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william-croft avatar image

Existing Phoenix inverter, wish to purchase and add a MultiPlus in parallel.

I have an entirely off-grid installation with an existing Phoenix (48V/5000VA) 230V inverter and wish to purchase a MultiPlus (48V/5000VA) 230V inverter/charger to be installed in parallel configuration. The primary goal is redundancy (in case one inverter fails) and to enable charging of the batteries (if needed) from a 3kW generator (continuous 2.5kW capability). A secondary purpose would be to increase the power output capability.

I know there can be compatibility issues that have to be taken into consideration with paralleling.

The original firmware that the Phoenix inverter came with was 2624413. I have updated the Phoenix inverter from v413 to the latest v482 firmware version today, so if the MultiPlus doesn't come with the latest firmware I am more than capable of updating that to the same version.

I would be seriously concerned if a new MultiPlus didn't come with firmware starting with 26 (VE.Bus - new microprocessor, 230VAC) now, but I've cross checked the list of models document and 2624 is listed as "MultiPlus 48/5000/70-100 (+EasySolar)". It is literally the only model on that list that is 70-100 (70-amp battery charging and 100-amp AC transfer capability).

Am I correct in concluding that if I purchase a 2624 (i.e. a MultiPlus 48/5000/70-100) and update the firmware to v482, if needed, then it should be capable of being paralleled with the existing Phoenix inverter?

Second question is, if I was to purchase the MultiPlus and it failed to parallel could I instead fall back on a configuration to feed the AC output from the Phoenix into the AC input of the MultiPlus to increase the output capability?

I already have a changeover switch in the configuration to change the house AC supply from the Phoenix to the generator and could easily reconfigure that output to feed into the AC input of the MultiPlus instead. I'm not sure how the MultiPlus would handle that changeover from the Phoenix to the generator, I suspect it wouldn't too well, and it might get more complicated if the "Dynamic current limiter" setting needed to be enabled for the sake of the generator.

In the worst case scenario, I would feed the Phoenix output into the MultiPlus input and keep the inverters and generator separated by the changeover switch. This would provide the redundancy and increase in power capability. In this case, if I wanted to meet the goal of charging the batteries I would need to purchase a Skylla 48/50 TG Charger, which is practically doubling the cost as it's price isn't much different from the MultiPlus and it'd probably more beneficial to just buy another MultiPlus and just use that purely as a charger (if it can be configured that way). Really don't think I could stretch the budget to handle this.

My preference would be to parallel the Phoenix and feed the generator into the MultiPlus charger, this would eliminate the need for the changeover switch entirely and I think more likely to meet all the goals, but it would also be nice to know that even if I do everything right, there was a fallback position if the paralleling did not go as planned.

Happy to take advice if anyone has a better option to achieve the goals.

MultiPlus Quattro Inverter ChargerPhoenix Inverterparallelmultiplus in parallel
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For further reference, the document "VE.Bus firmware versions explained" located at https://www.victronenergy.nl/upload/documents/manual-VE.Bus-firmware-versions-explained-EN.pdf clearly states:

"Units with old and new microprocessors can be used together in parallel and three-phase installations without any problems."

This says that the first two digits don't have to be the same at all, one could be 19 and the other 26 (as these are the two family groups for 230V), or 20 and 27 (120V family). This statement actually undermines the commonly quoted advice that the units must be identical. Obviously, if you can parallel units with different microprocessors then the units are not identical, and the test in the software for whether units are identical has to be at some other level than merely matching hardware. The firmware package would be the obvious candidate for matching "indentical" units.

The table in the document then shows that the model number must be identical, which is the 3rd and 4th digits in the firmware number.

Then while as the last three digits are the firmware number must also be identical, that is software that can be updated easily to match, so it is of no real consideration when purchasing the unit. The only consideration here to make is that it must be the same on both units, so that if you were actually running old and new microprocessor units then you would need to use either 150 to 199, or 2xx firmware:

150 to 199 are firmware versions with Virtual Switch functionality for the old and the new microprocessor.
200 to 299 are firmware versions with Assistant functionality, for old and new microprocessor

Anyway, I'm getting a price on the MultiPlus now and if its feasible I'll tackle this and let everyone know how it goes.

Absolute worst case is I just can't get them to go together at all and I retire the Phoenix to storage for redundancy in case the inverter fails. Then we just continue life as it is, scheduling the higher power appliances so they aren't run at the same time. This will allow me to fulfil both of the primary goals, redundancy and charging the batteries from the generator. Not really a worst case at all.

5 Answers
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

tl;dr

No, you can't parallel a MultiPlus and a Phoenix.

https://www.victronenergy.com/live/ve.bus:manual_parallel_and_three_phase_systems

Parallel/three phase is only possible with same units. You can't combine 26XX with 26YY.

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Thank you for taking the time to respond.

As indicated in my original post, the first 4 digits of my Phoenix inverter's firmware are 2624, which under Victron's own list of models is "MultiPlus 48/5000/70-100 (+EasySolar)". I would be buying that exact model of MultiPlus, the firmware numbers would be identical 2624xxx and 2624xxx, not 26XX with 26YY .

There is also the matter of my 2nd question, can I feed the output of the Phoenix into the input of the MultiPlus to achieve an increase of the total power output instead?

uenpia avatar image
uenpia answered ·

You can not parallel a Phoenix and a Multiplus!

According to the manual: Parallel, split- and three phase VE.Bus systems [Victron Energy]

All units in one system must be the same type and firmware version, this includes same size, system voltage, and feature set. The type is indicated by the first four digits of the firmware version number.

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Thank you for taking the time to respond.

As indicated in my original post, the first 4 digits of my Phoenix inverter's firmware are 2624, which under Victron's own list of models is "MultiPlus 48/5000/70-100 (+EasySolar)". I would be buying that exact model of MultiPlus, the firmware numbers would be identical.

There is also the matter of my 2nd question, can I feed the output of the Phoenix into the input of the MultiPlus to achieve an increase of the total power output instead?

Phil Gavin avatar image
Phil Gavin answered ·

I don't know the answer to your question, but I think it is a valid one, not to be summarily dismissed.

I had the experience of being unable to parallel two Phoenix 48 5000's because the first four digits of the firmware were different. When I investigated further, I found out that both these chips were in fact Multiplus chips. The firmware difference was related to a different size transfer switch on the Multipluses.

Of course, neither of the Phoenix's actually had transfer switches, so I thought the distinction quite absurd. (It is a thread on this board, somewhere).

In any event, it led me to be of the opinion that the Victron software is purely firmware number driven. That the software doesn't know the difference between a Multiplus and a Phoenix of the same firmware. I have never tested this theory, but I think it is certainly not to be ruled out as an option with a waive of the hand.

You will still have to use units of the same firmware, for the Phoenix and the Multi, and I reckon you would have to adjust current limits and things accordingly. I think it might work.

If you try it and it works, (or doesn't) please report back with your findings. It is something I have wondered about for a while.

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Thank you for your response.

I think you may be right about it being driven by the firmware number as everything I have looked into about it refers back to the firmware numbers.

Nothing that I have looked at from all of the Victron documentation tells me that what I want to do can't be done, but I did see your post, and it led me to consider the second option if it couldn't be paralleled. That is, feeding the AC output of the Phoenix into the MultiPlus to increase the overall capacity. I know you can't do that on the Phoenix as there is no AC in, but I'm not insane for thinking that the MultiPlus can do that am I? From what I understand, the MultiPlus reads the AC input and synchronises with the Voltage and Frequency, to enable it to add its own AC power during the transfer, effectively increasing the total power output. If it can do this for a generator input, I figure that it should have no problems working with a Phoenix output that I suspect would be cleaner.

According to the MultiPlus manual, it can accept Input frequency range 45 - 65 Hz and Input voltage range 180 - 265 VAC so there is certainly a larger than I would expect tolerance for handling different voltage and frequency.

So for your post (https://community.victronenergy.com/questions/766/phoenix-inverters-in-parallel.html), there is a response from mvader (Matthijs Vader, CEO of Victron Energy), and I quote:

For the technical side: the requirement for those four numbers needing to be identical is a design choice. And though yes by the sound of it, its probably technically possible (for Inverters in this case) to make them work in parallel even though the numbers are different. But no, for reasons of keeping it simple, we're not likely to change that policy.

It seems explicitly stated there that it is the firmware number that is the key and I'm looking to make sure that I purchase a MultiPlus that matches.

Good Luck, please let us know how you get on.

I think it may work, there are some settings such as AC input limits that will now not be spread across units as in a conventional paralleling scenario. I doubt if it works it will be supported.

I think there is a post on this forum about someone successfully cascading inverters. I have never done that, although I have wondered. I don't think it will be supported either. You may have issues unless there is a Grid AC supply into the Multi, a self-generated AC might not be a stable enough AC power source. In other words, a Multi onto a multi, with a stable grid behind the first leg may work, but I don't know that yours will. Especially, if frequency shifting is involved. This wouldn't be an option I would rely on.

Two separate systems on a single battery bank I have done with success. of course they cannot be paralleled on the AC side. Remember, you can AC-couple a Phoenix with a PV inverter on its AC out. It is a bidirectional device and will charge batteries. ( I have done that with success as well). There are rules to doing that, so observe them.


Vance Mitchell avatar image
Vance Mitchell answered ·

In answer to the second part of your question, it is commonly referred as Cascading Inverters

It can be especially useful if you are using different battery banks for each inverter and I think it will be the most likely option for you.

Edit; If you choose to go this way you will need to ensure that the multiplus is not trying to charge when running from the Phoenix inverter. The easiest way I can think of to help with this would be to have a double throw switch turning the phoenix inverter on and also signalling the aux. in on the multiplus. this could then be used to signal the 'Charge Current Control' assistant.

If anyone with experience with this configuration has overcome this problem differently I would be interested to hear alternatives.

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offroadflow avatar image
offroadflow answered ·

Any news on this one..?

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