BREAKERS???

[2windy]

I have some 120 volt AC breakers, a fuse box with screw in type fuses w/disconect. Can these AC controls be used on my DC wind genny, or should all DC type controls be used?

[veewee77]

Don't attempt to use AC breakers on a DC circuit, especially higher voltage DC.  The AC breaker trips differently and if there is sufficient voltage and current, the AC breaker will tri but the blue flame arc will remain and cause a fire and etc.

IOW, use DC stuff for DC.

Doug

[georgeodjungle]

i agree:

it's like using ac switches for dc.

[srnoth]

What's wrong with that? I just put a capacitor between the two legs of the swicth, and that keeps the voltage down enough to prevent arcing. Maybe this could work for using AC breakers with AC? I know for a fact that AC breakers do trip when they are overloaded with DC current. Does anyone know if using capacitors across the two legs of the breaker will work?

Cheers,

Stephen.

[srnoth]

Edit: "...using AC breakers with DC..."

[dinges]

It's very simple. If the breaker says that it's useable for AC, use it for AC. If it says DC, use it for DC. If it only says AC, don't use for DC. And reverse.

AC (50/60Hz) goes through zero 100 times per second, so the arc that starts when opening the breaker or switch gets extinguished. In DC, the arc can continue to exist for much longer, causing damage to the breaker/switch.

I only use breakers/switches that have a KEMA-keur (or VDE); like your Underwriter's Laboratory (UL). And only use for the way the manufacturer specifies. I.e. no tricks, capacitors, etc.

Many switches can be used for AC and DC, but usually the ratings for DC are much lower. Because of the arc that occurs and doesn't get automatically extinguished.

Hope this is of help, Stephen.

But I don't suppose Trizzybob understands all this. Oops, I meant 2windy.

Peter.

[srnoth]

Thanks dinges/Peter,

I guess that explains why running 10 amps DC through a 15 amp AC switch fried it pretty quickly ;-).

I can't remember where I heard about that capacitor thing, but I needed to use an AC relay with DC for a little make-shift project I was experimenting with (nothing permenant or high amperage). Without a capacator it would ark and weld the contacts together, but since I installed a small capacator it works like a bute (I only use this circuit about twice a month though!).

For anything high-amperage though you should most definately only use breakers that are rated for DC. What I have found though is that it is actually easier to use fuses. Basically, what the breakers are there for is so that a short in your system doesn't destroy your electronics and cause your batteries to explode! If you keep such mistakes down to a minimum, fuses are actually easier. I just bought several fuse holders and a few dozen 35 amp automotive fuses (glass cylinder type, very cheap). If you are going for a cheap/low-cost solution, I definately recommed fuses over some sort of makeshift contraption using AC breakers. With fuses, if there is a short you KNOW that they are going to blow, and stop any further damage. Plus they're easy and affordable to replace.

Hope this helps,

Stephen.

[adelaide]

what dc volt u using ?/ outhers would that still be prob if 12 v?

[commanda]

3 Amp Circuit Breaker

These circuit breakers are rated at 250VAC

- SAA approved.

Specifications:

• Maximum voltage 250VAC or 50VDC
  
• Will hold 100% of rated current indefinitely at 25°C
  
• Will trip within one hour at 125% of load at 25°C
  
• Will trip within 4 seconds at 150% of rated load
  
• Mounting hole diameter 12mm
  
• Size 35(H) x 30(D) x 14(W)mm
  
• 3 AMP
  
  

These are available in Australia from Jaycar

http://www.jaycar.com.au

They have a range of different currents, search for "circuit breaker".

I imagine Digikey and others would also carry them.

DISCLAIMER: I have no vested interest in Jaycar, 'cept that I shop there.

Amanda

[Opera House]

I use regular house breakers on DC simply because they were there (a house that lost grid connection).  Just about any mechanical metal make/break switch can be used up to 24V.  Above that, materials of the contact will vaporize and sustain an arc.  Silver and copper are really bad.  The real problem with standard home breakers is they are fairly high in resistance.  A little voltage drop doesn't matter much at 120V, but it does at 12V.  Another problem is the contact material tends to form an oxide layer that is normally broken down at higher voltages and doesn't at lower voltages.  I have to flip my breakers once in a while to clean the contacts.

[elvin1949]

Those contact's will weld themselves together

and BURN your house down.Replace then.

 I SMELL SMOKE

later

elvin

[Chet]

   Claiming no special knowledge myself, I rely on guys like this:

www.ibiblio.org/london/alternative-energy/homepower-magazine/archives/7/07pg27.txt

   who have more experience with alternative energy than most people you can name.

Chet

[srnoth]

Hmm. Very interesting. So according to those folks AC breackers will work. They do work in my experience, so I would tend to aggree with them. I guess the best option is to use AC breakers as well as fuses, the fused being a slightly higher capacity so that they will blow if the breaker fails to trip.

Stephen.

[dinges]

I don't rely on guys like this;

I rely on guys like KEMA, VDE and UL. And on what the manufacturer guarantees his products can be used for.

This also means I don't use cheap switches/breakers that don't have one of these proofs. And yes, my electronics shop salesman has given me a stupid look when I gave him back one of his switches, made in China, without any of the proofmarks on them. Something like that never happened to him before (he said).

But I'm known to be very conservative/risk aversive (most insurance companies are like that too, BTW!)

Peter.

[cjbotkin]

Hi Guys...  I'm using some DC breakers from "john drake".

Here is the site... these are reasonable and made for DC.

http://www.solarseller.com/dc_circuit_breakers_12_volts_to_125_volts.htm

[Chet]

   So according to the John Drake site ( as well as Backwoods Solar ), the Square D breakers recommended by Dankoff and Mooney are in fact approved for DC use by UL, reassuring no doubt to those worshipping at that particular altar.

Chet