Parallel Inverters - Fault Code 60

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TitchRSA
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Parallel Inverters - Fault Code 60

Post by TitchRSA » Wed, 05 Jun 2019, 14:57

Greetings from a newbie.

I have 2 x 5048MS inverters configured for off-grid and parallel mode - single phase domestic use.

This system is backed up by a generator ‘utility’ supply when needed - manual start.

The system is a new install and has been working for 2 weeks. The generator has not been needed in this time.

Today the user connected the generator and the one inverter popped up a fault code 60. This is a ‘current feedback’ error according to the manual - and is usually an indicator of a live-neutral conflict/cross-over.

The user disconnected the generator, removed all loads, switched off the inverter, switched off PV and switched off battery - then reversed the process switching all back on (without the generator connected) - and the fault code 60 was gone.

I have traced all the PV system wiring with the generator disconnected and there is no conflict/cross-over of AC input/output live or neutral - nor does there appear to be any low resistance between live and neutral.

Any suggestions why this fault may be appearing when the generator is connected - and why only on one of the two parallel inverters?

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coulomb
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Re: Parallel Inverters - Fault Code 60

Post by coulomb » Wed, 05 Jun 2019, 19:23

TitchRSA wrote:
Wed, 05 Jun 2019, 14:57
Greetings from a newbie.
Welcome to the forum.
Today the user connected the generator and the one inverter popped up a fault code 60.
I happened to be investigating this very error for InfiniSolar 10 kW models last night.

Looking at the 72.20 firmware, I see that this is triggered when the battery power is less than (more negative than) -1200 W for 3 checks in a row (10 ms apart), or less than -2000 W instantaneously. So that's some serious reverse power (pulling power from the AC output [ edit: presumably from the other inverter's output ]).

I assume that the generator is connected to the AC-in terminals of both inverters? And that you've checked for goofy things like loose neutral wires?

Something that others have found: if the current sharing cables aren't connected tightly, this sort of error can come up.

I suppose it could be due to a load with a very poor power factor. Is that possible, at least for short periods of time (e.g. a large induction motor with no or low load)?
Any suggestions why this fault may be appearing when the generator is connected - and why only on one of the two parallel inverters?
The settings are supposed to harmonise between paralleled inverters... have they, particularly for settings 03 (AC input voltage range) and 28 (output mode, should both be PAR) ?

I assume that one inverter says MS or HS (master) and the other SL (slave)? Was it the master or slave that came up with the fault? The one with the fault is presumably one that is not outputting enough power.

Do the inverters roughly share the power equally on larger loads? My guess is no, and that the current sharing cables, or possibly wonky settings, are the reason.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

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coulomb
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Re: Parallel Inverters - Fault Code 60

Post by coulomb » Wed, 05 Jun 2019, 19:56

See also this post. I don't know what to make of it, but I don't have paralleled machines.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

TitchRSA
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Re: Parallel Inverters - Fault Code 60

Post by TitchRSA » Wed, 05 Jun 2019, 21:04

Welcome to the forum.
Many thanks for the welcome and the response @coulomb

Looking at the 72.20 firmware, I see that this is triggered when the battery power is less than (more negative than) -1200 W for 3 checks in a row (10 ms apart), or less than -2000 W instantaneously. So that's some serious reverse power (pulling power from the AC output [ edit: presumably from the other inverter's output ]).
Not sure I understand this. How does the inverter get to such a high negative battery value? The batteries were low when this happened hence the need for the generator to charge the batteries.

I assume that the generator is connected to the AC-in terminals of both inverters? And that you've checked for goofy things like loose neutral wires?
Yes and yes. I used an ohm-meter to check all cabling from end-to-end (and in-between).

Something that others have found: if the current sharing cables aren't connected tightly, this sort of error can come up.
I did check these at install time but quite likely there may be a loose wire. I will need to get to site later this week as its in the bush.

I suppose it could be due to a load with a very poor power factor. Is that possible, at least for short periods of time (e.g. a large induction motor with no or low load)?
Not sure - but there is not much in the dwelling. Fridge, Washing machine, kettle, lights, oven. Its currently used on odd occasions - a ‘holiday’ home as such.

The settings are supposed to harmonise between paralleled inverters... have they, particularly for settings 03 (AC input voltage range) and 28 (output mode, should both be PAR) ?
I used the Master - Slave status to ensure all settings were the same. I think it was the Slave that gave the fault code. Setting 03(APL) and 28(PAL) were correct. Now wondering if the APL setting is a good choice as thats quite a low end and fridge/washing machine might ‘stutter’? The units were happily working with loads until the generator was applied. But I am not sure what happened when the fault code came up. The user was about to leave site when I was called about the fault code - at that stage the generator had been switched off.

Do the inverters roughly share the power equally on larger loads? My guess is no, and that the current sharing cables, or possibly wonky settings, are the reason.
When testing during installation the loads seemed to be close enough - but not exact. The loads were low though - around 1000W on each inverter. So sharing was in place under low load. I am not sure what the user load was at the time the fault wss noticed. I do suspect that the battery had got low from overnight use - hence the user need for the generator to prop the batteries up. Also not sure how long the user ran the generator with this fault on.

Note: There are 2 x 4kWh LiFePO4 batteries on the system - close to the distribution box - which is close to the inverters. Both batteries are connected in parallel and shared on common connection by both inverters.

[/quote]

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Re: Parallel Inverters - Fault Code 60

Post by TitchRSA » Wed, 05 Jun 2019, 21:14

Hi @coulomb
See also this post. I don't know what to make of it, but I don't have paralleled machines.
My PVA arrays are separate estates for each inverter - as instructed in the manual. A rather obscure instruction I must say.

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Re: Parallel Inverters - Fault Code 60

Post by coulomb » Thu, 06 Jun 2019, 08:01

TitchRSA wrote:
Wed, 05 Jun 2019, 21:04
Not sure I understand this. How does the inverter get to such a high negative battery value?
The power has to come from the other output.

I've just realised that fault code 60 (error 60) only comes up when in battery mode. When charging from utility, you have to be in line mode (shows "BYPASS" on the LC Display). I assume that you have setting 01 = Uti, so that whenever the generator is running, it powers the load, and the inverter is available to be used in reverse to charge the battery. In this case, I assume that the inverter power will be a large negative value; you do want to suck power from the output (now connected to the AC-in and loads), and it has somewhere to go: the battery DC-DC is set up in reverse, so that it takes power from the DC bus (~400-500 V DC) and charges the battery with it.

Most likely what is happening is that the inverter-charger is rejecting the generator as being "out of spec" and ignoring it. Then, even in Uti mode, "Solar and battery energy will provide power to the loads only when utility power is not available". So the battery may be getting very low at this point, possibly becoming somewhat high in internal resistance, and/or possibly the BMS is disconnecting the battery briefly, or otherwise limiting the power. This is wreaking havoc with the inverter-charger's algorithms, and one of the two units is providing less power or possibly less voltage from its inverter when the other is still running as much as is needed. Perhaps under those circumstances, power will flow from one inverter to the other.

Axperts/PIPs are very fussy about generator quality. I have yet to figure out what that's about. It was absolutely horrible with very early firmware; they fixed that by about 72.40 (which is well before your presumed 72.10 or 72.20 or 74.XX). It may be that you'll need to replace the generator with one that these inverter-chargers work with, probably one that has an inverter incorporated into it. They seem to provide much better frequency or voltage stability that these inverter-chargers seem to demand.

Check that when the inverter is running, the "tennis ball" (AC input icon) is solid (not flashing, it can be flashing for a few seconds), and also the word "BYPASS" with its dotted line from the AC-in to the load:

LCD AC in.png
LCD AC in.png (613.25 KiB) Viewed 342 times
Yes and yes. I used an ohm-meter to check all cabling from end-to-end (and in-between).
I prefer to also use the "tug every wire" method of verifying that it's not an intermittently good connection, or only a good connection at low current.
I suppose it could be due to a load with a very poor power factor.
Not sure - but there is not much in the dwelling. Fridge, Washing machine, kettle, lights, oven.
That sounds like a no then. No large power tools or air compressors.
Now wondering if the APL setting is a good choice as thats quite a low end and fridge/washing machine might ‘stutter’?
You will very likely need APL; UPS is too picky by far for most generators.
The units were happily working with loads until the generator was applied.
Interesting, but it may be due to the low battery rather than the generator, and I suspect that the generator wasn't being used anyway.
When testing during installation the loads seemed to be close enough - but not exact.
That sounds OK. It's never exact, especially at low loads.

[ Edit: oops, pressed Submit too soon. ]
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

TitchRSA
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Posts: 5
Joined: Wed, 05 Jun 2019, 14:00
Real Name: Titch

Re: Parallel Inverters - Fault Code 60

Post by TitchRSA » Thu, 06 Jun 2019, 15:36

Thanks @coulomb
The power has to come from the other output.
Correct - but thinking about it there may be some serious inductance when the generator first starts up. I will have to go to site and see if I can replicate the way the fault was caused. It may also have been because the generator was not up to speed and that the input AC isolators were ON at generator startup?
I've just realised that fault code 60 (error 60) only comes up when in battery mode. When charging from utility, you have to be in line mode (shows "BYPASS" on the LC Display). I assume that you have setting 01 = Uti, so that whenever the generator is running, it powers the load, and the inverter is available to be used in reverse to charge the battery. In this case, I assume that the inverter power will be a large negative value; you do want to suck power from the output (now connected to the AC-in and loads), and it has somewhere to go: the battery DC-DC is set up in reverse, so that it takes power from the DC bus (~400-500 V DC) and charges the battery with it.
Program settings are #01=Utl and 16=CUt. The idea is that when the generator is applied it provides output to load and as these are LiFePO4 I figure the batteries will charge quicker from generator than solar - and this may also happen at night. I could use #16=SnU but prefer the generator to do all the work.
Most likely what is happening is that the inverter-charger is rejecting the generator as being "out of spec" and ignoring it. Then, even in Uti mode, "Solar and battery energy will provide power to the loads only when utility power is not available". So the battery may be getting very low at this point, possibly becoming somewhat high in internal resistance, and/or possibly the BMS is disconnecting the battery briefly, or otherwise limiting the power.
The inverter being out-of-spec may well be the case - it is a new and small generator though. I will check the specs - thanks. I have subsequently found out the battery wasn't low - but the user saw the icon at half and decided he would top up the battery before he left site. So low battery was probably not part of the cause.
Axperts/PIPs are very fussy about generator quality. I have yet to figure out what that's about. It was absolutely horrible with very early firmware; they fixed that by about 72.40 (which is well before your presumed 72.10 or 72.20 or 74.XX). It may be that you'll need to replace the generator with one that these inverter-chargers work with, probably one that has an inverter incorporated into it. They seem to provide much better frequency or voltage stability that these inverter-chargers seem to demand.
If it is the generator I will have a hard time selling the idea of a replacement generator. :D
Check that when the inverter is running, the "tennis ball" (AC input icon) is solid (not flashing, it can be flashing for a few seconds), and also the word "BYPASS" with its dotted line from the AC-in to the load: LCD AC in
Thanks - will need to check when next on site. For now the system is running fine without the generator - so not that urgent.
I prefer to also use the "tug every wire" method of verifying that it's not an intermittently good connection, or only a good connection at low current.
Haha - yes - goes without saying. Funny you should say that - there was a PV connection with exactly that problem - the tightening clamp on the DC circuit breaker had broken.
You will very likely need APL; UPS is too picky by far for most generators.
Thanks - will leave it alone then.

Your responses are most appreciated.

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