ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals

>> Home   >> Electrical-Photos   >> Classifieds   >> Subscribe to Newsletter   >> Store  
 

Photos of the Week:

Wire Your House $17.95
Wire Your House $17.95

Random Gallery Image:
Recent Gallery Topics:
What in Tarnation?
What in Tarnation?
by timmp, September 10
Plumber meets Electrician
Plumber meets Electrician
by timmp, September 10
Who's Online Now
0 members (), 707 guests, and 30 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Page 1 of 3 1 2 3
#210577 07/11/13 11:33 AM
Joined: Mar 2004
Posts: 829
B
BigB Offline OP
Member
We are seeing a lot of "mini split" AC units. As an example, let's say we have a mini split with an MCA of 11 amps, and a maximum fuse or circuit breaker of 25 amps per the nameplate. The wiring method is Romex. Wiring the unit with 14/2 would satisfy the MCA, however I believe it would violate 250.122 due to the 25 amp OCPD. To comply with 250.122, using Romex it seems we would need 10/2, no? Am I missing something?

Last edited by BigB; 07/11/13 11:34 AM.
Horizontal Ad
Joined: Apr 2002
Posts: 7,413
Likes: 8
Member
You have to determine the OCP that you are installing to determine the EGC for the circuit.

Using the nameplate MAX of 25 OCP would require #12. This is based on 250.122 table in '11 NEC as I read it.



John
Joined: Jun 2004
Posts: 613
S
Member
Originally Posted by BigB
We are seeing a lot of "mini split" AC units. As an example, let's say we have a mini split with an MCA of 11 amps, and a maximum fuse or circuit breaker of 25 amps per the nameplate. The wiring method is Romex. Wiring the unit with 14/2 would satisfy the MCA, however I believe it would violate 250.122 due to the 25 amp OCPD. To comply with 250.122, using Romex it seems we would need 10/2, no? Am I missing something?


BigB...The first sentence of 250.122(A) says that in no case shall the EGC be required to be larger than the circuit conductors supplying the equipment...

Joined: Jun 2004
Posts: 613
S
Member
Originally Posted by HotLine1
You have to determine the OCP that you are installing to determine the EGC for the circuit.

Using the nameplate MAX of 25 OCP would require #12. This is based on 250.122 table in '11 NEC as I read it.



I use the Minimum Circuit Ampacity to size my branch circuit conductors for an AC unit...

Joined: Jan 2005
Posts: 5,476
Likes: 3
Cat Servant
Member
Please note that the 2014 edition will have changes to this requirement in air conditioning article.

Joined: Mar 2004
Posts: 829
B
BigB Offline OP
Member
Ah so I was missing something. The scary part is I am pretty sure I knew that at one time. Getting old is no fun.

Last edited by BigB; 07/11/13 11:33 PM.
Joined: Apr 2002
Posts: 7,413
Likes: 8
Member
Perhaps a little clearer....

BigB example is 14/2NM, but he said 25 amp OCP, using the nameplate max figure.

Using the max OCP, a #12 EGC would be required, so using NM he has to use 12/2.

Yes, the EGC does not have to be larger than the circuit conductors, 'oversize' EGC to my knowledge is not available.

IMHO, I believe that he did not read Table 250.122 where the amperage col. jumps from 20 amps for #12, and 60 amps for #10.




John
Horizontal Ad
Joined: Jun 2004
Posts: 613
S
Member
Originally Posted by BigB
Ah so I was missing something. The scary part is I am pretty sure I knew that at one time. Getting old is no fun.


I agree with the getting old and memory loss...

Joined: Apr 2002
Posts: 7,413
Likes: 8
Member
short:
Ditto!!


John
Joined: Jun 2004
Posts: 613
S
Member
Originally Posted by HotLine1
Perhaps a little clearer....

BigB example is 14/2NM, but he said 25 amp OCP, using the nameplate max figure.

Using the max OCP, a #12 EGC would be required, so using NM he has to use 12/2.



I'm not sure I follow you Hotline...

When doing AC units the nameplate has all the info for sizing the branch circuit wiring...and sizing the overcurrent device.

For example...if the nameplate gives a MINIMUM BRANCH CIRCUIT AMPACITY of 30amps and a MAXIMUM BRANCH CIRCUIT OVERCURRENT DEVICE of 50amps...

I will wire the unit with 10-2 romex and connect it to a 50amp breaker.

Follow me?

shortcircuit

Page 1 of 3 1 2 3

Link Copied to Clipboard
Advertisement:-Right


Tools for Electricians
Tools for Electricians
 

Member Spotlight
Potseal
Potseal
Saskatchewan
Posts: 264
Joined: February 2013
Top Posters(30 Days)
Admin 3
CSS 1
Popular Topics(Views)
365,206 Are you busy
288,079 Re: Forum
266,761 Need opinion
New Page 2
Powered by UBB.threads™ PHP Forum Software 7.7.5