code vs specs

[nick@venture]

i have a split refrigerant system where the wiring installed between the outside unit and inside unit is 12 awg on a 20 amp breaker. there is a communication cable that runs with it. the unit is not running properly. the manufacturer is stating the oversized wire is causing interference and should be down sized to 16 awg. is there an allowance in the code to go with there spec vs nec? what is that reference?

 

[Dennis Alwon]

I have wired many of these units with a 14/3 or 12/3 nm cable and never had a problem. Not sure how you can do it the way they want

 

[infinity]

The NEC only cares about you following the manufacturers instructions that are part of the listing of the equipment. {110.3(B)}

 

[cadpoint]

Welcome to the Forum!

We need the face plate info! Model numbers, ETC...

 

[charlie b]

You did not give us enough information to help you troubleshoot. What do you mean by saying the unit is not working properly? What is it doing that it should not do, or not doing that it should do? Also, did you put in the #12 wire, or was that part of the manufacturer's internal wiring? If you put it in, then can you look up what the manufacturer's installation instructions say to use?

I will say that oversized wire will not cause interference. That is total nonsense, and I would call the manufacturer's bluff.

Welcone to the forum.

 

[GoldDigger]

One of the problems with some manufacturers split systems (particularly mini-splits in which one unit gets its power through the other unit) is that there is a conflict between the manufacturer's specifications for the interconnecting wire and the NEC requirements for the same wiring.
It seems to me that the interconnect in those cases is field wiring, not part of the listed equipment, and so the NEC governs in the event of a conflict.
One example is when the manufacturer specifies use of SJx cable where the NEC does not allow it.
I could see a remote possibility that use of oversize wire could allow a higher than expected peak current, but using short wire would have exactly the same effect.
Now, for the communications cable, I could see a problem with replacing the specified type with individual wires of any kind.

Tapatalk!

 

[kwired]

i have a split refrigerant system where the wiring installed between the outside unit and inside unit is 12 awg on a 20 amp breaker. there is a communication cable that runs with it. the unit is not running properly. the manufacturer is stating the oversized wire is causing interference and should be down sized to 16 awg. is there an allowance in the code to go with there spec vs nec? what is that reference?

I would be asking them what is next, as changing the conductor size is likely to do little to the performance. Too small or too long of conductors is more likely to cause trouble than too large or being very short in length.

 

[SceneryDriver]

i have a split refrigerant system where the wiring installed between the outside unit and inside unit is 12 awg on a 20 amp breaker. there is a communication cable that runs with it. the unit is not running properly. the manufacturer is stating the oversized wire is causing interference and should be down sized to 16 awg. is there an allowance in the code to go with there spec vs nec? what is that reference?

I call shenanigans on the manufacturer regarding wire size being the cause if the interference. If however, the power wiring between the two units should have been of a shielded type (does one unit contain the variable speed drive for the motor in the other unit?) I can see wire type possibly being an issue.

Can you physically separate the communications cable from the power wiring? You didn't put the coms cable in the same conduit as the power wiring, did you?

It's slightly astounding to me that their coms system, whatever it is, is so susceptible to interference. I've seen unshielded CAT5 cable run in industrial control panels with all sorts of interference sources, and the Ethernet coms didn't care in the least. Sounds like lazy engineering on the part of the manufacturer to me.


SceneryDriver

 

[kwired]

I call shenanigans on the manufacturer regarding wire size being the cause if the interference. If however, the power wiring between the two units should have been of a shielded type (does one unit contain the variable speed drive for the motor in the other unit?) I can see wire type possibly being an issue.

Can you physically separate the communications cable from the power wiring? You didn't put the coms cable in the same conduit as the power wiring, did you?

It's slightly astounding to me that their coms system, whatever it is, is so susceptible to interference. I've seen unshielded CAT5 cable run in industrial control panels with all sorts of interference sources, and the Ethernet coms didn't care in the least. Sounds like lazy engineering on the part of the manufacturer to me.


SceneryDriver

If it is type of system I suspect it is, there is only one lead that is specifically for control, and one of the other two leads is common to both power and control - they have to be in the same cable or raceway.