Electric panel layout + shunt ?

sunbunny

Looking for constructive comments about my proposed electric panel layout.
I have 6 pairs of batteries. 2 pairs to each battery switch, then to the 3/8 x 1.75"x24" + bussbar. CC, AC charger and inverter to + buss.
I'm a little OCD about some things.... would kind of prefer that + and - were in seperate boxes. The dark paper and buss bar represent the neg. DC bus bar box ( have a 9"x 1/4x2 bar for the - ). I'll have a 4/0 wire from the large negative side buss bar (to left of batteries) to the smaller - buss box. Batteries wired with 1/0 of equal lengths.
Have read that + and - for inverter should run close and parralell... how close ? How can there be a breaker and keep them close ?
Found another box about 12x14" that I might put the 2 breakers And the -buss bar in...

Also wondering if I can just bolt the buss bar on to the shunt ?

Thanks

BB.

Re: Electric panel layout + shunt ?

One caution about bolting large chunks of metal together... If there is a wide temperate range--You can get differential expansion between the copper bus bars and the backing/structure support (plywood in your case?). Thermal cycling can cause damage to attachments. Check everything is tight and you don't see any "fretting" (dark metal dust from "friction" from small movements of mechanical attachments).

Sometimes, that is why a short length of cable can be your friend when dealing with large/heavy bus bars.

In the big scheme of things--If you will be installing the bus bars in a reasonably temperature stable room (insulated shed/etc.) you should be OK.

One other recommendation--I really do not like to place electrical connections on plywood backer board (for long term/permanent electrical systems). I would suggest something less flammable (sheet rock, green board, concrete backer board (Hardy Board? thanks Vic), metal electrical enclosure, over a metal screen, etc.). Electrical connections sometimes become loose/corroded and you don't want the heat lighting off the plywood. Similar, you don't want anything flammable under the electrical panel where falling flaming bits can light off cardboard boxes/carpeting/etc. on the floor or work bench. A metal shelf under the installation is fine too.

Much of my engineering design/systems design was around UL/Code requirements to reduce the risk of fire in power/computer systems.

-Bill

Vic

Re: Electric panel layout + shunt ?

Hi sun..

I would not mount the bus bar ON the Shunt. The bus bar should be mounted on insulated standoffs, and the Shunt attached to the bar.

Insulated Standoffs:
http://www.stormcopper.com/design/standoff-insulator-chart.htm

The above link just shows a good electrical standoff, but may be expensive from that source.

If you could place the positive buss in a piece of electrical Gutter, mounted on two insulated standoffs. If you had a largish steel box, you could place both busses in one box.

You really MUST use a Fuse or Breaker between the positive buss and the inverter. Multiple strings of batteries in parallel really have fuses or breakers protecting against a short in a battery in one string from large fault currents provided by the other string/s.

Regarding the fire resistant substrate (if all of the electricals are not contained in a metal box). Backer board is quite fragile. But Hardy board (or Hardy Panel - I forget) is quite tough and is reasonably fire-resistant ... And so on.

FWIW, just my opinions. Have Fun, Vic

sunbunny

Re: Electric panel layout + shunt ?

Thank you, gentlemen !
Are 'plastic' electrical boxes a bad idea ? They are NEMA 4x , UL... all that stuff. I have another coming to enclose the - sub-buss.

I made standoffs for the big bars out of PVC. Will that be ok ? Was planning on making a Lexan cover for the large + buss.

All the componenents will be in a closet in a 20' shipping container and the batteries outside in an insulated box.

Any comments on spacing between the components ? I made that mock up out of what came to hand first; 33" wide but will probably use 36" wide 'something' .

I've read lots of threads looking for a clue about what size breaker to use for the individual battery pairs..... I really like the Blue Seas product but they are a bit pricey and I would prefer a breaker to a fuse.The switchable breakers from NAWS look good >$168 for 6 50 amp, $228 for 6 60 amp. Batteries are SunExtender/Lifeline 104 amp at 24 hour rate.

Thanks

Vic

Re: Electric panel layout + shunt ?

Hi sun..

Plastic boxes that are UL listed should be just fine, perhaps I should not have said, "steel" box.

Look at these breakers:
http://www.solar-electric.com/pamodccibr.html

They are very good, and the Real Deal, however, it is easiest to mount them in the MidNite Quad Box, which is not dirt cheap. These MN breakers should be mounted vertically, with the "ON" position UP. The Quad box does not have much room for large cables, or for large conduit entry/exit. You could perhaps adapt a different box.

Some people do use the Blue Seas terminal-mounted fuse holder for battery string protection, but know you prefer breakers. The DIN-Rail breakers are also good, but they are much less solid mechanically. Plus, the DIN breakers will not accommodate large wire.

Sizing battery protection breakers can be a bit difficult, as peak currents need to be considered, as does the current verses time curve of the exact breaker model that is being used (not to try to make it too complex).

Have Fun, Vic

sunbunny

Re: Electric panel layout + shunt ?

Those breakers would be great, Vic but they are to protect each battery pair/wire so I would need either 6 boxes or lots more wire !! Six batteries at 6" wide plus an inch between them = 41"wide battery bank. Half is 21" for each wire plus the distance to the box...Probably add up to 18 feet of wire ! Which is really only about 8 feet extra but puts a big crimp in my layout...

Maybe I could mount the breakers individually flat to the wall and make a plastic or Lexan cover for each one ?

The point of buying the large buss bars was to make the wires shorter.

Thanks for the reminder about the Hardieboard products ! Even have a local source ! And I've been looking for something like that for heat protection around my woodstove.

Vic

Re: Electric panel layout + shunt ?

sun ..

Well, that might be where the, "You could perhaps adapt a different box" might come into play.

Again, know that you mentioned preferring breakers, but there are always this style Fuse Holder:
http://www.bluesea.com/products/5191/MRBF_Terminal_Fuse_Block_-_30_to_300A

Those fuses and holders are not too expensive, and quite compact.

A friend, who was an AHJ, has "flying breakers" at the batteries, hanging on flying 4/0 cables. This has worked and is stout enough. We all do our best, and some of us bend the Code a bit ... all things in moderation.

Vic

NorthGuy

Re: Electric panel layout + shunt ?

You can use a box like this. NAWS also sells MidNight breakers with DIN mount up to 63A.

Vic

Re: Electric panel layout + shunt ?

Hi NG,

You are correct, and did reference the DIN-Rail MN breakers above, but, these breakers do not handle large cable well (not even the double-wide 80 & 100A jobs). Even the Quad box does not have very much space to route large cable (think sunbunny was thinking of 1/0 cable) the Baby and BigBaby boxes have very very little space to route large cable.

Just from my experience, not to pick too much, Vic

NorthGuy

Re: Electric panel layout + shunt ?

Vic wrote: »

You are correct, and did reference the DIN-Rail MN breakers above, but, these breakers do not handle large cable well (not even the double-wide 80 & 100A jobs). Even the Quad box does not have very much space to route large cable (think sunbunny was thinking of 1/0 cable) the Baby and BigBaby boxes have very very little space to route large cable.

I agree. The thikest wire that you can install in these breakers is probably #2. Although it would be stretching it. #1/0 is definitely too thick.

They have nice DC disconnect boxes with one big breaker, but they're sor of pricey.

sunbunny

Re: Electric panel layout + shunt ?

Woo-hoo ! Flying breakers Why didn't I think of that...I have several in vehicles.... Then I can use the MNEDC breakers ! Thanks, Vic !
Maybe I'll buy another chunk of copper bar and make angles that bolt to the battery terminals to mount the breakers.....
I'm trying not to have many chunks of wire in each run because it opens more possibilities for unequal lengths and bad connections.

I've been guessing when it comes to the resistance of copper buss bars... does anyone know of a table that is appropriate for DC amps ? Storm Copper has a table but it's about AC and skin effect and temperature rise.

Thanks !