DC Isolator or no DC Isolator that is the question

[JH69]

Sensible yes, good practice, yes, in a multi string environment almost essential for maintenance and testing. Mandatory ... No as SMA have said it is adequate

Version 3 of the guide says ..



So to the the letter it meets the final clause.

The guide goes on to say:


We ALWAYS fit DC isolators, because on an industrial sized installation the thought of pulling the ESS to break 17+kW of DC is horrendous.. On a recent job we used 4 pole isolators to work on two strings, however we are unlikely to be doing that again because when you make one pair live to test the string you've now got the other pair live also. also some of our strings run close to 1000V Voc and you get a b*****y great spark if you try to seperate those after doing an Isc test without first opening the isolator!

We have 4KWp panels (15 x 265w, 2 strings, one of 6 panels, and the other 9 panels). 15m DC cable run. The inverter is in the garage next to Consumer Unit.

Would you still be concerned an a 4kwp domestic install?

 

[sedgy34]

We have 4KWp panels (15 x 265w, 2 strings, one of 6 panels, and the other 9 panels). 15m DC cable run. The inverter is in the garage next to Consumer Unit.

Would you still be concerned an a 4kwp domestic install?

If your talking about the 15 mtr run of dc cable that's nothing to be concerned about

 

[Worcester]

Not sure, however according to the tests it does comply with the 'International Standard' for PV Isolation and Switching

http://files.sma.de/dl/3562/ESS-BEN074812.pdf
http://files.sma.de/dl/3491/TECHESS-13-AE3106.pdf
and
http://files.sma.de/dl/1367/BG_ESS_08013-ZEEN121313.pdf


I think you'd have trouble INSISTING they install one if they don't want to, unless you are prepared to pay for it.

 

[moggy1968]

bought this up on my assessment, assessor would be happy on an SMA inverter to have no seperaste isolator. The SMA one breakes both -ve and +ve.
However, I always have and always will fit a seperate isolator for maintainance and testing purposes, and emergency isolation of the inverter (eg when it's on fire!) which is the whole point of isolators!

 

[valet]

Hi any idea what make is this dc isolation switch?

 

[Gavin A]

nope, suggest you find an AUS forum to ask that question on. Also, is that not an inbuilt DC isolator in the inverter?

 

[infinity]

The DC isolator looks like an IMO,

 

[SibertSolar]

Agreed, looks like an old version IMO unit before they increased the size of the enclosures.

 

[The Solar King]

This is what the draft DTi (or what ever it is called) 3rd edition says:

To allow for maintenance and inspection tasks to be carried out safely, a means of isolation needs to be provided on the dc side of an inverter. The means of isolation shall:

• Isolate all live conductors (PV array positive and negative)
• Be readily accessible and immediately adjacent to or incorporated into the inverter

Note: For many smaller systems, inverter isolation and string isolation (see section 2.1.12) may be provided by the same devices (eg plug and socket connectors). As noted in section 2.1.7, plug and socket connectors must be labelled "Do not disconnect d.c. plugs and sockets under load".

A switch disconnector shall be provided on the dc side of the inverter.

• The switch must isolate all live conductors (typically double pole to isolate PV array positive and negative conductors)
• The switch must be rated for dc operation at the system voltage maxima as calculated in section 2.1.2.
• The switch must be rated for dc operation at the system current maxima as calculated in section 2.1.2.
• The switch must be labelled as "PV Array DC Isolator" with On and OFF positions clearly marked. Switch enclosures must also be labelled with "Danger - Contains live parts during daylight'. All labels must be clear, easily visible, constructed and affixed to last and remain legible for as long as the enclosure.
• The switch should be located adjacent to, or integrated into the inverter.

A circuit breaker may be used as the d.c. switching device provided it meets all the above requirements.

Note: Switching a.c. is less demanding than switching d.c. (with an a.c. supply, the voltage passes through 0 V many times a second). A switch must be rated to break dc, an ac rated switch is not acceptable or safe.

An additional d.c. switch may be specified for systems with long d.c. cable runs (typically at the point of cable entry into the building) so as to provide a means of isolating the cable for safety reasons or maintenance works.

Systems using micro‐inverters may omit the d.c. switch disconnector where all of the following requirements are met:

• The micro inverter is located immediately to the rear of the PV modules
• The micro inverter is plugged directly into the flying leads provided by the module manufacturer (no extensions to the flying leads may be used)
• The micro inverter and dc cables are generally inaccessible or only accessible to trained or authorised personnel
• The d.c. conductors between the module and micro inverter are adequately protected against mechanical damage

NOTE: A roof mounted PV installation where the micro-inverters are located on the rear of the PV modules and where access is only possible by first removing some of the PV modules is a typical scenario where switch disconnectors can be omitted. Where the same inverters are brought into a loft void, it is expected that a switch disconnector would be required.


So integral isolators are OK if you meet the above.
Still awaiting this fabled document.

 

[jason121]

nope, suggest you find an AUS forum to ask that question on. Also, is that not an inbuilt DC isolator in the inverter?

Is that not an Froinius inverter, they have AC isolators built in .

 

[Gavin A]

Is that not an Froinius inverter, they have AC isolators built in .

The isolator is right next to the DC inputs so I did a sherlock holmes impression and deduced that it ought logically to be a DC isolator, but Fronius are an alien concept to me so you could well be right.