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Advice on wiring Sunsynk 5kW


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Hi everyone

I have a 5kW Sunsynk inverter which I would like to use as a loadshedding backup. I may install pv's later.

Please could the experts here take a look at my proposed wiring and advise accordingly, particularly in regard to legal compliance and Sunsynk recommended practice.

 Thanks.

wiring diagram ver1.pdf

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Based on how I did my Sunsynk:-

1) You don’t need the first Changeover switch, as the grid connection is a T off the main grid wires going to the non-essential circuits and you have a double pole mcb to isolate the inverter, you do need the second changeover switch, to power the essential circuits, in case of a problem with the inverter 

2) Don’t believe you need the 25 amp mcb’s before the spd’s 

3) As the Sunsynk is capable of 35 amp pass through, better to use 35 amp mcb’ and 6 mm2 wire

4) Please correct me if I am wrong, don’t think you need spd’s on the load side.

 

Edited by Tariq
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1 hour ago, Tariq said:

Based on how I did my Sunsynk:-

1) You don’t need the first Changeover switch, as the grid connection is a T off the main grid wires going to the non-essential circuits and you have a double pole mcb to isolate the inverter, you do need the second changeover switch, to power the essential circuits, in case of a problem with the inverter 

2) Don’t believe you need the 25 amp mcb’s before the spd’s 

3) As the Sunsynk is capable of 35 amp pass through, better to use 35 amp mcb’ and 6 mm2 wire

4) Please correct me if I am wrong, don’t think you need spd’s on the load side.

 

Many thanks for the reply.

1) Good point.

2) One of the things I was unsure about. The spd data sheets indicate the requirement for a fuse or mcb on each input line (if the spd doesn't have this built in). The Sunsynk manual shows one mcb on the earth line of the spd, in addition to the 35A mcb on the inverter output. I have not seen this configuration (the mcb on the earth line) anywhere else.

image.png.92a37b72bbf6c1550ef9e5239052d426.png

3) Yes, the 32A mcb's should be 35A

4) Sunsynk recommend spd's on both sides (I think, I could be misinterpreting this).

image.png.f6236a90823ee2eef4e01139da6d461c.png

 

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Just something to look out for the RCD1 on the incoming side might trip once the neutral and earth bonding relay switches on. I am not familiar with the Sunsynk my Axpert tripped the earth leakage when it was wired like this. Maybe someone who has done done the Sunsynk can advise.

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10 minutes ago, Gerrie said:

Just something to look out for the RCD1 on the incoming side might trip once the neutral and earth bonding relay switches on. I am not familiar with the Sunsynk my Axpert tripped the earth leakage when it was wired like this. Maybe someone who has done done the Sunsynk can advise.

Thanks, how did you resolve this?

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@Gerrieis right, the inverter input is connected directly to the incoming main grid supply through the 35 amp double pole mcb, then both my essential and non essential circuits have individual rcd’’s .

yeah, not too sure on the mcb on the spd ground wire, I just have the spd on the input side of the inverter

Edited by Tariq
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13 minutes ago, Tariq said:

@Gerrieis right, the inverter input is connected directly to the incoming main grid supply through the 35 amp double pole mcb, then both my essential and non essential circuits have individual rcd’’s .

yeah, not too sure on the mcb on the spd ground wire, I just have the spd on the input side of the inverter

So the only way to avoid rcd 1 tripping is to wire it such that the inverter is not protected by an rcd. Is that legal?

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image.png.70fa0f6de7507c677ab82e6495227961.pngBased on the above circuit diagram and picture, you already have the 35 amp mcb, so you don’t need the two 25 amp mcb’s, just an mcb on the ground wire of the spd ( which I don’t understand)

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Posted (edited)
5 hours ago, Tariq said:

image.png.70fa0f6de7507c677ab82e6495227961.pngBased on the above circuit diagram and picture, you already have the 35 amp mcb, so you don’t need the two 25 amp mcb’s, just an mcb on the ground wire of the spd ( which I don’t understand)

 

1 hour ago, Vassen said:

To me, it doesn’t make sense to have a circuit breaker on a protection device. If for some reason the breaker is off, you then effectively have no protection and there’s no way fir you to know that the breaker is off u less you look at it physically unlike other circuit breakers where you would know something isn’t working. 
 

You also need (well, not sure if it’s needed but I included it) a main switch between the changeover and the essential loads RCD. This is to isolate the essential loads DB.  

I guess the reason for the mcb immediately in front of the spd is the difference in trip values between the mcb on the input/output of the inverter (in my case 35A) and  the recommended mcb in front of the spd (in my case 25A), to prevent catastrophic destruction (fire) of the spd. These values however may be close enough in my case not to be relevant. Additionally the mcb's on the  input and output of the inverter only trip on an overcurrent on the live line. An overcurrent on the neutral line won't be detected. This will not be of concern on the output of the inverter where the neutral earth bond is in close proximity, but on the input line, the neutral earth bond could be 500m away and on a different earth point, more than enough for lightning to induce a damaging spike.

https://www.lsp-international.com/why-install-a-scb-surge-circuit-breaker-in-front-end-of-spd-surge-protective-device/

https://www.ecmweb.com/power-quality-reliability/article/20886952/the-basics-of-using-circuit-breakers-with-surge-protectors

I am not sure of any South African regulations concerning the use of circuit breakers immediately before an spd, but I do know that the UK regulations specifically require such a device if the spd does not have one built in.

All of the literature I have read shows the spd mcb to be immediately before the spd, not on the earth line as shown in the Sunsynk documentation. I can only surmise this is because they want to maintain a level of protection if only one line of the spd gets damaged by a spike. 

Thanks for the all the input, I have done a lot of reading up on the matter, but still have not been convinced either way. However given the low cost of mcb's relative to the equipment, I might just go with the configuration I posted above.

@Vassen, I didn't include a main switch between the changeover and essential loads rcd as the SPT240 has a centre off position. I am not sure if this is sufficient.

Edited by ianm
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  • 4 months later...

Hi Ianm,

Have you installed your inverter??

I'm currently going through this planning phase.  I have my 5kw Sunsynk and Hubble AM2 batteries.   My wiring diagram is similar to yours.  Just wanted to know if it all worked out well (if you installed).

One question I still have, the Neutral Earth Bond Contactor, I see you have the Earth as going to the DB Earth, did that work fine.  Also, is installing the Neutral Earth Bond Contactor a requirement in SA??  I notice @Leshen also always install these.

Some advice on this would be welcome.

Regards

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@Tariq and @ianm

I refer to Ianm's diagram and the following as per the Sunsynk Manual:

image.png.2573366c3f6ece9ea8b46d1dc6d8fa7e.png

Question to you guys, do you have the neutral bonding on your systems as per this diagram??

Per Ianm's diagram I do not notice that drawn in.

And if you have the neutral bond, did you make the bond at the inverter or in the separate DB close to the Inverter (not the Main DB)??

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Hi @MyOwnPower

I have installed (almost) exactly as indicated in my last diagram. All working perfectly since April. The only change was to install a double pole mcb on the main input instead of the single pole. Not strictly necessary, but I preferred it that way. 

If the inverter does not have an automatic earth neutral bond, then the earth neutral relay is an absolute requirement. Without this, in the absence of grid power, the neutral can float at more than a hundred volts, a dangerous situation.

I used a 250V contactor for the earth neutral bridge, located in the inverter sub-db.

My recommendation is to keep the neutrals separate as per my diagram.

Regards

Ian 

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Ian,

Just one further question, I notice on your diagram that the Earth for the Earth Bond Relay says "DB Earth".  So did you connect it back to the Main DB Earth??  Do you therefore not have a separate earth spike installed for the Relays' earth connection??

Regards,

Rian 

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Hi Rian

I use the DB earth for the earth bond contactor. If I were to use a separate earth spike, it would just be near to the existing one, so there is no point.

Regards

Ian

20210816_164722.thumb.jpg.e22f03fed26193988055da3232119bc4.jpg

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  • 3 weeks later...
On 2021/08/12 at 11:15 AM, Tariq said:

As far as I know, you cannot hook the neutrals together as shown in the diagram

i installed the neutral bonding relay in a small db adjacent to the inverter, which also houses the double pole circuit breaker, surge protector and changeover switch

@Tariq  Does this mean that you do not common the neutrals on the grid and load connections?

 

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  • 2 months later...

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