Circuit Breaker? Line-load|Up-down

sunbunny · November 2013

Here's a pic of the circuit breaker for each battery pair. Load is attached to the battery to have the breaker verticle. Is this correct ?
These particular breakers don't say up and down but other slightly larger ones I have, do. Why are they like that ?

And also... the circuit breaker for the charge controller: which is line/load, controller or battery ?

Sign me;
Curious

Thanks

Cariboocoot · November 2013

Re: Circuit Breaker? Line-load|Up-down

Well that's an installation that wouldn't pass inspection. But it might work, even though it exposes a lot of metal (not safe and likely to corrode).

Some breakers do have markings on them for LINE and LOAD because they are polarized and work best when connected that way. Some do not because they are meant to go in holders which define the sides and only allow connection one way.

Are those DC breakers? The markings are hard to make out in the picture.

Although it does appear to be mounted upside down: at the bottom terminal it seems to say "LOAD" and that is connected to the battery which should be "LINE" (which appears near the top terminal).

As a rule breakers are meant to be mounted vertically (this is not critical; most AC boxes mount them horizontally for example) so that the lever in the up position is "ON" and the LINE (power source) will be on the top terminal.

BB. · November 2013

Re: Circuit Breaker? Line-load|Up-down

Line is typically the "high current" source and loads are the distribution circuit... So as Marc said, we would assume the breaker Line should be connected to the battery bank.

And, especially for DC breakers (and large/high voltage AC breakers), there is usually an arc quenching channel/area where the hot arc rises into a series of fingers/maze that lengthen the arc and cools it--To cause it to quench. For those breakers, if you mount then upside down (or other unapproved orientation), the arc can go into the wrong parts of the breaker (and cause it to fail).

Some breakers designed specifically for DC have a permanent magnet near the contacts/arc path. The magnetic field is there to "blow out" the arc to the side. In those breakers, sometimes if you have the "wrong" +/- current flow, the magnet can pull the arc into the breaker workings and cause problems.

New DC breakers are supposed to be required to not be polarity sensitive as it is not always clear or possible to know the polarity of the current flow (on an inverter-charger--The current flow reverses between inverting and charging modes).

If it is not clear on the breaker--Contact the seller or the mfg/distributor and ask. It would be terrible to spend the time and money on expensive breakers and find out that they are installed "backwards" or not correct for the task at hand.

-Bill

zoneblue · November 2013

Re: Circuit Breaker? Line-load|Up-down

Those are carling dc rated breakers, the panel mount versions that midnite sell. I understood that those particular ones arent polarity sensitive, but they are marked line and load. I seem to recall Robin explaining that those labels are there for comfort, ie people got used to the labels.

I would mount them 'on' up, as thats the time honoured convention if for no other reason.

Secondly, mounting a device that produces nice big arcs, on another device that produces both hydrogen and oxygen, is not the wisest of things!

Note too that the carlings are made from a brittle high temp grade of polymer. Beware over tightening the nuts, the shell can sometimes shatter.

sunbunny · November 2013

Re: Circuit Breaker? Line-load|Up-down

Thanks for the replies. I called NAWS and they said up/down doesn't matter and, yes, Line should be to the battery.

So this all adds up to several different answers....

Zoneblue: they are going on AGM batteries; does that change your opinion about gasses ? And thanks for the tip on tightening...I was wondering about brittleness.

Since electricity does flow both in and out of a battery, I'm inclined to mount them as shown so switch down is off. I could make some little boxes for them if anyone thought that would help. The batteries will be in a plywood box outdoors and the otherside of a steel wall from the rest of the system.

Thanks again

zoneblue · November 2013

Re: Circuit Breaker? Line-load|Up-down

While it is true that energy can flow in and out of batterys the worrying condition is always flowing out of, so when in doubt line goes to bat plus.

However the documentation for those breakers is here:

http://www.midnitesolar.com/documents.php?productCat_ID=16&productCatName=Breakers&model=MNEDC5,%20MNEDC10,%20MNEDC15,%20MNEDC20,%20MNEDC30,%20MNEDC40,%20MNEDC50,%20MNEDC60,%20MNEDC70,%20MNEDC80,%20MNEDC90,%20MNEDC100%20Breaker&product_ID=197

While the panel mounts are rated for both ac and dc i would still mount them line to bat.

Re AGM, the code doesnt distinguish between sealed v unsealed for the reason that when the sh%t hits the fan, many things tend to go wrong at once. If the bank was being overcharged and venting gases through the valves, at time of breaker pop, then you have the mother of all dramas. Ive seen it happen!

The rule (here anyway) is no ignition sources within 500mm of the bank. Any kind of bank.

Its a good bit of ingenuity, but better further away for sure.

sunbunny · November 2013

Re: Circuit Breaker? Line-load|Up-down

Well, then... I can probably figure out how to mount the copper angles and breakers to the battery switches which will be on the in side of the wall. Might have to straighten them out again and drill a bigger hole. Or just make them shorter. That still doesn't solve the switch position vs line/load.... maybe they will all be at a 45* angle with big labels

I'll have to think about it and play with the parts.
I've got some 4"x4" PVC square tubing to enclose anything too exposed.

I don't mind using a little more wire but I'm trying to avoid more pieces of wire because I figure every wire presents 4 connection points and a copper bar is 2.

Thanks for the help !

jcheil · November 2013

Re: Circuit Breaker? Line-load|Up-down

Perhaps just use terminal fuses. Someone posted a link to them here a while ago but they are sealed fuses so if they do blow there will be no chance of an explosion, plus they take up so little space on the battery post you will hardly know they are there.

BB. · November 2013

Re: Circuit Breaker? Line-load|Up-down

Terminal fuses:

Attachment not found.

http://www.bluesea.com/products/category/Fuse_Blocks/Terminal_Fuse_Blocks

-Bill

zoneblue · November 2013

Re: Circuit Breaker? Line-load|Up-down

Bill how do these fuses compare in terms of interupt capacity with T class or better? Are they literally vacuum sealed? Im struggling to see how something so small can work as well as the recomended 2lb carling circuit breaker / t class fuse?

sunbunny · November 2013

Re: Circuit Breaker? Line-load|Up-down

The Blue Seas 5191 are about $30 for the mount and the fuse each plus shipping. I already own 6 of the circuit breakers at $14.85 from NAWS.

I'd read several comments to 'have a circuit brkr/fuse as close to the battery as possible' .... hadn't really thought of the explosion hazard.

Any comments about using the Carling/Midnight breakers as switches ?? I could possibly eliminate the battery switches ?

I've come up with a tenative plan to mount the breakers horizontal and attached to the battery switches with the copper bars. It will mean having the breaker 'gutter' stick out a couple inches beyond the switches but will all be protected from accidental contact.

BB. · November 2013

Re: Circuit Breaker? Line-load|Up-down

Blue Sea does have specifications:

http://www.bluesea.com/products/5190/MRBF_Terminal_Fuse_-_300A

Requires the use of Terminal Fuse Blocks PN 5191 or PN 2151—do not mount the fuse directly to the battery terminal

Interrupt rating satisfies ABYC requirements for DC Main circuit protection on large battery banks

Ignition protected—safe for installation aboard gasoline powered boats

Clear window—visual indication of blown condition

Color coded for each amperage

Amperage
300A

Maximum Voltage
58V DC

Interrupt Capacity
10000A @ 14V DC
5000A @ 32V DC
2000A @ 58V DC

Weight
0.06lb (0.03 kg)

From BlueSea Class T type fuses:

http://www.bluesea.com/products/5119/Class_T_Fuse_-_300_Amp

Extremely fast short-circuit response

20,000 Ampere Interrupt Capacity (AIC)

Amperage
300A

Maximum Voltage
160V DC

Interrupt Capacity
20000A @ 160V DC

Weight
0.30lb (0.14 kg)

No listing for use around gasoline engines for the Class T fuse.

Class T much higher voltage and AIC rating... But also a physically, much larger device.

Breakers are designed to be "reused"--so they end up being much larger/heftier to meet the requirements.

But even breakers used at high currents (such as electric water heaters) do fail after 10-30+ years (even if never tripped). Heat and thermal cycling just are hard on everything.

-Bill

jcheil · November 2013

Re: Circuit Breaker? Line-load|Up-down

I had a VERY high end stereo system in my car, back in the day, and had a 100a circuit breaker installed right at the battery under the hood.

One day, eating dinner at my house, heard an explosion and ran outside to see flames coming from under the hood.

The top of the battery was gone from the explosion. Managed to save the car, but from that point on the installer (and I) would NEVER put a circuit breaker anywhere near a battery. And since then I always carry a fire extinguisher in ALL of my vehicles

NorthGuy · November 2013

Re: Circuit Breaker? Line-load|Up-down

jcheil wrote: »

I had a VERY high end stereo system in my car, back in the day, and had a 100a circuit breaker installed right at the battery under the hood.

One day, eating dinner at my house, heard an explosion and ran outside to see flames coming from under the hood.

The top of the battery was gone from the explosion. Managed to save the car, but from that point on the installer (and I) would NEVER put a circuit breaker anywhere near a battery. And since then I always carry a fire extinguisher in ALL of my vehicles

Most likely, you just "boiled" all the water out of the battery and exposed plates warped and arced. Breaker may have nothing to do with that. When I was buying Generac, I found lots of stories on the Internet of its batteries exploding for exact this reason.

jcheil · November 2013

Re: Circuit Breaker? Line-load|Up-down

NorthGuy wrote: »

Most likely, you just "boiled" all the water out of the battery and exposed plates warped and arced. Breaker may have nothing to do with that. When I was buying Generac, I found lots of stories on the Internet of its batteries exploding for exact this reason.

It was a brand new high capacity interstate battery installed only a few days prior when the breaker was installed. So could have also been a defect, but the signs pointed to the breaker. All I knew was that it sucked

Vic · November 2013

Re: Circuit Breaker? Line-load|Up-down

sunbunny wrote: »

I'd read several comments to 'have a circuit brkr/fuse as close to the battery as possible' .... hadn't really thought of the explosion hazard.

Any comments about using the Carling/Midnight breakers as switches ?? I could possibly eliminate the battery switches ?

I've come up with a tenative plan to mount the breakers horizontal and attached to the battery switches with the copper bars. It will mean having the breaker 'gutter' stick out a couple inches beyond the switches but will all be protected from accidental contact.

sunbunny,

Your AGM batteries are considerably more immune to this explosion hazard compared to Flooded batteries. It CAN still happen during an overcharge situation, though.

MidNite has mentioned that their DC breakers are rated for 5,000 plus cycles at rated current, as a minimum. However, when used as switches, the exact manner in which the breaker's bat (or switch's knob) is manipulated when someone is switching a it, will affect the nature of any arc that occurs. This also holds true for those Blue Seas battery switches. For 12 volt systems, any breaker/switch contact arcing is less of an impact on the contacts than for higher DC voltages.

Would recommend that Magnetic-Hydraulic DC breakers NOT be mounted in a horizontal orientation. The MN DC breakers are Magnetic-hydraulic.

I do like the Carling DC breakers, and MN MAY now be carrying them. But the older Carling and Airpax breakers were not rated for continuous duty at rated breaker current. The MN (and OB) DC breakers are rated for continuous duty (at least for the CBI units). FWIW. Opinions, Vic

Vic · November 2013

Re: Circuit Breaker? Line-load|Up-down

An Update;

sunbunny asked about any required orientation of the MidNite DC breakers on the MN Forum.

Halfcrazy Ryan replied that ANY orientation is OK, except "with the handle pointing straight up", which would require some de-rating.

SO, I was wrong about horizontal orientation being ill-advised. This is good news to me, as have wanted to place a MN DC breaker just outside battery boxes, and vertical orientation makes things a bit more difficult. Vertical also would make the battery cable (from CCs) a bit longer.

Sorry for the noise. Vic

Circuit Breaker? Line-load|Up-down

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