Phil Gavin avatar image

Phoenix inverters purchased seperately not connecting in parallel.

I tried to parallel 2 phoenix inverters, both 48V 5kVA units and physically identical, bought 3 months apart.

Victron's VE BUS configure software would not allow me to do it. ( the units are not identical.)

My further investigation showed me that Phoenix inverters use Multiplus microprocessors. unit.

The reason I cannot parallel the units is that in one inverter I have a Multiplus 48V 5kVA 70-100 chip and in the other unit I have a Multiplus 48V 5kVA 70-50 chip.

That means I have chips that relate to a Multiplus with a 100 Amp transfer switch and a 50 Amp transfer switch respectively. However Phoenix inverters do not have transfer switches at all.

So I cannot parallel these units because the software disqualifies me for differences in the size of transfer switches that are redundant functionality in a Phoenix inverter.

There is no indication of this rating in the Phoenix manual, (why would there be it doesn't have a transfer switch?), and no physical indication on the unit. My suppliers re-ordered the second incompatible phoenix using the same order code as the first. The difference only becomes apperent when the software cross-references the serial numbers.

Yes, the Multiplus units call attention to the transfer switch rating, but these aren't Multiplusses,

These Phoenix inverters were chosen specifically for there ability to be paralleled, a big Victron selling point.

Somebody didn't consider the law of unintended consequences when using the Multiplus chip in a Phoenix inverter.

This has been an extremely inconvenient experience, it will be 10 months before I am back in this country to recommission the replacement unit.

I commission protection relays for a living, and have experience with all the big name offerings, and a career of realistic expectations of equivalent products.

I know that with this sort hidden incompatibility issue the onus is on the manufacturer to put it in big bold writing in the Phoenix manual at the very least.

Somebody dropped the ball.

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9 Answers
mvader (Victron Energy) avatar image
mvader (Victron Energy) answered ·

Hey Phil, sorry to hear about this. And I understand your frustration. It should have been mentioned more clearly.

Guy has already added it to the Parallel and Three-phase manual this morning, see third bullet in the "important" list at the top:

And, we'll make the product manual more clear as well. And, the part-number perhaps should have been changed; though that has lots of consequences in various areas; I don't have a good solution for how to manage that; yet.

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.

I hope this clears it up; even though you might not like it. And I'm really sorry for the trouble caused. Let me know if there is any issue in exchanging the unit.

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WKirby avatar image
WKirby answered ·

No, not the serial numbers. Take it up with your supplier that they have provided you with two units with different FIRMWARE numbers.
In this case, the factor under debate is the transfer relay. There are different firmware versions even down to the detail of the capacity of the transfer relay. The very reason for this is to ensure that units with different capacities of transfer relay are not used in a single (parallel) installation.

What I'm going to highlight below is what any Victron Installer / Supplier should know. If your orders are some time apart then they should be asking you (their customer) for what you currently have in order to ensure that your receive what you need:

Firmware version labels are affixed to the microcontroller. The supplier should be paying particular attention to this number, not so much the serial number.
The Firmware number is comprised of seven digit number xxxxxxx.hex which describes the firmware version as shipped. The first four digits identify the precise model of your unit and these four digits will never change regardless of how many firmware updates have been applied since it was shipped. It could be interpreted as the hardware version. Put another way, it relates to the hardware features available in the unit. (An inverter will never see AC-IN, so whether the microcontroller constantly signals a non-existent transfer relay is of no consequence to the operation of the Inverter it's self).
The last three digits are the firmware revision number and may well be different to the label if firmware updates have been applied since the shipping date.
What is important is that the first four digits are the exactly the same across all units to be paralleled. This convention applies to MultiPlus, Quattro whatever you have.
If the last three digits are different, then that is easily rectified with a firmware update either by the supplier or by yourself if you feel confident enough to perform such an action.

I hope this provides some clarification into how the versioning system works, at least for the products that we are discussing here. You (the customer) may not have known this without reading Victron's extensive and publicly available documentation, but a Supplier or Installer should know this.

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Phil Gavin avatar image
Phil Gavin answered ·

Thank-you M.Vader.

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Phil Gavin avatar image
Phil Gavin answered ·

Sorry, about dropping the issue, I have been travelling internationally.

I see Ben has picked up where I dropped off.

He has also picked up on the the point that this is an ARTIFICIAL difference.

Victron designer's used two different chips in batches without considering the paralleling incompatibility. The Phoenix inverter manual does draw attention to firmware, but only to the first 2 digits and the last three. Which were identical in this case.

I contend that, yes the unit's are identical and therefore it was a design error to not standardize on the chip.

"and nobody knows what other changes are inside." Don't tout training and make statements like that.

In any event it is twaddle, without further evidence I contend these are two standard multiplus chips, there different applications are clear, when deployed in the Phoenix an unnecessary soft artificial restriction prevents paralleling.

It was an unconsidered result of thinking you could use different chips because the transfer switch functionality is not needed in the Phoenix.

Now, that is QC issue within Victron's design function, it should have been picked up it standard type-testing. Don't pass off an inherent design flaw as the QC responsibility of the supplier or installer.

Unless you can point to a technical reason why those two inverters should have different chips:

"and nobody knows what other changes are inside."

doesn't cut it.

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Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Regarding feedback from Ben, We are installing in the real world, so it will never be perfect.

The goal is minimise to potential number and consequence of the imbalances and irregularities. A line has to be drawn somewhere, and it was drawn at requiring identical units. I don't think it is unreasonable, though it can of course be frustrating.

You are right that there are other factors outside of the control of Victron, which will impact our equipments performance. There are enough opportunities for unexpected issues through system imbalance as it is.

Nevertheless, this requirement will not be changing. It should be known loud and clear that if you wish to parallel Victron inverters:

  • It should be done by an installer with previous experience and support from a trained distributor
  • It should be done with parts that have been specified and supplied for a parallel system at time of purchase.

I believe that these systems are sufficiently complicated and expensive that there is some onus on the distributors and installers to do their research on what is required. These requirements were already existing, but in light of this post I am now increasing the prominence at the top of the parallel systems manual under WARNING heading.

Other equipment that is able to be connected in parallel such as MPPT's and DC to DC converters do not have these strict requirements.

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Re: "identical units", the (unusual) issue here is that it sounds like Phil's units are in fact hardware-identical. But a simplification in Victron's software/firmware deployment strategy means that the configuration software cannot tell that the units are the same.

Phils units have different hardware processors inside. They were created from a different batch run, and nobody knows what other changes are inside.

ben avatar image ben ♦ Guy Stewart (Victron Community Manager) ♦♦ ·

Yeah, I see what you're saying. If the control board has different logic or uses a newer protocol to sync the waveforms, it might mess up the parallel stack even if the underlying power circuitry is the same.

Note that this issue is definitely not that clearly-described in the PDF manuals and datasheets. The concept of "hardware ID" is not articulated there, that I can see.

Re: "specified for parallel at time of purchase", that is a perfectly reasonable restriction for Victron to elect, but it is not anywhere in the marketing material, datasheets, or in your updates on the wiki.

Of course one of the real-world scenarios is that someone elects a single Victron inverter today, knowing that he/she has the option to size up to a parallel configuration tomorrow. I think you are suggesting that those customers should find another vendor if they want to preserve an upgrade path?

It was specified in the manual that only trained installers are advised to attempt parallel and multiphase installations. This identical-part restriction is covered in the training.

Today and tomorrow would probably be ok, 6 months or 36 months later is extremely unlikely to be compatible.

If a customer wished to use Victron equipment, but months later wished to upgrade to more capacity, I would advise they do not use a parallel configuration, but perhaps an inverter/charger setup where one is connected into the AC-input of the other.

That is also an advanced design, requiring training.

ben avatar image ben ♦ Guy Stewart (Victron Community Manager) ♦♦ ·

I don't mean to bother you, but "the manual" definitely does not cover this for your full range of inverters.

Take the small Phoenix Compact 1200-2000kVA line. Here, the datasheet touts the parallel feature, and the manual talks about the parallel setup, but there is no link to the wiki page.

Moreover, in my part of the world, a pair of small stacked inverters is very common and there are many Victron competitors who offer these. No one would really consider this an "advanced" installation and there are no requirements to pursue extra training.


ben avatar image ben ♦ Guy Stewart (Victron Community Manager) ♦♦ ·

Obviously a 3-phase 90kVA setup is a lot different here and the due diligence (and expertise on hand) during system commissioning should be much higher.

But my point is, it's not documented very well in the material available on the web, and the standard in some industries where some of these kinds of inverters are used does not align with the Victron approach/policy.

It's fine to be different (I love Victron for being that way), but in this specific case, please be aware that you are enforcing restrictions but under-documenting them, for sure.

Re "other equipment" compatibilities, my broader point was that there is an n^2 interoperability challenge at Victron (and any successful vendor). As more products are released, the number of possible combinations of products grows geometrically.

Taking extra care to try to document what is compatible and what is not, and keep it a living document, might be a good thing. It is unrealistic to expect any single dealer, installer, or customer to track the huge number of possible combinations at this point. A compatibility matrix is something you could consider establishing.

Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

A parallel configuration requires extremely precise balancing.

This can come down to the variation in resistance between two identically branded switches or wire join.

The variations between unit design or part changes can introduce resistance imbalance between the units. And other consequent issues.

The issue here isn't that you are not using the transfer switch functionality of the processor, but that different units were supplied to you when identical units are necessary.

Configuration of parallel systems is for advanced users, and very often with close support by a local distributor or supplier. Then units intended for use in parallel systems are specified when purchasing as identical, and for parallel use.

There is a very clear Warning notice on the front page of the parallel systems manual here:

We do not support untrained and/or inexperienced installers working on these size systems.
...hire an installer that does have experience with these large systems, for both the design and the commissioning.

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While much of what you say rings true, I take issue with the requirement for ultra-precise balancing.

The reality is that in any real-world system, there can be imbalance downstream of the Victron equipment. The wiring, fuses, overcurrent protection, and so on will all have tolerances and will create circuit imbalance.

Moreover, the Victron equipment itself will be placed slightly differently and have slightly different thermodynamics because of ventilation, spacing, and so on.

A simple parallel stack of inverters can be reasonably expected to tolerate these differences.

Phil Gavin avatar image
Phil Gavin answered ·

At the risk of repeating myself there are no transfer switches on this unit, so there is no actual hardware incompatibility.

If you order a multiplus with a 50A transfer switch there no requirement to intrusively open up a static sensitive equipment to confirm the 3rd and 4th digit on a IC on the circuit board.

The expectation is you get what you order, without having to don an anti-static wrist strap.

Now if you order a phoenix it does not have a transfer switch, so there is no ordering option.

Why should it now be an unspoken expectation to open the unit up?

There are 8 phoenix firmware versions, none of which relate to this 48V 5kVa unit.

My contention is if there is only one ordering option, and the incompatibility issues actually relate to an entirely different product range, then it is unreasonable to expect a buyer to be aware of issues at a microprocessor based level by intrusive measures.

The selling point is that it is parallel connectable. Somehow that gets put across very loudly the product support is also put forward.

The argument that somebody should've known is an unreasonable one, when the issue is so subtle and undocumented in this particular product's manual.

After having commissioned literally 1000's of MW of power systems over 30 years that use micro-processor equipment, I have a pretty good idea about what is due diligence from the middleman and what is a reasonable expectation of the manufacturer's responsibility.

But, in any event I'd like to hear from Victron now.

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I agree, this sounds unrealistic to me. Victron/your dealer should make this right.

In combining other Victron products in new and "exciting" ways, I have encountered other issues and compatibility limitations as well. I think it would be a good idea for Victron to create a master document that calls out known limitations and points of interest with regard to various combinations of product.

My experience is that the dealers cannot be expected to keep track of all of these idiosyncrasies in the product compatibility, because the product line-up is so huge.

Phil Gavin avatar image
Phil Gavin answered ·

There is no subtle difference barring the serial numbers.

Are you suggesting that I should take it up with my supplier that the units have different serial numbers?

Because that is only knowable difference between these units. They are identically spec'd.

And a repeat order.

Only by performing a firmware upgrade and cross-referencing the firmware version against the firmware list could I establish the phoenix inverters use multiplus chips. There is no documentation that indicates this.

The multiplus chip difference relates to the current capacity of the multiplus transfer switch.

You CAN'T order different Phoenix inverters based on the current capacity of the transfer switch because the Phoenix inverter DOESN'T have a transfer switch.

There is no ordering choice, ergo it is Victron's problem when I order "IDENTICAL" items and get items with subtle, unknowable, undocumented differences.

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WKirby avatar image
WKirby answered ·

In the documentation it says that the units need to be IDENTICAL. I think you knew this information beforehand and you knew this when you placed the order with your supplier.

I assume that you conveyed the importance of the units being identical to your supplier. I also assume that you conveyed to your supplier your circumstances surrounding your access limitations to the site.

So, if your supplier has provided two units which are not IDENTICAL then surely you need to take this matter up with them.

The way that the firmware is implemented should be of little consequences, the fact remains that both versions of firmware need to be IDENTICSL regardless of what features are physically present or what features you have the choice to use or not.

I can understand your frustration especially in your circumstances, but to me, the documentation is clear and correct - the units need to be IDENTICAL, no subtle differences at all. It's out of Victron's control if you supplier does not fulfill you requests.

I don't work for Victron, I'm just expressing my own opinion.

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