NAWS battery disconnect switch 9001e rating questions 48 volts maybe ?

vtmaps wrote: »

read this: http://www.amplepower.com/primer/burnt_sw/index.html

--vtMaps

A nice expose.
If I recall correctly the unit that failed was a cheap off-shore imitation product and not one of the well respected Blue Sea products. But it does show in general what can go wrong at high currents with a poor design.

Hi new2..,

As inetdog has mentioned, these switches are NOT rated for a 48 V battery system.

AND, IMO, these switches would most probably not be Code in residential, or commercial power systems.

Believe that your system is still a Grid-connected Backup Power system, or similar, so being Code and possibly needing to pass Inspections would probably be important to you.

Real DC-Rated circuit breaker/s should be able to accomplish much of what you are trying to do, could easily be mounted in a metal box, and pass Inspections -- to the extent that inspections would be necessary.

But Inspections or not, believe that a DC switch-rated breaker mounted in a metal enclosure would be the safest thing to do, without spending a lot of money on some other approach.

More opinions. Good Luck, Vic

Hi again new2,

It is the sense of many here, that you are trying to do things correctly, at least, this is my opinion.

SO, in spite of what you appear to want others to say, I M O, These battery switches are NOT APPROPRIATE for application in systems with 48 V batteries, or any system with a battery voltage above 32 V nominal, as I read Wind-Sun's advice.

Additionally, even if these switches were actually rated for 48 V Flooded battery applications, my guess is that they would not be Code ... just an additional opinion.

You will probably want some form of protection -- a circuit breaker of fuse -- for each string of batteries. When you select an appropriate DC rated breaker, and mount them correctly in a Listed enclosure, you should be able to have most of or all of the function that you wish the B S switch to perform, save for low cost.

EDIT: It is a bit curious that the "Sales Sheet" that is Linked to from the wind-sun site, shows an image of a switch that says "32 V Max", and some of the switches shown on the W-S site DO say 48 V Max. But, still, to me Max means Maximum -- never to exceed, etc < end edit.

I am not a Code guru, so quite possibly, I'm wrong about the Code aspects.

All FWIW, Vic

Hi new2,

Well, the protective Fuse or Breaker that I was trying to refer to is the device that protects each parallel string from Fault currents resulting from a short in a battery. These fault currents can be quite high.

Recall that the fusing current for 4/0 copper cable is a bit over 3,000 amps. So it is fairly common Safety practice to place an OCPD in each parallel battery string to keep huge fault currents from causing a battery explosion, etc.

Again, we each have our own style in designing a power system, so if Power Pole connectors go with your motif, then, go for it ... you have a fairly large investment in your system, especially after you get the PV modules and racking, etc ... but ...

Good Luck, Vic

Vic wrote: »

EDIT: It is a bit curious that the "Sales Sheet" that is Linked to from the wind-sun site, shows an image of a switch that says "32 V Max", and some of the switches shown on the W-S site DO say 48 V Max. But, still, to me Max means Maximum -- never to exceed, etc < end edit.


All FWIW, Vic

One possibility is that the manufacturer decided to avoid confusion and possible liability and mark the switch with the nominal system voltage of 32V, allowing for an Equalize voltage of 40V or more. Instead of the absolute max of 48V.

inetdog wrote: »

You can put in another breaker if you can find one of the relatively small number of non-polarized ones. Fuses, for course, could care less about the current direction.

All of the Midnite panel mount breakers are non-polarized. Only their din-rail breakers are polarized. This should work well for you because the larger sized breakers (which are what you want) are panel mount.

--vtMaps

Vic wrote: »

The way that I had read that relatively post from Robin on the MN Fourm, was that...

There have been at least half dozen posts from Ryan or Robin on the Midnite forum about this. Here's the most recent (by Robin):

Our panel mount breakers are non polarized, but the din rail breakers are not yet non polarized.

--vtMaps

vtmaps wrote: »

There have been at least half dozen posts from Ryan or Robin on the Midnite forum about this. Here's the most recent (by Robin):
--vtMaps

Thanks vt for phrasing this SO succinctly.

1. Sorry new2, that I was wrong about polarity sensitivity.

2. All of the E-Frame breakers that I have purchased recently, have been Carling, and were ordered trough Distribution as MidNite breakers, although, see no special marking on them. Even those sold as for Schneider DC applications (usually for CCs) were Carling (80 and 100 A, E - Frame) and probably came from MN.

Here is the link from the MN Solar site to the Specs for the MNEDC 125 breaker -- is it to the Carling data:
http://www.midnitesolar.com/pdfs/Carling_E_Series.pdf

Have used Airpax breakers E in the past for DC applications, mostly CC ins and outs. The design of this breaker is superior, IMO, but these breakers may be polarity sensitive.

It is great that you are interested in designing a robust, safe system.

Are unable to place the these two breakers in the Schneider Conduit box? Or is it that the inverter and that box (the PDP?) are located inside a structure?

There could be a bit of a nit regarding the Listing of a box that you choose to place these battery breakers into, especially if it is repurposed If there is an Inspection, this would probably fly, but who knows. You probably would need a 3R type enclosure, and those might be a bit hard to find ... am not a Code guy.

FWIW, Good Luck, Vic

Hi new2,

I wish I knew. It appears that Robin, THE Founder of MidNite Solar says, in many, many ... many quoteS from MidNite Forum PostS, that the Panel Mount breakers ARE non polarized. The MNEDC125 IS a Panel Mount breaker.

But, as an Engineer, I would want to see this stated in writing from the Manufacturer, in their specs -- I cannot find such a statement there.

I DO believe MidNite, and Robin, boB and the entire MidNite crew are trustworthy, so if Robin says it is so, I do believe it.

Just make certain that you specify MidNite MNEDC125, or whatever you need, and that should do the job.

If I were writing a PO for these items, I would specify, that they MUST be non-polarized, or not polarity sensitive, but this probably would cause consternation with your Supplier.

It is astonishing to me, that this important information is not in the manufacturer's specs. Although, it all might have to do with the Safety Agency Listing process and Liability. Perhaps the manufacturer cannot say that it is not sensitive to polarity UNTIL it has been tested AND Listed/Accepted by some agency like ETL, UL, CSA, etc.

I am certainly not in a position to pass judgment on weather these breakers are, indeed, not sensitive to polarity!

For now, a single fuse should protect you, and perhaps, if you provided the ability to retrofit breakers later (when it might be noted in the Mfg specs), you could be OK.

Realize that, with the disconnect function provided by a breaker, you could be able to Rest one string of batteries, to determine the SOC of that string by Resting voltage (after temperature compensation). For sealed batteries, this is a very good thing.

FWIW, YMMV, and Good Luck, Vic