24V DC breaker, 125A - 250 amp

guest; are you using 12/12 volt 3 wire? pos 12v, 0v, neg 12. other wise why not a single pole. perry

I am using two 12V batteries, connect - on one to + on the other and therefore get 24 V system, According to regulations I have to fuse both - and + poles on a 24 VDC system.

You may find that 2-pole breakers for that level of current are a bit thin on the ground.

You could use a 3-pole MCCB, but you have already ruled that out. They generally come in 1-pole, 3-pole and 4-pole variants, and in my experience are usually cheaper than purpose-built DC breakers.

Only 76A in a 50mm2 conductor???? What part of the world do you live in that has such tight regulations on ampacity? By the table on the wall above my desk, copied from AS/NZS 3008 (Australian/New Zealand standard), a 50mm2 copper cable ampacity ranges from 211A (free air) to 125A (enclosed in thermal insulation).

If your cable is too large for the terminals, there are devices you can buy from electrical wholesalers called crimp-downs or shear bolts which will assist. Otherwise you can make up adaptors from short pieces of copper busbar to allow you to terminate your cables with crimp lugs of the correct size.

Best of luck.

Thanks for your reply

I am currently using MerlinGerin 3pole, but they are expensive, and the space is always an issue in small boats.

The "regulations for small boats" I have to follow are diffrent from everything else, yes I know. It is in Icelandic but You can see the list for conductor size on page 4 on this link http://sigling.is/lisalib/getfile.aspx?itemid=2400 the first Amp. column is for continious load

On bigger ships I can load 50mm2 with 150Amp. And on shore even more.

Dear Guest,

Dear Guest,

In the Data Center we are often faced with very high amperage requirements. Although these are almost universally 48 Volt DC the concept is the same. Wire sizes however will be a concern. If you will follow the link below to Emerson Power you will find some of the breakers that will fit your requrements. For this size of breaker you will most assuredly need a distribution panel of specific design. Emerson can help with this as well.

Good Luck!

Rock1

http://www.emersonnetworkpower.com/EnergySystems/pdf/power-psa/PDS-A-044.pdf

Try AEE. They have a plethora of dc breakers and fuses in the 125-250A range. Will a fuse block suffice? They are much cheaper.

I have used Carling breakers in lower current applications. I cannot say whether they have anything appropriate. have a look at:

http://circuit-breakers.carlingtech.com/index.asp

Thank you I just found this yesterday, I have send them email, If their prices are aceptable then this is what I am looking for

Hi,

Cable size is a real bugbear, particularly for the DC fraternity it seems! (at least you don't have pf to worry about! But if you need the 'big stuff' to comply then you must use it. A useful comment about fitting a crimp or similar device to the end of the conductor to permit insertion into the terminal is OK provided the mechanical contact is perfect and remains so otherwise you are in line for a nasty surprise when it burns out one day; I've had it happen on a 110VDC traction motor feeder

There is a simple solution however and it involves 'tinning' the end of the cable and ditto the crimp before physically deforming the latter, it must be copper also, followed by a quick heat using a pencil flame to unite the two( protection of the insulation is paramount so don't go cooking away!). This will avoid any problems due to either crimp efficiency failing or in an aggressive atmosphere the onset of corrosion. This simple trick will enable your installation to carry all the I you will ever need. Oh yes, don't use plumbers solder!! use an electrical quality self fluxing variety or else everything I've said so far is @@@@.

How about the battery isolator switch for a heavy goods vehicle? Is there a breaker's yard nearby from where one might be sourced?

I can get a switch, that is no problem, I need to make one main distribution panel for the smaller distribution panels in the boat and there I need 125 - 250 A fuses or breakers. Imagine if you are in the open sea and you have all your fuses blown, you are in deep sh**. But if you have a tripped breaker you just fix the problem and reset the breaker and sail away. My problem is to get 2pole breaker rated for 32VDC and 250Amps without having to sell my car to pay for the thing. For one 3 pole 250A Breaker I have to pay $600.

If you can get by with a 125A 2-pole, there are options which should be a little cheaper.

Referring to the GE brand (not to plug them but because I know them well), they supply a range of 1, 2, 3 and 4-pole MCBs up to 125A. A 2-pole 125A will cost you substantially less than $600 I would think. Here is a link : http://www.geciasia.com/apo/products/industrial/component/14.htm Other MCB manufacturers may have something equivlent.

I have seen milti-pole MCBs used in CD systems where the poles are commoned up to increase the current rating - usings a 2-pole 125A breaker with the ploes paralleled to create 250A protection. I am not sure if this will be something that you can get away with in your boat however.

Yes, if I could use MCB I would do it. But most MCB brands incl GE are not rated for 32VDC current for 125-250A. I have to be able to connect 95mm2 wire to the breaker, MCB is not made for that.

Perhaps you had better clarify just what you mean by "125-250A". Do you mean am adjustable circuit breaker where you can adjust the trip current anywhere between 125A and 250A?

If you need adjustment, you are probably going to have to go to an MCCB, as these are available with adjustable trips but as far as I am aware MCBs are not.

The GE Hti breakers are rated for DC, up to 48V per pole.

If you need a fixed 125A 2-pole breaker, the GE Hti in 125A 2-pole will do fine for up to 48V.

If you need a fixed 250A 2-Pole breaker, use the 125A 4-Pole Hti and parallel-up the poles into pairs.

As I tried to explain above, terminating fat cables into small box terminals is just a matter of technique and does not involve any real difficulties. It is just a matter of fabricating the right pieces of copper.