Temperature Limitations - 75C vs 90C

[Flapjack]

I've read some of the other threads on this topic, and I understand that while equipment may be provided with 90C lugs, it is likely tested and listed at 75C. I'm trying to find out if this is the case for some 1,500VDC equipment (i.e. inverter, combiner box, disconnect) for a design in order to size the cable. The datasheets for the equipment in question all say the lugs are rated at 90C. I reached out to the manufacturers and asked if the equipment is listed to 75C or 90C, and they all replied 90C. I'm a bit skeptical since all the threads on this site say that barely any equipment is listed at 90C.

Should I ask the equipment manufacturers for the UL listing to get a definitive answer on the temperature rating? Has anybody else gone down this path for 1,500VDC equipment?

 

[paulengr]

I've read some of the other threads on this topic, and I understand that while equipment may be provided with 90C lugs, it is likely tested and listed at 75C. I'm trying to find out if this is the case for some 1,500VDC equipment (i.e. inverter, combiner box, disconnect) for a design in order to size the cable. The datasheets for the equipment in question all say the lugs are rated at 90C. I reached out to the manufacturers and asked if the equipment is listed to 75C or 90C, and they all replied 90C. I'm a bit skeptical since all the threads on this site say that barely any equipment is listed at 90C.

Should I ask the equipment manufacturers for the UL listing to get a definitive answer on the temperature rating? Has anybody else gone down this path for 1,500VDC equipment?

If it’s labeled 90 C have at it. It’s convenient when available.

A lot of lugs for controls and residential use are 75 C. Just because this is so common doesn’t mean you HAVE to use it. In fact UL 508A strips down the temperature charts to only 60 C to guarantee some things.

 

[jim dungar]

If it’s labeled 90 C have at it.

Just remember the temperature rating of the lug body is not necessarily the rating of the complete termination.

 

[electrofelon]

I've read some of the other threads on this topic, and I understand that while equipment may be provided with 90C lugs, it is likely tested and listed at 75C. I'm trying to find out if this is the case for some 1,500VDC equipment (i.e. inverter, combiner box, disconnect) for a design in order to size the cable. The datasheets for the equipment in question all say the lugs are rated at 90C. I reached out to the manufacturers and asked if the equipment is listed to 75C or 90C, and they all replied 90C. I'm a bit skeptical since all the threads on this site say that barely any equipment is listed at 90C.

Should I ask the equipment manufacturers for the UL listing to get a definitive answer on the temperature rating? Has anybody else gone down this path for 1,500VDC equipment?

I am also skeptical that the terminations are rated for 90. I dont know what to tell you other than to prod the manufacturer more.

Would you actually be using conductors at their 90 degree rating if allowed? Seems unlikely to me considering the typical voltage drop concerns in PV systems.

 

[don_resqcapt19]

Just remember the temperature rating of the lug body is not necessarily the rating of the complete termination.

Exactly, many lugs are marked for 90°C or even 105°C, but the equipment that the lugs are on is only rated for use with the 75°C ampacities

 

[pv_n00b]

If it lands on a circuit breaker or fuse terminal I have only seen those listed up to 75°C due to the fact that fuses and CBs are thermal devices rated at 40°C, 50°C for the new PV fuses. If you are landing on busbar then you can go with the lug rating if the equipment manufacturer does not put a limit in the manual.
Be careful about DC combiners. I've seen manufacturers say they are listed for 90°C conductor terminations but that is only for the output busbar, the inputs that land on the fuses are rated for 75°C.

 

[Carultch]

If you are landing on busbar then you can go with the lug rating if the equipment manufacturer does not put a limit in the manual.

How does this apply for transformer secondary busbars, assuming the device on the opposite end of the conductor is 90C rated?

What are some examples of equipment where you can take credit for this, and some examples where you still have to use the 75C rating despite AL9CU lugs that you separately install?

Is it only equipment that is otherwise empty, with nothing but busbar, where you get to take credit for this? Or are there examples where the busbar is part of other equipment, where it could apply?

 

[pv_n00b]

The manufacturer's instructions for installation are the first place to look. The second is NEC 110.14(C) which provides guidance for terminal temperature ratings to use if the device is unmarked. NEC 110.14(C)(2) allows separately installed connectors, such as those used to land on busbar, to be used at the temperature rating of the connector.