garage door openers

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elecmen

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Electrician
Is it permissible by code to have 2 1/2 HP garage door openers on the same 20A circuit? Please provide code reference. Thanks
 
First, is it an "advertised" 1/2 HP? In the case of garbage disposals, they play with numbers to make their motors sound bigger than they are. I'm not sure if it's the same with GDOs.

If it's a legitimate pair of 1/2 HP motors, then I would say maybe: The answer would be no, unless they are interlocked to not run at the same time, which is unlikely. Reference 430.24, and it's third exception.

But I lack confidence in my answer. :)
 
Also, consider 430.42(a)? I also am not confident enough to make a call... I think he meets 430.24's first exception.

Jeremy
Tulsa, Ok
 
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The problem I had with that is, I don't know if the GDO is one of the motor types mentioned in Table 420.22(E), and which one.

I mean, I may have unwittingly wired a couple GDOs together in the past, but I never really thought about it... :D
 
elecmen - maybe you can tell us what the nameplate says.

After looking at some tables, I think you're right about 430.24 ex 3.

1/2 hp maximum allowable LRA at 115v is 45 according to "ASA c50.2 Par 2-9.1 Table 13" and the starting current is over 20- so I think if you hit UP on both of them at the same time you'd throw the breaker.

Jeremy
Tulsa, Ok
 
I tihnk I'd be looking in article 422 rather than 430. This seems more like an appliance than a motor, but it is a motor operated appliance so there are a bunch of cross references in the code.

Do the instructions demand an individual branch circuit?
Is the nameplate current rating less than 10 amps?
If there is no nameplate, then its off to article 430.

A 20A circuit should easily run a 1 HP motor. Two half HP motors should be about as easy.

I think 422.10(A) if you consider both GDO's to be one function, or 422.10(B) if these are separate. Section 422.10(A) takes you to 210.23. So you couldn't have lights or non-fastened-in-place equipment on this circuit.
 
jerm said:
...so I think if you hit UP on both of them at the same time you'd throw the breaker.
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I don't think so: The instantaneous range for circuit breakers is typically six to eight times the handle rating IIRC, so two 9.8A GDOs starting at the same instant would likely not trip the breaker, IMO.

By the way, Jeremy: if you want, you can program your signature in and save some effort by clicking here. :)
 
What is the problem with this installation. The 1/2 hp motor probably draws less than 7 amps.
Jerm said:
1/2 hp maximum allowable LRA at 115v is 45 according to "ASA c50.2 Par 2-9.1 Table 13" and the starting current is over 20- so I think if you hit UP on both of them at the same time you'd throw the breaker.
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I doubt the breaker would ever trip on overload given the short time that it would take to open the doors.
 
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sguinn said:
This may be irrelevant but how many times has someone with two GDO's opened both at the same time?:confused:
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It's not irrelevant but you do have to consider both doors may be opened at the same time. Again, I think this is a non issue give the HP of the openers.
 
Thanks for the replies. It is a commercial grade liftmaster GDO. I do not know the model number etc. I will try to look at the opener tomorrow and let you know.
 
Since you are not required to install an outlet for a garage door opener and since the electrican does not install the opener and likely has any idea how big it will be I could see where people would not have a concern since how many of these are installed in trac homes around the country that were not sized to the opener?

Sorry if that's hard to read it quiting time.:grin:
 
georgestolz said:
By the way, Jeremy: if you want, you can program your signature in and save some effort by clicking here. :)
Click to expand...


You'd think after 50 posts I'd get around to doing that. I know it's there...

6 to 8 times huh? I didn't realize that standard breakers would tolerate that much. I know some of the breakers we use (they have a four letter code but I can't recall it right now) are specifically rated to handle larger inrush for a longer amount of time than a typical breaker.

But I'm stuck in this pre-engineered commercial world, never have to figure the hard stuff out. Just follow spec, string pipe, fill with wire, terminate... drop in a few lights... NEXT...

At 7 amps each (14 total) there wouldn't be any reason not to put them both on the same circuit.

But I know up on two doors at the same time is common- and down on every one of them at the same time is even more likely.

Jeremy
Tulsa, Ok
 
Info on GDO: model# MT5011 1/2 HP 115V 1PH 7A W/P 1753. The motor data plate reads: 1/2 HP 6 FLA. So is there anything in the code forbidding me from putting 2 of these on the same circuit?
 
gserve said:
Info on GDO: model# MT5011 1/2 HP 115V 1PH 7A W/P 1753. The motor data plate reads: 1/2 HP 6 FLA. So is there anything in the code forbidding me from putting 2 of these on the same circuit?
Click to expand...

A 20 amp circuit would do just fine with those specs.
 
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