tim89s
Member
- Location
- Brush Prairie WA
Can you use a 60 amp breaker and wire on 40 amp noncontinuous restive load? Please give code section if there is one.
Thank you
tim
Thank you
tim
Oversized circuit
- Thread starter tim89s
- Start date
- Status
- Location
- Logan, Utah
You must provide overcurrent protection for the 40 amp resistive load.
Chris
Chris
- Location
- Connecticut
- Occupation
- Engineer
Generally, yes you can.
210.23 Permissible Loads. ...An individual branch circuit shall be permitted to supply any load for which it is rated. A branch circuit supplying two or more outlets...shall supply only the loads specified according to its size as specified in 210.23(A) thru (D).
210.23(D) Branch Circuits Larger than 50 Amperes. Branch circuits larger than 50 amps shall supply on nonlighting outlet loads.
210.23 Permissible Loads. ...An individual branch circuit shall be permitted to supply any load for which it is rated. A branch circuit supplying two or more outlets...shall supply only the loads specified according to its size as specified in 210.23(A) thru (D).
210.23(D) Branch Circuits Larger than 50 Amperes. Branch circuits larger than 50 amps shall supply on nonlighting outlet loads.
- Location
- Logan, Utah
The branch circuit would be fine but the load may need overcurrent protection set at 40 amps. We really need to know what the load is to determine if this set up is acceptable.
Chris
- Location
- Connecticut
- Occupation
- Engineer
tim89s
Member
- Location
- Brush Prairie WA
The load is a three phase power supply used for testing equipment.
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
And does it come with any instructions regarding overcurrent protection?
tim89s
Member
- Location
- Brush Prairie WA
No instructions. For simplicity sake lets assume its a heater. Could I protect it with a 60 amp
breaker and wire. This may sound stupid but I thought the ocpd was for the wire. I didn't think the code cared about the device it was serving.
breaker and wire. This may sound stupid but I thought the ocpd was for the wire. I didn't think the code cared about the device it was serving.
Yes it "cares".
Power supplies are not in the list. Fixed-Electric Space Heating is...??? In what type of facility is this to be used? What will it be used for, i.e. what will be tested? Anything else that might help accurately categorize it to one of the listed equipment types...?
tim89s
Member
- Location
- Brush Prairie WA
The power supply changes the voltage from 208 to 300 volts and increases the frequency from 60the to 10000hz. I am not sure what they are testing to be honest. They build alot of stuff for airplanes. I am guessing they are testing a motor that is used on a airplane.
Hard to nail down to a listed category. Sounds similar to an adjustable-speed drive system covered by Article 430 Part X, but its requirements don't put a cap on circuit rating.
Let me ask this, why are you considering this 60A circuit in the first place? Is it an existing unused circuit?
How are you establishing the 40A load value?
Do you have access to the equipment? Can you determine what the first-supplied component(s) are inside it?
Does it have a nameplate with electrical supply or consumption data on it, and if so what is that data?
Short on information, short on answer
tim89s
Member
- Location
- Brush Prairie WA
It is an existing unused circuit. Nameplate is 40amps. Thank you all for the info. Table 240.3 sent me in the right direction.
You have:
1: Minimum Circuit Ampacity. That is the minimum wire size you have to use for that circuit. The breaker HAS to protect that wire size(with some exceptions).
2: Then you have Maximum Overcurrent Protection. That is the MAXIMUM OCPD the manufacturer consider safe to install. Sure the #6 wire is protected by the 60A breaker, but the equipment is not. Keep in mind the manufacturer uses a lot smaller wires running around their equipment, so to get the UL listing, there's a maximum overcurrent protection that will work safely with their wires, terminals, contactors and other equipment.
1: Minimum Circuit Ampacity. That is the minimum wire size you have to use for that circuit. The breaker HAS to protect that wire size(with some exceptions).
2: Then you have Maximum Overcurrent Protection. That is the MAXIMUM OCPD the manufacturer consider safe to install. Sure the #6 wire is protected by the 60A breaker, but the equipment is not. Keep in mind the manufacturer uses a lot smaller wires running around their equipment, so to get the UL listing, there's a maximum overcurrent protection that will work safely with their wires, terminals, contactors and other equipment.
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