Hi,

 

I am looking at buying or assembling my own AC protection box. What I need to ask is, what is the recommended size of the incoming (supply circuit breaker) and the output from inverter circuit breakers, I am trying to use all Hager breakers and change over switches and then Beny surge protection devices.

My thinking is this (I could be totally wrong the supply to the inverter could be either 32A or 35A) The Output from the inverter you could go for the same 32A or 35A is this correct? Where is the best place online to look for already assembled AC protection boxes for ideas?

 

Hi,

 

I am looking at buying or assembling my own AC protection box. What I need to ask is, what is the recommended size of the incoming (supply circuit breaker) and the output from inverter circuit breakers, I am trying to use all Hager breakers and change over switches and then Beny surge protection devices.

My thinking is this (I could be totally wrong the supply to the inverter could be either 32A or 35A) The Output from the inverter you could go for the same 32A or 35A is this correct? Where is the best place online to look for already assembled AC protection boxes for ideas?

You need a 12 way DB if you include an E/Leakage and a 63A transfer switch using 4 bays. A 40A transfer will use only 2 bays. 

Any sparky will be able to provide the wiring of the items required. 

Max continuous AC pass-through current is ~35A for the 5kw so 40A breakers paired with 6 sqmm cable works well. What are the Beny AC surge protector max operating voltage? I'd go for something around 270-280V. Perhaps consider adding both an essentials and non-essentials change-over switch - the latter being useful if you have electric non-essentials like the stove/geyser which you can then choose to manually switch to run off the inverter if necessary (e.g. for extended 24 hour+ outages that are becoming ever more common these days as infrastructure melts down...).

Layout kind of the depends where the inverter DB is relative to the main DB.

Edited September 23, 20232 yr by AlexTZA

They recommend a 32A breaker for grid and load in the manual.

 

Hi,

 

I am looking at buying or assembling my own AC protection box. What I need to ask is, what is the recommended size of the incoming (supply circuit breaker) and the output from inverter circuit breakers, I am trying to use all Hager breakers and change over switches and then Beny surge protection devices.

My thinking is this (I could be totally wrong the supply to the inverter could be either 32A or 35A) The Output from the inverter you could go for the same 32A or 35A is this correct? Where is the best place online to look for already assembled AC protection boxes for ideas?

 

 

They recommend a 32A breaker for grid and load in the manual.

 

I saw it says 40A on the grid breaker and 32A on the load breaker.

 

Max continuous AC pass-through current is ~35A for the 5kw so 40A breakers paired with 6 sqmm cable works well. What are the Beny AC surge protector max operating voltage? I'd go for something around 270-280V. Perhaps consider adding both an essentials and non-essentials change-over switch - the latter being useful if you have electric non-essentials like the stove/geyser which you can then choose to manually switch to run off the inverter if necessary (e.g. for extended 24 hour+ outages that are becoming ever more common these days as infrastructure melts down...).

Layout kind of the depends where the inverter DB is relative to the main DB.

The Beny  surge protectors says:

Voltage: 385V AC

Max. Discharge Current: 40kA

No. of poles: 2

Protection Class: Type II

Operating Temperature: -40°C to 85°C

 

On the device I can see 275v

Edited September 23, 20232 yr by Greglsh

 

Max continuous AC pass-through current is ~35A for the 5kw so 40A breakers paired with 6 sqmm cable works well. What are the Beny AC surge protector max operating voltage? I'd go for something around 270-280V. Perhaps consider adding both an essentials and non-essentials change-over switch - the latter being useful if you have electric non-essentials like the stove/geyser which you can then choose to manually switch to run off the inverter if necessary (e.g. for extended 24 hour+ outages that are becoming ever more common these days as infrastructure melts down...).

Layout kind of the depends where the inverter DB is relative to the main DB.

That sound exactly how I want to set it up, I am going to put the Stove, 2 Geysers a granny flat and a 18 000 btu aircon on a non-essentials DB. I would like to be able to change over the non-essentials as I have timers on the geysers so will be able to control them if needed. How many change over switches would I need for this and how many poles?

You need two changeover switches. One for essentials, one for non-essentials. As grid and inverter power sources are wired into both, you should get the 63A two pole Hager switch. 

I would recommend you use 40A input and output breakers (with 6mm cable) for the inverter if you want to to allow the full pass through current. The Sunsynk manuals are a bit of a spastic hit and miss sometimes. If you read the Deye 5kw manual, they recommend 40A breakers on both sides (32A for the 3.6kw version on the load side)

 

 

You need two changeover switches. One for essentials, one for non-essentials. As grid and inverter power sources are wired into both, you should get the 63A two pole Hager switch. 

I would recommend you use 40A input and output breakers (with 6mm cable) for the inverter if you want to to allow the full pass through current. The Sunsynk manuals are a bit of a spastic hit and miss sometimes. If you read the Deye 5kw manual, they recommend 40A breakers on both sides (32A for the 3.6kw version on the load side)

 

 

Wanted to ask do both of these change over switches go into the AC protection box or in their relative essential and non-essential DB boxes. Trying to work out the size of the AC protection box. Also do you need E/L in the AC protection boxes or only in the 2 Db's?

 

Wanted to ask do both of these change over switches go into the AC protection box or in their relative essential and non-essential DB boxes. Trying to work out the size of the AC protection box. Also do you need E/L in the AC protection boxes or only in the 2 Db's?

It largely depends where the inverter and DB are relative to each other. If they are relatively close (i.e. on the same wall) then the change over switches and inverter switch gear can go into a single board. If not, then you will need one board by the inverter, which contains all the inverter switch gear and one by the main DB that contains the changeover switches. You want the changeovers near the main DB so that you don't have to run an essentials AND non-essentials load cable back to the main DB from the changeover outputs. You'd probably be fine with two 18-way DIN boards if they are split and maybe a 24-way if a single. Rather make the boards a bit too large - easier to wire and add things later.

 

I have a freehand drawing of the layout and the equipment I am looking to do in the AC changeover box does this look correct? Sorry for the very basic drawing.

AC_ChangeoverDB.pdf

I would like someone to have a look at my basic drawing, what I wanted to ask is do I need the first 40A mcd (on the far left) or can I do away with this one. I have seen other boxes online that don't have this and some people say you have to have this??

@AlexTZA If you would not mind having a look please.

@Greglsh

The 40A breaker should be a double pole isolator as the main sub DB disconnect. The SPD and feed cable would be protected by an upstream breaker in the main DB.

Note, I'm not an electrician so you should have any installation checked out/signed off by one.

Edited September 28, 20232 yr by AlexTZA

Thanks @AlexTZA

 

Will definitely have a qualified person doing the install, I was also thinking that there would already be one in the "main DB" so I was thinking I could get rid of it completely. I only see a 63a isolator is that okay? Sorry I know you said you not an electrician but maybe someone else will also read this and comment if you not 100% sure.

P.S. Thanks for taking the time.

@Greglsh

I'm reasonably familiar with the SANS standards but would still go with the advice of an experienced and trusted electrician, if you can find such a person. They especially need to understand the solar and DC side of things as well which is really the most dangerous part of an installation and unfortunately tends to be rather lacking. The number of installs I've seen where a CoC was issued but the install was so obviously not compliant and/or downright dangerous is rather concerning.

Yes, a 63A double pole isolator is fine as that is just it's maximum switchable current rating. This will allow for complete and safe disconnection of power to the inverter in case of maintenance. This board should be mounted within arm's reach of the inverter. The main thing with breakers is they are normally not rated as disconnection devices, hence the requirement for an isolator where all incoming power can be disconnected. Breakers are there to limit current flow to protect downstream cabling from current that would exceed the cable rating. So generally if the size of a cable changes downward somewhere, you need a breaker to protect the cable

Happy to hear from a learned electrician master that can school us but understandably most don't like to share their trade knowledge for free.

@AlexTZA said:

The main thing with breakers is they are normally not rated as disconnection devices, hence the requirement for an isolator where all incoming power can be disconnected.

I just wonder why would they be used to protect a whole house in the main DB if not suited. Forget for a moment any PV system and it's DC side. 

Why are MCBs normally rated to be able to disconnect 2.5 or 5kA no matter what amp rating they are? 

Edited September 28, 20232 yr by Scorp007

@Scorp007

Maybe my choice of wording wasnt the best. Both isolators and circuit breakers obviously disconnect power. Breakers are for automatic safety. Isolators are used for safe permanent disconnection of parts of a circuit. Probably due to the physical construction/design of a circuit breaker, they are not considered as safe permanent isolators of power. SANS requires an isolator for safe permanent power disconnection for maintenance etc. Some switchgear is rated for isolation as well as breaking. A good example of this is the traditional CBI main switch which has a mixed white/green switch handle (white meaning breaker, green for isolator). Similarly, a CBI earth leakage switch has a green handle, indicating it is an isolator and can used as such if protected by a breaker. 

Here's a decent summary of the difference I found online: https://www.beny.com/isolator-vs-circuit-breaker/

The withstand current rating I believe you are referring to (usually 3/6kA) is the peak current the device can disconnect/withstand for a short period without being damaged, usually under short circuit conditions. Although the device would have some lower designed trip current, it needs to be able to withstand worst case conditions before tripping without failing so that it can actually trip and do its job. That's why the withstand current will be standardised (3kA residential) for breakers regardless of their rated trip current.

 

@Scorp007

Maybe my choice of wording wasnt the best. Both isolators and circuit breakers obviously disconnect power. Breakers are for automatic safety. Isolators are used for safe permanent disconnection of parts of a circuit. Probably due to the physical construction/design of a circuit breaker, they are not considered as safe permanent isolators of power. SANS requires an isolator for safe permanent power disconnection for maintenance etc. Some switchgear is rated for isolation as well as breaking. A good example of this is the traditional CBI main switch which has a mixed white/green switch handle (white meaning breaker, green for isolator). Similarly, a CBI earth leakage switch has a green handle, indicating it is an isolator and can used as such if protected by a breaker. 

Here's a decent summary of the difference I found online: https://www.beny.com/isolator-vs-circuit-breaker/

The withstand current rating I believe you are referring to (usually 3/6kA) is the peak current the device can disconnect/withstand for a short period without being damaged, usually under short circuit conditions. Although the device would have some lower designed trip current, it needs to be able to withstand worst case conditions before tripping without failing so that it can actually trip and do its job. That's why the withstand current will be standardised (3kA residential) for breakers regardless of their rated trip current.

Thanks. Yes we tend to see everybody using green handle E/L without overload but not all CBI units are green. You do get the same model with a white lever which has the overload incorporated. It us really a matter of pricing why we use the cheaper option. 

Most DIN rail E/L that I have come across have overload and E/L in one unit taking 2 spaces. 

May be just taking about samantics around some words used that do have a different meaning. 

@AlexTZA

Edited September 28, 20232 yr by Scorp007

 

Thanks. Yes we tend to see everybody using green handle E/L without overload but not all CBI units are green. You do get the same model with a white lever which has the overload incorporated. It us really a matter of pricing why we use the cheaper option.

100% correct - I forgot about the combined CBI ELR w/overload exactly for the cost reason 😄

 

100% correct - I forgot about the combined CBI ELR w/overload exactly for the cost reason 😄

You k ow our old toppies years gone buy hardly ever used the green version. Cost between the 2 were not worth it. As rules changed we used the E/L with overload as the main switch instead of having a double pole main switch and another 2 spaces just for the E/L. 

kA rating of an MCB is the maximum current it can safely interrupt in case of a short circuit. If the current goes beyond this value, the circuit breaker could be damaged. kA rating is known as the short circuit withstand capacity or ultimate breaking capacity of a circuit breaker not the bi- metal current(thermal) disconnect current.This is the reason when issuing a coc there is a specific sequence followed. 1. Loop impedance test to ensure fault currents the impedance to ground is low enough( TN- C 0.8omhs TN-CS 0.35omhs) to shunt fault currents effectively to ground especially with lightning strikes. 2. Pssc- prospective short curcuit current(ka rating).

Isolator normally interrupts both live and neutral never to be confused with mcb's it is not an isolator and visa versa unless stipulated by specs.

What earthing arrangement did the premises have? TNCS?
We perform an external earth fault loop impedance test (Ze) on the incoming supply with the earth disconnected and the installation isolated plus we do earth fault loop impedance testing (Zs) from the farthest end of any circuits we install to ensure MCB protection times are met.

Do the test at the main switch with it off. The ripple relay will not influence the reading at all. What must be tested at all the points of consumption for the COC is the earth continuity to the DB. This must comply with the regs according to the CB rating of the particular circuit. The local supplier is obligated to rectify a non-compliant loop impedance reading immediately. If you cannot get hold of a local supply employee willing to lift his backside you can resort to threats of claims for damages and the possible charges of culpable homicide being laid against said authority as well as public denounciation in the interest of consumer safety as well as fraudulent abuse of monopoly.

Edited September 28, 20232 yr by TaliaB

 

Max continuous AC pass-through current is ~35A for the 5kw so 40A breakers paired with 6 sqmm cable works well. What are the Beny AC surge protector max operating voltage? I'd go for something around 270-280V. Perhaps consider adding both an essentials and non-essentials change-over switch - the latter being useful if you have electric non-essentials like the stove/geyser which you can then choose to manually switch to run off the inverter if necessary (e.g. for extended 24 hour+ outages that are becoming ever more common these days as infrastructure melts down...).

Layout kind of the depends where the inverter DB is relative to the main DB.

@AlexTZA I wanted to ask is it okay to have a 40A MCB on the inverter output as well. I am a bit worried that this is 8.8Kw . In the manual it says 32A. I bought 2 x 40A Hager MCB's but I don't want to over current the output. Has anybody run with a 40A MCB on the 5Kw SunSynk output

 

This is from the SunSynk Manual for the 3.6 and 5Kw

4.7. Connecting the AC

 

Before connecting to the grid, please install a separate AC breaker between the inverter and the grid. Also, it is recommended that installs an AC breaker between the backup load and inverter. This will ensure that the inverter can be securely disconnected during maintenance and fully protected from overcurrent. For the 3.6/5KW model, the recommended AC breaker for backup load is 32A/40A.

Then a few lines down it has this table, so the above says 32A for 3.6Kw and 40A for 5Kw (As I read it), then the table below says 40A input and 32A output???

 

Yeah, the manual is confusing. Go with what's in the table.

 

@AlexTZA I wanted to ask is it okay to have a 40A MCB on the inverter output as well. I am a bit worried that this is 8.8Kw . In the manual it says 32A. I bought 2 x 40A Hager MCB's but I don't want to over current the output. Has anybody run with a 40A MCB on the 5Kw SunSynk output

 

This is from the SunSynk Manual for the 3.6 and 5Kw

4.7. Connecting the AC

 

Before connecting to the grid, please install a separate AC breaker between the inverter and the grid. Also, it is recommended that installs an AC breaker between the backup load and inverter. This will ensure that the inverter can be securely disconnected during maintenance and fully protected from overcurrent. For the 3.6/5KW model, the recommended AC breaker for backup load is 32A/40A.

Then a few lines down it has this table, so the above says 32A for 3.6Kw and 40A for 5Kw (As I read it), then the table below says 40A input and 32A output???

 

I don't agree with 6mm² protected by a 40 amp breaker. If you run the cable in trunking it is derated to 32 amps. I ignore that table when doing Sunsynk installations i use 10mm² with a 40amp breaker. For the small price diffrence i am sure the wires won't heat up especially in bypass and charging of the battery at the same time.

@TaliaB Thanks for the reply, so you use 40A for inverter supply and output with 10mm supply and output from the inverter to the essentials DB.