Long wire run/Use aluminum wire?

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DavidB
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Long wire run/Use aluminum wire?

Post by DavidB » Thu Feb 20, 2003 2:34 pm

In my installation the PSPV will need to be aprox. 300ft from the controller. At my amperage for the array I am looking at I will need 2/0 in Cu or 4/0 Al or even 250 Al. All the local electric places only carry USE in Al, but will cut to any length. I would therefore have to have any Cu USE trucked in, probably on a 1000ft roll [img]images/smiles/icon_sad.gif[/img]

I have also noticed some RE dealers say only to use copper from array to controller. Why is this? I know you have to worry about oxidation, but isn't there something that you can do about that? If I want the wiring to last as long as the panels should I use aluminum? If I use Al I will need some way to connect the larger guage to the PSPV since it only accepts 1/0.

Thanks for any info.

wd8cdh
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Long wire run/Use aluminum wire?

Post by wd8cdh » Mon Feb 24, 2003 2:54 pm

Hi david,

Aluminum is very safe and long lasting...IF... it is installed properly. You need to use CU/AL rated terminal blocks to connect to the smaller wires on both ends and also coat the cable ends with an approved anti-oxidant. You also must use a torque wrench to tighen the screws.

But before going to the large wire, can you post your configuration? You might be able to reconfigure the system and save on wire. For example, one of my systems is 12V with the batteries over 75 feet from the panels. I saved considerable money on the wiring by configuring the panels for 48 volts and use a MPPT charge controller similar to the MX60 at the batteries to convert from high voltage/low current from the panels to low voltage/high current to charge the batteries. I saved over 75% on the wire.

Ron

<small>[ February 24, 2003, 04:55 PM: Message edited by: Ron Schroeder ]</small>

Christopher

Long wire run/Use aluminum wire?

Post by Christopher » Thu Feb 27, 2003 6:39 pm

Very good point Ron. USing a higher voltage PV array with a MPPT type controller can really improve the performance of the system and can even save money.

The MX60 can have a 36, 48 or even 60 vdc nominal PV array charging a lower voltage battery. The open circuit should not exceed 120 vdc. Three of the 24 vdc modules is to high of an open circuit at this point.

Also - you can parallel two runs of smaller cable instead of going with the 250 MCM wire. Easier to pull and handle - and sometimes cheaper. The connection of the parallel conductors can be made separate from the PSPV also - you can have a #2 AWG go out of the PSPV to a "pull" box where the #2 is spliced to the larger cables using a split bolt connector that is then taped or a power distribution block.

wd8cdh
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Long wire run/Use aluminum wire?

Post by wd8cdh » Sun Mar 02, 2003 10:39 pm

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Christopher Freitas:
<strong><snip>The connection of the parallel conductors can be made separate from the PSPV also - you can have a #2 AWG go out of the PSPV to a "pull" box where the #2 is spliced to the larger cables using a split bolt connector that is then taped or a power distribution block.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I personally prefer the power block method. Power blocks come in a wide veriety of configurations of wire sizes. Ine of the ones that I have will take 2 cables up to 4/0 on one side and 6 cables up to #2 on the other side.

I know that the PSDC is allready punched for power distribution blocks. I don't know if the PSPV is but I think there is enough room for a couple of them.

Christopher,
Do you sell the power distribution blocks?

Another possability for combining large wire to smaller ones is the TBB terminal block. Not sure the larges wire size for it but it will allow many wires to be paralleled.

Ron

<small>[ March 25, 2003, 10:08 AM: Message edited by: Ron Schroeder ]</small>

DavidB
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Long wire run/Use aluminum wire?

Post by DavidB » Mon Mar 03, 2003 9:15 am

Thanks for the info. I had already determined that 48v nominal was a necessity. I had even been talking with boB Gudgel about going to a 60v nominal using KC-120's but it seems that would put Voc too high.. especially factoring in temperatures of -20c. I was looking at 16 panels to start, with capacity for 24 without having to lay more wire.

I was surprised though when I checked on 4/0 copper USE and it was only $1.54/ft (down $0.07/ft from just 2 weeks ago). Last time I checked before that(1+ years) I know it was well over $2/ft. 2/0 is $0.98/ft copper, $0.54/ft aluminum. Perhaps at those prices it would be better to just use the copper?

wd8cdh
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Long wire run/Use aluminum wire?

Post by wd8cdh » Mon Mar 03, 2003 3:57 pm

Hi David,

Figuring on your array being 42 amps at 68 volts with 6 strings of 4 120 watt panels, you should have about 3.6% voltage drop with either 4/0 aluminum or 2/0 copper or 2 parallel runs of #2 copper. The parallel runs of #2 might be the easiest thru conduit due to flexability. Also you might consider making 2 arrays so you can meter them individually at the inverter. It is easy to split the PSPV into two circuits and the lugs will fit #2 if I remember correctly.

Ron

<small>[ March 25, 2003, 10:02 AM: Message edited by: Ron Schroeder ]</small>

Christopher

Long wire run/Use aluminum wire?

Post by Christopher » Mon Mar 03, 2003 4:05 pm

The PSPV accepts up to #1/0 AWG for both the ground busbar and the positive busbar lug.

We did not put in holes for the power distribution blocks in the PSPV. We also do not sell them - but we offer the TBB's instead. Grainger has good prices on the power distribution blocks.

Thanks for responding on this Ron.

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Long wire run/Use aluminum wire?

Post by ericwahl » Mon Mar 03, 2003 5:20 pm

I have also noticed some RE dealers say only to use copper from array to controller. Why is this? I know you have to worry about oxidation, but isn't there something that you can do about that?

Yes you can use NO-OX on the terminals, and Cu/Al stuff, and tighten repeatedly. The thing you can't do anything about is if there is ever a pinhole breach of the wire insulation, the aluminum will turn to powder. So to me that indicates conduit, which then kind of negates the advantage of the cheap USE Al.

Eric

wd8cdh
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Long wire run/Use aluminum wire?

Post by wd8cdh » Tue Mar 04, 2003 2:58 am

Hi Eric,

Most terminals on RE equipment is not rated for CU/AL so in general, you should not connect aluminum wire to them even with NO-OX. The Power Distribution Blocks are rated for CU/AL and are quite suitable for transition to copper to attach to the RE equipment. Properly tightened to the correct torque, they do not need to be retightened. I have used aluminum for long runs for many years and have never had any problems where properly installed, even underground.

P.S. I would never use it for wiring to outlets even with CU/AL rated outlets.

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Long wire run/Use aluminum wire?

Post by ericwahl » Wed Mar 05, 2003 5:07 pm

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Ron Schroeder:
<strong>Hi Eric,

Most terminals on RE equipment is not rated for CU/AL so in general, you should not connect aluminum wire to them even with NO-OX. The Power Distribution Blocks are rated for CU/AL and are quite suitable for transition to copper to attach to the RE equipment. Properly tightened to the correct torque, they do not need to be retightened. I have used aluminum for long runs for many years and have never had any problems where properly installed, even underground.

</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">good points. What I meant to say was you CAN use it. But if someone has rocky soil the need for conduit or sand may negate the cost advantage of readily-available direct-buriable Al.
I have direct-burial Aluminum all over the place underground at my homestead. But if I were to do it over I would do more conduit for peace of mind, and therefore perhaps use Cu.

Eric

"P.S. I would never use it for wiring to outlets even with CU/AL rated outlets."
Me neither. But just out of curiosity, if Al is so great, why not? [img]images/smiles/icon_biggrin.gif[/img] just kidding.

wd8cdh
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Long wire run/Use aluminum wire?

Post by wd8cdh » Fri Mar 07, 2003 5:09 pm

As an interesting obscure point, aluminum has better conductivity than copper....per pound.

Bob Klecha
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Post by Bob Klecha » Sun May 30, 2004 8:56 pm

I also have a 300ft distance from array to controls, using (9) 150 watt
24 volt panels, 3 in series to a PSPV to an MX60...i was under the impression i could use the 3 in series...is this no longer true? :?

boB

Post by boB » Mon May 31, 2004 3:36 pm

Yes, you can use 3 -- 24 V panels in series as long as it doesn't get too cold outside.

The general rule of thumb is that too cold would be around 0 degrees F. or colder.

boB

Bob Klecha
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Post by Bob Klecha » Tue Jun 01, 2004 11:36 pm

What happens if it does get that cold? does the breaKer shatter? :P

boB

Post by boB » Wed Jun 02, 2004 10:08 am

What happens when a solar panel (Wireless fusion receiving antenna) gets cold is that the voltages go higher. If it gets too cold then the Voc can exceed the 140 Volt limit on the MX60.

In normal circumstances, the colder weather is good because it puts the MPP voltage higher and you can also usually get more power from the system. This is fine except sometimes with those 72 volt systems which can be right on the edge of working great or breaking the system.

boB

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Post by Logan Bryce » Wed Jun 02, 2004 10:32 am

The MX60 starts flashing and will not work until the PV voltage drops below the 140V Max Voltage. Once the panelÔÇÖs heat up it will latch and start working, but you will loose all the power until it does latch. Here in Montana, I am running several sets of, 3 sharp 185 in series. It does cause a problem when the temp drops below 0Deg F.

Logan
Pine Ridge Products LLC
P.O. Box 2334
Great Falls, MT 59403

www.pineridgeproducts.com

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