Garage Doors - plug vs. hard wired (multiple doors per circuit?)

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Dennis Alwon said:
The part that is confusing about appliances is that we have an entire article on appliances and then an entire article on a/c. So why call it an appliance. It just seems to confuse matters.
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By NEC definition of appliance - a typical garage door opener is an appliance. An A/C is an appliance also - especially a single enclosure unit like a window AC. Art 422 does send you to art 430 and 440 when you have motor operated appliance or one with a hermatic refrigerant compressor. Technically you have an appliance and need to read and follow 422 and go to other articles where it refers you to them.

Art 100:
Appliance.
Utilization equipment, generally other than industrial, that is normally built in standardized sizes or types and is installed or connected as a unit to perform one or more functions such as clothes washing, air-conditioning, food mixing, deep frying, and so forth.

Air conditioner is even in the examples they used in the definition. I think garage door openers are built in standard sizes/types and are normally installed as a unit.

When do you not have an appliance becomes a good question. I think in general you can start with equipment that is motor driven, but generally is not shipped with a motor and/or controls for that motor. A lot of industrial machinery is this way, but not all of them are either. Many augers, conveyors, grinders, mill machines, are examples of equipment I see frequently that you buy the machine and the motor separately. The machine supplier maybe sells you a motor but the machine manufacturer usually doesn't include a motor already installed on the machine.
 
The garage door opener has more than a motor -- there are lights and controls in it. Therefore, I'd use the nameplate amps and be done with it (and hope that nameplate included any 125% factor for its motor, as I don't want to add that to it too).

I don't see any diversity factor in the NEC other than a .75 factor for 4 or more appliances on a feeder or service. But that rule doesn't apply to a branch circuit. Same with 220.60 (non co-incident loads).

I'd really like to see an addition to the NEC allowing short duration fastened-in-place appliances (e.g. garbage disposals, garage door openers) to have a branch circuit demand factor applied so you can load those circuits up a bit more.
 
suemarkp said:
I'd really like to see an addition to the NEC allowing short duration fastened-in-place appliances (e.g. garbage disposals, garage door openers) to have a branch circuit demand factor applied so you can load those circuits up a bit more.
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Trust me I tried writing a proposal-- I could not come up with anything and got overwhelmed. I probably should have tried to make it simple and just add something in the appliance area.
 
NEW INFORMATION
The garage door opener in my garage is 1/2HP, 120V, 6A nameplate.

Sooooo.........
At 6A I could actually put 3 on a circuit?

Plus the service size stays reasonable.
 
olc said:
NEW INFORMATION
The garage door opener in my garage is 1/2HP, 120V, 6A nameplate.

Sooooo.........
At 6A I could actually put 3 on a circuit?

Plus the service size stays reasonable.
Click to expand...
to comply with NEC - I think so, otherwise I'd bet you could put 2-3 more on a circuit and seldom if ever have a 20 amp breaker trip.
 
olc said:
NEW INFORMATION
The garage door opener in my garage is 1/2HP, 120V, 6A nameplate.

Sooooo.........
At 6A I could actually put 3 on a circuit?

Plus the service size stays reasonable.
Click to expand...

kwired said:
to comply with NEC - I think so, otherwise I'd bet you could put 2-3 more on a circuit and seldom if ever have a 20 amp breaker trip.
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When appliances/motors are concerned we can put more than 80% of the circuit capacity?

20 amp circuit x 80% = 16 amps
6 amps x 3 = 18 amps
 
mjf said:
When appliances/motors are concerned we can put more than 80% of the circuit capacity?

20 amp circuit x 80% = 16 amps
6 amps x 3 = 18 amps
Click to expand...

422.10(A) sends you to art 430 part II for motor operated appliances.

Table 430.22(E) would allow use of smaller conductors if the motor actually has an intermittent duty rating, but if it is a continuous duty rated motor you actually need to use 140% of motor full load current for conductor ampacity- this is before getting into multimotors on a circuit.

430.24 says for multiple motors/ motors and other loads you determine conductor ampacity based on:
following:
125 percent of the full-load current rating of the highest rated motor, as determined by 430.6(A)
Sum of the full-load current ratings of all the other motors in the group, as determined by 430.6(A)
100 percent of the noncontinuous non-motor load
125 percent of the continuous non-motor load.

So that would be 125% of largest motor plus 100% all other motors and 100% all lamps or other aux equipment, plus 125% of any additional continuous load if there would be any.

3 - 6 amp motors would give you 19.5 amps - but you still need to add lights if there are any. But 6 amps on the nameplate of such an appliance - how do you break down motor and other loads - they won't necessarily parallel NEC with nameplate markings the way air conditioning equipment usually does:? A unit marked 6 amps is rated 6 amps, but that is for worst case, and for no longer then these run could be applied to an overloaded condition and still never trip overcurrent protection. Put it on a really hard moving door and make it pull 10 amps - it gets the door opened before motor overload would trip. Run several cycles in a short time and you might trip motor overload though.
 
422.10(A) refers to Article 430 for motor operated appliances "not having a marked rating".

I think I can use the marked rating (6A).
 
mjf said:
That brings me right back to my question:


When appliances/motors are concerned we can put more than 80% of the circuit capacity?

20 amp circuit x 80% = 16 amps
6 amps x 3 = 18 amps
Click to expand...

I still say 125% of largest motor plus the other loads.

Appliance nameplate with just a single input amp rating vs motor nameplate plus lamps/other loads may make this one a headache if you want to absolutely comply with NEC though. And I believe most door operators will just have a single number for an amp rating with no other details.
 
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