Minisplit Wiring

[roger]

Ok I think you are saying there is no printed info on the wires? I guess you could splice to THHN inside the box but it just seems silly for five feet. But who ever said the NEC made common sense!

:thumbsup:

Roger

 

[kwired]

Yeah plain romex or SO cord to a minisplit is way wrong.
UF is at least listed for a wet location.

Well the manufacturers designing this circuit still need to comply with 310.15(B) (16) a 14 AWG circuit (feed to the indoor unit). Now they have 14 AWG on a 20 or even 25A breaker, UF is only listed for 15 amps. They use TC which is THHN the manufacturer uses the 90C column 14AWG = 25A.
Thats my guess.

conductor ampacity is not the problem we have a conductor with at least 15 amps ability but only has maybe a 1 amp load on it. Overcurrent protection is where an issue may exist.

 

[jap]

. But who ever said the NEC made common sense!

The NEC makes perfect sense..... the funny thing is listening to all of us idiots trying to figure it out.

JAP>

 

[tortuga]

conductor ampacity is not the problem we have a conductor with at least 15 amps ability but only has maybe a 1 amp load on it. Overcurrent protection is where an issue may exist.

Right and groundfault + short circuit protection. My concern is somehow something short circuits that 14 AWG conductor ( a CATV installer accidentally drills into one of those lineset 'raceways' or a squirrel moves in, etc)
Will the 20-30Amp breaker clear the fault?
I really hope I am wrong, but take a close look at one of those outdoor units, the minisplit manufacturer is just directly tapping off the outdoor compressor supply circuit without supplementary overcurrent protection to feed 240V to the indoor unit.
240.4 however directly links overcurrent protection to ampacity as it states "Conductors, other than flexible cords, flexible cables, and fixture wires, shall be protected against overcurrent in accordance with their ampacities specified in 310.15"
Now the manufacturer whom has taken over designing this circuit goes to to the table 310.15 and has to use the ampacity of UF/NM in the 60C. However since they may have 105C rated terminal blocks they can use the 90C table for THHN and there we have 25 amps for #14.
So they save millions of dollars by not installing supplementary overcurrent protection and just 'requiring' 90C rated wire that can be fused at 25A.
To me it is very strange to allow a manufacturer to 'design' a 240V circuit on 14AWG wire protected by a 20-30A inverse time circuit breaker into a residence.

 

[kwired]

Right and groundfault + short circuit protection. My concern is somehow something short circuits that 14 AWG conductor ( a CATV installer accidentally drills into one of those lineset 'raceways' or a squirrel moves in, etc)
Will the 20-30Amp breaker clear the fault?
I really hope I am wrong, but take a close look at one of those outdoor units, the minisplit manufacturer is just directly tapping off the outdoor compressor supply circuit without supplementary overcurrent protection to feed 240V to the indoor unit.
240.4 however directly links overcurrent protection to ampacity as it states "Conductors, other than flexible cords, flexible cables, and fixture wires, shall be protected against overcurrent in accordance with their ampacities specified in 310.15"
Now the manufacturer whom has taken over designing this circuit goes to to the table 310.15 and has to use the ampacity of UF/NM in the 60C. However since they may have 105C rated terminal blocks they can use the 90C table for THHN and there we have 25 amps for #14.
So they save millions of dollars by not installing supplementary overcurrent protection and just 'requiring' 90C rated wire that can be fused at 25A.
To me it is very strange to allow a manufacturer to 'design' a 240V circuit on 14AWG wire protected by a 20-30A inverse time circuit breaker into a residence.

Even a 40-50 amp breaker is likely sufficient for short circuit and ground fault protection, and overload protection may already be in place on the blower motor, which will inherently protect the conductor also. We do this all the time with motor circuits, conductor only sized to motor full load current,- usually 125% of FLA but reason for that has nothing to do with overcurrent protection, we put up to 175% time delay fuse or 250% inverse time breaker on it for short circuit/ground fault protection and depend on motor overload protection to also protect conductor from overload.

 

[jap]

To me it is very strange to allow a manufacturer to 'design' a 240V circuit on 14AWG wire protected by a 20-30A inverse time circuit breaker into a residence.

Look at the bright side. At least that 14 ga wiring for those split units is much larger than most residential ballasted fluorescent fixtures that are installed on 15 and 20 amp circuits that never get an eye batted at.

JAP>

 

[kwired]

Look at the bright side. At least that 14 ga wiring for those split units is much larger than most residential ballasted fluorescent fixtures that are installed on 15 and 20 amp circuits that never get an eye batted at.

JAP>

There are allowances for that in the code also. We even plug 18 AWG lamp cords into receptacles supplied by a 20 amp circuit breaker, and that is acceptable as well.

 

[hvacsplitman]

Split Systems Wiring

Split Systems Wiring

This post is quite old, depending on which version of the NEC code you are working on - Type TC or TC-ER is non compliant per the NEC. Here in PA and NJ is is currently being rejected by inspectors. Other non armored products are available in the market in place of TC.