Energy Matters Forums

[jono2b]

Why would you use a breaker anyway. Use isolators and if you need protection PV fuses.

Most people use breakers since they are generally just as cheap as an equivalent isolator anyway, and there seems to be a bigger range. Are there any isolators in particular you would recommend? Especially high voltage ones?

This is a serious issue as a lot of TL inverters have high voltage windows. I just looked at one with 850V max

Yeah I agree. ABB make a 4 pole circuit breaker which is rated for 1600V (400 per pole) when used in this manner. The specs say 1200V, but 800V on each set of two poles is ok as long as there is never more than 1200V across it which there won't be.
It is expensive and physically quite big but can do the job for strings up to 666 Voc (800/1.2). Above that I don't know what to use.

Speaking direct with manufacturers, the rest of the world are not even considering this an issue. Why are we so special?

I'd like to know more about this too. In the US their standards limit PV arrays to 600V and all their inverters have to have the isolators built-in so its probably not that big an issue. In Germany I think they may not require external isolators (like Australia does) since for SMA inverters the built-in ESS seems to be ok. This only disconnects the positive leg so perhaps they only require an isolator on one pole. I'm not too sure why that is ok though...

[SolarInstalla]

So the practicalities are what i am concerned with, what would be a suitable isolator to use for the PV array to satisfy the VOC x 1.2 rule?

Also, I guess I should be using 10A string fuses as string protection on the roof instead of 10A double pole dc breakers when there are 2 or more strings?

[rg767]

you definitely shouldn't be using [EDIT: polarised] breakers as a string fuse - in a fault condition they get reverse current flow through them.

[rg767]

DKSH do a good 700V isolator for about $120.

[jono2b]

DKSH do a good 700V isolator for about $120

Which one is that? I've seen a 600V which they sell, which is made by Multi-Contact. And is a fair bit cheaper than that.

In any case I don't think it solves SolaInstallers problem.

So the practicalities are what i am concerned with, what would be a suitable isolator to use for the PV array to satisfy the VOC x 1.2 rule?

If you are looking for something that complies with the CEC's rules of 1.2x Voc per pole, then I would recommend a 4 pole 1000V breaker. Eltech make one.

[rg767]

Yes on the price i am not quoting wholesale.

K&N do a heap of different combos one of which could help.

[franks]

I Can see the CEC will mandate HRC fuses, Diodes and Switched Isolators, Between PVs and Inverter just to be safe to cover all possible fault cases.

[rg767]

Fuses won't really help at all for isolation. It is really up to the standards committee to make a decision about polarised circuit breakers, not the CEC.

For a long time there though there was no funding for standards development, and so here we are.

[franks]

Makes you wounder what does the $880 CEC Acretiation fees are used for , your builder, sparky, plumber, cabler, licencing fees are fraction of the CEC.
The CEC should be checked by the ACCC for price gouging!

[franks]

The mistake with DC breakers is assuming you need the full Voc covered on both -ve and +ve. It's just not the case, something I believe the CEC has admitted.

[/quote]

What, a 1st year apprentce knows the 2 poles with respect of the voltage source are in Series, so the rating is doubled if used as a single pole
How Can the CEC get it so wrong?