Hi

I am busy installing a 5kw Sunsynk inverter about 30m from my main house DB and I am not sure about the regulations regarding wiring to and from the inverter.

According to my calculations 5kw at 220v would draw max 23A.

Would it be allowable and would it be legal to use 6mm twin and earth rated at 43.6A for the wiring to and from the inverter from my main DB?

49 minutes ago, Adri76 said:

Hi

I am busy installing a 5kw Sunsynk inverter about 30m from my main house DB and I am not sure about the regulations regarding wiring to and from the inverter.

According to my calculations 5kw at 220v would draw max 23A.

Would it be allowable and would it be legal to use 6mm twin and earth rated at 43.6A for the wiring to and from the inverter from my main DB?

The 1st pass is current and 6mm is fine. The 2nd test is the voltage drop over the distance to inverter and back and in this case the voltage drop is 7.7% and AFAIK the allowed drop is still only 5% at any point of the installation. Even 10mm will have a 5.3% drop and the drop to the end point of supply has not been taken into account. 

Current installation guys can correct me on this. Tables are different and mine only shows 38A for 6 sq mm. 

Edited February 11, 20233 yr by Scorp007

1 hour ago, Adri76 said:

Hi

I am busy installing a 5kw Sunsynk inverter about 30m from my main house DB and I am not sure about the regulations regarding wiring to and from the inverter.

According to my calculations 5kw at 220v would draw max 23A.

Would it be allowable and would it be legal to use 6mm twin and earth rated at 43.6A for the wiring to and from the inverter from my main DB?

The Sunsynk 5kw pass through current is 35A so using 6mm twin+ earth you are almost on the limit of 38A the Surfix cable can handle. If you run 6mm twin+earth in conduit(reference method A) then the current rating is 32A. For  distance of 30 meters i would use 10mm cable with 40A curcuit breaker. Rating of 10mm twin+ earth in conduit   ( reference method A) 44A

Just remember that the supply to the inverter will be more than 5kw when the batteries are charged from the grid. (supply amps to Inverter = Load amps + battery charging) 

I also have 6mm is 38A for installation in trunking, but have volt drop of the 6mm @ 4.63% over 60 meters. 

This is still a bit confusing.

If I use a wire size calculator (I've tried a few) and enter 220v, 50A load over 30m with 3% voltage drop I get a recommended wire size of 6 awg or 4mm diameter. 

Are these online calculators wrong or am I missing something?

9 hours ago, Adri76 said:

This is still a bit confusing.

If I use a wire size calculator (I've tried a few) and enter 220v, 50A load over 30m with 3% voltage drop I get a recommended wire size of 6 awg or 4mm diameter. 

Are these online calculators wrong or am I missing something?

I will not use a generic wire size calculator from the internet. Wire manufacturers have specific specs in their catalogs. Use a reputable wire manufacturer and suppliers as the market is being flooded with sub standard cables and wires from China a big problem in the electrical industry. Any reputable supplier wil give you the cable test sheet on request. Alvern and Abedaire is reputable manufacturers. I can't understand your reluctance to use 8mm or 10mm as i would pay more now and use 16mm for future capacity.  In future should you need to upgrade from 5kw inverter to 8kw or 12kw even 2x5kw then you don't need to run an upgrade cable especially not for that distance. 

I think part of the problem is that the SANS regulations I am reading are using mm2 when stating cable sizes and I am talikng about diameter. Is the 16mm cable you are recommending 16mm2 or 16mm diameter? 

16mm2 is 4.5mm diameter.

Edited February 12, 20233 yr by Adri76

They explain the cable size thing/voltage drop very clear in the SANS code. There are a lot of factors to consider. Like, is the cable in open air, is the cable in a conduit, is it underground, is it in concrete, length of cable, copper or aluminium cable. Then very important the length, voltage and amps.

In South Africa we work with mm2. Over your distance, out of experiance I will use 16mm2 red and black single core house wire and 10mm2 earth wire in a 25mm conduit. Please stay away from normal Twin and earth unless you want to replace it in 5 years time. If you need to shoose between twin & earth and surflex, surflex is the much better option.

Surflex has a metal sheet around the live, neutral and wire. The purpouse of that sheet is to protect the live and neutral from moisture as well as act as a type of earth in case of cable damage. Picture yourself that if you cut away the insulation on twin & earth and you also cut away the insulation of the red/live wire alone. Now if you touch that bare live copper, what will hapen? The only thing that will trip is the 10 or 20 amp breaker. Then you will have a nasty shock already.

If you damage the surflex you first have to cut through the metal sheeting then you will reach the live wire making a short already. In that case it will trip the earth leacage immediately.

Thanks Sakkie, that makes a lot of sense. 

I think the only confusing part is the labelling of the locally available cable.

If you look online you will get some suppliers listing their cable in mm2 and some just mm.

I have double checked now and the length of the cable run would probably be closer to 15-20m.

I have to run cable both ways. (to and from the main DB)

Would I have to put each direction in it's own conduit or is it allowable to have both in one conduit?

 

 

Edited February 12, 20233 yr by Adri76
Correction

20 hours ago, Sakkie Swart said:

They explain the cable size thing/voltage drop very clear in the SANS code. There are a lot of factors to consider. Like, is the cable in open air, is the cable in a conduit, is it underground, is it in concrete, length of cable, copper or aluminium cable. Then very important the length, voltage and amps.

In South Africa we work with mm2. Over your distance, out of experiance I will use 16mm2 red and black single core house wire and 10mm2 earth wire in a 25mm conduit. Please stay away from normal Twin and earth unless you want to replace it in 5 years time. If you need to shoose between twin & earth and surflex, surflex is the much better option.

Surflex has a metal sheet around the live, neutral and wire. The purpouse of that sheet is to protect the live and neutral from moisture as well as act as a type of earth in case of cable damage. Picture yourself that if you cut away the insulation on twin & earth and you also cut away the insulation of the red/live wire alone. Now if you touch that bare live copper, what will hapen? The only thing that will trip is the 10 or 20 amp breaker. Then you will have a nasty shock already.

If you damage the surflex you first have to cut through the metal sheeting then you will reach the live wire making a short already. In that case it will trip the earth leacage immediately.

Getting those 3 cable through a 25mm conduit won't be fun. 

5 minutes ago, Chris_S said:

Getting those 3 cable through a 25mm conduit won't be fun. 

I am thinking of using 32mm conduit, but I am not sure if it is allowed.

Edited February 13, 20233 yr by Adri76

Why not consider a multi-core armored cable which can go in the ground without additional conduit.

It has to go in the ceiling, but I have decided to get a qualified electrician to spec and supervise the project so that I will be able to get a COC and not have any problems.

Thanks everyone for your input.

On 2023/02/11 at 10:06 PM, JacquesVDM said:

Just remember that the supply to the inverter will be more than 5kw when the batteries are charged from the grid. (supply amps to Inverter = Load amps + battery charging) 

I also have 6mm is 38A for installation in trunking, but have volt drop of the 6mm @ 4.63% over 60 meters. 

May be a stupid question. Is the AC grid charging not on the input to inverter and the load on the essential output. Thus 2 different cables? 

5 hours ago, Adri76 said:

I am thinking of using 32mm conduit, but I am not sure if it is allowed.

No limitation on the maximum size of conduit. The minimum is covered for ease of pulling in each size of conduit. 

May be someone with the K factor per wire size can place it here. 

Edited February 13, 20233 yr by Scorp007

I think maybe there is a misunderstanding with the question, I actually wanted to know if it is permissible to have the cables going to the inverter from the DB and the ones going back to the DB in the same conduit. (I'm not even sure it would be possible to get 4 x 16mm and a 10mm in the same conduit)

Yes, I think that would be best. I don't want to do the work and have to redo anything come inspection time.

I want to use a 35A breaker as that is the max passthrough current of the inverter and 10mm2, but I will see what the elec. says.

2 hours ago, Adri76 said:

I think maybe there is a misunderstanding with the question, I actually wanted to know if it is permissible to have the cables going to the inverter from the DB and the ones going back to the DB in the same conduit. (I'm not even sure it would be possible to get 4 x 16mm and a 10mm in the same conduit)

If my question earlier is answered you will know if you can. 

2 hours ago, Scorp007 said:

On 2023/02/11 at 10:06 PM, JacquesVDM said:

Just remember that the supply to the inverter will be more than 5kw when the batteries are charged from the grid. (supply amps to Inverter = Load amps + battery charging) 

I also have 6mm is 38A for installation in trunking, but have volt drop of the 6mm @ 4.63% over 60 meters. 

May be a stupid question. Is the AC grid charging not on the input to inverter and the load on the essential output. Thus 2 different cables? 

Yes, two different cables, but the supply cable to the inverter must carry both the charging current for batteries and the load current as the load will be supplied from the grid while charging. You can set the grid charging current though.

With shielded cable I guess it would not be a problem, but I suspect with unshielded cable the EMF might be a problem.

1 minute ago, JacquesVDM said:

Yes, two different cables, but the supply cable to the inverter must carry both the charging current for batteries and the load current as the load will be supplied from the grid while charging. You can set the grid charging current though.

I have gone through all the Sunsynk manuals I could find, and cannot find any reference to the max AC current the inverter could theoretically draw. (inverter/bypass/charging combined)

5 hours ago, Adri76 said:

With shielded cable I guess it would not be a problem, but I suspect with unshielded cable the EMF might be a problem.

No problem running both in the same but not sure if there are regulations against it. For PV systems AC and DC must be split but even this won't present a problem in real life. It is just comms and voice data that picks up interference when mixed with AC or DC. 

I have quite a bit of experience where AC and DC are used in the same cable with no problems. 

Just one more question: There is a N/E bond outside my house in the box where the cable enters the house.

Do I use a common neutral/earth from there for my essential loads on the inverter output side, or should I still keep the neutral on the essential loads separate from the main house neutrals and use a contactor for N/E bond?

 

On 2023/02/13 at 9:21 PM, Scorp007 said:

No problem running both in the same but not sure if there are regulations against it. For PV systems AC and DC must be split but even this won't present a problem in real life. It is just comms and voice data that picks up interference when mixed with AC or DC. 

I have quite a bit of experience where AC and DC are used in the same cable with no problems. 

Ac an Dc cables are not allowed to run in the same trunking or wireway Sans regs does not allow it. See below:

SANS 10142-1 6.1.10

6.1.10 Conductors that form part of a d.c. installation shall not be run in the
same wireway as conductors that form part of an a.c. installation