1000 V THWN-2/THHN

[SunFish]

We are starting to do 1000 V systems, normally we pull THWN-2/THHN from the combiner boxes down to the inverters but we are having trouble finding THWN-2/THHN that is rated for 1000 V. I'm curious if other people have found this wire rated for 1000 V or if they are using something else for the output circuits from combiners to inverters?

 

[kwired]

We are starting to do 1000 V systems, normally we pull THWN-2/THHN from the combiner boxes down to the inverters but we are having trouble finding THWN-2/THHN that is rated for 1000 V. I'm curious if other people have found this wire rated for 1000 V or if they are using something else for the output circuits from combiners to inverters?

Having trouble finding it or are not finding it at all? I could be wrong but don't think you will find any rated more then 600 volts.

 

[GoldDigger]

One (expensive) option is PV wire. That is 1000V by default and is also available up to 2000V.
You may also find higher rated cable, but less likely individual conductors.

 

[Carultch]

One (expensive) option is PV wire. That is 1000V by default and is also available up to 2000V.
You may also find higher rated cable, but less likely individual conductors.

I think PV wire really may be your only option for systems over 600V. Other than using a serious beast of a medium voltage cable. Do you know of any examples?

FYI, PV wire isn't 1000V by default. There is usually a 600V version and a 1kV/2kV version.

 

[don_resqcapt19]

Dual rated DLO/RHW is has either a 1,000 or a 2,000 volt rating. That will be a lot more expensive that THWN-2, maybe even more expensive than PV wire.

 

[SunFish]

Thanks all! Follow up question: Does my EGC also have to be rated for 1000 V (PV Wire) or can I use THWN-2/THHN rated for 600 V with my EGC?

 

[GoldDigger]

Thanks all! Follow up question: Does my EGC also have to be rated for 1000 V (PV Wire) or can I use THWN-2/THHN rated for 600 V with my EGC?

Since your EGC could even be bare copper or Al wire, the insulation rating does not apply if you choose to insulate it. JMO.

 

[Carultch]

Dual rated DLO/RHW is has either a 1,000 or a 2,000 volt rating. That will be a lot more expensive that THWN-2, maybe even more expensive than PV wire.

You also have to be careful with finely stranded wire with DLO wiring. And make sure your terminations are listed to fit that stranding class, or else find a way to adapt.

 

[Carultch]

One (expensive) option is PV wire. That [can be] 1000V [rated] and is also available up to 2000V.

It is more expensive than the equivalent wire size in THWN-2. But the tradeoff is that you can use a much smaller size, for a given amount of power.

Double the operating voltage means half the current. And also a quarter of the Ohmic power losses you need to curtail. So in any event, it means that your minimum local wire size for the combiner output will have less metal for a given amount of power, and it will also mean that it is less likely you'd need to upsize wires to curtail voltage drop.

Voltage is cheap, current is expensive. Because you pay for voltage with plastic, and current with metal.

 

[kwired]

It is more expensive than the equivalent wire size in THWN-2. But the tradeoff is that you can use a much smaller size, for a given amount of power.

Double the operating voltage means half the current. And also a quarter of the Ohmic power losses you need to curtail. So in any event, it means that your minimum local wire size for the combiner output will have less metal for a given amount of power, and it will also mean that it is less likely you'd need to upsize wires to curtail voltage drop.

Voltage is cheap, current is expensive. Because you pay for voltage with plastic, and current with metal.

But the higher the voltage the more quality the plastic is as well. 1000 volts rating maybe is similar quality plastic as 600 volts, but is more of it in general.

 

[PVfarmer]

Talk to these people.

http://www.awcwire.com/faq-solar-cable.aspx

[h=3]Are PV Wire and USE-2 Wire appropriate for above-ground or underground applications?[/h]Both single-conductor PV Wire and single-conductor USE-2 Wire are appropriate for use in exposed outdoor arrays, according to Sec. 690.31 (B) of the National Electrical Code (NEC). However, according to UL experts, it is now more common to choose PV Wire for exposed applications, and USE-2 Wire for underground use.

[h=3]Can I use THHN wire instead of PV Wire or USE-2 Solar Wire to save money?[/h]No, not to replace Photovoltaic Wire or USE-2 Solar Wire. THHN wire is general purpose building wire which can be used in many applications in many industries. While THHN wire can be used in some solar applications and it is cheaper than many solar cables, it cannot be used where standards call for Photovoltaic Wire or USE-2 Wire. Doing so could cause failures, as THHN lacks the added construction strengths of specialized cables such as Photovoltaic and USE-2 Wire.

[h=3]Can I customize my solar cables?[/h]Absolutely! Customization services for Photovoltaic Wire (PV Wire), USE-2 Solar Wire & THHN for solar applications include custom printing and striping. For THHN we also offer cut & strip and twisting.

 

[ggunn]

Can I use THHN wire instead of PV Wire or USE-2 Solar Wire to save money?

No, not to replace Photovoltaic Wire or USE-2 Solar Wire. THHN wire is general purpose building wire which can be used in many applications in many industries. While THHN wire can be used in some solar applications and it is cheaper than many solar cables, it cannot be used where standards call for Photovoltaic Wire or USE-2 Wire. Doing so could cause failures, as THHN lacks the added construction strengths of specialized cables such as Photovoltaic and USE-2 Wire.

The difference is UV resistance, not construction strength; the insulation adds very little to the tensile strength of conductors. For wiring exposed to sunlight you must use USE-2 or PV wire, but you can transition to THWN-2 when the wiring moves into conduit if it's a 600V or less system.

 

[Carultch]

The difference is UV resistance, not construction strength; the insulation adds very little to the tensile strength of conductors. For wiring exposed to sunlight you must use USE-2 or PV wire, but you can transition to THWN-2 when the wiring moves into conduit if it's a 600V or less system.

I don't think they are talking about the tensile strength of the cable assembly as a whole, but rather the local tensile & shear strength of the insulation, where it is subject to physical abuse as an exposed wiring method. I agree that the UV stability matters as well.

In large sizes, 100A and greater, it is common to find black THWN-2 wire that is UV stable. Not as common for other colors.

XHHW-2 datasheets tell a similar story, that in sizes (typically #6 and larger), that it is UV stable or sunlight resistant.


In applications where you would use these larger sizes, such as a combiner output that is routed along a racking system with rubber-coated loop clamps (instead of a closed raceway), would that be enough to establish that the wire is permitted in this use?

I can see XHHW-2 being permitted in this application, but much less likely THWN-2. In fact, many XHHW-2 datasheets indicate that it is suitable for similar wiring methods in generic applications, like on a messenger wires XHHW-2 is made from the same XLPE material as most PV Wire and USE-2, just not as thick.

I understand that exposed wiring methods for any and all ungrounded PV systems on the DC side, require PV wire. I'm mainly gearing this question toward sub-600V systems with a grounded conductor.

 

[PVfarmer]

We are starting to do 1000 V systems, normally we pull THWN-2/THHN from the combiner boxes down to the inverters but we are having trouble finding THWN-2/THHN that is rated for 1000 V. I'm curious if other people have found this wire rated for 1000 V or if they are using something else for the output circuits from combiners to inverters?

Pardon me, I was kinda vague. Looks like there's only one option, in 14-10 AWG only.

PVfarmer Talk to these people.
http://www.awcwire.com/faq-solar-cable.aspx



http://www.alliedelec.com/Images/Products/DataSheets/BM/OLYMPIC_WIRE_CABLE/70194401.pdf
^^^ 1000V
AWM 1452 to 1453*
*14-10 AWG only.

 

[Carultch]

Pardon me, I was kinda vague. Looks like there's only one option, in 14-10 AWG only.

PVfarmer Talk to these people.
http://www.awcwire.com/faq-solar-cable.aspx



http://www.alliedelec.com/Images/Products/DataSheets/BM/OLYMPIC_WIRE_CABLE/70194401.pdf
^^^ 1000V
AWM 1452 to 1453*
*14-10 AWG only.

You can get PV wire in nearly all sizes. Encore and Southwire have datasheets with numerous sizes. Encore is the most common in my region.

The #14 to #10 range is probably set by the kinds of field connectors you can get.

 

[PVfarmer]

You can get PV wire in nearly all sizes. Encore and Southwire have datasheets with numerous sizes. Encore is the most common in my region.

The #14 to #10 range is probably set by the kinds of field connectors you can get.

Whoops, I was vague again- that's the only 1000V THHN I can find.
And you might want to check Allied's prices compared to Southwire's...

 

[kwired]

Whoops, I was vague again- that's the only 1000V THHN I can find.
And you might want to check Allied's prices compared to Southwire's...

The only conductor rated 1000 volts in the table in that link was not type THHN or THWN.
The conductor may look similar but is not the same thing.

 

[PVfarmer]

The only conductor rated 1000 volts in the table in that link was not type THHN or THWN.
The conductor may look similar but is not the same thing.

Well...I'm assuming the OP person is looking for a "building wire" alternative to PV or USE wire, so the AWM 1452 to 1453* *14-10 AWG only is that sort of thing- but it isn't rated for wet.

I think for 1000V building wire, the jacket has to be nylon?

My own personal opinion is get the fancy (PV or USE) wire for the best price you can find- as long as you don't mind general lack of headaches being the biggest part of pay back for it.
It might cost 2x as much, but that isn't a lot over 20 years.

Here's another possibility with pretty much all sizes.
Not sure if the 90 degree thing is a problem, however.
http://www.industwire.com/index_files/Page460.htm
Gasoline and oil resistant. Wet or dry locations. All surface printing is under nylon jacket. Optional use as appliance wire, (AWM) 105°C 600V or 90°C 1000V.

 

[Carultch]

Here's another possibility with pretty much all sizes.
Not sure if the 90 degree thing is a problem, however.
http://www.industwire.com/index_files/Page460.htm
Gasoline and oil resistant. Wet or dry locations. All surface printing is under nylon jacket. Optional use as appliance wire, (AWM) 105°C 600V or 90°C 1000V.

I don't think the NEC usually allows you to take credit for the 105C rating of a wire anyway. Can anyone think of an instance where it allows you to do that? Most of the time, the 90C rating of wire is the highest ampacity for which you can take credit. Mostly for use in conditions of use calculations. You still are limited to the 60C or 75C column, prior to your derate calculations, for terminations.

For that particular wire type, the 1000V equivalent of THWN-2, do you get to take advantage of the 1000V rating in wet locations? That's the part I'm not finding in its specs.

Also, there doesn't seem to be a unique identifier of this wire, to verify its use instead of standard THWN-2. So if spec'ing it, you'd have to work very closely with the procurement team of the installer. And critically analyze your distributor's quotes.

 

[GoldDigger]

The sizing for use of fixture wire with lampholders may be an implicit recognition of the 105C rating, but it is not in a derating table AFAIK.