Units hvac question for hvac experts

[hhsting]

I have indoor unit and an outdoor unit hvac. Outdoor unit is fed from panelboard circuit breaker B1.

Outdoor unit then has cable C1 that feeds indoor unit. So outdoor unit feeds indoor unit with cable C1.

What protects the cable C1 and how to size cable C1 or is cable C1 considered part of indoor and outdoor unit system and size is determined by manufacturer instruction?

 

[hbiss]

So outdoor unit feeds indoor unit with cable C1.

... is cable C1 considered part of indoor and outdoor unit system and size is determined by manufacturer instruction?

Yes.

-Hal

 

[hhsting]

Yes.

-Hal

Sorry but i dont follow. Which one?


Sent from my iPhone using Tapatalk

 

[tortuga]

The NEC does not have any classification for circuits run between pieces of equipment other than branch circuit or feeder does it?
Or I suppose Class 1-3 circuits.
I say then C1 is either part of branch circuit B1 and is sized per that breaker
or
Circuit C1 has UL approved supplemental protection where it originates 240.5(A) in the outdoor unit

 

[ActionDave]

Protect cable C1 from what? Rodent damage?

 

[hillbilly1]

Cable C1 is probably a DC circuit generated from the outdoor unit, thus protected by outdoor unit, being a part of the manufactures equipment, is not covered by the NEC.

 

[tortuga]

Cable C1 is probably a DC circuit generated from the outdoor unit, thus protected by outdoor unit, being a part of the manufactures equipment, is not covered by the NEC.

Around here, as soon as any wiring method leaves equipment (in this case the outdoor unit) to go to other equipment (indoor unit) that wiring is covered by the NEC. 90.2(C) unless exempted in 90.2(D). If a wiring method like tray cable is supplied by the HVAC manufacturer it still needs to be installed per chapter 3 (EDIT or 725 if power limited)

 

[hillbilly1]

I noticed the last one I installed, the manufacturer provided a coated mc cable whip, unlike the previous ones that just had a jacket over the wires.

 

[augie47]

A few years ago we went through a lengthy process involving manufactuers, UL, and distributors when the first mini-splits appeared. They actually came with a SO or SJ cord or TC cable for inter-connection. As it turned out those units were supplied thu Canada and ETL listed so UL had no input and we were advised the factory recommended install met Canadian Code. Most of the units we investigated had internal protection on the inter-connect cable which varied between line voltage, low voltage and DC. Our installs were most jacketed MC until the '17 changes allowing TC without a conduit,.
Lately, like hillbilly, we see jacketed MC by the manufacturer.

 

[tortuga]

A few years ago we went through a lengthy process involving manufactuers, UL, and distributors when the first mini-splits appeared. They actually came with a SO or SJ cord or TC cable for inter-connection. As it turned out those units were supplied thu Canada and ETL listed so UL had no input and we were advised the factory recommended install met Canadian Code. Most of the units we investigated had internal protection on the inter-connect cable which varied between line voltage, low voltage and DC. Our installs were most jacketed MC until the '17 changes allowing TC without a conduit,.
Lately, like hillbilly, we see jacketed MC by the manufacturer.

Exactly that's why I am so certain, becasue at that time with those SO cords they shipped with, I was stuck between AHJ and big HVAC company.
The Company was saying they were allowed 'as part of the equipment listing' and the AHJ just laughed and failed it.

With the smaller residential units that we do often you can plainly see the L1 and L2 are just jumpered to the indoor unit from the line side of the terminal block, usually they add a choke, so those indoor wires are still part of the branch circuit in that case. I have a photo of a terminal block I'll dig up.

 

[don_resqcapt19]

A few years ago we went through a lengthy process involving manufactuers, UL, and distributors when the first mini-splits appeared. They actually came with a SO or SJ cord or TC cable for inter-connection. As it turned out those units were supplied thu Canada and ETL listed so UL had no input and we were advised the factory recommended install met Canadian Code. Most of the units we investigated had internal protection on the inter-connect cable which varied between line voltage, low voltage and DC. Our installs were most jacketed MC until the '17 changes allowing TC without a conduit,.
Lately, like hillbilly, we see jacketed MC by the manufacturer.

It really doesn't matter what agency lists the product, but it does have to be listed to a standard that applies in the US. A product listed, even by UL to a standard that does not apply in the US, is not suitable for use in the US.
ETL is just a listing agency and is not a standards writing agency. They must list to a published standard that applies where the product is to be used.
UL is both a standards writing organization and a listing agency. Most of the standards that apply to electrical equipment used in the US are written by UL. Even UL lists products to standards that do not apply in the US, A UL mark with a C next to it, is listed to a standard that only applies in Canada and cannot be used in the US. There are some products that are listed to both US and Canadian standards and the UL mark will have a "C" on onside of it, and "US" on the other side. That product can be used in both countries as it complies with both standards.

 

[tortuga]

In case your interested, here is a look at a typical outdoor compressor unit terminal strip I see from major brands.
Its a 18k BTU unit (residential install) with one indoor head, Nameplate says 20A Max OCPD.
12/2 romex branch circuit from the panel to the disconnect, liquid tight with 12 THHN to terminal strip.
14 AWG tray cable to the indoor unit.

The two hots are just jumpered to the right screw terminals for the indoor unit.
Presumably this terminal block is rated 75C, if so the 20A OCPD is OK for the 14 AWG.

 

[augie47]

It really doesn't matter what agency lists the product, but it does have to be listed to a standard that applies in the US. A product listed, even by UL to a standard that does not apply in the US, is not suitable for use in the US.
ETL is just a listing agency and is not a standards writing agency. They must list to a published standard that applies where the product is to be used.
UL is both a standards writing organization and a listing agency. Most of the standards that apply to electrical equipment used in the US are written by UL. Even UL lists products to standards that do not apply in the US, A UL mark with a C next to it, is listed to a standard that only applies in Canada and cannot be used in the US. There are some products that are listed to both US and Canadian standards and the UL mark will have a "C" on onside of it, and "US" on the other side. That product can be used in both countries as it complies with both standards.

don, the details are fuzzy due to it being a few years ago and my aged brain but as I recall it wasnt a case of the unit's listing (ETL) but the fact that they were manufactured in Canada and supplied with an interconnecting cable that was acceptable in Canada but not acceptable by the NEC (don't recall if it was cord or TC). Just recall it was a mess as installers were buying a "package" that didn't meet NEC and that led to a lot of discussion as to the type of cable acceptable and the ampacity required from which we determine most were protected by internal over-current protection,.

 

[Dennis Alwon]

It really doesn't matter what agency lists the product, but it does have to be listed to a standard that applies in the US. A product listed, even by UL to a standard that does not apply in the US, is not suitable for use in the US.
ETL is just a listing agency and is not a standards writing agency. They must list to a published standard that applies where the product is to be used.
UL is both a standards writing organization and a listing agency. Most of the standards that apply to electrical equipment used in the US are written by UL. Even UL lists products to standards that do not apply in the US, A UL mark with a C next to it, is listed to a standard that only applies in Canada and cannot be used in the US. There are some products that are listed to both US and Canadian standards and the UL mark will have a "C" on onside of it, and "US" on the other side. That product can be used in both countries as it complies with both standards.

So UL writes the standard and tests the product based on what the manufacturer wants tested? That was what I heard from a UL person.
Does UL have to follow the NEC codes? My understanding is that it doesn't have to follow the NEC. For instance, Cutler Hammer used to make a 400 amp meter main where there was no bus bar between the meter base and the panel buss.

Instead, they ran 1 set of 3/0 compact copper conductors for 400 amps. I brought it up to our state engineer at the time and he went nuts and made calls to the manufacturer and UL. He got back to me saying I could hook it up since UL tested the equipment and it passed. Apparently, they got calls from all over the country about that issue.

I get it that it is a piece of equipment so they do not have to follow the NEC because it is self-contained, however with a mini split once you leave the unit, IMO you would have to follow NEC rules.

 

[don_resqcapt19]

So UL writes the standard and tests the product based on what the manufacturer wants tested? That was what I heard from a UL person.
Does UL have to follow the NEC codes? My understanding is that it doesn't have to follow the NEC. For instance, Cutler Hammer used to make a 400 amp meter main where there was no bus bar between the meter base and the panel buss.

Instead, they ran 1 set of 3/0 compact copper conductors for 400 amps. I brought it up to our state engineer at the time and he went nuts and made calls to the manufacturer and UL. He got back to me saying I could hook it up since UL tested the equipment and it passed. Apparently, they got calls from all over the country about that issue.

I get it that it is a piece of equipment so they do not have to follow the NEC because it is self-contained, however with a mini split once you leave the unit, IMO you would have to follow NEC rules.

The tests are always specified in the product standard. If the manufacturer wants the product listed to the standard, the product must successfully pass all of the tests specified in the standard. If the product is not subjected to all of the required tests in the product standard, it cannot be listed to that product standard.

UL does look for compliance with the NEC when they write standards, if the NEC would apply. The NEC does not apply to the internal wiring of a product. The meter main would be an example of that issue. It is very likely, that when the rules in the NEC are applied to that installation, it would not require the neutral to have an ampacity that exceeds 200 amps, but of course it could. Internal wiring of listed equipment is also often done using the 90°C column of Table 310.17. That ampacity is 350 amps, and it would be a very very rare case where any 400 amp service would have a required neutral ampacity anywhere near 350 amps.

The mini split, along with the interconnecting cable is listed as a single piece of equipment. Typically the cable is supplied or specified by the manufacturer. You, as the electrician, install that cable, and the only code requirements are those related to the physical installation of the cable. The size and type is covered by the listing.

 

[wwhitney]

UL does look for compliance with the NEC when they write standards, if the NEC would apply. The NEC does not apply to the internal wiring of a product. The meter main would be an example of that issue. It is very likely, that when the rules in the NEC are applied to that installation, it would not require the neutral to have an ampacity that exceeds 200 amps, but of course it could. Internal wiring of listed equipment is also often done using the 90°C column of Table 310.17. That ampacity is 350 amps, and it would be a very very rare case where any 400 amp service would have a required neutral ampacity anywhere near 350 amps.

Dennis's example didn't mention the neutral, my understanding is that it was 3/0 Cu for the ungrounded conductors.

Cheers, Wayne

 

[tortuga]

The mini split, along with the interconnecting cable is listed as a single piece of equipment.

Do you have a source for that?
My experience with UL 1995 is to the contrary, it only covers 'internal wiring' and paragraphs like 4.3 state NFPA 70 covers and limits 'field wiring' between units.
So if you or someone can point to a specific section in UL 1995 where they size the ampacity of wire connecting the outdoor and indoor units that would clear this up.
In several places in UL 1995 they refer back to the NEC for CSA for sizing cords and wires.

 

[Dennis Alwon]

The tests are always specified in the product standard. If the manufacturer wants the product listed to the standard, the product must successfully pass all of the tests specified in the standard. If the product is not subjected to all of the required tests in the product standard, it cannot be listed to that product standard.

UL does look for compliance with the NEC when they write standards, if the NEC would apply. The NEC does not apply to the internal wiring of a product. The meter main would be an example of that issue. It is very likely, that when the rules in the NEC are applied to that installation, it would not require the neutral to have an ampacity that exceeds 200 amps, but of course it could. Internal wiring of listed equipment is also often done using the 90°C column of Table 310.17. That ampacity is 350 amps, and it would be a very very rare case where any 400 amp service would have a required neutral ampacity anywhere near 350 amps.

The mini split, along with the interconnecting cable is listed as a single piece of equipment. Typically the cable is supplied or specified by the manufacturer. You, as the electrician, install that cable, and the only code requirements are those related to the physical installation of the cable. The size and type is covered by the listing.

Don, you are saying the wire ampacity inside the cabinet is based on free air? That doesn't sound right to me especially with the heat generated from the 2- 200 amp breakers

And yes I was talking about all 3 conductors being 3/0. Two hots and one neutral.

 

[don_resqcapt19]

Don, you are saying the wire ampacity inside the cabinet is based on free air? That doesn't sound right to me especially with the heat generated from the 2- 200 amp breakers

And yes I was talking about all 3 conductors being 3/0. Two hots and one neutral.

I am saying that is the case on some equipment that I have installed, but have not seen it on the type of equipment you are talking about.

Do you have a source for that?
My experience with UL 1995 is to the contrary, it only covers 'internal wiring' and paragraphs like 4.3 state NFPA 70 covers and limits 'field wiring' between units.
So if you or someone can point to a specific section in UL 1995 where they size the ampacity of wire connecting the outdoor and indoor units that would clear this up.
In several places in UL 1995 they refer back to the NEC for CSA for sizing cords and wires.

can't find any specific language, so could be wrong

 

[mtnelect]

This is one of our installation.