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jetstram61 avatar image
jetstram61 asked

AC in, MultiPlus 2 ESS

Hi,

We are looking to install an ESS with a Multiplus 2 48/3000.

We already have a 4KW grid tied solar array, so reading the ESS manual it looks like a parallel AC grid tied option is best for us.

We have an electrical engineer coming to look at our existing set up and install the ness components and wiring.

When operating in ESS mode I believe the only AC connection to the MultiPlus required is the AC IN (parallel AC grid tied). I assume therefore that the Multi uses this AC to charge the batteries with XS solar, and then in inverting mode it uses the same AC connection to push power back to the consumer units attempting to balance the loads and not draw from the grid ?

If this is correct and if we also wanted to provide head space for an second Multiplus in the future would a 32Amp supply (with the ness isolators / fuses) be suitable for AC in ?

I have a basic understanding of the system but would like a bit more knowledge so I can understand the options when chat with the engineer.

Thanks for reading this

ESS
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2 Answers
Jason - UK avatar image
Jason - UK answered ·

If you are using the Multiplus with AC in only connections for ESS, you will need either a ET112 meter on your incoming supply, or a Victron 100A current sensor. I recommend the 100A current sensor as its more reactive, cheaper to buy and easier to fit onto you meter tails. The only downside to your set up will be if you lose power to your property, you will not be able to use battery backup to power the property, but it does give a very simple way to provide a ESS to an existing system. In short, what you are proposing is the same as most other ESS out there, a single connection onthe AC side for invert and charging.

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Jason - UK avatar image Jason - UK commented ·
Are you going for a Multiplus II GX for a non GX version with the separate Cerbo GX device?
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jetstram61 avatar image jetstram61 Jason - UK commented ·
Thanks Jason. We were looking at a non GX model as I'm quite handy with the raspberry pi so am in process of looking in that as a GX option...

I was coming to the same conclusion ref the current sensor - the only issue being it will be about 15m away from the Multi and I'm not sure its extendable that far - maybe you know more ?

Regarding the AC connection - do you think a 32 Amp line will be fine for 2 Multi's in parallel at a later date ?

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Jason - UK avatar image Jason - UK jetstram61 commented ·

Is the 32A the limit of the breaker or the limit of the cable size?

If its on a 32A breaker, as an example, I have a 5kVa 48v Multiplus II unit and when I was first commissioning the unit, my unit would trip a 63A Type B breaker due to the inrush when first powering on the unit. After several quick resets of the MCB, it would stay on but each time I allow the unit to power off for a period of time, if I powered the Multiplus from DC (as you are meant to - if you have enough DC charge that is) im fine but if I did not have enough charge in the batteries, turning on the AC to power the multi not be problematic on a 32A breaker. With correct use you should be ok.

If the cable is rated for 32A, you should be fine but double check with your installer as several factors can effect the rating of a cable like level of containment, buried in a wall and or insulation, length, etc.

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jetstram61 avatar image jetstram61 Jason - UK commented ·
Thanks again for the info.

Regarding the 32A question - I should have phrased that better. - When the engineer asks me what size of supply would he want me to fit, I just want to give him the correct answer ! So basically the question would be what size is best ?

Our house was doubled in size a few years back and we have 2 consumer units connected to each other with a very heavy wire (looks to be the same size as the the tails going into the original unit) - The Multi(s) will sit in the attic very close to this cable so in an ideal world I could ask the electrician to parallel connect the AC into this cable -( unless there is some legislation stopping this ) - so I suppose no real limit on breaker or cable size but just want to ask him to put the most suitable option in ? - sorry for the questions


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Jason - UK avatar image Jason - UK Jason - UK commented ·
@jetstram61 Not a problem asking questions mate, we all have to learn. If you only ever turn on the inverter with a fully charged battery pack before turning on the AC, you'll always be fine with a single unit as I think the 3kVa unit is a max 22amps. 2 units and you could have a incidental current of 44amps which will cause a 32 amps Type B to trip. You wouldn't be able to keep 44amps going for long before the inverter overheats so 32amp would be on the edge of a realistic situation. Really you need your installer to be advising you on correct cable sizes and the required correct size of any safety device. Remember the MCB is there to protect the supply to the appliance/s, not the appliance itself.


I stated with a 40A breaker on my 5kVa which was useless in dealing with the Multiplus, so I increased the cabling to 10mm and a new 50A break but still it tripped when I turned on the multi so 63A type 2 and its appears trouble free now.

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jetstram61 avatar image jetstram61 Jason - UK commented ·
Thanks again - and totally agree with your comments ref the installer. I just like to have done my homework a bit so I understand better when they make their suggestions. 10mm was the size in the back of my head so thats good to hear. One last question with the current sensors - can I use a secondary sensor for the PV output ? I believe the Grid sensor goes straight to the Multi but can the PV one go to the GX (or Pi). Or would it be best to use an ET112 for the PV (the Solar Inverter will be sitting very close to the Multi so no access or 'cable extension' issues !
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Jason - UK avatar image Jason - UK jetstram61 commented ·
@jetstram61 I have my 100A Victron current sensor on my incoming tails, then another CT sensor on the PC output which is the 40A Victron CT senor. As I have the GX version of the Multiplus II, I have my 40A sensor connected to Aux2 on my GX unit. If you went for the 40A sensor as well, I believe you connect that to the Aux input. The ET112 defiantly goes in to the GX USB via a RS485 to USE device. I have the ET112 as well but stopped using it because of how delayed the response is to controlling the ESS. When a clous comes over the PV array, it takes a moment for the ET112 to react therefore you end up dumping energy onto the grid in the KW's for several seconds.
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jetstram61 avatar image jetstram61 Jason - UK commented ·
Perfect thanks. I'll change to current sensors from the ET112's on the order - cheaper as well !
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jetstram61 avatar image jetstram61 Jason - UK commented ·
Hi again Jason. I have another question that's come up. In order to view the battery SOC on the remote console will we need a smart shunt, or does the multi measure this internally and feed the display ? I know a smart shunt is needed when any other system is also charging the batteries such as more PV via an MPPT straight to the batteries but the question is do we need one beforehand so we can see the SOC on the screen.

Thanks

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Jason - UK avatar image Jason - UK jetstram61 commented ·

@jetstram61 Im running my Multiplus II 5kva unit on a pass-though ESS arrangement also with loads on the AC in1 side of things as I want the UPS protection on my critical items in the house - server, AS (compressor doesn't like power cuts), PC, and I also have my PC on AC out1 so in the event of a supply failure, I can keep 95% of my appliances operational in the house with power coming from the PV still.

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Jason - UK avatar image Jason - UK jetstram61 commented ·
I wish I went for the non-GX version of the Multiplus, more so knowing I could have gone massive by using a RPi. I use those things for so many applications around my house.
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jetstram61 avatar image jetstram61 Jason - UK commented ·
Yes, they are great little things. We run home assistant on one and have a couple of others round the house. One runs volumio which is really good !
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h-copter avatar image h-copter jetstram61 commented ·

@jetstram How did you end up measuring the grid current? CT or meter? If CT, did you extend the cable to 15m? How is it all working? Thanks


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ian-mcv avatar image
ian-mcv answered ·

Hi,

Sorry to hijack the thread but Im looking to do the same thing I think. multiplus-ii-gx-wiring.jpgThis is roughly my idea of how the wiring will go. I think I did fing something in one of the manuals somewhere saying that the AC IN connection was bi-directional but cant find it again.

Does it look ok?


multiplus-ii-gx-wiring.jpg (122.1 KiB)
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