Minisplit Wiring

[augie47]

Mini-splits and their associated wiring have been a real PIA for the inspectors in this area.
In regard to the wire size, one of the local inspectors discussed it with the manufacturer and found there was internal protection in the outside unit for the interconnecting cables but I don't recall the manufacturer (I will try to find out).
Lengthy conversations with UL, ETL and the manufacturers have produced little change in some of their literature suggesting mini-split TC cable and SO cord for the interconnection.

 

[kwired]

Wouldn't all this reduction of wire size just because there's a motor in the system be null and void if the unit was capable of having backup heat strips added?

JAP>

I don't see it as a reduction in wire size just an allowed increase in overcurrent protection level, just like is allowed for other motors and motor operated appliances.

This image (see post #8) is interesting as it implies the 24v is referenced to the line neutral. Nothing wrong with that as long as the product is listed but if someone were to attach any external devices to that 24v, it would be line referenced. Of course the neutral ideally should be at or within a few volts to of ground.

Most standard residential HVAC and heating uses an isolated 24v ac system. One side of the 24v may be grounded but it's certainly not tied to the neutral.

When these units are used in the US they are used at 208 or 240 volts and connected to two ungrounded conductors. If used in European countries or others with similar power distribution systems - they very well may be operating at 240 volts but on a 240/416 volt wye system and therefore are connected to a "neutral" conductor.


I think part of the reason why there has been so much conflict with electrical installation of these is they are somewhat new in the US, but were originally designed for use in other countries. Sure they have been around the US for a while now but have been in other places much longer.

 

[MasterTheNEC]

I saw TC once and it looks like se cable. Is it really that different?

Inner conductors are the same, the sheathing is 30 mils on SE-R and TC can range upwards of 120 mils per UL 1277. The main different beyond the sheathing difference is the fiberglass binder that is required by UL 854 for SE Cables and binders in general are not required in UL 1277 for Type TC cables, but not prohibited of course if it is needed to maintain roundness. The TC-ER has to meet the same crush and impact requirements in UL 1569 as MC Cable as well which SE-R doesn't have to meet.

Bottom line, its more robust and of course code limitations and size limitations between the two products of course as you are already familiar with. Thats about a summary.

 

[tortuga]

I don't see it as a reduction in wire size just an allowed increase in overcurrent protection level, just like is allowed for other motors and motor operated appliances.

I like the way you stated that " increase in overcurrent protection level". From what I could tell it goes 240.4(G) -> 440.21-> 440.22(G) manufacturer gets to size it.

I looked into this recently when I was asked to connect a Daikin outdoor unit that called for a 30A circuit to the outdoor unit, then they supply a 14 awg TC-ER to each indoor unit. As per the instructions that's how I installed it.
Inside the connection box on the outdoor unit I could see that the 240V L1 and L2 were just jumpered to S1 and S2 like in that diagram posted earlier and appear to have no other protection than the 30A breaker until they got to the indoor unit.
So I was just wondering about this 14 AWG TC-ER cable. Assuming the plastic 'gutter' the mechanical contractor runs the line-sets in is considered a 'raceway' or 'cable tray system' 336.129(2), Looks like the TC-ER tray cable supplied by the manufacturer is marked THHN and they are using the values of THHN. I also sometimes use 14/3 UF instead of the TC-ER if the line-sets go more than 6 feet outside the 'raceway'.

 

[kwired]

I like the way you stated that " increase in overcurrent protection level". From what I could tell it goes 240.4(G) -> 440.21-> 440.22(G) manufacturer gets to size it.

I looked into this recently when I was asked to connect a Daikin outdoor unit that called for a 30A circuit to the outdoor unit, then they supply a 14 awg TC-ER to each indoor unit. As per the instructions that's how I installed it.
Inside the connection box on the outdoor unit I could see that the 240V L1 and L2 were just jumpered to S1 and S2 like in that diagram posted earlier and appear to have no other protection than the 30A breaker until they got to the indoor unit.
So I was just wondering about this 14 AWG TC-ER cable. Assuming the plastic 'gutter' the mechanical contractor runs the line-sets in is considered a 'raceway' or 'cable tray system' 336.129(2), Looks like the TC-ER tray cable supplied by the manufacturer is marked THHN and they are using the values of THHN. I also sometimes use 14/3 UF instead of the TC-ER if the line-sets go more than 6 feet outside the 'raceway'.

I wouldn't call the channel they run lines in a raceway or even cable tray, it is just a chase to run the lines in. UF, MC, NM cables are just as suitable to run in such a chase - with limitations on some of them if on the exterior of course.

IMO those other cable types or even conductors in raceway would be fine, have no idea why the manufacturers seem to think you must use TC cable, but some won't honor warranty if you don't use TC cable from what I understand.

 

[tortuga]

I wouldn't call the channel they run lines in a raceway or even cable tray, it is just a chase to run the lines in. UF, MC, NM cables are just as suitable to run in such a chase - with limitations on some of them if on the exterior of course.

IMO those other cable types or even conductors in raceway would be fine, have no idea why the manufacturers seem to think you must use TC cable, but some won't honor warranty if you don't use TC cable from what I understand.

I am guessing its because the TC is actually 90C rated THHN and UF cable is 60C and they are using that 90C THHN rating for some reason.

The manufacturer of 'Line Hide' advertises "Not just for HVAC. Hide any exteriorcabling, piping, or wiring.
www.lskair.com/Catalogs/LineHide%20Catalog.pdf
Clearly its not a chapter 3 wiring method...

 

[kwired]

I am guessing its because the TC is actually 90C rated THHN and UF cable is 60C and they are using that 90C THHN rating for some reason.

The manufacturer of 'Line Hide' advertises "Not just for HVAC. Hide any exteriorcabling, piping, or wiring.
www.lskair.com/Catalogs/LineHide%20Catalog.pdf
Clearly its not a chapter 3 wiring method...

But they aren't even using it anywhere close to max ampacity even if it were 60C, I don't think it has anything to do with temp rating.

 

[spark master]

I've seen a professional HVAC guy install a mini split. He shoves 14/3 Romex in seal tight, and runs that from the indoor unit, to the outdoor unit.
#1 It's commercial, no Romex allowed.
#2 How about the paper wrapper in Romex sucking up moisture outside.

I suggested he run to the home depot, and buy THHN, but he wouldn't listen.

This is the biggest mini split installer for my area, listed on the Mitsubishi web site, as a super pro dealer. Why does Mitsubishi promote him.... because he sells the most units in the zip code.
But he SUCKS !!!!
Sure, he can vacuum down a line set, but he's clueless on electric. Totally clueless.

Guess the small details don't count.... Such is life.........................

 

[kwired]

I've seen a professional HVAC guy install a mini split. He shoves 14/3 Romex in seal tight, and runs that from the indoor unit, to the outdoor unit.
#1 It's commercial, no Romex allowed.
#2 How about the paper wrapper in Romex sucking up moisture outside.

I suggested he run to the home depot, and buy THHN, but he wouldn't listen.

This is the biggest mini split installer for my area, listed on the Mitsubishi web site, as a super pro dealer. Why does Mitsubishi promote him.... because he sells the most units in the zip code.
But he SUCKS !!!!
Sure, he can vacuum down a line set, but he's clueless on electric. Totally clueless.

Guess the small details don't count.... Such is life.........................

I have seen many HVAC guys that are really good at HVAC, but are horrible electricians.

Romex not allowed in commercial - not entirely true, but still not allowed outdoors even when inside a raceway.

Does this guy ever get inspected by an electrical inspector? If not an electrical license holder he can be fined for wiring without license in many places, of course he needs to get caught by the right person in most instances.

 

[spark master]

I have seen many HVAC guys that are really good at HVAC, but are horrible electricians.

Romex not allowed in commercial - not entirely true, but still not allowed outdoors even when inside a raceway.

Does this guy ever get inspected by an electrical inspector? If not an electrical license holder he can be fined for wiring without license in many places, of course he needs to get caught by the right person in most instances.

I know the local codes. No Romex in commercial in my area code. and the paper sheath will wick moisture immediately.

In this situation, my job ended at the HVAC disconnect.

But he vacuumed down the line set to 5 micron or whatever it is, and he watched it for hours.... He did all the flare fittings perfectly with this special tool. Measured out the Freon to the oz.. as the line set was particularly long.

But don't know the difference between THHN & Romex........ or just doesn't care, because he thinks it doesn't matter.

 

[kwired]

I know the local codes. No Romex in commercial in my area code. and the paper sheath will wick moisture immediately.

In this situation, my job ended at the HVAC disconnect.

But he vacuumed down the line set to 5 micron or whatever it is, and he watched it for hours.... He did all the flare fittings perfectly with this special tool. Measured out the Freon to the oz.. as the line set was particularly long.

But don't know the difference between THHN & Romex........ or just doesn't care, because he thinks it doesn't matter.

HVAC guys don't get that much training on NEC, some maybe no training at all.

From my understanding newer refrigerant systems you need to be particular on a clean and sealed system. System performance is impacted when you don't have the right amount of refrigerant, slow leaks were never really acceptable but have a bigger impact on performance then they did with older refrigerants. Newer systems run at higher pressures as well so a small leak sort of isn't as small as it was before.

 

[tom baker]

The NEC need to look at these minisplits in more details fro the next code cycle. Also the use of 14/4 SO should be banned as well unless the wire is specifically listed for in-wall use?

The units are listed...
Make a public input for the 2020 Cycle, you have a few days to do that.

 

[tortuga]

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

But they aren't even using it anywhere close to max ampacity even if it were 60C, I don't think it has anything to do with temp rating.

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.

 

[Andy Delle]

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.

Well plain Romex would be OK if transitioned to SealTite outside via a Bell box extension (code where I am, no "poke through's" allowed to the back of an exterior mounted box). Just pull the sheath off inside the box. Most Romes uses THHN wires these days.

 

[roger]

Just pull the sheath off inside the box. Most Romes uses THHN wires these days.

Not true, check some and see if the individual conductors are identified per 310.120, without this identification the wires would not be compliant.

BTW, it would have to be THWN (I know all new THHN/THWN is dual rated, just nitpicking)

Roger

 

[Andy Delle]

Not true, check some and see if the individual conductors are identified per 310.120, without this identification the wires would not be compliant.

BTW, it would have to be THWN (I know all new THHN/THWN is dual rated, just nitpicking)

Roger

Not following you here? All romex (and MC) I have ever seen uses color coded conductors. Black, White, Red.

I run 14/3 Romex into a wall box with a say 5 foot tail. I strip the sheath at the box and through a flanged Bell box extension I run the three 14/3 wires through SealTite to the condenser. I may even also run the 240v source through the same Sealtite via another 12/2 romex into the wall box*. I would mark the 12/2 black and white wires with say blue and yellow tape or if using exterior conduit, just run different colors.. The bare Romex grounds would both be bonded to the wall box and extend up to the condenser via a green #12.

Why would that not be compliant?

* Assume there is a disconnect within 50 feet LOS.

Note this Bell box flange setup is how Los Angeles county requires HVAC feeds. They do not allow cable or conduit to punch through a wall and enter the rear of a box or disconnect. They told me it was a moisture issue between the box and the wall.

 

[jap]

Not following you here? All romex (and MC) I have ever seen uses color coded conductors. Black, White, Red.

I run 14/3 Romex into a wall box with a say 5 foot tail. I strip the sheath at the box and through a flanged Bell box extension I run the three 14/3 wires through SealTite to the condenser. I may even also run the 240v source through the same Sealtite via another 12/2 romex into the wall box*. I would mark the 12/2 black and white wires with say blue and yellow tape or if using exterior conduit, just run different colors.. The bare Romex grounds would both be bonded to the wall box and extend up to the condenser via a green #12.

Why would that not be compliant?

* Assume there is a disconnect within 50 feet LOS.

Note this Bell box flange setup is how Los Angeles county requires HVAC feeds. They do not allow cable or conduit to punch through a wall and enter the rear of a box or disconnect. They told me it was a moisture issue between the box and the wall.

If standard NM is not allowed in a raceway that's considered a wet location with the sheath left on it , how can it be allowed in a raceway that's considered a wet location with the sheath stripped off of it ?

JAP>

 

[Andy Delle]

If standard NM is not allowed in a raceway that's considered a wet location with the sheath left on it , how can it be allowed in a raceway that's considered a wet location with the sheath stripped off of it ?

JAP>

I would think with the sheath stripped off, that fiber paper would be gone too.

What is the code reference that dis-allows Romex inside exterior raceway, specifically Sealtite or EMT?

 

[roger]

Not following you here? All romex (and MC) I have ever seen uses color coded conductors. Black, White, Red.

MC conductors are individually marked, NM conductors are not, since the individual conductors in NM are not identified you can not use them outside the sheath.

I would think with the sheath stripped off, that fiber paper would be gone too.

That is not the problem

What is the code reference that dis-allows Romex inside exterior raceway, specifically Sealtite or EMT?

300.9 and 334.10(A)

Roger

 

[Andy Delle]

MC conductors are individually marked, NM conductors are not, since the individual conductors in NM are not identified you can not use them outside the sheath.

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!