Breakers Sizing

Started by SolarVet, April 25, 2014, 10:19:26 AM

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SolarVet

I have a question. I will be using 2 ga Welding cable from my battery box. But I will be using 2 pair  , 2 Postive wires and 2 Negative wires. from battery box to central place inside my house. I want to use 300 amp rating.
Is it okay to use 150 amp Bussman Breakers on each pair. Instead of one 300 amp Breaker.
12 volt system

zoneblue

#1
Quote from: SolarVet on April 25, 2014, 10:19:26 AM
I have a question. I will be using 2 ga Welding cable from my battery box.

Welding wire is ok, but  not ideal for a number of reasons.

QuoteBut I will be using 2 pair  , 2 Postive wires and 2 Negative wires. from battery box to central place inside my house. I want to use 300 amp rating.

No dont do that. Small differences in the resistance of the wires can lead to uneven current sharing leading to ampacity exceeding spec. If you do it, you must either fuse each wire, or make sure that each wire has enough ampacity to take the whole load alone.

Quote
Is it okay to use 150 amp Bussman Breakers on each pair. Instead of one 300 amp Breaker.
12 volt system

Again, use proper breakers. Bussman do not have good interupt ratings. Use Carling or Cbi. They are neither expensive nor hard to get.

I appreciate the desire to take the path of least resistance, buying whats locally available, but unfortunately dc systems are a speciality area and you need specialty gear. For the wire go to an electrical dealer (where electricians shop), and get proper 600v double insulated stranded wire., of the correct guage. For the breakers order them online from Naws or AltE.

One other thing: use conduit between the battery and the breaker to protect against cable damage. Batterys are reasonably dangerous things.
6x300W CSUN, ground mount, CL150Lite, 2V/400AhToyo AGM,  Outback VFX3024E, Steca Solarix PL1100
http://www.zoneblue.org/cms/page.php?view=off-grid-solar

fiddlerkelly

Zoneblue what are the reasons.

Welding wire is ok, but  not ideal for a number of reasons.

zoneblue

Well it does depend on the particular wire. "Welding" wire varys a lot. What you are looking for is wire with double insulation layers, and where the strands are fine but not too fine. Temp rating should be 90*C.
6x300W CSUN, ground mount, CL150Lite, 2V/400AhToyo AGM,  Outback VFX3024E, Steca Solarix PL1100
http://www.zoneblue.org/cms/page.php?view=off-grid-solar