Isolators

[synergy power]

Does the Electronic Solar Switch on a SMA inverter act as a DC isolator? Also, Do you need an AC isolator at the garage unit, when it can just be isolated from the garage unit?

 

[yellowvanman]

Yes well I think so, but put in a lockable as well - assessor will usually be looking for one.
For the ac you still need an ac isolator to enable double pole lock-off.

 

[jimbill]

Most new sma inverters have an integral dc isolator, usually a pull down handle. A lockable AC isolator is needed at the garage unit plus a non lockable AC isolator at the inverter if it's in a different location to the garage unit.

 

[Jon.berry]

Check the manual for most SMA inverters with this ESS it has useful info, also they state in there manuals "do not disconnect in a short circuit situation" and "wait until it is dark to operate"...

 

[Earthstore]

If you use the DC isolator on the Inverter,and do not fit a seperate one, how, in the future, could anyone work on or change the Inverter without risk of injury.
Of course, electricians could always work at night...

 

[BruceB]

Pull out the DC isolator then disconnect the DC plugs one at a time. Although there will be voltage in them, there will be no current and no exposed metal parts that you are able to touch, so not that dangerous in my view.

 

[moggy1968]

so why all those labels saying 'do not disconnect under load'?
you have to have a DC isolator. anything else is just skimping, why would you not put one in except to try and save a couple of quid?

 

[BruceB]

If there is no current flowing because you have pulled out the dc isolator then it is not 'under load'.

Yes, I think it is skimping a bit and having a 'proper' isolator can facilitate testing. But under 7671 pulling a plug out has always been an acceptable means of isolation. Not under load of course.

I have come round to the view that 'proper' dc isolators with an sma inverter are wasteful duplication. In their instructions with the Tripowers the phraseology to my mind means SMA do not expect additional dc isolation beyond that which they provide. I am about 1/4 Scottish. A decent DC isolator can be £30 rather than a couple of quid.

 

[Jon.berry]

I have spoken to SMA directly and they themselves recommend a seperate DC isolator before the inverter.

 

[BruceB]

Interesting.
What is the point of the ESS then? It is a significant aditional design and manufacturing cost.
Power-one have an optional equivalent isolator, but I have not seen it offered specifically in this country.
My point on Tripower instructions stands and having looked at TL instructions they are similar.

I wonder was that advice from someone based in the UK office who was reflecting historical UK practice rather than SMA design intentions?

 

[Jon.berry]

found this

 

[Jon.berry]

SMA installation guide

 

[BruceB]

What is the point you are making?
The first of the 2 posts above mentions the circuit breaker, but that is the mcb on the ac side.
The other ones are talking about a fault condition where for safety the Tripower short circuits the array.
I do not see they are relevant to the discussion really.

 

[Jon.berry]

I am saying that in a fault condition when you would want to possibly use an isolator on-load, as in a short circuit condition there will be current even if you have isolated the AC side then you have to wait until it is dark to use a switch intended for safety...

 

[BruceB]

In that fault condition, if you have an external dc isolator and you switch it off then you are going to bring to fruition the risk that sma are trying to avoid by short-circuiting the array, namely you will have reverse current through a string which could cause a fire. (Unless you have a separate isolator for every string which would be a belt and braces way of doing it.)

(See the first bit of yellow highlighting in the second of your six attachments above)