Author Topic: Voltage Ratings for DC Busbars  (Read 416 times)

Strait Runner

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Voltage Ratings for DC Busbars
« on: October 04, 2022, 11:12:38 AM »
In my application, I am replacing an old solar 12Vdc installation (Siemens M75 as I recall) from the early 1990's that has 6 parallel runs of 10 Ga solid conductor cable run from the roof to the charge controller in the battery room.  This was all installed when the house was built.  I would like to reuse these parallel runs of cable if possible since they are already there and will reduce the voltage drop. 

I now have two sets of three (3), 390 watts panels connected in series.  Each panel has an open circuit voltage of 49 Vdc/panel.  for 3 panels in series that's ~ 150 Vdc.  I'm looking for a busbar is to connect the parallel runs to the 2 conductors for each bank of panels on the roof and to connect the other end of the parallel runs to the 2 sets of 2 conductors going to the Midnite Classic in the battery room.  The maximum dc voltage rating for busbars I've found is 70Vdc.  Is it correct to use the open circuit voltage of 3 x 49 Vdc/panel from the 3 panels in series (ie 150 Vdc) for the busbars dc voltage rating?  If so, where do I get busbars rated at 150Vdc?


Vic

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Re: Voltage Ratings for DC Busbars
« Reply #1 on: October 04, 2022, 04:41:23 PM »
Hi Strait Runner, Welcome to the Forum.

The following busbars, come to mind,  but do not know their max voltage ratings:

https://www.solar-electric.com/search/?q=mntbb

These are commonly used for PV input, and also for 240 V AC.  There is a short bar, of the same design,  just fewer cable positions:

https://www.solar-electric.com/search/?q=mnsbb

Would these work with your Classic 200 (or 250) ?

Vic
« Last Edit: October 04, 2022, 04:45:32 PM by Vic »
Off Grid - Two systems -- 4 SW+ 5548s, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 3X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  Thanks MN for Great Products/Service/Support!

Strait Runner

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Re: Voltage Ratings for DC Busbars
« Reply #2 on: October 06, 2022, 03:00:23 PM »
Thanks Vic.  I expect that these will work, but I'm being a bit anal about the dc voltage ratings.  I wouldn't want my insurance to be void if the cabin burns down!  The components you referenced are listed under the MidNite brand.  Does anyone from MidNite monitor this forum?

Vic

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Re: Voltage Ratings for DC Busbars
« Reply #3 on: October 06, 2022, 03:26:04 PM »
Hi Strait ..,

YES a number of MidNite Principals,  and Tech Support folks, attend here, on most days.  Although they all are quite busy, now,  as the newest two HV Charge Controllers are being shipped to Beta testers,  and the new Rosie Inverter Charger,  is not far behind that,  so,  those folks are probably very, very busy elsewhere.

This type Busbar is used in the ETL Listed MidNite E-panels, as a PV input bar, for some models (usually it is the Short version.  The fact that there appears to be no voltage rating noted in the Docs, is just an oversight (IMO).

Short of a quick phone call to MN Tech Support (if you are Stateside), or an e-mail, should clear things up.

Will try to look further for docs,  sorry that this is all that I "know", at this point.   Vic
Off Grid - Two systems -- 4 SW+ 5548s, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 3X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  Thanks MN for Great Products/Service/Support!

Vic

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Re: Voltage Ratings for DC Busbars
« Reply #4 on: October 06, 2022, 03:39:08 PM »
Strait  ..,

Try downloading the Hi-Res image of the Magnum PAE E-panel:
...   fileDownloads/mag44_epanel_parts%20(3).zip

This image can be found on the MN Solar site: Products>E-panels>Magnum ... PAE>Photo Download  ...

On the top page of this Product listing,  in the Description, the Max DC Voltage, is note, an this whole panel, is ETL Listed for the US and Canada.

The Short Busbar at the top, center of the E-panel says PV (something)   ...

This panel has a Max DC Voltage rating of, "300 Volts",  so to me, this would be the miimum for these bars, Vic
« Last Edit: October 06, 2022, 03:43:49 PM by Vic »
Off Grid - Two systems -- 4 SW+ 5548s, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 3X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  Thanks MN for Great Products/Service/Support!

UpNorthMan

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Re: Voltage Ratings for DC Busbars
« Reply #5 on: October 06, 2022, 08:01:25 PM »
I looked  at the drawings for a random set of bars  and the spec said 600 volts. So you should be good.  See the link below.
Ed
 https://www.midnitesolar.com/pdfs/MNTBB2-15.pdf
1000W panels Kid CC 184 ah battery bank @ 48v
Weekend cabin, 250w inverter.
Waiting for the new inverter to be released so I can finish my install!

Vic

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Re: Voltage Ratings for DC Busbars
« Reply #6 on: October 06, 2022, 08:29:30 PM »
Thanks, Ed,
I only glanced at the dimensional drawing,  not expecting it to have ratings.

600 V seemed like the obvious rating,  as that is the most common voltage rating for the insulation of cable used, to connect to the bars.

Thank you for splainin' that.   Vic
Off Grid - Two systems -- 4 SW+ 5548s, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 3X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  Thanks MN for Great Products/Service/Support!

Strait Runner

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Re: Voltage Ratings for DC Busbars
« Reply #7 on: October 12, 2022, 09:58:06 AM »
Thanks Ed and Vic.  Looks like I can relax and order these busbars!
Ken

Strait Runner

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Re: Voltage Ratings for DC Busbars
« Reply #8 on: October 13, 2022, 08:58:22 AM »
In my haste to find a busbar with voltage rating higher than 70 Vdc, I was pleased when Vic pointed out the 250 AMP / 600VOLT rating on the drawing for the MNTBB2-15.  However I later realized that the drawing didn't indicate if this was an AC or DC rating.  Apparently there is a difference.  I will see what Midnite Support can do to clarify this.

boB

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Re: Voltage Ratings for DC Busbars
« Reply #9 on: October 13, 2022, 12:12:21 PM »
Probably RMS rating so AC or DC
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