Using 90°c wire at 90°c ampacity

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Coppersmith

Coppersmith

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Electrical Contractor
If I am reading the specs correctly, Polaris connectors are rated at 90°c. If I am running 90°c wire between two panels with 75°c terminals and I terminate the wire in Polaris connectors and then run a short length of larger wire sized at 75°c ampacity to the panel terminals, can I use the 90°c column on the ampacity chart to size the wire? This might save some money on larger wire sizes.
 
Coppersmith said:
If I am reading the specs correctly, Polaris connectors are rated at 90°c. If I am running 90°c wire between two panels with 75°c terminals and I terminate the wire in Polaris connectors and then run a short length of larger wire sized at 75°c ampacity to the panel terminals, can I use the 90°c column on the ampacity chart to size the wire? This might save some money on larger wire sizes.
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Yes- Mike even had a vid on it. Very doable.
 
Yes it's permitted but might raise a few eyebrows in the field if done that way. Also if you're concerned about voltage drop the smaller conductors used at their 90° C ampacity might be a problem.
 
infinity said:
might raise a few eyebrows in the field if done that way
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I'm always raising eyebrows because I know the code better than most inspectors (as does everybody here) so I'm usually just inside the line between compliant and not which confuses inspectors who are used to seeing people stay either well within the line or way outside.

infinity said:
if you're concerned about voltage drop the smaller conductors used at their 90° C ampacity might be a problem.
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That's actually where I started out thinking about this. I just ordered a bunch of wire and as soon as I hung up the phone it occurred to me that I was using 90°c wire and maybe I had oversized the wire too much for VD purposes. I looked back at the VD calculator I was using (https://www.southwire.com/support/voltage-drop-calculator.htm) and it says that it bases it's sizing recommendations on 60°c wire.

But maybe I'm confusing myself. Is the VD actually linked to the insulation temp? Seems like they are two separate issues.
 
Coppersmith said:
I'm always raising eyebrows because I know the code better than most inspectors (as does everybody here) so I'm usually just inside the line between compliant and not which confuses inspectors who are used to seeing people stay either well within the line or way outside.



That's actually where I started out thinking about this. I just ordered a bunch of wire and as soon as I hung up the phone it occurred to me that I was using 90°c wire and maybe I had oversized the wire too much for VD purposes. I looked back at the VD calculator I was using (https://www.southwire.com/support/voltage-drop-calculator.htm) and it says that it bases it's sizing recommendations on 60°c wire.

But maybe I'm confusing myself. Is the VD actually linked to the insulation temp? Seems like they are two separate issues.
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They are separate. What that calculator is really saying is that the VD is based on the wire size you would use if you based the wire size on 60C.
 
If the load is large and runs 24/7 you will be costing the owner a lot of money over the life of the installation as the I²R losses are greater when you use the 90°C conductors at their 90° ampacity.
 
don_resqcapt19 said:
If the load is large and runs 24/7 you will be costing the owner a lot of money over the life of the installation as the I²R losses are greater when you use the 90°C conductors at their 90° ampacity.
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Well, what if they had the building heat on? Then I would be saving them money.:D
 
Coppersmith said:
But maybe I'm confusing myself. Is the VD actually linked to the insulation temp? Seems like they are two separate issues.
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VD is not directly linked to insulation temperature, but there are connections.

If you run at the higher 90C ampacity, then that means you are running at higher current density, meaning more voltage drop per foot.

Also the resistance of copper (and aluminium, and most other conductors) increases with temperature. So if you are actually running with the wire at 90C, the voltage drop per amp will be greater than running the wire at lower temperature.

If you have a 90C conductor connected to a polaris block connected to a short length of conductor sized for 75C, then heat will be carried through that connection and might reach your 75C termination. So one could argue that you need a certain minimum length of 75C sized conductor to separate the 75C termination from the 90C conductors...but I don't think this is explicit in code anywhere.

-Jon
 
Coppersmith said:
Well, what if they had the building heat on? Then I would be saving them money.:D
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Might even help bankrupt business collect fire insurance, if not using medium voltage cable to handle continuous operation at 90c.

If insurance can't prove listing violation of equipment, they can't deny claims when continuous use @ 90c fails, or burns down the building.

If building still stands after low-voltage cables burn up, quarterly profits increase with repeat business generated for replacement failures.

A perfect specimen of Caveat emptor, and workmanship the public should expect from most knuckle-dragging contractors.
 
ramsy said:
Might even help bankrupt business collect fire insurance, if not using medium voltage cable to handle continuous operation at 90c.

If insurance can't prove listing violation of equipment, they can't deny claims when continuous use @ 90c fails, or burns down the building.
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Proper use of 90C conductors at 90C is not bad workmanship nor necessarily poor design.

Loads of systems built with 60C conductors used at 60C ampacity, when properly installed, lasted in service for many years past reasonable expectations. I expect 90C installs to be no different.

-Jon
 
Coppersmith said:
I would need to see a code reference before I believe that.
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The connections cannot be in the enclosures where the supply and load terminations are located.

215.2(A)(1)(a) Exception No. 2

Exception No. 2: Where a portion of a feeder is connected at both its
supply and load ends to separately installed pressure connections as
covered in 110.14(C)(2), it shall be permitted to have an allowable
ampacity not less than the sum of the continuous load plus the noncontinuous
load. No portion of a feeder installed under the provisions of
this exception shall extend into an enclosure containing either the feeder
supply or the feeder load terminations, as covered in 110.14(C)(1).
 
winnie said:
Proper use of 90C conductors at 90C is not bad workmanship nor necessarily poor design...
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No equipment below 600 V exists listed for 90c operation. It has never bean allowed or permitted, due to listing violations.

CAUTION ON USING LUG RATINGS

Manufacturers commonly use 90 °C-rated lugs (i.e., marked AL9CU) on equipment rated only 60 °C or 75 °C. The use of the 90 °C-rated lug in this type of equipment does not allow the installer to use 90 °C wire at the 90 °C ampacity. The Underwriters Laboratories® General Information on Electrical Equipment Directory states the following about terminations: “A 75 °C or 90 °C temperature marking on a terminal (e.g., AL7, CU7AL, AL7CU or AL9, CU9AL, AL9CU) does not in itself indicate that a 75 °C or 90 °C insulated wire can be used unless the equipment in which the terminals are installed is marked for 75 °C or 90 °C.”

For electrical equipment rated for 600 V and less, terminations are typically rated at 60 °C, 75 °C or 60/75 °C. No distribution or utilization equipment is listed and identified for the use of 90 °C wire at its 90 °C ampacity. This includes distribution equipment, wiring devices, transformers, motor control devices, and even utilization equipment such as HVAC, motors, and light fixtures. Installers and designers who have not realized this fact have equipment that does not comply with the National Electrical Code and that has been turned down by the electrical inspector.

Some equipment requires the conductors that are terminated in the equipment to have an insulation rating of 90 °C, but an ampacity based on 75 °C or 60 °C. This type of equipment might include 100% rated circuit breakers, fluorescent lighting fixtures, etc., and is marked to indicate such a requirement.
 
ramsy said:
No equipment below 600 V exists listed for 90c operation. It has never bean allowed or permitted, due to listing violations.

CAUTION ON USING LUG RATINGS

Manufacturers commonly use 90 °C-rated lugs (i.e., marked AL9CU) on equipment rated only 60 °C or 75 °C. The use of the 90 °C-rated lug in this type of equipment does not allow the installer to use 90 °C wire at the 90 °C ampacity. The Underwriters Laboratories® General Information on Electrical Equipment Directory states the following about terminations: “A 75 °C or 90 °C temperature marking on a terminal (e.g., AL7, CU7AL, AL7CU or AL9, CU9AL, AL9CU) does not in itself indicate that a 75 °C or 90 °C insulated wire can be used unless the equipment in which the terminals are installed is marked for 75 °C or 90 °C.”

For electrical equipment rated for 600 V and less, terminations are typically rated at 60 °C, 75 °C or 60/75 °C. No distribution or utilization equipment is listed and identified for the use of 90 °C wire at its 90 °C ampacity. This includes distribution equipment, wiring devices, transformers, motor control devices, and even utilization equipment such as HVAC, motors, and light fixtures. Installers and designers who have not realized this fact have equipment that does not comply with the National Electrical Code and that has been turned down by the electrical inspector.

Some equipment requires the conductors that are terminated in the equipment to have an insulation rating of 90 °C, but an ampacity based on 75 °C or 60 °C. This type of equipment might include 100% rated circuit breakers, fluorescent lighting fixtures, etc., and is marked to indicate such a requirement.
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Sure, but that is not we are talking about. We are talking about splicing to 75 degree ampacity wire with a 90 degree rated connector before terminating on the equipment.
 
electrofelon said:
Sure, but that is not we are talking about. We are talking about splicing to 75 degree ampacity wire with a 90 degree rated connector before terminating on the equipment.
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Show me any equipment raceways listed for 600 V or less and identified for use of 90 °C wire at 90 °C ampacity, and I'll show you Hell frozen over.
 
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packersparky said:
Check out the diagram on this page for an example of what this thread is discussing.

http://www.electricallicenserenewal...ation-Courses/NEC-Content.php?sectionID=245.0
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Yes, this is precisely what I described.

Bonus question: 110.14(C)(2) seems to be about feeders exclusively. What if we are not talking about a feeder? What if we are talking about branch wiring going to utilization equipment? Does the 75 to 90 degree transition still have to be in a separate box on either side?[FONT=&quot] [/FONT]
 
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