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Question about using AC trip switches or circuit breakers for DC

Question about using AC trip switches or circuit breakers for DC

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  #1  
Old 05-28-14, 07:53 AM
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Question about using AC trip switches or circuit breakers for DC

Hello

I have been asking around as I want to change my existing set up of toggle switches and fuses.

The toggle switches I have installed, I donít trust them they rated at 12V 25 amp with blade connections or spade connectors. I have a concern that the spade connectors yellow in colour cannot carry the stated load. I am also that these switches are not what they are made out to be.

I have been told that I can use ordinary AC domestic circuit breakers in a DC 12 Volt circuit.

All I have to do is rate them up by 30%. Meaning for a 10 amp load I should use a 15 amp trip switch and I will be ok.

Does this sound correct, apparently the logic is it is the amps that will heat the bi-metal strip causing the switch to trip.

I am a bit weary to do this as I am not sure of myself.

I would appreciate some advice.

Kind regards

Godfrey
 
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  #2  
Old 05-28-14, 11:57 AM
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I would not use an AC circuit breaker on a DC load. To be honest, I don't know if or how effective they would be, but I wouldn't use something that's safety related if they aren't rated for it. You can get DC rated breakers.

As for the switches you have, is there a reason you don't trust them to handle their rated ampacity? I found a reference online that Yellow spade connectors are rated at 48amps (I admittedly don't know whether this is manufacturer specific or not). Of course, this assumes they are crimped/connected correctly.

Hope this helps a bit... if you can provide some details on what you're actually doing, maybe others will be able to give you more precise suggestions.

-Mike
 
  #3  
Old 05-28-14, 09:29 PM
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You can buy DC circuit breakers.
 
  #4  
Old 05-29-14, 03:56 AM
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Dear Mike

Thank you for taking the time to reply to my posting.

I have been unable to source DC circuit breakers locally but I will canvass more suppliers and see if they could order in for me if needs be. I would rather have the right thing.

I live in South Africa in Durban and we have become flooded with cheap imports from China. I am not sure if a lot of what we see in the shops here is safe or rated correctly or even tested.

My switches are of the toggle type, and are 'rated' at 12v 25 Amp yet when I put my fingers on their plastic sides, they feel warm under a load of 6 or 7 amps. If they are warm at such a low amperage then how will they later handle a load of say 21 amps at 12 volt or so.

My concern with spade connectors especially the yellow ones is the seem frightfully thin and narrow around the neck and there again it seems to be a point of weakness to me. To carry a load of say 10 or 20 amps @ 12 volts the wire size needs to be at least 6mm^2 or more. Then when you look at the spade and the narrow neck on the spade. I wonder if it is going to be a point where the current will choke and heating will occur.

Mike what I am doing is this.

Where is live power outages are a reality for a variety of reasons and are a constant headache.

Over the years I have built a solar power system. I have panels charging a battery bank via a controller. I started small and have expanded slowly.

I wanted to replace the toggle switches for the reasons outlined above and the fuse box with circuit breakers.

I want the system to be safe and autonomous and not worry about the system other than a weekly clean of the panels and odd check. I have made up my own lights using strip led's to light our yard at night. The system was completely autonomous at 11 lights and ran for 3 years with no issues.

Currently, I am on a drive to expand the system. I want to add a second panel and have now 15 such lights drawing about 5.1 amps at 12.1 volts. I am in the process of expanding further so that in the end all my outside lights and the internal garage lights are powered by light from solar panels.

Thank you for taking the time to read this and any help or advice you hight be able to give me.


Regards

Godfrey
 
  #5  
Old 05-29-14, 11:18 AM
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I honestly don't have much experience with 'high' amperage low voltage equipment. So I'm really just basing it on device ratings and such - which you're right, cheap imports can push those ratings a bit.

I order many of my electrical components from Digikey. Invalid Request
I know they ship to many global locations, though I can't comment on shipping costs, etc. They have a HUGE inventory of circuit breakers, switches, and everything else you might need. Their inventory is actually quite overwhelming.
 
  #6  
Old 05-30-14, 02:20 AM
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Thank you for the suggestion about Digikey if all else fails I will contact them and order in what I need. But first I will broaden my enquiries locally and see if I can source what I need locally before trying to import as that can prove very expensive. Thank you again.

Regards

Godfrey
 
  #7  
Old 05-30-14, 02:45 AM
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Good News

I have just received a call from Voltex here in Durban to effect that they can source DC circuit breakers for me.

Thank you every one for your help and suggestions.

Regards

Godfrey
 
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