Circuit Breaker kVA rating for 2.5 - 8kW Inverter Air Conditioners

[grub]

Hi peoples,

Long time no post.

Quick question.

I've always purchased Single Phase 240 Volt (Australia) 6kVA C/B's. The other day my sparky informed me that I can use 4.5kVA C/B's instead. I know there isn't a great deal of cost savings but I can get hole of a heap of 4.5kVa's fairly cheap. I'm just not sure as I've always purchased 6kVA's as was informed years ago.

Anyway I did a google search to no avail, any information would be great.

Thanks peeps,

Grub!

[chilliwilly]

They will be fine as long as the prospective short circuit current test value isn't any greater than 4.5 ka. If you or your sparky have a pscc tester, then you need to verify the value of pscc before hand.

Over here 6ka is about the average value for mcbs, they range from 1-9ka. Any higher, then mccbs will be required to cope with the higher values, the closer you are to the sub the greater the value of pscc. The old rewireable fuses range between 1 and 4kva (S1a-S4a UK designation). And will still suffice where values are low.


The truoble is with the mccbs over mcbs is the extortionate price. It can be cheaper to use switched fuses as the cartridge fuses have superior breaking capacities over mcbs and mccbs, ranging from 16.5-80ka.


Sorry to waffle on but I do tend to get carried away at times.