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Old 08-14-2012, 06:03 PM   #16
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The only place in 310.16 where I see #8 listed for 45 amps is in the AL and 90 degree column.

Copper #8 at 60 degrees is 40 amps and at 75 would be 50.

Maryland does not have a state adopted code. It varies according to each county, but always seems to be based on the NEC although the edition changes. What county told you you needed to size for the max breaker size?

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Old 08-14-2012, 06:03 PM   #17
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Originally Posted by turnermech View Post
The OP asked for braker and wire size to disconnect. Are you talking about wire size from disconnect to equipment?
Its all the same...
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Old 08-14-2012, 06:05 PM   #18
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Why do you think the numbers exist on the nameplate to begin with?

for min and max. there is also a recomended by manufacture which is not on name plate I bet this units recomended is not 10 wire.
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Old 08-14-2012, 06:06 PM   #19
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Its all the same...
I agree just checking I have seen some make these same arguement you are making with inspectors about the wip and the intermal overload.
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Old 08-14-2012, 06:08 PM   #20
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OP. Use no smaller then an 8 gauge. 10 will have a slight voltage drop. but it may also cause your compressor to labor when it starts.

The NEC allows motor load only circuits to have a higher amp breaker then the nomial listing of the wire. Its a section in the NEC that is often missed by many.
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Old 08-14-2012, 06:08 PM   #21
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Quote:
Originally Posted by turnermech View Post
Why do you think the numbers exist on the nameplate to begin with?
They tell you the minimum wire size you need to run and the maximum breaker you can install. They dont relate to each other.
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Old 08-14-2012, 06:09 PM   #22
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Quote:
Originally Posted by beenthere View Post
OP. Use no smaller then an 8 gauge. 10 will have a slight voltage drop. but it may also cause your compressor to labor when it starts.

The NEC allows motor load only circuits to have a higher amp breaker then the nomial listing of the wire. Its a section in the NEC that is often missed by many.
#8 is going to have a voltage drop at startup as well... we are talking 80' at 240v...
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Old 08-14-2012, 06:14 PM   #23
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Turnermech, I think you are missing the fact the the motor itself contains the overload protection, this is where the MCA comes from, the Maximum breaker size is only providing ground-fault and short circuit protection, without this type of setup, it would be very hard to start motors without tripping the breaker on startup...
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Old 08-14-2012, 06:18 PM   #24
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Here, read up...
http://ecmweb.com/code-basics/air-co...tion-equipment
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Old 08-14-2012, 06:22 PM   #25
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Quote:
Originally Posted by stickboy1375 View Post
#8 is going to have a voltage drop at startup as well... we are talking 80' at 240v...
Yes, but it will be less voltage drop. Many 5 tons tend to dim the homes lights when they start. personally, I would run a 6 gauge, to help minimize light dimming. The OP can use 10, 8, or 6, but he may have some severe light dimming.

Don't forget, a 5 ton compressor can have a LRA of 130 plus amps.
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Old 08-14-2012, 06:23 PM   #26
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MCA = minimum circuit ampacity. Table 310.16 allows #10 THWN to carry 35 amps. If the OP wants to run NM cable on the interior portions of the circuit they are limited to the 60 degree column and need to run #8.

#12 is good for 25 amps at the 60 degree column. The 20 amp restriction is imposed by by 240.4(D). Article 240 also says that other Article like 420 and 440 can over-ride these.
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Old 08-14-2012, 06:25 PM   #27
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Quote:
Originally Posted by turnermech View Post
Why do you think the numbers exist on the nameplate to begin with?

for min and max. there is also a recomended by manufacture which is not on name plate I bet this units recomended is not 10 wire.
The loads imposed have already been calculated by the manufacturer. If they did not want to allow #10 they should have raised the minimum circuit ampacity on the dataplate.
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Old 08-14-2012, 06:39 PM   #28
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Quote:
Originally Posted by beenthere View Post
Yes, but it will be less voltage drop. Many 5 tons tend to dim the homes lights when they start. personally, I would run a 6 gauge, to help minimize light dimming. The OP can use 10, 8, or 6, but he may have some severe light dimming.

Don't forget, a 5 ton compressor can have a LRA of 130 plus amps.
Dude, you could run 4/0 al. And the lights will still have voltage drop, the issue resides from the utility side.
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Old 08-14-2012, 06:48 PM   #29
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I talking about 10-2, 8-2, & 6-2 romax. I think some of these issues come for some are talking wire in conduit. the amp rating are not the same for each.

I stand by my statement of 10-2=30 amps 6-2 = 60 amps (8-2 I always have to look up as far as it being 40 or 45 and I don't carry the code book home from the office). I would say the OP is not going to run conduit he is going to run romax.
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Old 08-14-2012, 06:50 PM   #30
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Quote:
Originally Posted by stickboy1375 View Post
Dude, you could run 4/0 al. And the lights will still have voltage drop, the issue resides from the utility side.
Not always. under sized wire to an A/c or heat pump can cause it also.

You run what you want for your customers, I'll run wire sized more for the max amp, and lower voltage drop.

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