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Posted By Topic: Stand alone power system. Gen/Solar

Sam1234
May 10 2018 08:12

Hi there. I am installing an off grid system. Solar with back up gen. I recall from a previous post the mention of having only one MEN link at the main switchboard and having to remove the link at the genorator? I cant find referrence to this anywhere in the standards so i am doubting my memory. Another question is whether or not the gen has to be hard wired, or if a plug in arrangement is acceptable. Everything will be located in a shed with a sub main feeding the house distribution board. Help much appriciated. Many thanks.

   

AlecK
May 10 2018 09:59

You need to be looking in AS/NZS 3010.

The answers to both your questions are there
   

pluto
May 10 2018 17:32

AS/NZS 3010 will not give all information required you also need AS/NZS 4509 to get some of the photovoltaic (PV) details.

The best simple drawing ro show the correct arrsngement is AS/NZS 3010 figure 2.1 (b) and (c) or fig 2.1 (b) or (c).

The sequence is importand so the grid backfeed facilty of the PV inverter does NOT backfed in to the generating set, unless it is specially designed to able to do so.
   

Sam1234
May 10 2018 20:38

Thanks Aleck and Pluto for your replies. Great to see you are both forever there as a source of support.

Working through 3010 and reading it on every other page, it is now clear that the MEN link in the genset is to be removed.

As for the hard wiring vs plug arrangement I am still not sure. Primary source of power in my installation is the inverter connected to the batteries, (batteries charged by PV), the genset is backup but is a permanent part of the installation.

In 3010, 4.4 shows connection of "portable" genset to dedicated wiring system done with a plug (no internal gen MEN link). However I am thinking that 2.11.2.2 is saying that this connection should be hard wired? Am I correct?

I have also picked up that 2 pole isolation should only be at the gen itself. Within the main switchboard only the phase should be isolated in the change over arrangement.

From talking to the generator supplier, it sounds like none of the above is the norm.

Thanks
Sam
   

pluto
May 10 2018 21:23

Sam1234 May 10 2018 20:38
Your comments (part only)
Your comment 1
Working through 3010 and reading it on every other page, it is now clear that the MEN link in the genset is to be removed.

My comment 1
Also don't forget that the every cheap 2 to 3 kW generating sets ($ 300 to $400 approx) can NOT be used as they ususlly have a centre tapped output winding which is earthed. This type of generasting set can NOT be used in all arrangements showen in Sections 1 through to section 4.

cheapie generating sets can be used to power portable tools when directly plugged into the socket outlet on the gnerating sets.

In general inverter type generating sets are usually isolated ouput but their cost is usually highr than the cheapie generating sets.

Your comment 2
As for the hard wiring vs plug arrangement I am still not sure. Primary source of power in my installation is the inverter connected to the batteries, (batteries charged by PV), the genset is backup but is a permanent part of the installation.

In 3010, 4.4 shows connection of "portable" genset to dedicated wiring system done with a plug (no internal gen MEN link). However I am thinking that 2.11.2.2 is saying that this connection should be hard wired? Am I correct?

My comment 2
hard wired gnerating sets means they can NOT be used for other purposes.

if plug and socket connected gnerating sets are able to be easily used for other purposes.

Your comment 3
I have also picked up that 2 pole isolation should only be at the gen itself.
Within the main switchboard only the phase should be isolated in the change over arrangement.

My comment 3

The generating sets is another system of supply (IT) until the electrical output has reached the neutral to earth link (so called MEN link) in the main switchbaord is reached, then the system of supply changes to TN-C-S (so called incorrectly MEN).

The upcoming inclusion of other systems of supply will mean that all will need to correctly understand TN-C-S (so called MEN) first and then learn some more about IT and TT systems of supply. While TN-C-S will be a lot more common the other systems of supply can deliver greater electrical safety in some cicumstances.

Your comments 4
From talking to the generator supplier, it sounds like none of the above is the norm.

My comment 4
That would be incorrect, most can't you if there generating set they are selling is an isolated output, RCD protected output or earth centre tapped type, until they know this they will not be able to advise end users correctly.

Until the errors in AS/NZS 3010 are fixed, there is no point in trying to do an education programme of how to install generting sets correctly AND safely.

However look at appendix C of as/nzs 3010 and you will see a very simple connection arrangement for smal geerating sets in domestic installations.
   

peter
May 11 2018 08:25

Hi
You may find that you use an inverter charger.
Outbacks FXR can be configured a number of ways, and with generator input directly to the inverter charger you can supply directly to the house and charge battery's simultaneously.
There is an internal transfer switch within the inverter .
   

pluto
May 11 2018 09:05

peter May 11 2018 08:25

Your comment
You may find that you use an inverter charger.
Outbacks FXR can be configured a number of ways, and with generator input directly to the inverter charger you can supply directly to the house and charge battery's simultaneously.
There is an internal transfer switch within the inverter .

My comment
I'm well aware of the Outback system, but the question you must consider before using such a device, is it poosible for the generating set input and/or inverter output can backfeed into the incoming mains supply to the electrical installation?

Such protection must also be able withstand the maximum out of phase voltages between the incomimg mains supply, inverter output and the generating set input to the device. S
ome devices only use relays for live conductors switching and will or do NOT have 460 volt insulation, therefore can NOT used in the manner proposed by the device manufacturer.
   

peter
May 11 2018 10:26

In an off grid situation would it be ok ?

   

pluto
May 12 2018 10:12

It depends on the configuration of the internal wiring of the power controller.

They all vary so much that a simple "one size fits all" statement is not adquate so you have to do detailed look at each type.