40 amp branch circuit

[K2500]

But the 30 Amp disconnect would be protected by the 40 A breaker which is a violation, correct?

The breaker provides only SC and GF protection.

Check out 430.62, 430.24

 

[K2500]

If this is a dwelling unit, then I think 210.23(C) kills the idea.

I agree that is what it implies, but the lack of the word "only" in any of the paragraph makes it read permissive rather than exclusive. Though the intent is obvious... or is it? I can't tell which.

 

[kwired]

But the 30 Amp disconnect would be protected by the 40 A breaker which is a violation, correct?

If the 30 amp disconnect has a minimum of 40 amp conductor supplying it, no violation.

If the 30 amp disconnect has less than 40 amp conductor supplying it then the portion less than 40 amp is a feeder tap. As long as it complies with rules of 240.41(B), no violation

I am aware that motors are not sized in 210:grin:, but this is not a motor found in a paper mill, this is part of a piece of equipment. So where do you draw the line when to size off 430 versus 210. what if you have equipment that has a motor as only one part, but also includes other non motor loads?

Actually with the equipment you have you may want to start reading article 422 - appliances, and depending on exactly what you have, your answer may be in 422 or it may send you to other articles such as 210 or 430.

422.3 Other Articles.
The requirements of Article 430 shall apply to the installation of motor-operated appliances, and the requirements of Article 440 shall apply to the installation of appliances containing a hermetic refrigerant motor-compressor(s), except as specifically amended in this article.

Can you elaborate on this? You lost me.

The two smaller motors may be acceptable on a single circuit if inverse time breaker is 250% or less of full load current of smallest motor. The requirements that may allow this send you to different areas of the code and it is easy to get lost. Start with 430.53, it may send you to 430.52, 240.4(B), 430.40, 430.22. 240.4(B) will allow you to use next higher standard overcurrent device, 240.6 says that 15 amps is lowest standard size inverse time circuit breaker so if they will start on a 15 amp breaker, that part is met.

Putting either of the smaller ones on with the 19 amp motor would mean that the breaker will exceed 250% of the smaller motor full load current, and 15 amps. Pretty much eliminates the possibility of putting other loads on with the 19 amp motor without additional overcurrent protection.

 

[rhamblin]

If the 30 amp disconnect has a minimum of 40 amp conductor supplying it, no violation.

I am still lost on this, I am sure I am missing something simple here, but isn't the disconnect an extension of the circuit which is protected at 40 amps. Therefore the disconnect could be drawing 39 A through it, burn up because it is not rated for that amount of current and never trip the breaker out. I am planning to pull #8 THHN to the disconnects but it seems like they would need to be 60A disconnects.

 

[kwired]

I am still lost on this, I am sure I am missing something simple here, but isn't the disconnect an extension of the circuit which is protected at 40 amps. Therefore the disconnect could be drawing 39 A through it, burn up because it is not rated for that amount of current and never trip the breaker out. I am planning to pull #8 THHN to the disconnects but it seems like they would need to be 60A disconnects.

It is not going to draw 39 amps for very long if it only has 30 amp or smaller fuses in it. That is why it is there. You have same thing if you have a 400 amp fused switch as a service and then tap lets say 8 fused switches of any rating smaller than 400 amps to supply whatever it is you are working with. The tap conductors will not carry more current than the connected load, but do need to be sized according to tap rules so they are not compromised during a short circuit or ground fault event that happens on the supply side of the tapped disconnect.

A similar situation is in a loadcenter. Say you have a 200 amp main breaker. The busses are protected from short circuits and ground faults by the main breaker @ 200 amps. The buss is the feeder. Now plug in some smaller breakers. The plug on the breaker is the tap connection, inside the case is the overcurrent device for the lower amperage circuit connected to the load side.

 

[rhamblin]

It is not going to draw 39 amps for very long if it only has 30 amp or smaller fuses in it. That is why it is there. You have same thing if you have a 400 amp fused switch as a service and then tap lets say 8 fused switches of any rating smaller than 400 amps to supply whatever it is you are working with. The tap conductors will not carry more current than the connected load, but do need to be sized according to tap rules so they are not compromised during a short circuit or ground fault event that happens on the supply side of the tapped disconnect.

A similar situation is in a loadcenter. Say you have a 200 amp main breaker. The busses are protected from short circuits and ground faults by the main breaker @ 200 amps. The buss is the feeder. Now plug in some smaller breakers. The plug on the breaker is the tap connection, inside the case is the overcurrent device for the lower amperage circuit connected to the load side.

Good point.:grin:

So then I would need to make sure the provisions of 240.21 apply correctly if using a 30 Amp disconnect?

Which after reading 240.21(B)(1), mounting a 30 Amp disconnect on this 40 Amp circuit will meet NEC guidelines.

Thanks for all the help guys.

 

[glene77is]

Why would you do that-- buy a disconnect that is made for the purpose. By the time you try and do what you say it will cost you a lot more money.

Dennis,
Basically, agreed.

He bought $2,000 worth of equipment for $200,
now why should his electrician consider doing a $800 wiring job for $80 ???
No logic there.

The wire and material may end up costing
more than the 'bargain' price for the equipment !
Plus the Time charge.

IMO, similar to your suggestion,
Drop an 80A sub-branch to a Sub-Panel (maybe near the equipment),
then sub-branch to each equipment,
appropriate for 210 and 430 (if that applies at all) to each peice of equipment.

In terms of business, 'sell' the idea of future expansion
and 'productive solutions' for this installation.

As usual, I like your 'line' of thinking.

 

[kwired]

Good point.:grin:

So then I would need to make sure the provisions of 240.21 apply correctly if using a 30 Amp disconnect?

Which after reading 240.21(B)(1), mounting a 30 Amp disconnect on this 40 Amp circuit will meet NEC guidelines.

Thanks for all the help guys.

And if you have a 40 amp conductor supplying the 30 amp disconnect you have no tap conductors so 240.21 is not a player. A tap conductor is one that has an ampacity rating less than the overcurrent device protecting it (except for service conductors - they have different sets of rules covered in 230)

 

[danickstr]

this guy made a steal of a deal on the equipment, so I have to make sure he steals the electrical work from me as well, otherwise, its not worth it to him.

run a sub panel and make him pay for two 60 amp 2 poles breakers, and then feed the stuff as you would for a normal small shop, with dedicated runs to the gear.