circuit? [Re: Hormel1144]
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6804
Loc: Brick, NJ USA
IMHO, your concern at the time of installation is that you do not exceed the rating of the device controling the load.

The circuit is protected by the 20 amp OCP, which is compliant.

For example; you install 6 recess fixtures with 75 watt lamps, totaling 450 watts. The load on the device is within spec, even if it is two ganged.

Some time after you do the above; someone replaces the lamps with 150 watt lamps! The dimmer takes the bullet!!

Code compliance is 'at the time of installation/inspection'. There is no crystal ball, no lady reading the future, and the NEC is not 'idiot proof'.

A 120 volt 20 amp circuit calcs to 2400 watts, max load for non-continuous, and would be compliant. Common trade practice is NOT to load any circuit to 'max'.
_________________________
John

Top
#211313 - 10/03/13 10:30 PM Re: Can I use a 600W Toggle dimmer in a 20A circuit? [Re: Hormel1144]
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9045
Loc: Estero,Fl,usa
This is an interesting question. I suspect the real answer would be if U/L added the requirement of a fusible link in the device to blow if the allowable current was exceeded but, as far as I know it is not in the listing standard.
I suspect from experience that the triac would simply short and make it a switch.
Dimmers seem to fail "on".
_________________________
Greg Fretwell

Top
#211316 - 10/04/13 05:00 PM Re: Can I use a 600W Toggle dimmer in a 20A circuit? [Re: Hormel1144]
renosteinke Offline
Cat Servant
Member

Registered: 01/22/05
Posts: 5305
Loc: Blue Collar Country
Ever try to find a dimmer rated for the full ampacity of a circuit? Good luck - and, if you find one, it will have a metal cover the size of a dinner plate, just to dissipate the heat.

Even most light switches are not rated for the full current- look closely, and you'll find plenty with straps stamped "10A."

It appears there has never been a requirement for a switch to be capable of anything more than controlling the intended load.

Top
#211320 - 10/04/13 06:38 PM Re: Can I use a 600W Toggle dimmer in a 20A circuit? [Re: Hormel1144]
BigB Offline
Member

Registered: 03/31/04
Posts: 727
Loc: Tucson, AZ USA
This brings up a topic which is a pet peeve with me, inspectors who will try to enforce "idiot proofing". There is nothing in the code that I know of that requires us to go over the minimum requirements "in case" someone comes later and adds something. The "what ifs" could go on forever and my answer to them is whoever does the "what if" at a later date will be responsible for whatever is needed at that time.

Top



ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals