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

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olc

Senior Member
Garage with multiple garage doors (think apartment building with separate garage):
Garage doors are typically plug in?
1/2HP or 3/4 HP any difference?

If they are plug in can the circuits be figured using plug load calc (180W)? So theoretically 13 could be put on one 20A circuit?

I would not do that but is there a reason not to put a few on a circuit?
 

olc

Senior Member
Is my answer in 210.23 - i.e. because the cord and plug connected equipment (door opener) is fastened in place the total load of the equipment can not exceed the circuit rating (which essentially means a separate circuit for each 1/2 H/P motor plus the light)?
 

olc

Senior Member
If there is a separate circuit per opener but the openers are cord and plug connected - is the feeder/service calculation 180W (per receptacle) or the actual fastened in place motor load? (obviously in this case a bid difference)
 

Dennis Alwon

Moderator
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Location
Chapel Hill, NC
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Retired Electrical Contractor
If you know the load you cannot use 180Va especially if it is a residence.210.23 is the appropriate code article
 

kwired

Electron manager
Location
NE Nebraska
I would lean toward going with nameplate amps and not horsepower.

Strict reading of NEC may limit you to only one or two on a circuit, but reality says you can have three maybe even four and never have a breaker trip on overload. If you hit the button for four units all at one time you probably have better chance of breaker tripping because of starting current, but once you get past that point, you could have 30 or even 40 amps pulled on a 20 amp circuit and if they shut off within 30 seconds or so probably doesn't trip the 20 amp breaker. And opening all the doors at one time would be more likely in a single owner/occupant garage then in multi occupant garage.

So I guess the real answer comes down to what an inspector may accept or reject.
 

cadpoint

Senior Member
Location
Durham, NC
Welp, I floated over to the 430's.

I can't make it pass 430.24 to work with either combinations of a (2)1/2 or (2)3/4 HP motors, using
a 20 amp circuit.
 

kwired

Electron manager
Location
NE Nebraska
This is equipment fastened in place. If "cord-and-plugconnected utilization equipment not fastened in place, or both, are also supplied" (items in quotations is directly quoted from 210.23(A)(2)) I see no reason you can't connect up to 20 amps nameplate rating to a 20 amp circuit and be compliant with NEC. If you get units with nameplate amps of 10 or less there should be no problem with two on a 20 amp circuit and if you can get units with nameplate of 6.66 amps or less then you should be able to put 3 on a 20 amp circuit. That should make NEC happy, I have many times in a three car garage put all three on one circuit and never had callbacks because breakers don't hold, even though it may not meet NEC.

These are motor operated appliances and you you need to go to 422 first, though that will send you to 430 for some things.
 

Dennis Alwon

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Location
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This is interesting because 210.23(a) thru (D) does not really apply to 2 motors with nothing else connected however 210.23 does seem to allow 2 0r more outlets but nothing else.

Most garage door opener I have seen are usually fed from the lighting circuit or the garage receptacles. If this is the case it changes the outlook of the situation as 210.23(A)(2) would come into play

IMO the entire setup is a joke as you would never trip those garage door opener's since they would never be on at the same time. If they were it would only be for a short while and the breaker would not trip. IMO.
 

James L

Senior Member
Location
Kansas Cty, Mo, USA
Occupation
Electrician
Considering that one horsepower is 745 va (6.2 amps @ 120v)...a 1/2 horse motor would be 3.1 amps

Also consider that it is technically a non-ccntinuous load, not running at least 3 hours.

Also consider that the chances are very slim, of numerous doors being operated simultaneously

I would have no problem putting 6-8 door openers on one 20-amp circuit
 

jimdavis

Senior Member
Considering that one horsepower is 745 va (6.2 amps @ 120v)...a 1/2 horse motor would be 3.1 amps

Do not confuse output power with input power. One horsepower is equivalent to 746 watts. That does not consider a motor's efficiency or power factor. Table 430.248 lists the FLC of a 1/2 HP, 115V motor at 9.8 amps.
 

GoldDigger

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Location
Placerville, CA, USA
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Retired PV System Designer
But in the situation you propose (multiple units with individual doors) such a circuit would have to come from a house panel and meter, yes? And for that you would definitely not want receptacles too. :)
 

Dennis Alwon

Moderator
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Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Considering that one horsepower is 745 va (6.2 amps @ 120v)...a 1/2 horse motor would be 3.1 amps

Also consider that it is technically a non-ccntinuous load, not running at least 3 hours.

Also consider that the chances are very slim, of numerous doors being operated simultaneously

I would have no problem putting 6-8 door openers on one 20-amp circuit

What will work and what is code are two different animals. I agree with what you say but the NEC will not allow 8 doors on the 20 amp circuit

Also if you have a 1/2 hp motor you must use Table 430.248 which states 1/2" hp single phase 115v motor are to be figured at 9.8 amps
 

Dennis Alwon

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Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
You don't accept that assertion that the opener is an appliance and not just a motor?


To be honest I don't see it as an appliance although the definition is pretty loose. If you look at the examples that are given at the end it endorses my gut on this-- except for the a/c. There lies the whole problem. I don't see an a/c as an appliance either. Heck almost everything would fit under appliance
 

iwire

Moderator
Staff member
Location
Massachusetts
Garage with multiple garage doors (think apartment building with separate garage):
Garage doors are typically plug in?
1/2HP or 3/4 HP any difference?

If they are plug in can the circuits be figured using plug load calc (180W)? So theoretically 13 could be put on one 20A circuit?

I would not do that but is there a reason not to put a few on a circuit?

I will toss out some other thoughts. :)


The door opener would have to be listed for hard wiring, you can't just cut the plug off a cord and hard wire it.

You would have to provide an individual disconnecting means for each opener.
 

iwire

Moderator
Staff member
Location
Massachusetts
You don't accept that assertion that the opener is an appliance and not just a motor?

To be honest I don't see it as an appliance although the definition is pretty loose.

:?

I can't see it as anything but a motor operated appliance.

There lies the whole problem. I don't see an a/c as an appliance either.

:huh:

They sell them at the appliance store.

Heck almost everything would fit under appliance

How would that be bad? :huh:
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
I think garage door openers are one of those items where the marked horsepower is not a real number .... just a marketing number. I would use the nameplate current per Exception #3 to 430.6(A)(1) for any calculations.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
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.
 

olc

Senior Member
A few thoughts:

By the definition of an appliance - it is an appliance. How does this change anything (how can I use the diversity)? I am looking for a strict NEC installation.

My example is a residential garage but it is not a dwelling unit.

Installation instructions I have seen include instruction on how to change from cord & plug to direct connect.

At this point I have decided on individual branch circuits. The remaining question is can I use any diversity for the feeder/service size?
 
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