Manufacturers specs vs. NEC

[Dennis Alwon]

In chapter 9 Note to the table it states the following:

(4) Where conduit or tubing nipples having a maximum
length not to exceed 600 mm (24 in.) are installed between
boxes, cabinets, and similar enclosures, the
nipples shall be permitted to be filled to 60 percent of
their total cross-sectional area, and 310.15(B)(3)(a) adjustment
factors need not apply to this condition.

 

[kwired]

Manufacturers can't over rule the code.

How many conductors were in the flex?

Manufacturers can get a product listed though, to be listed it doesn't need to comply with code. If this flex assembly is a stand alone listed product it doesn't need to comply with code, you must install it according to any instructions that are part of the listing though.

If you modify a product that is listed, the AHJ has the ability to reject it, re-evaluate it (primarily using code as basis of evaluation or possibly listing standards for same/similar products, require third party listing agency to evaluate it...

 

[jaylectricity]

Installed wiring today for an A/C condenser that called for minimum circuit ampacity of 19.2 and max breaker of 30.

I ran 10-2 for it. But I considered using a nearby 12-2 that was a dedicated circuit for a window A/C that had been pulled back and left hanging.

I mean... I REALLY considered it. But in the end, the customer pays for a new circuit and I didn't want to chance it.

 

[kwired]

Installed wiring today for an A/C condenser that called for minimum circuit ampacity of 19.2 and max breaker of 30.

I ran 10-2 for it. But I considered using a nearby 12-2 that was a dedicated circuit for a window A/C that had been pulled back and left hanging.

I mean... I REALLY considered it. But in the end, the customer pays for a new circuit and I didn't want to chance it.

19.2 is less then 20 last time I checked. Even 12 AWG NM cable @ 60C is code compliant - if no ampacity adjustments are required.

People tend to forget you don't have to make any adjustment to MCA values. MCA is going to be 125% of largest motor (compressor) plus 100% of all other loads and on a typical AC condenser unit the blower is the only other load. Take away maybe 1.5 amps for blower leaves you with 17.7 x.80= about 14 amps for the compressor rated load add the 1.5 for the blower back in and that unit maybe only draws max current of 15.5 amps - still afraid 12 AWG is too small?

Would you typically run 10 AWG for any other load that is rated 15.5 amps?

 

[Smart $]

Manufacturers can't over rule the code.

How many conductors were in the flex?

No they can't... but my understanding is that external wiring furnished as part of listed equipment or as a listed accessory thereto is only subject to the listing standard. It may not meet the NEC and an AHJ has full authority to approve or not, even when installed per listing, labeling, and manufacturer's instructions.

 

[Dennis Alwon]

This is the section that covers it.
Inspect the installation; not the listed equipment.
2011 NEC 90.7

It is the intent of this Code that factory-installed internal
wiring or the construction of equipment need not be
inspected at the time of installation of the equipment, except
to detect alterations or damage, if the equipment has
been listed by a qualified electrical testing laboratory that is
recognized as having the facilities described in the preceding
paragraph and that requires suitability for installation in
accordance with this Code.

This is stating if the unit is a listed unit then it need not be inspected except for alterations or damage done after the listing was dne.

 

[zbang]

What seems to be, at least partly, missing from the discussion is that the NEC's goal is to making sure that installations field-constructed out of parts are safe however they're used, whereas NTRL listings make sure that a complete assembly build under controlled conditions and used in a specific way is safe. Think of is as buying a car or building your own from parts. (Or the rules for manufactured homes.)

To pick on a specific- conduit fill. Why does the NEC set specific limits? So the wires inside don't overheat and cause a fire. The NEC usually doesn't know how each conductor is used, so there are specific limits (and exceptions). OTOH when a manufacturer puts a piece of flex between two parts of a machine, they do know how each wire is used and the current limits/etc, so they can decide that it's safe under whatever listing standard they use and know the NRTL will enforce them.

To grab a somewhat absurd example, my clothes iron is rated 1100 watts and has a 18g cord. UL doesn't have a problem with this.

 

[jaylectricity]

19.2 is less then 20 last time I checked. Even 12 AWG NM cable @ 60C is code compliant - if no ampacity adjustments are required.

People tend to forget you don't have to make any adjustment to MCA values. MCA is going to be 125% of largest motor (compressor) plus 100% of all other loads and on a typical AC condenser unit the blower is the only other load. Take away maybe 1.5 amps for blower leaves you with 17.7 x.80= about 14 amps for the compressor rated load add the 1.5 for the blower back in and that unit maybe only draws max current of 15.5 amps - still afraid 12 AWG is too small?

Would you typically run 10 AWG for any other load that is rated 15.5 amps?

You're right. I suppose the benefit is that if they were to upgrade to a bigger condenser in the future they'd be all set for it.

And honestly, I don't think the one they bought is big enough for what they're doing with it.