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-   -   5 Ton Compressor Electrical Supply (http://www.diychatroom.com/f17/5-ton-compressor-electrical-supply-153647/)

Pintle 08-14-2012 08:51 AM

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?

turnermech 08-14-2012 03:25 PM

6-2 wire, 50 amp breaker

stickboy1375 08-14-2012 03:51 PM

Quote:

Originally Posted by Pintle (Post 988265)
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...

turnermech 08-14-2012 03:59 PM

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.

turnermech 08-14-2012 04:02 PM

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.

stickboy1375 08-14-2012 04:28 PM

Quote:

Originally Posted by turnermech (Post 988569)
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?

turnermech 08-14-2012 04:35 PM

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.

stickboy1375 08-14-2012 04:36 PM

Quote:

Originally Posted by turnermech (Post 988603)
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.
http://i171.photobucket.com/albums/u...ecwb15fig2.jpg

turnermech 08-14-2012 04:48 PM

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.

turnermech 08-14-2012 04:50 PM

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

stickboy1375 08-14-2012 04:51 PM

Quote:

Originally Posted by turnermech (Post 988612)
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...

stickboy1375 08-14-2012 04:51 PM

Quote:

Originally Posted by turnermech (Post 988614)
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...

turnermech 08-14-2012 04:58 PM

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.

stickboy1375 08-14-2012 05:00 PM

Quote:

Originally Posted by turnermech (Post 988624)
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?

turnermech 08-14-2012 05:03 PM

The OP asked for braker and wire size to disconnect. Are you talking about wire size from disconnect to equipment?


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