DC Isolators

keefy · Nov 18, 2011

I bought some DC isolators that looked wrong yesterday, wrong in at first the switch was red and yellow not the typical Grey for DC.

Also no internal links and the unit clearly stated AC23, looked just like a 4 pole AC islator.

Guy promised me it was OK but I swapped anyway. Replacements just turned up (different manufacturer) and guess what? Red switch again, AC23 on isolator. Only difference is the links are in there.

Any one got any experience of this being OK or am I just getting ripped because everyone is desperate?

bumcrack · Nov 18, 2011

What does the labelling say ?

keefy · Nov 18, 2011

Scame 590.GE2014

SibertSolar · Nov 18, 2011

You would (perhaps) be surprised at the number of AC isolators out there being fitted as DC disconnectors.......see here for reasons why you shouldn't

sharpener · Nov 18, 2011

The data sheet for the Scame 590.GE2014 at http://www.scame.ir/Documents/ISOLATORS%20Series.pdf appears to say the DC rating for a purely resistive load is 20A at 300V, but for a mixed resistive and inductive load 25A at only 250V (or with the poles in series 10A at 600V). So depending on the system design it might be OK but looks a bit marginal.

SibertSolar · Nov 18, 2011

The reason why the current/voltage ratings are de-rated so severely is simply because it's an AC isolator designed for breaking AC, not designed for load-breaking DC. You would have to be very careful to select the right unit for the job and I'd personally be quite worried about load breaking the DC with one more than once or twice.....

sharpener · Nov 18, 2011

SibertSolar said:
I'd personally be quite worried about load breaking the DC with one more than once or twice.....

Quite agree, yr link to very much to the point. In theory you could just about get away with it for a 4 kW array, but unless the Scame unit has a spring-trip mechanism as described in the IMO article (which I doubt) I wouldn't want to give it houseroom, least of all in the loft where I couldn't see/smell it. Ideal companion for a Mastervolt inverter to judge by the other thread!