HVAC breaker terminals

T

TwistLock

Senior Member
Location
California
Occupation
Electrician
Mfg. label on A/C condenser says MCA 28.3 with 50a max breaker. So #10Cu to a 50a ocpd. Simple enough. Done. But the Homeline 50a 2pole has printing on the case that only describes #8 (or #6 ~ #2). Is this a lug restriction for all use scenarios?
I can run 4ft of #8 from breaker to the existing junction box & splice to the remainder of the run that uses #10 but I’m curious if I have an out here?

#8 or #10.jpg
 
...not to mention torque values often group #12 / #10 in the same range, then go slightly higher for #8 etc. so torquing to 45 most likely is an over-torque.
 
TwistLock said:
But the Homeline 50a 2pole has printing on the case that only describes #8 (or #6 ~ #2). Is this a lug restriction for all use scenarios?
Click to expand...
It's #8 for 60/75°, #6-#2 for 75° only. I would just use a 40 amp breaker if you already ran #10's.
 
infinity said:
It's #8 for 60/75°, #6-#2 for 75° only. I would just use a 40 amp breaker if you already ran #10's.
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35-60 amp breakers all have same terminals. I just checked out on line documents and QO has same conductor size rating as well for 35-60 amps.

I'm about 99% certain that many years ago at least the QO breakers accepted at least 10 AWG but likely even accepted 14 AWG for the 35-60 amp units? Not sure what or when this might have changed.

Then there is the QOM series main breakers that go from 50 up to 125 amps and their lugs are all rated for 12 to 2/0 AWG. Makes sense right?

I know for fact I have terminated 10 AWG and maybe even 12 AWG many times over the years for AC units, motors, and other applications that may allow higher OCPD than the general rules allow on the 35-60 amp breakers.
 
TwistLock said:
Nope.
View attachment 2579373
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• Maximum Overcurrent Protection (MOP): The
MOP value is the maximum overcurrent protection.
The MOP value is marked on the nameplate,
and is determined by the manufacturer of
the end-use equipment as follows:
(RLC or BCSC × 2.25) + other loads
Other loads would include condensing fans,
electric heaters, coils, etc., that operate concurrently.
In our example, the marked MOP is 45
amperes, calculated by the manufacturer of the
end-use equipment as follows:
(19.9 × 2.25) + 1.5 = 46.275 amperes
(round down to the next lower
standard size: 45 amperes)
See Section 440-22.

As an example, not based on your label.
 
kwired said:
35-60 amp breakers all have same terminals. I just checked out on line documents and QO has same conductor size rating as well for 35-60 amps.

I'm about 99% certain that many years ago at least the QO breakers accepted at least 10 AWG but likely even accepted 14 AWG for the 35-60 amp units? Not sure what or when this might have changed.

Then there is the QOM series main breakers that go from 50 up to 125 amps and their lugs are all rated for 12 to 2/0 AWG. Makes sense right?

I know for fact I have terminated 10 AWG and maybe even 12 AWG many times over the years for AC units, motors, and other applications that may allow higher OCPD than the general rules allow on the 35-60 amp breakers.
Click to expand...
Yeah, I see that now... You know, I don’t use Homeline but thought their all in one would be perfect for this job. There’s a lot of quirks with Homeline that I’m not liking. Their better (PON) SPD can be used but only lower on the tandem stabs on this particular panel model (no big deal but some inspectors want SPD next to main) and the only SPD listed on cut sheet has a pigtail and half the surge rating. Their DF breakers neutral lug can only be torqued outside panel in hand, they rivet on these weak ass key hole panel hanging straps with a tiny loose rivet and the straps easily bend. One of these straps is located a half inch directly behind the threaded hub for overhead services (this model). I guess my gripe about the screws on the neutral terminal bar being hidden behind any DF breaker goes with out saying. And I don’t know if it’s only Homeline but you have to use a 2 pole 30a GFCI, losing a space, b/c they don’t make a single pole 30a GFCI breaker for 120 RV plugs. (just whining)
 
kwired said:
40 amp as I mentioned has the same terminals. 35-60 amp all have same terminals.
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I've never used Homeline so I'm surprised that a 40 amp breaker doesn't accept #10's when I threw that out there. #10's and a 40 amp OCPD are common for AC units.
 
infinity said:
I've never used Homeline so I'm surprised that a 40 amp breaker doesn't accept #10's when I threw that out there. #10's and a 40 amp OCPD are common for AC units.
Click to expand...
QO 35-60 amp breakers all have same terminals as well and mention same conductor rating as Homeline does.

I never realized the minimum conductor is 8 AWG until this thread brought it to my attention. I been using QO seemingly forever and could swear they used to have smaller than 8 AWG at one time for minimum conductor. Will be looking at some older breakers when I get the chance to see what they say.

I know I've used smaller on motors and AC unit circuits many times over the years.
 
I'm old school and prefer to use the smallest fuse or circuit breaker. Even with a possible high inrush current my thinking is that you most likely could get by with a 40 amp circuit breaker. With fuses found that if I used quality time delay fuses for plain Jane two & four pole NEMA frame motors could usually get by only going 125% over motor FLA.Same with circuit breakers. The full load Amps of both motors is only 22.8 9 amps. They arrived at the 28.3 minimum CKT ampacity by correctly multiplying the largest motor by 1.25 then adding the small fan motor to come with the 28.3 amps. Once full speed is reached the two motors will be drawing 22.89 amps ( only on hot days ) so a 40 amp circuit breaker is 174.6 % more then running current.My first inefficient central AC unit that was in the house when we purchased it was on a 40 amp breaker. Tried a 30 amp breaker but it would trip a few times every summer. Next AC unit ran great on a 30 amp circuit breaker. The fairly high efficient 2.5 ton AC unit that I had installed 8 years ago is running on a 20 amp breaker while calling for a maximum circuit breaker of 30 amps. Wires from terminal block appear to only be #14 copper.
 
I agree in the past the breakers almost always accepted smaller wire. Now just another thing to check.

Probably illegal but I do it anyhow It is common for me to strip the wire and double it over and put it in the lug if the lugs are large. just think its better
 
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