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CB Solar - PV1800 5KVA Schematic


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Hi,

 

I'm new to the forum and need some guidance. I've got a CB Solar PV1800 5KVA insatlled, understand this is a rebranded Axpert or Must inverter but struggling to get technical details of the device. I understand Voltronic is the manufacturer of the device?

City of Cape Town requires that I register my solar installation, depends who you talk to in the registration team but some rightfully sees this as an off grid system since I can only power the load from Munic supply or from PV/Batteries, I can't combine the two. Others see this as a grid tied system (Frustratingly) because it has an AC input.

For the off grid system I'm allowed to haev an auto transfer switch to switch my Solar DB from Solar to Eskom but if it's built into the inverter (as is with my model) I need to provide schematics to prove this, unfortunately Rubicon is unable to assist with the request - doubt the person even knows what I'm talking about...

 

Has anyone got any info on the device? I've found the service manual but doesn't go into the details of the internal relays, found one pic on the forum for the 1-3KVA models that actually shows the internal relay very nice but trying to explain to the munic that I found this axpert drawing for a different model but it'll work the same is just going to cause frustration...

The device is fairly old... details below

Model : PV18-5KVA MPK

S/N : MPV18-5K201506220044

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2 hours ago, booysenc said:

I've got a CB Solar PV1800 5KVA insatlled, understand this is a rebranded Axpert or Must inverter but struggling to get technical details of the device. I understand Voltronic is the manufacturer of the device?

Voltronic Power are the manufacturers of the genuine Axperts, which come by a wide variety of names. Must Power is the first of the clone manufacturers.

Quote

...some rightfully sees this as an off grid system since I can only power the load from Munic supply or from PV/Batteries, I can't combine the two. Others see this as a grid tied system (Frustratingly) because it has an AC input.

I think your only hope is to convince them that it's an off-grid system. They are in fact sold as off-grid systems.

Quote

Has anyone got any info on the device?

The model PV1800 ususally indicates that it's a clone manufactured by Must Power. See my page Do I Own a Clone?

Clone manufacturers usually don't provide technical documents of any sort, let alone a schematic or even a block diagram.

Quote

I've found the service manual but doesn't go into the details of the internal relays, found one pic on the forum for the 1-3KVA models that actually shows the internal relay very nice but trying to explain to the munic that I found this axpert drawing for a different model but it'll work the same is just going to cause frustration...

If even genuine Axperts, say a Mecer, has to provide a block diagram from a service manual with the Mecer name and model on it, that's unlikely to happen, and a lot of owners are going to be in a lot of trouble. Many of the service manuals are completely unbranded. The following block diagram, which sounds like what you want, is from a service manual that is branded Voltronic Power:

Block_diagram.png

Quote

The device is fairly old... details below

Model : PV18-5KVA MPK

S/N : MPV18-5K201506220044

The above suggests that it's one of the first clones ever made, possibly serial number 0044, made in 2015/June/22. The first warning about the Must Power clones appeared in November 2015.

Good luck finding your technical documentation; I think  you're going to need it (the luck). At least, Must Power is a fairly large manufacturer in their own right. Perhaps start at this page, with the "downloads" tab, or talk to one of the online assistants:

https://www.mustpower.com/pv1800-mpk-series-high-frequency-solar-inverter-1kva-5kva/

Edited by Coulomb
Six digit date in serial number
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2 hours ago, booysenc said:

City of Cape Town requires that I register my solar installation, depends who you talk to in the registration team but some rightfully sees this as an off grid system since I can only power the load from Munic supply or from PV/Batteries, I can't combine the two. Others see this as a grid tied system (Frustratingly) because it has an AC input. 

For the off grid system I'm allowed to haev an auto transfer switch to switch my Solar DB from Solar to Eskom but if it's built into the inverter (as is with my model) I need to provide schematics to prove this, unfortunately Rubicon is unable to assist with the request - doubt the person even knows what I'm talking about...

We've discussed this to death. Cape Town is very strict about this... right now they won't even allow Victron Multiplus inverters other than the listed Multigrid and Multiplus-II models, and these inverters have extensive certifications in other countries! If they won't allow the Multiplus, you don't have a snowball's chance in hell of signing off your Voltronic clone, unless you make it completely off-grid. The transfer switch in these units quite possibly doesn't even satisfy SANS regulations for a changeover switch and it is questionable if you are even allowed to use it as a UPS let alone an embedded generator.

You're likely going to need to remove the connection to AC-in and install a separate external approved changeover. This is my understanding.

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6 hours ago, booysenc said:

City of Cape Town requires that I register my solar installation, depends who you talk to in the registration team but some rightfully sees this as an off grid system since I can only power the load from Munic supply or from PV/Batteries, I can't combine the two. Others see this as a grid tied system (Frustratingly) because it has an AC input.

There is no confusion. 🙂 

In very simplistic terms: (as we have had this chat over and over)
If you connect any UPS / Generator to any DB board you need a CoC that says it meets the regulations.
Have solar panels, then you have two options: Grid-tied or Off-grid.
Off-grid you must register the panels and show CoCT that your inverter is feeding separate circuits, never your DB.
Grid-tied you need a CoC and engineering report when registering your inverter.

And if you have an approved inverter with panels connected to the DB and it has batteries, like me, then jury is out at this moment in time of what else.

The bottom line: If your inverter is not on CoCT's list, irrespective of the make, keep us posted on how you got it approved.

See here: Is your system legal? Capetonians have till 31 May 2019 to register their systems

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I agree but off grid could also supply my inverter DB which then supplies all my circuits in my house.

 

Main DB can supply power to the transfer switch and that then selects if my inverter DB is supplied from Eskom or inverter, not both (hence still off grid as its output is never connected to the grid), just need to know how I can prove my inverter has this changeover built in, or just spend a few rand and install whatever is approved to do the auto chopover (hate spending money if it's not needed)

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1 hour ago, The Terrible Triplett said:

never your DB

No, it's perfectly allowed to feed your main distribution board from an inverter... as long as the grid is completely disconnected at that point, in other words, the changeover switch must be installed before the main DB. Or you need to split the DB so your backup loads are completely separate, and then the same applies: That second half is either on the inverter or on the grid, but cannot possibly be connected to both.

1 hour ago, booysenc said:

need to know how I can prove my inverter has this changeover built in

If the changeover complies with SANS 60947-6 or IEC 60947-6, then you're done. But so far I have not seen a single one with such certification. It seems to be bundled with something else, and it is simply too expensive to buy all these documents to try and figure it out. At a minimum, it needs some kind of safety paperwork, and the Axpert and its clones has none. Nothing. Nada. So we know there is a changeover in there (obviously... empirically proven), but there is no certification as to its quality.

1 hour ago, booysenc said:

spend a few rand and install whatever is approved

@ebrsa wrote about this, he says he will likely install an approved changeover. They cost around 7k. About as much as the inverter itself.

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@plonkster the Socomec 9323 2006 transfer switch from http://www.em.co.za/Home/Load-Break-Changeover-Switches/#9  will handle 63A and is the smallest and cheapest remote control transfer switch I have found so far.  That is if you call the price of R10758.54 Vat included cheap. It does seem to have the appropriate certification though, IEC 60947-6-1. If anyone can point me to a less expensive alternative I would appreciate it.

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1 minute ago, booysenc said:

can I buy solid states relays to switch?

The disconnect must be a physical contact.

It must be interlocking, in other words you must have a pair of these switches, and it must be impossible for both to be on at the same time.

You must switch both live and neutral.

Changeover must be break before make: You must disconnect the grid first, and only upon proper feedback from that switch that it is really open are you allowed to close the inverter-side switch.

Also, solid state relays are generally Thyristors with an opto-isolator for driving it. Thyristors can suffer from unintentional triggering (good designs usually include a snubber circuit of some sort), so I doubt it will be good enough. Even if you do manage to electrically interlock two of them, you cannot guarantee interlocking.

Short answer: No.

Consult an electrician, but I still think two physically interlocking contactors with the right current rating will be sufficient, and should cost about half of the Socomec switch. Eg, ABB has very nice hardware that you assemble almost like lego (though note in this video it is wired for reversal of a 3-phase motor, so ignore the bit between 1:50 and and 2:20. Also see this one from around 2:10 onwards to explain the theory.

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spoke to City of Cape Town, the response was that they don't like contactors since the contacts can burn and remain closed (applicable to any switch basically) - really think they are just trying to be difficult.

my follow up question was what can I use and the response was "we only review and approve the application, we don't know what's out there on the market" 

round and round we go...

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1 hour ago, booysenc said:

they don't like contactors since the contacts can burn and remain closed

Yes, but then the _other_ contactor cannot engage, because its auxiliary N/C contact remains open, plus the mechanical lock-out between the contactors ensures that the grid remains disconnected. Which is the whole point...

1 hour ago, booysenc said:

we only review and approve the application, we don't know what's out there on the market

The guys doing the paperwork are not trained electrical engineers by the looks of it. Makes sense too... those guys are too valuable to stick behind desks 🙂

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Based on all the many informed views thus far expressed, it would seem to me that if one wishes to use an Axpert inverter in CofCT and need grid power at times, there is no other choice than to install a transfer switch such as the Socomec I referred to earlier. So far there does not appear to be a recommendation of any other option that may pass the certification tests. It may very well also apply to me in Swartland but that is a matter I have yet to determine. And I would ask again, does anyone have a less expensive solution perhaps.

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9 hours ago, phil.g00 said:

It most have been an approved item since the year dot everywhere they use motors.

It's used for star/delta starters too. If your interlocking fails you end up with a dead short over all three phases. My point: This is not rocket science, it is very well understood by every electrician, because it is used for things like motor starters and reversers. It's heavy duty and even if somehow it does get stuck... well then the other side can't engage.. which is the bloddy point of the exercise.

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24 minutes ago, booysenc said:

Could probably just use a 2NC 2NO 63A contactor too?

There is some sort of reason why this is not good enough. I spoke with @anotherbrownbear about this before, but I cannot remember if we ever came to a conclusion.

Edit: The Schneider FAQ says you must use two. Haven't yet found any other info on this.

Edited by plonkster
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Does anyone know if there is a standard that says contacts must break before make unless otherwise specified?

Still working on the idea of 2NC 2NO contacts, I don't need electrical or mechanical interlocking since it's only one device, if the contacts are fused together I won't be able to change the state of the device in any case.

 

But... the manufacturer doesn't explicitly state the contacts will for a brief moment all be open while being energized/de-energized, was hoping if it complies to whatever iec standard that the break before make is included in that standard

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41 minutes ago, booysenc said:

Does anyone know if there is a standard that says contacts must break before make unless otherwise specified?

It's in SANS 10142-2-1, for UPS installations. Since this inverter is a UPS utilised in an SSEG setup, it has to comply with the UPS rules in SANS.

44 minutes ago, booysenc said:

Still working on the idea of 2NC 2NO contacts

I am pretty sure that will not be good enough. About 82%. I made that up, but it is close. There is a reason why every howto/youtube video explains how to do this with two interlocking contactors (it is because everyone does it that way).

I think the reason might be that there is no feedback mechanism. You're supposed to open the grid, and only when you get feedback that the grid connection is indeed open are you allowed to close the alternative supply's connection. This happens automatically with the auxiliary contacts on a two-contactor setup, but not with a single one.

There is also another difference: With a two-contactor supply there is a natural "both disconnected" position when both contactors are de-energized. Not so with a single one.

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