40 amp branch circuit

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rhamblin

rhamblin

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Kaukauna, Wisconsin
I have a customer that just purchased a drill press, sander and chop saw. The current for each is 3.5, 6 and 19 amps respectively. I am trying to find a way to put them all on one circuit, because there is limited space in the breaker panel. All items are 3 phase. So if I put them all on a 3 phase 40 amp breaker, it will cover the power required for the items. 1st question: Is it permissible to run 3 - 40 amp receptacles in 3 seperate 4 sq boxes fed from the same circuit. I have seen this many times with 15 and 20 amp circuits, but I don't think I have ever seen more than one receptacle on the same circuit over 30 amps. 2nd question: Is it permissible to put a small (3.5 amp motor) on a 40 amp circuit? And likewise for the other items.
 
The best way, since your limited on breaker space, is to run the 40 amp circuit to a j-box, then split it to 3-30 amp fusible disconnects, with each fused down to the proper amperage for each piece of equipment. (or do what Dennis said, either way will work)
 
rhamblin said:
The current for each is 3.5, 6 and 19 amps respectively.
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It it against code to plug the first two loads into receptacles on 40a circuit? I didn't think the BC OCPD is used to current-limit plugged-in loads?

If the loads won't be used simultaneously, I would think a smaller circuit could still be used.
 
Or use a Combination Starter mounted to each piece of equipment, each with its own breaker or fused disconnect specific to the motor associated. Then you could use a plug and receptacle for each combo starter if you need to move the equipment.
 
Jraef said:
Or use a Combination Starter mounted to each piece of equipment, each with its own breaker or fused disconnect specific to the motor associated. Then you could use a plug and receptacle for each combo starter if you need to move the equipment.
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It is a beautiful yet overwhelmingly expensive solution. :grin:
 
Thanks for the ideas guys. But I am still curious about my original two questions. I looked in the 2008 code book at a couple articles and didn't see anything that actually disallowed what I am thinking about doing.

See if my logic is correct. This would would be a branch circuit, 210.19(A)(1) says I need to plan for 100 percent of the noncontinuous load of all of the connected loads for the ampacity of the conductors. I come up with 28.5 amps. So I will put them on a 40 amp breaker. I am considering these loads to be noncontinuous. 210.20 says the OCPD needs to be at least 100 percent of the noncontinuous load. 40 amp breaker.

210.21 (B)(3) says I can put 40A or 50A receptacles in. So from what i understand the answer to my first question is yes, I can put multiple 40A receptacles on the same 40A circuit.

As far as the 2nd question, installing a small piece of equipment on a 40 receptacle, I can't find anything in the code book that disallows this. Or rather does the code say that a small piece of equipment can't be protected by a larger breaker. Here I am basically protecting a 3.5A drill press with a 40 Amp breaker. 430.53 says that I need to protect the smallest motor (via 430.52) at maximum (800 percent) which is (3.5A x 800 percent = 28 Amps, which can then be moved up to a 30 amp breaker because of 430.52(C)(1)(exc. no. 1). But this is not enough ampacity to protect all 3 pieces of equipment, because of 210.19(A)(1).

So basically I just proved that I cannot put all three items on one 40 amp breaker. So now I need to look at what the cheapest option is to protect the items. The cust. was able to get all of the equipment for around 200 dollars at a local auction. So to spend alot of money to wire the items up is not cost effective. These would be back up equipment.
 
Hillbilly1 suggested "The best way, since your limited on breaker space, is to run the 40 amp circuit to a j-box, then split it to 3-30 amp fusible disconnects, with each fused down to the proper amperage for each piece of equipment."

I am getting creative here but would it have to be a fusible disconnect. What if i get a 4 11/16" box and mount a fuse holder inside of it rather than a fusible disconnect. Maybe i would have to mount a 6x6 box or whatever. All of the equipment has plugs on it so I don't need a seperate disconnecting means. It seems that I have seen this before, just not sure if it is legal.
 
The question I would ask is couldnt a 25 or 30 amp circuit be used. Is all the equipment being used at the same time or only one piece at a time, maybe someone could tell if that violates code.
 
rhamblin said:
I am getting creative here but would it have to be a fusible disconnect. What if i get a 4 11/16" box and mount a fuse holder inside of it rather than a fusible disconnect.
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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.
 
I think that Dennis has the best idea. If the main panel is not maxed out amperage wise, put in a 60 amp sub-panel. You said that there is limited space in the panel, so if the sub-panel will fit with the building's current load adding the sub-panel will give your customer a little room to grow, maybe you can even install a larger than 60 amp panel. Then he won't be faced with the same problem when he wants to add another piece of equipment. He bought this equipment for $200 but that is only the cost of the equipment, that is not his entire cost if he wants to USE the equipment.

I disagree with wiseguy's idea.
wireguy8169 said:
The question I would ask is couldnt a 25 or 30 amp circuit be used. Is all the equipment being used at the same time or only one piece at a time, maybe someone could tell if that violates code.
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If I were the customer and you hooked up my equipment in my machine shop, and told me "the job is done, you just can't use it all at the same time." I would not be pleased. He is in the business of working efficiently to make money, not standing around waiting till someone else is done.
 
hillbilly1 said:
The best way, since your limited on breaker space, is to run the 40 amp circuit to a j-box, then split it to 3-30 amp fusible disconnects, with each fused down to the proper amperage for each piece of equipment. (or do what Dennis said, either way will work)
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Wouldn't I have to use 60 amp disconnects instead of 30 amp? Because it is a 40 amp circuit.
 
rhamblin said:
... Here I am basically protecting a 3.5A drill press with a 40 Amp breaker. 430.53 says that I need to protect the smallest motor (via 430.52) at maximum (800 percent) which is (3.5A x 800 percent = 28 Amps, which can then be moved up to a 30 amp breaker because of 430.52(C)(1)(exc. no. 1). But this is not enough ampacity to protect all 3 pieces of equipment, because of 210.19(A)(1).

So basically I just proved that I cannot put all three items on one 40 amp breaker. So now I need to look at what the cheapest option is to protect the items. The cust. was able to get all of the equipment for around 200 dollars at a local auction. So to spend alot of money to wire the items up is not cost effective. These would be back up equipment.
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That 800 percent is for an instantaneous trip circuit breaker. For an inverse time breaker, which is what typical breakers that plug into a load center are, maximum is 250%.

See if my logic is correct. This would would be a branch circuit, 210.19(A)(1) says I need to plan for 100 percent of the noncontinuous load of all of the connected loads for the ampacity of the conductors. I come up with 28.5 amps. So I will put them on a 40 amp breaker. I am considering these loads to be noncontinuous. 210.20 says the OCPD needs to be at least 100 percent of the noncontinuous load. 40 amp breaker.
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Motor branch circuits are sized according to article 430 and not 210.

One branch circuit is not allowed in this installation, the two smaller loads may be allowed on a single branch circuit but neither one would be allowed on the same circuit with the larger load.
 
If this is a dwelling unit, then I think 210.23(C) kills the idea. If it is not a dwelling unit, then I would ask whether the three tools come with cord caps that plug into a 40 amp receptacle. If not, how will you get them plugged in, without voiding the listing?
 
rhamblin said:
I have a customer that just purchased a drill press, sander and chop saw. The current for each is 3.5, 6 and 19 amps respectively. I am trying to find a way to put them all on one circuit, because there is limited space in the breaker panel. All items are 3 phase. So if I put them all on a 3 phase 40 amp breaker, it will cover the power required for the items. 1st question: Is it permissible to run 3 - 40 amp receptacles in 3 seperate 4 sq boxes fed from the same circuit. I have seen this many times with 15 and 20 amp circuits, but I don't think I have ever seen more than one receptacle on the same circuit over 30 amps. 2nd question: Is it permissible to put a small (3.5 amp motor) on a 40 amp circuit? And likewise for the other items.
Click to expand...


Often this kind of equipment already has some kind of built in overload protection, so you only have to worry about SC protection.
 
kwired said:
Motor branch circuits are sized according to article 430 and not 210.
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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?:confused:
 
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