Dimmer question
- Thread starter Sharpie
- Start date
- Status
bphgravity
Senior Member
- Location
- Florida
The rating of the dimmer in watts should be based on the load to be served, not the branch circuit rating it is installed in.
Sierrasparky
Senior Member
- Location
- USA
- Occupation
- Electrician ,contractor
I second that
drbond24
Senior Member
- Location
- Barboursville, West Virginia
You 2nd celtic's agreement, or are you actually 3rding the original response by bhpgravity? Just want to make sure I know where I'm at in line.
I agree as well, so therefore I'm 4thing bhpgravity's response, 3rding celtic, and 2nding sierra. I've also obviously ran out of things to do at the end of the day.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
The same thing would apply to a snap switch. You could have a 15 amp switch on a 20 amp circuit.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Well, I plead the 5th!
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Only if the load is not greater than 15a.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
chris kennedy
Senior Member
- Location
- Miami Fla.
- Occupation
- 60 yr old tool twisting electrician
Same applies to the 600 watt dimmer.
600 watt dimmer on a 15A load, smoke.:grin:
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
The load downstream cannot be greater then the 15 amp( or 600 watt dimmer) switch so that issue is not a problem.
Twoskinsoneman
Senior Member
- Location
- West Virginia, USA NEC: 2020
- Occupation
- Facility Senior Electrician
Common sharpie has a great point. If I decide my load is going to be only 1 amp I still have to have 12awg but I can put in a 1 amp rated switch??
glene77is
Senior Member
- Location
- Memphis, TN
Guys,
Someone should tell the OP
that the heat dissapation plate may get very hot.
Someone should tell the OP
that the heat dissapation plate may get very hot.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Yes but a switch is not overcurrent protection. The circuit is protect at the 20 amps. The switch will break down only from load side current. I can't imagine what it would be like if we had to have 2000 watt dimmers for every dimmer
Twoskinsoneman
Senior Member
- Location
- West Virginia, USA NEC: 2020
- Occupation
- Facility Senior Electrician
I was comparing the switch to the wire... not the OCPD. Why should any wire on the load side of the switch be required to have a rating higher than the switch?
Not sure what this means... unless you are referring to a short on the line side of the switch not effecting the switch...
I agree it just doesn't make sense...
That's kinda my point. If you can put a 15A switch in a 20A branch circuit, then why can't the wire on the load side of the switch be 14AWG? We do the same sort of thing with motor loads. and what about an appliance cord being 18 or 16 AWG? If the lighting on the load side is designed properly, what's the difference from these other examples?
K8MHZ
Senior Member
- Occupation
- Electrician
The reason for the max rating on switches is different than what it is used for in conductors.
The max rating of a switch is not only the amount of current it can carry, but the amount of load that can be placed on the contacts while making and breaking for the expected life of the switch. The DC rating of a switch will always be lower than the AC rating, but the same is not true of a conductor.
If a switch fails due to excess current, the arc and damage will be constrained to the switch and/or the enclosure and will result in an open circuit, disconnecting the load.
If a conductor fails due to excess current the conductor will become a heating element. If it is not in conduit the hot conductor may start a structure fire. If it is in conduit, the insulation will melt causing conductors to become shorted. This can either create more damage to the conductors or it may energize a conductor that is not supposed to be energized.
A switch rated at 15 amps will carry much more than that while closed and can carry a bit more than that while being switched, it's just that the excess current will shorten the life of the contacts.
The max rating of a switch is not only the amount of current it can carry, but the amount of load that can be placed on the contacts while making and breaking for the expected life of the switch. The DC rating of a switch will always be lower than the AC rating, but the same is not true of a conductor.
If a switch fails due to excess current, the arc and damage will be constrained to the switch and/or the enclosure and will result in an open circuit, disconnecting the load.
If a conductor fails due to excess current the conductor will become a heating element. If it is not in conduit the hot conductor may start a structure fire. If it is in conduit, the insulation will melt causing conductors to become shorted. This can either create more damage to the conductors or it may energize a conductor that is not supposed to be energized.
A switch rated at 15 amps will carry much more than that while closed and can carry a bit more than that while being switched, it's just that the excess current will shorten the life of the contacts.
Twoskinsoneman
Senior Member
- Location
- West Virginia, USA NEC: 2020
- Occupation
- Facility Senior Electrician
JMO but I disagree to the implication that the over current condition on the switch has less potential to do damage than the same current applied to similarly rated wiring on the load side of the switch. Just speculation but I think because of the switching contacts the switch also has the potential to fail before the wire (assuming similar rating and similar over current)
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