EGC Size HVAC Outdoor unit

[tom baker]

This is existing HVAC outside unit
MCA 23.3 amps
MCA 40
Installer ran 10 AWG THHN from 30 amp breaker, with #12 EGC
I added a j box in feed to HVAC outside unit
I think the EGC should be #10?
Or I could refeed with #12 THHN which is how I would of done it my self

 

[don_resqcapt19]

Yes, the equipment grounding conductor is sized per the OCPD rating and Table 250.122, unless that would make the EGC larger than the circuit conductors.

 

[mtnelect]

This is existing HVAC outside unit
MCA 23.3 amps
MCA 40
Installer ran 10 AWG THHN from 30 amp breaker, with #12 EGC
I added a j box in feed to HVAC outside unit
I think the EGC should be #10?
Or I could refeed with #12 THHN which is how I would of done it my self

In my opinion, since HVAC condensing units are subjected to harsher running conditions than premises wiring, I always use the 60-degree column for amperage ratings. Also, some manufacturers require 60-degree rating on their name plate insulation to prevent the use of smaller wire size.

 

[wwhitney]

Yes, the equipment grounding conductor is sized per the OCPD rating and Table 250.122, unless that would make the EGC larger than the circuit conductors.

It's a little bit odd: 250.122(A) says "The equipment grounding conductor shall not be required to be larger than the circuit conductors supplying the equipment," while 250.122(D)(1) says "The equipment grounding conductor size shall not be smaller than determined by 250.122(A) based on the rating of the branch-circuit short-circuit and ground-fault protective device."

These two statements are simply in conflict. Yet everyone seems to agree that the statement in 250.122(A) takes precedence. Obviously the way it is phrased means it intends to take precedence. But I don't think the NEC actually permits 250.122(A) to amend 250.122(D), does it?

Cheers, Wayne

 

[MyCleveland]

In my opinion, since HVAC condensing units are subjected to harsher running conditions than premises wiring, I always use the 60-degree column for amperage ratings. Also, some manufacturers require 60-degree rating on their name plate insulation to prevent the use of smaller wire size.

Could you give an example on your last sentence. Not clear on what your stating.

 

[mtnelect]

Could you give an example on your last sentence. Not clear on what your stating.

This is an example of a HVAC manufacturer using 60-degree wiring. I always refer to the manufacturer's installation instructions, before wiring.

 

[infinity]

This is an example of a HVAC manufacturer using 60-degree wiring. I always refer to the manufacturer's installation instructions, before wiring.

I don't see Note A as a requirement to use only the 60° C conductor rating. It's just telling you how the numbers were derived.

 

[rc/retired]

I don't see Note A as a requirement to use only the 60° C conductor rating. It's just telling you how the numbers were derived.

Hooray!

 

[mtnelect]

Hooray!

This is a manufacturer's recommendation for refrigeration systems only and not a NEC (National Electrical Code) requirement. Not following the manufacturers recommendations could result in the warranty not being covered.

 

[infinity]

Note A also says 50' of conductor so if you're going to say that it applies to all installations then you cannot use more than 50' of conductor.

 

[mtnelect]

Note A also says 50' of conductor so if you're going to say that it applies to all installations then you cannot use more than 50' of conductor.

For conditions longer than 50 feet you might want to increase the wire size for voltage drop. Reducing the wire size in refrigeration systems is not a good idea.

 

[don_resqcapt19]

It's a little bit odd: 250.122(A) says "The equipment grounding conductor shall not be required to be larger than the circuit conductors supplying the equipment," while 250.122(D)(1) says "The equipment grounding conductor size shall not be smaller than determined by 250.122(A) based on the rating of the branch-circuit short-circuit and ground-fault protective device."

These two statements are simply in conflict. Yet everyone seems to agree that the statement in 250.122(A) takes precedence. Obviously the way it is phrased means it intends to take precedence. But I don't think the NEC actually permits 250.122(A) to amend 250.122(D), does it?

Cheers, Wayne

(A) really should be parent or charging text and not a first level subdivision.

 

[rc/retired]

This is a manufacturer's recommendation for refrigeration systems only and not a NEC (National Electrical Code) requirement. Not following the manufacturers recommendations could result in the warranty not being covered.

I'm not dissing your trade by any means, however, (there's always a however in life), recommendations, should, could and such would be hard to become a shall or shall not. JMHO

Ron

 

[MyCleveland]

This is an example of a HVAC manufacturer using 60-degree wiring. I always refer to the manufacturer's installation instructions, before wiring.

I have never ran across this note.
Are they trying to build in a safety factor for starting conditions by increasing the wire size using 60C column?
Are they trying to state the internal components are only 60C terminals?

I tried calling the tech support, but he hold music makes me want to hang myself.

So I am still unclear on what they are trying to convey.

 

[mtnelect]

I have never ran across this note.
Are they trying to build in a safety factor for starting conditions by increasing the wire size using 60C column?
Are they trying to state the internal components are only 60C terminals?

I tried calling the tech support, but he hold music makes me want to hang myself.

So I am still unclear on what they are trying to convey.

The NEC (National Electric Code) has Article 440 to address the special requirements of refrigeration equipment, and Section IV, Branch-Circuit Conductors Section 440.31:

"The provisions of Part IV and Article 310 specify ampacities of conductors required to carry the motor current without overheating under the conditions specified except as modified in 440.6(A), Exception No. 1. The provisions of these articles shall not apply to integral conductors of motors, to motor controllers and the like, or to conductors that form an integral part of approved equipment."

Informational Note: See 300.1(B) and 310.1 for similar requirements.

In my opinion, the manufacturers of HVAC equipment don't want the wire sizes reduced. Remember that refrigeration equipment is required to run for long periods of time, under very harsh conditions.