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Old 08-14-2012, 08:51 AM   #1
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5 Ton Compressor Electrical Supply


I just picked up a slightly used 5-Ton Heil R410A split system. I don't have any installation instructions and can't find any on the web. Power is 208-230 volt, 1 phase. The compressor label says Minimum Circuit amps - 34.2 but also says Max Fuse 50 amps. Nearly 80 feet to evaporator; unit set up to run in winter; located in Maryland. What size breaker, cable and disconnect fuses do I need to use?

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Old 08-14-2012, 03:25 PM   #2
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6-2 wire, 50 amp breaker

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Old 08-14-2012, 03:51 PM   #3
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Originally Posted by Pintle View Post
The compressor label says Minimum Circuit amps - 34.2 but also says Max Fuse 50 amps.
If you are using NM (romex), then #8 AWG, if you want to use THHN/THWN, then you can use #10 AWG... Both fed from a 50 amp breaker. Are you sure it doesn't say MAXIMUM FUSE OR BREAKER? Take a picture of the name plate if you are not sure.... This will save you some money.

Using 6 AWG is a waste of money...

Last edited by stickboy1375; 08-14-2012 at 03:55 PM.
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Old 08-14-2012, 03:59 PM   #4
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my code book allows 45 amps from 8 wire, which you could do. A 45 amp breaker is twice the cost of a 50 (don't ask me why). 10 wire is only good per code for 30 amps.
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Old 08-14-2012, 04:02 PM   #5
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6-2 romax is around a 1.00 per foot my cost. 8-2 not much less. I have worked in 7 counties in Maryland same state as your location what I told you is what MD requires.
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Old 08-14-2012, 04:28 PM   #6
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my code book allows 45 amps from 8 wire, which you could do. A 45 amp breaker is twice the cost of a 50 (don't ask me why). 10 wire is only good per code for 30 amps.

Which code book are you using? what year?
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Old 08-14-2012, 04:35 PM   #7
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we fall under national electrical code the wire sizes are as I stated. yes they are in the book. Where do yours come from? They look like the goodies electrical pocket guide. I hold a master HVAC lic and a Restricted Master Electrical lic.
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Old 08-14-2012, 04:36 PM   #8
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we fall under national electrical code the wire sizes are as I stated. Where do your come from? They look like the goodies electrical pocket guide. I hold a master HVAC lic and a Restricted Master Electrical lic.
Well, # 10 thhn is good for 35 amps my friend... and I think you have been over wiring your AC units. Read up on 240.4 (G)



This is just an example on how to size an AC unit.

Last edited by stickboy1375; 08-14-2012 at 04:41 PM.
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Old 08-14-2012, 04:48 PM   #9
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assuming 10 is good for 35 amps (which I don't agree) are you saying you would recomend running a unit with a MCA of 34.2 on a 35 amp breaker? because I would not. What code book did your post come from?

10 wire for example will carry more than 35 or 30 for sure it depens on lenght of run and temp. but it is not allowed in maryland. Or any state falling under the national electrical code.
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Old 08-14-2012, 04:50 PM   #10
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just looked at the pic you posted again. You can't run a unit with a MCA of 22 on 12 wire either. 12 wire good for 20 amps
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Old 08-14-2012, 04:51 PM   #11
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Originally Posted by turnermech View Post
assuming 10 is good for 35 amps (which I don't agree) are you saying you would recomend running a unit with a MCA of 34.2 on a 35 amp breaker? because I would not. What code book did your post come from?

10 wire for example will carry more than 35 or 30 for sure it depens on lenght of run and temp. but it is not allowed in maryland. Or any state falling under the national electrical code.
Im sorry you are misguided on this subject... but the truth of the matter is you are missing some important information.

It is allowed in maryland, because maryland IS under the NEC, The maximum breaker is ONLY providing ground fault and short circuit protection, the minimum circuit ampacity is the branch circuit wiring, this is why the breaker can be much higher...
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Old 08-14-2012, 04:51 PM   #12
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Originally Posted by turnermech View Post
just looked at the pic you posted again. You can't run a unit with a MCA of 22 on 12 wire either. 12 wire good for 20 amps
Yes you can... sorry you missed the boat.... I already told you to check out Table 240.4(G) and check out 240.4(D) while your at it, You might as well read article 440 also...

Last edited by stickboy1375; 08-14-2012 at 04:57 PM.
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Old 08-14-2012, 04:58 PM   #13
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Where does the pic come from? Is it from the NEC?

this is copied form the NEC page.
The NFPA 70: National Electrical Code (NEC) is adopted in all 50 states. Electrical wiring and equipment requirements protect people and property from electrical hazards. Provisions for residential and commercial/industrial electrical installations address every topic -- from wiring and protection, to wiring methods and materials, to special occupancies such as hazardous (classified) locations, and special equipment such as solar photovoltaic (PV) systems.

What I have said is what required in Maryland. What I have said is how the inspectors of the 7 counties I work in will want. The OP is in MD.
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Old 08-14-2012, 05:00 PM   #14
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Originally Posted by turnermech View Post
Where does the pic come from? Is it from the NEC?

this is copied form the NEC page.
The NFPA 70: National Electrical Code (NEC) is adopted in all 50 states. Electrical wiring and equipment requirements protect people and property from electrical hazards. Provisions for residential and commercial/industrial electrical installations address every topic -- from wiring and protection, to wiring methods and materials, to special occupancies such as hazardous (classified) locations, and special equipment such as solar photovoltaic (PV) systems.

What I have said is what required in Maryland. What I have said is how the inspectors of the 7 counties I work in will want. The OP is in MD.
Look, im under the NEC, the graphic is from the NEC, you're being misinformed unless the state has an amendment about Table 240.4(G), Which in no way and hell it exists.


Why do you think the numbers exist on the nameplate to begin with?

Last edited by stickboy1375; 08-14-2012 at 05:03 PM.
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Old 08-14-2012, 05:03 PM   #15
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The OP asked for braker and wire size to disconnect. Are you talking about wire size from disconnect to equipment?

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