# A/C Mini Splits and Code



## macmikeman (Jan 23, 2007)

I've never used an so cord between the compressor and the fan coil unit. In commercial jobs I just pipe the thing all the way. In dwellings I run (whatever size required)-3 wire cable. ** You are correct, running a 14-3 connection between compressor and fan coil is a code violation when the unit is protected at 20 or 30 amps, but yet millions of the same violation is performed in that instance. In the ac industry, it seems that factoid is universally overlooked.
Most electrical inspectors will not find a problem with it either. I have looked at most of the big boys schematics carefully to see if they have internal current limiting protection of the control cables for 15 amp but they do not. As far as putting a disconnect at the fan unit, if you first put a locking disco method at the compressor or a lock out unit on the circuit breaker at the panel you should not have to add a switch at the fan coil.


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## nrp3 (Jan 24, 2009)

I thought that the connection between the two units was low voltage. When I have done these, all I have ever done was run power to the disconnect and flex to the outdoor unit. The power cable was run to inside unit along with the line sets, sometimes under some sort of sleeve. The plumber/HVAC guys have always done between the inside and out, at least on my jobs.


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## Magnettica (Jan 23, 2007)

The ones I have done have all been 120 volt control wiring. We are talking about mini-split systems right?


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## nrp3 (Jan 24, 2009)

uh oh, I may have assumed...


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## Sven (Jul 16, 2010)

*Mini*

Well, this is new to me as well. In our case, we feed 2 condensors with #12 - 208 volt single phase and then run 2 sets of 14-3 solid to units in ceiling grid. I talked with tech of fujita today and said 2 leads L1 and L2 carry 208 volts to unit, 1 is return path (his words?), and 1 is a signal wire.


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## nitro71 (Sep 17, 2009)

I saw this gal do some mini splits one time, wow! Things are probably different in Sweden I would imagine. Bet the gals can really do mini splits over there : )


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## idontknow (Jul 18, 2009)

nrp3 said:


> I thought that the connection between the two units was low voltage. When I have done these, all I have ever done was run power to the disconnect and flex to the outdoor unit. The power cable was run to inside unit along with the line sets, sometimes under some sort of sleeve. The plumber/HVAC guys have always done between the inside and out, at least on my jobs.



When we install mini split systems, we use either 18-5 t-stat wire if the interconnect is low voltage, or 14-12 gauge wire in carflex. Also, we zip tie the wiring to the lineset.


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## idontknow (Jul 18, 2009)

I see the load on the evap unit is .5 amps. Is it protected somehow? With that small of an amp draw you could use t-stat wire. Even if you have to add a fuse (or two) to protect the wiring it'dbe a hell of a lot cheaper than using 14/3 SO

Most of the units we install with high voltage evaps have fuses in em.


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## macmikeman (Jan 23, 2007)

Lets put this a different way. Mitsubishi, Sanyo, Fujitsu mini split systems- Larger than 9,000 btu are 208/240 volt two wire and ground fed. The compressor calls the fan coil functions with a three wire plus ground control scheme. I have seen MG units that supply a SO type cord for the same control, but around here the electrical inspectors will give you trouble for those (machines are nice units though). The control wiring for the above mentioned units is spelled out in the installation manual to be #14. However there is no built in current limiting devices so that seems to me to be a conflict with the nec wire size protection ruling, especially when the nameplate on the compressor on some units calls for minimum 24 amps feed wire. Still I am a capitalist, and therefore am able to overlook certain limitations, especially since all the local authorities pat my installs on the back and say "nice job Mike". So I will often use 14-3 to a wp box on the building exterior where I switch to sealtite and thwn. Never had a fan coil go into loc rotor on me yet, but I have wired thousands.


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## Sven (Jul 16, 2010)

*1 conduit*

Hey Mc or whomever. The HVAC guys came and went and sealed their hole. Do you see anything against code on running the 2 condensor circuits line side with the 4 wires going out from condensor to the Mini Splits. 7 Current carrying conductors total in same 3/4 EMT conduit ? It's all 120/208 but 1 signal wire?? 

Sven


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## macmikeman (Jan 23, 2007)

Sven said:


> Hey Mc or whomever. The HVAC guys came and went and sealed their hole. Do you see anything against code on running the 2 condensor circuits line side with the 4 wires going out from condensor to the Mini Splits. 7 Current carrying conductors total in same 3/4 EMT conduit ? It's all 120/208 but 1 signal wire??
> 
> Sven


I don't see a problem Sven doing it that way, so long as all other wiring conditions are met like using the right size wire and temperature ratings and so forth and so on..


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