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donlstewart asked

MultiPlus II line conditioning ideas

We have very low quality utility power with over 100 brownouts and brief power outages a day (Costa Rica). The engineer we hired was instructed to build an active UPS system with line conditioning. He just completed an install of MultiPlus IIs and a battery bank. We immediately realized the power outages are gone but our surge protectors and the small UPS units are still clicking and beeping in response to the poor utility service. I am not an electrician but know enough now that I’ve seen the install and operators manual I know enough to see we received a passive (parallel) installation. Great for covering our brief (minutes) outages, but doing nothing to protect our electrinic devices. Can anyone here provide guidance on what can be done or be added to stabilize our utility service short of a complete system replacement?

voltageac
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7 Answers
Trevor Bird avatar image
Trevor Bird answered ·

@donlstewart the multiplus 2 monitors the input for lower voltage and high voltage surges and will disconnect from mains in either case. For a 240volt system commonly the low voltage may be as low as 180 volts before disconnecting and as high as 270volts before disconnecting. These levels can be adjusted if that range is too wide and you would prefer tighter limits.

When the variation is too great and the disconnection does take place the unit switches to inverter mode and still supply power so you will not see any change to the power supply.

I think in most cases the provision of the Multiplus will provide the conditioning you require.


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donlstewart avatar image donlstewart commented ·

Are there and disadvantages to tightening those setting to trigger at 220 and 240? That would mean more time on battery power but our brownouts and outages are almost always momentary.

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Fideri avatar image Fideri donlstewart commented ·

@donlstewart

Just be aware that whatever the setting, mains power will just "pass through". It will not be "conditioned" by the inverter unless it goes to the battery as DC first.

F.

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donlstewart avatar image donlstewart Fideri commented ·

I understand that this is a passive (parallel) system. Not what I ordered but it is what I got.

Looking to some subject matter experts here for the best path to correcting the issue.

So I was asking if setting the failover voltages to 220 & 240 has any negative side effects.

The goal is to eliminate the need for individual UPS and surge devices protecting our electronic devices in the house. Necessary because we have poor quality utility power here in Costa Rica.

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lifeingalicia avatar image
lifeingalicia answered ·

you may want to watch this video about grid settings

https://www.bluepower.pro/victron-veconfig-grid-settings-tab-tutorial/

Setting the limits to a more "sharp" reaction will engage it more often but still you have the 20ms

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donlstewart avatar image donlstewart commented ·

Thank you, those videos give me something to work with. Seems worth trying to set the inverters to switch early as voltage starts dropping. The 20 millisecond failover should not be noticeable. Only issue is wear and rear on the Multiplus units because voltage drops and short power outages are a constant here… over 100 times a day that we notice and probably many more we do not.

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donlstewart avatar image donlstewart commented ·

Thank you. Will watch those and play with the trigger settings. That only leaves the concern over wear and tear on the inverters when they are being activated maybe 100 times a day. I now fear this system can be tuned to provide stable power, but will wear out quickly if I do that.

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lifeingalicia avatar image lifeingalicia donlstewart commented ·

Well basically you need to find a balance of aceptable brown out and low/high voltage, the relays may wear out if permanent switching occurs under very high load. MTBF (mean time between failure) depends on the current flowing at switching time but the average is in the millions. I don't know if you also have PV. Important: The Multies are rated in VA not W. The difference being the power factor e.g usually about 0 .8 a Multi 3000 can run 2400w continuously but still may cut out due to overheating after a while.

Multies are fairly adaptable. If you are worried you could use the "Weak shore power" "Peak shaving" settings that will draw less permanent power from the grid etc.

Also they have AC1 and AC2 out AC1 is "UPS" whereas AC2 out just sheds the connected load.

Have fun

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sharpener avatar image
sharpener answered ·

You mention you have surge protectors already. It might be worth fitting these upstream of the Multis to protect them as well. If they are on the downstream side they will not provide any protection for the Multis when they have disconnected from the grid and are in inverter mode, there is still some separate circuitry connected and active in order to monitor the grid condition.

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donlstewart avatar image donlstewart commented ·

The UPS units we have are the small ones meant to support individual routers, computers, etc. A line conditioner between utility and the multiplus array would obviously deliver stable power for the voltage drops and reduce the frequency of triggers to battery backup.

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sharpener avatar image sharpener donlstewart commented ·

I meant this type of SPD https://www.tlc-direct.co.uk/Products/MK6820S.html. If fitted at the intake position it will clamp both the line and neutral voltage to within safe limits, thus saving the Multis from damage as in the extreme case the main incoming fuse will blow first.

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dennibu avatar image
dennibu answered ·

Ich denke, solange es parallel läuft, wird man diese kurzen Spannungsspitzen nicht verhindern können. Um das Problem ganz zu vermeiden, würde es helfen, die Akkus vom Netz zu laden und die Multis nur am Akku zu betreiben. Eventuell könnte man dann nur bei Überlastung das Netz dazuschalten.

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grfloater avatar image
grfloater answered ·

Maybe your solution from start should have been an "Online UPS", like https://www.apc.com/us/en/product-range/61918-smartups-online/#products - instead of what you call "parallel" with Multi (which is more like "line interactive" UPS).

If you have PV panels, you can charge the battery and then go "island" (disconnect AC in), if inverter power is enough (given temperature sloping, as well). Without panels, only from mains grid AC, you may restrict the limits for charging / inverting, as others proposed. Or/and you may put some automation, for connecting the AC in, such as a smart switch kicking in at night, or when battery is below SOC (you can use the Multi aux relay).

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Alexandra avatar image
Alexandra answered ·

@donlstewart

Other than tightening grid accepted parameters and switching on ups....

For this a solution could be to have one inverter connected to the grid for charging nothing connected to AC out. And a second one inverting only to loads (no ac input), so isolated from grid, that way you always have good voltage a sine wave on the loads but have the use of grid for battery maintenance.

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donlstewart avatar image
donlstewart answered ·

The engineer that did the design surprised me. He truly failed to understand how bad the utility power was and thought he was doing the right thing. They are returning and converting what we have to active by bringing the utility service in to a bank of battery chargers (AC to DC inversion). The MultiPlus units will then continuously provide conditioned power (DC to AC inversion) to our home from the battery bank. That leaves the chargers taking a beating from voltage drops and outages, but they are less sensitive to wear and tear then the MultiPlus inverters, there are 4 of them, and they are not expensive to replace.

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