Victron setup - wiring the AC

[Vagabondrobb]

Hi people,

I posted on here a good few months ago (see Solar Predicament) regarding advice around MCS and a 10kw ground mounted solar array I built (naively hoping a solar engineer would do the rest). Upshot is that because I built the array I could not get an MCS qualified installer to finish the job (with G100, which is what the DNO offered), and Scottish renewables insisted that there was no way to G100 (or in any other capacity) without MCS. I considered switching to Octopus but they could not guarantee non MCS connection before investigating, for a fee of £250. They also required the G100 to be approved, costing me another £750. At this point I didn’t fancy parting with a grand with no guarantee of getting connected.

As a solution, Bimble solar (based in Brighton) designed a Victron ESS system that would run in parallel to the grid, using a smart solar RS 450/200, 2 x 4.8 pylontec batteries, a Cerbo gx and 2.4kw multiplus II. As it would generate below the 3.6kw threshold, it would not be subject to restrictions/G99 etc. Not ideal, but I will get plenty of power from the batteries, and anything over 2.4kw will be supplemented by grid. I will probably add another Multiplus II further down the line (and not tell anyone).

I’ve hooked everything up DC side and all seems to be working as it should. I now need to hook the multiplus AC in/out to the mains, and install the meter (which communicates with multiplus/Cerbo. I’m quite comfortable doing the DC stuff, but I’d rather someone qualified did the AC stuff.

The thing is I live in the middle of nowhere and all electricians within a reasonable distance have either let me down or don’t have any solar knowledge and are reluctant to do the job. It’s not a big job at all - the solar gear is mounted in the hallway right next to the main box.

I have a couple of questions:

A) if I cannot find an electrician (and I’m trying my damned hardest), is hooking up the AC something that could feasibly be done by someone fairly sensible and competent? I’m guessing the fact I’m asking the questions means no, but hey.

B) Can I earth the DC gear (inverter etc) to the mains earth? Panels are mounted onto timber framed structure, so I’m assuming they are ok. I read that some people spike them, but it’s probably not necessary.

The answer is probably that I need an electrician, but no harm in asking I suppose!

Sorry for being long winded,

Cheers,

Robb

 

[johnb2713]

I have a couple of questions:

A) if I cannot find an electrician (and I’m trying my damned hardest), is hooking up the AC something that could feasibly be done by someone fairly sensible and competent? I’m guessing the fact I’m asking the questions means no, but hey.

In reality I would say yes but the experts on here will probably say officially no. You've done the DC work, that's the hard bit and you're still around to tell the story, taking sensible precautions you have L,N & E to connect at either end. Maybe one of the experts on here could help you?

B) Can I earth the DC gear (inverter etc) to the mains earth? Panels are mounted onto timber framed structure, so I’m assuming they are ok. I read that some people spike them, but it’s probably not necessary.

The inverter is both AC and DC device. The earthing of the inverter can get interesting if you intend to use the EPS output, your grid would be disconnected and dependent on how your earth connection is derived you can potentially end up with no earth.

The answer is probably that I need an electrician, but no harm in asking I suppose!

Ideally yes but they are normal (possibly?) human beings, nothing exceptional about them. If you two hands, two feet and only one head you can probably manage to get it up and running safely.

Any of you guys out there in Robb's area could lend him a hand?

 

[wgoldie]

I self installed a Victron multiplus 2 and Seplos 15.4kWh battery and I did the all the wiring myself. As johnb2713 says the DC side was a bit more involved. I had ran the ac wiring from the inverter to a new consumer unit I had fitted in garage. In my case the ac wiring circuit was only about 1.5mtrs long but I did do continuity and insulation resistance tests. I earthed the battery and inverter to the house earth. I am not using the Victrons maintained AC output so don’t have an earth rod. I may go down that route in the future.
I did find a local electrician to connect up the AC to the consumer unit but to be honest I would have done it myself if I didn’t find anyone. He just connected the cables to the breaker and switched it on.
A second pair of eyes to look over it and confirm the circuit breaker and cable sizes was worthwhile though.
I did the G99 paperwork (with help from this and Victron forum members). And although SPEN asked - “Once you have connected the PV and Battery Storage units, please send me back your commissioning documentation from your MCS Installer by replying to this email.” I just put “self installed” and they were happy with that. I should add that our existing PV was installed by a MCS contractor over a year ago but I got the impression that SPEN looked upon this as a new PV/battery installation.
Don’t know if this helps your situation but good luck. Dealing with SP isn’t easy.

 

[Vagabondrobb]

In reality I would say yes but the experts on here will probably say officially no. You've done the DC work, that's the hard bit and you're still around to tell the story, taking sensible precautions you have L,N & E to connect at either end. Maybe one of the experts on here could help you?


The inverter is both AC and DC device. The earthing of the inverter can get interesting if you intend to use the EPS output, your grid would be disconnected and dependent on how your earth connection is derived you can potentially end up with no earth.


Ideally yes but they are normal (possibly?) human beings, nothing exceptional about them. If you two hands, two feet and only one head you can probably manage to get it up and running safely.

Any of you guys out there in Robb's area could lend him a hand?

In reality I would say yes but the experts on here will probably say officially no. You've done the DC work, that's the hard bit and you're still around to tell the story, taking sensible precautions you have L,N & E to connect at either end. Maybe one of the experts on here could help you?


The inverter is both AC and DC device. The earthing of the inverter can get interesting if you intend to use the EPS output, your grid would be disconnected and dependent on how your earth connection is derived you can potentially end up with no earth.


Ideally yes but they are normal (possibly?) human beings, nothing exceptional about them. If you two hands, two feet and only one head you can probably manage to get it up and running safely.

Any of you guys out there in Robb's area could lend him a hand?

Thanks John,

It does seem like a pretty easy job, and I’m confident that I could do it no problem. I’m happy wiring in new circuits - lights and sockets etc, and wouldn’t think twice about most things. it’s just that I’m going to be dealing with the main supply - not something I’ve ever touched before, so I’m cautious. I guess it’s no different technically speaking.

In terms of EPS - we have a backup diesel generator on a manual transfer switch, so I’m not planning on using the other AC out on the inverter as of yet. If I do I will probably just have a double 13 amp socket for powering small devices rather than it powering a new circuit for essential loads.

 

[Vagabondrobb]

I self installed a Victron multiplus 2 and Seplos 15.4kWh battery and I did the all the wiring myself. As johnb2713 says the DC side was a bit more involved. I had ran the ac wiring from the inverter to a new consumer unit I had fitted in garage. In my case the ac wiring circuit was only about 1.5mtrs long but I did do continuity and insulation resistance tests. I earthed the battery and inverter to the house earth. I am not using the Victrons maintained AC output so don’t have an earth rod. I may go down that route in the future.
I did find a local electrician to connect up the AC to the consumer unit but to be honest I would have done it myself if I didn’t find anyone. He just connected the cables to the breaker and switched it on.
A second pair of eyes to look over it and confirm the circuit breaker and cable sizes was worthwhile though.
I did the G99 paperwork (with help from this and Victron forum members). And although SPEN asked - “Once you have connected the PV and Battery Storage units, please send me back your commissioning documentation from your MCS Installer by replying to this email.” I just put “self installed” and they were happy with that. I should add that our existing PV was installed by a MCS contractor over a year ago but I got the impression that SPEN looked upon this as a new PV/battery installation.
Don’t know if this helps your situation but good luck. Dealing with SP isn’t easy.

Thanks, always interesting to hear others experiences! Out of curiosity, what output is your Multiplus II?

And I wholeheartedly agree - dealing with SP certainly isn’t easy!

 

[wgoldie]

It’s the 5kVA version.

 

[johnb2713]

It’s the 5kVA version.

I have the 5kW Multiplus II GX, I was staggered to find on one occasion it was supplying 9kW, it continued for a few minutes before complaining about temperature. Amazing inverters, very well built and very heavy!

 

[binky]

Wiring into your consumer unit is not that hard, but a little duanting if you have not done this before. Just switch the entire board off before doing that. Strictly speaking it's anew curcuit, and notifiable work under Part P of building regs in England and Wales, and not something I would recommend for amateurs. However, if you can't get a sparky....


What size cable are you thinking if using?

 

[wgoldie]

I have the 5kW Multiplus II GX, I was staggered to find on one occasion it was supplying 9kW, it continued for a few minutes before complaining about temperature. Amazing inverters, very well built and very heavy!

Do you have “power assist” enabled. Mine seems to max out at 4.4kW. I am using AC IN 1 only, which may be the issue. Not a big deal as we seldom peak over 4.4 for any length of time.

 

[johnb2713]

Do you have “power assist” enabled. Mine seems to max out at 4.4kW. I am using AC IN 1 only, which may be the issue. Not a big deal as we seldom peak over 4.4 for any length of time.

No I dont.

Its just setup as a grid tied inverter with 14 kWh of LifeP04 batteries feeding it. The fans were absolutely screaming and the transformer noise was loud (ish) but it did it.

 

[Vagabondrobb]

Wiring into your consumer unit is not that hard, but a little duanting if you have not done this before. Just switch the entire board off before doing that. Strictly speaking it's anew curcuit, and notifiable work under Part P of building regs in England and Wales, and not something I would recommend for amateurs. However, if you can't get a sparky....


What size cable are you thinking if using?

Well, I’ve made the decision to do it!

I knocked up a diagram of everything as it currently stands - attatched.

Plan is to connect the Multiplus to only the house fuse board (we have another board for our annex and a few other consumer units for various outhouses etc, but the multiplus is far too small to power everything. There shouldn’t really be an occasion when the house box will pull more than 40A.

Anyway, I’m going to rejig everything eventually to maximise usage.

My thinking is to connect the house board directly to AC out 1, and to connect AC in to the main supply via a 32a breaker. I also have a E1112 meter which I’m guessing would be situated either before or after the breaker on the AC in? I gather that it can be used in a combination of ways.

Thinking of using 10mm2, possibly bigger to the breaker, in case I want to add another multiplus at some point.

 

[michael8554]

When Off-Grid on the generator, the earth is still connected to the Earth/Neutral TN-C-S connection on the house 80A grid supply ?

 

[Vagabondrobb]

When Off-Grid on the generator, the earth is still connected to the Earth/Neutral TN-C-S connection on the house 80A grid supply ?

The schematic is a visual representation of what I can see, and I knocked it up quickly for reference. It may not be 100% accurate! The generator is a portable Hyundai 6000se, and it is grounded.

 

[johnb2713]

My thinking is to connect the house board directly to AC out 1, and to connect AC in to the main supply via a 32a breaker. I also have a E1112 meter which I’m guessing would be situated either before or after the breaker on the AC in? I gather that it can be used in a combination of ways.

It depends on how you intend to operate the inverter. The way you suggest would mean that all of the house supply goes through the inverter, the Multiplus does have the circuitry to do this.
I run mine as a grid tied inverter, to do this you only need to connect AC In, the Multiplus can then take energy in to charge the batteries and it can also give energy out to minimise the grid import (my grid import runs at zero). The transition between inverter and grid is completely seamless, the energy out of the inverter via the AC INPUT connection back to your CU.

 

[Vagabondrobb]

Thanks John.

So the AC IN is bi directional! That actually makes a lot of sense with the ET112 meter.

I came across this video on the various wiring options for the Multiplus II - it's worth watching, especially if anyone is thinking of getting a multiplus II:

So I think my plan, for now, is to have the ET112 next to the main switch, and feed the Multiplus AC IN to a 32A breaker on the main board (referred to in video as "single legged" mode). So the multiplus basically supplements the grid supply with solar. I'll then have a small set of circuits on AC OUT that the batteries can power via inverter in event of a power outage.

Cheers,

Robb

 

[johnb2713]

Thanks John.

So the AC IN is bi directional!

Correct

So I think my plan, for now, is to have the ET112 next to the main switch, and feed the Multiplus AC IN to a 32A breaker on the main board (referred to in video as "single legged" mode). So the multiplus basically supplements the grid supply with solar. I'll then have a small set of circuits on AC OUT that the batteries can power via inverter in event of a power outage.

I installed a 2nd Consumer unit to supply my essential items and I have added an automatic changeover switch that changes the consumer unit supply to the EVS outputs in the event of a grid failure.