430.42(C) Cord-and-Plug-Connected Equipment

[Br4nd0n]

A little info about my situation before I get to the question: I'm relocating equipment to a new building for a customer and have only been to their existing location once to do a quick "look over" of what I'm dealing with. The existing electrical is a nightmare and cannot be matched, so I nabbed some general info in order to hit the code book and install everything properly. I have several uncertainties, but in an effort to take it one step at a time and not get overwhelmed, I'll focus this first post on just one area.

If you're still with me, thanks!

Referring to article 430.42(C) - If you have a cord-and-plug-connected piece of equipment that is under 1 HP, code requires the plug and receptacle to be rated at no more than 15A. If it's a dedicated circuit with only 1 receptacle (to keep other loads off) am I correct that due to 210.21(B)(1), the circuit breaker would be limited to 15A? I see nothing in article 430 that amends article 210.
My concern here is the starting amperage of the motor. Let's say 120V/12A piece of equipment - does anybody know what the typical inrush current would be?
430.42(D) goes on to say the breaker shall have sufficient time delay. Is this the key here? I'm not familiar with varying time delay options in standard inverse time circuit breakers. Do these breakers generally have enough time delay? I know they provide instantaneous short-circuit protection. Any input here?

 

[jumper]

A little info about my situation before I get to the question: I'm relocating equipment to a new building for a customer and have only been to their existing location once to do a quick "look over" of what I'm dealing with. The existing electrical is a nightmare and cannot be matched, so I nabbed some general info in order to hit the code book and install everything properly. I have several uncertainties, but in an effort to take it one step at a time and not get overwhelmed, I'll focus this first post on just one area.

If you're still with me, thanks!

Referring to article 430.42(C) - If you have a cord-and-plug-connected piece of equipment that is under 1 HP, code requires the plug and receptacle to be rated at no more than 15A. If it's a dedicated circuit with only 1 receptacle (to keep other loads off) am I correct that due to 210.21(B)(1), the circuit breaker would be limited to 15A? I see nothing in article 430 that amends article 210.
My concern here is the starting amperage of the motor. Let's say 120V/12A piece of equipment - does anybody know what the typical inrush current would be?

Edit. Exception says see 430.81(B)
430.42(D) goes on to say the breaker shall have sufficient time delay. Is this the key here? I'm not familiar with varying time delay options in standard inverse time circuit breakers. Do these breakers generally have enough time delay? I know they provide instantaneous short-circuit protection. Any input here?

I agree, nothing in 430 amends 210.21(B), you would have to be able to hard wire the machine to upsize the OCPD for inrush. You have nameplate data by chance?

Edit: exception says see 430.81(B).:slaphead: Gotta go look and see if it applies.

 

[jumper]

Aw, crapola, I think I have confused myself at this point. Sorry OP.:ashamed1:

 

[Br4nd0n]

you would have to be able to hard wire the machine to upsize the OCPD for inrush.

I agree, but then I'm looking at having to provide separate overloads - something I shouldn't have to do according to 430.42. I want to do this right, and that includes not doing anything excessive.

You have nameplate data by chance?

There are quite a few different pieces of equipment, and in my limited time only grabbed voltage and nameplate FLA listings. I now wish I had also paid attention to HP and maybe even duty cycle ratings. For the purpose of this post though, I'll just focus on the 120V/12A equipment - there will be 4 of these total.

 

[resistance]

Is this an auto start motor, and what is it being used for? Example of a stationary non-auto start motor appliance: disposal
Note what it says:The rating of the attachment plug and receptacle or the cord connector shall determine the rating of the circuit to which the motor may be connected, as provided in 210.21B.Where 210.21B limits the load on the receptacle based on the type of device being used. So, if you use a 20A circuit to serve a single 20A receptacle, then you would be limited to a max cord and plug connected load of 16 amps.

 

[resistance]

@Br,
Here is an example of how to size BC ground fault and short circuit protection. Lets assume the motor nameplate says: 120v, 1/2hp, 12A-single phase. Having an SF of 1.0. We plan to use an inverse time breaker (See T. 430.52).
-To size our BC GF and SC protection we are directed to consult T. 430.148. So: 9.8A(2.5% per T.430.52)=24.5A. In this case we can upsize the breaker to 25A per section 430.52C1 Ex1.
-Then size the BC conductor for a single motor sized at 125% of FLC, and T.430.148. So: 9.8(1.25)=12.25A. So #14CU per T.310.16 (2008 NEC).
-Then we can size the overload-using a dual element fuse. We would then note the name plate rating per NEC 430.6A, and 430.32. So: 12(1.15)=13.8A.
Note: The above was a taste, but gives a little info on how to calculate a specific motor load situation.

 

[Br4nd0n]

Resistance, I appreciate the detailed response, but I am already very familiar with those calculations and understand them. They do not pertain to my original post. Did you even read it?

I'm dealing with a cord and plug piece of equipment... with an existing 15A plug on it.

I do not want to install separate overloads if it's not needed and 430.42 leads to me to believe it's not. 430.42(C) requires a 15A rated plug and receptacle max when overloads are omitted per 430.42(A).

I want this on an individual branch circuit to keep other loads off. I believe article 210 will still hold true here and require a 15A breaker. Does a standard 15A inverse time breaker (Eaton type BR) typically have enough time delay [430.42(D)] to handle the inrush current?

To answer your first questions resistance - the equipment is some sort of "shaker" used in a cleaning process. It does not auto-start.

 

[augie47]

Br:
Interesting question.
They do manufacturer breakers with a high inrush factor. I have needed them for highh imrush dimmer applications and they might be helpful for the situation you describe. Worth a discussion with a geatr manufacturer.
(An example is SquareD QO115HM)