Inverter Wiring question - multiplus II 2x120, air cons

[jc1409]

I'm replacing some standalone chargers and a 2k w inverter for a Victron Multiplus II 2x120 charger/inverter. My boat is 12v DC, 120v AC, and takes 50a split phase shore power.

One benefit of the MPII will allow me to support running my air conditioners (or other high load items) even when shore power is suboptimal - e.g., with 30amp single phase shore power, I will have the option to invert to supplement the power supply and run things, if I want.

However, this means I will need to wire the inverter to connect to my air conditioner circuits. So when I'm not connected to shore power, if I turn on the air conditioner units (have 3 of them) - the inverter would try to supply enough power (and fail).

To use the MPII in this way and get the benefit of supplementing show power with the inverter, my conclusion is that I will just need to manage use of the air conditioners, while not on shore power - e.g., turn them off at circuit breaker to avoid anyone 'accidentally' turning them on and overloading inverter.

Is this correct? Any other ways to wire the MPII other than above?

For my install of the MPII, the only thing I will power with the 'shore power only/non-inverted' supply that I can think of will be the Water Heater on the boat - all other things will be wired and subject to inverting.

thanks for ideas.
Jeff

[more]

Originally Posted by jc1409

I'm replacing some standalone chargers and a 2k w inverter for a Victron Multiplus II 2x120 charger/inverter. My boat is 12v DC, 120v AC, and takes 50a split phase shore power.

One benefit of the MPII will allow me to support running my air conditioners (or other high load items) even when shore power is suboptimal - e.g., with 30amp single phase shore power, I will have the option to invert to supplement the power supply and run things, if I want.

However, this means I will need to wire the inverter to connect to my air conditioner circuits. So when I'm not connected to shore power, if I turn on the air conditioner units (have 3 of them) - the inverter would try to supply enough power (and fail).

To use the MPII in this way and get the benefit of supplementing show power with the inverter, my conclusion is that I will just need to manage use of the air conditioners, while not on shore power - e.g., turn them off at circuit breaker to avoid anyone 'accidentally' turning them on and overloading inverter.

Is this correct? Any other ways to wire the MPII other than above?

For my install of the MPII, the only thing I will power with the 'shore power only/non-inverted' supply that I can think of will be the Water Heater on the boat - all other things will be wired and subject to inverting.

thanks for ideas.
Jeff

RTFM usually help

https://www.victronenergy.com/upload...s-II_GX-en.pdf

[jc1409]

Originally Posted by more

RTFM usually help

https://www.victronenergy.com/upload...s-II_GX-en.pdf

You are right 🙂

Read through it once but will dig deeper based on your tip, because I must have missed the answer.
Jeff

[Dockhead]

You are correct.

To make this work right you need all the AC circuits run through the charger inverter. That is so current limiting and Power Boost is based on correct measurement of total AC load.

This works great, however, keep in mind inherent limitations of Power Boost. You need continuous loads to be less than what you are getting from shore or generator, so that Power Boost is powering short term overloads, and can return the expended power between those intermittent higher loads. It wont work to power a continuous load like aircon which is consistently greater than your shore supply. Note also that frequent cycling of batteries from Power Boost is hard on lead acid batteries. Lithium is much better for this kind of use.

I like my Multiplus a lot, but you still have to manage loads carefully. It works best when you manage liads so that Power Boost kicks in rarely.

Beware also the risk of killing your batteries if shore power is disconnected accidentally, and you don't notice that your whole boat is being powered from the inverter. Don't ask me how I know

[jc1409]

Thanks Dockhead, makes sense - and good to know about the limitations of Power Boost.

I do have the situation a lot at local Marinas where the Power Boost will come in handy, so will have to figure out new level of managing loads and keeping close eye on inverter drain. Not something I worry about so much in my current configuration without the Powerboost capability - all very manual- based now.

[Dockhead]

Make sure you mount the control panel in a place where it's easy to keep an eye on it.

If you go for one of the more sophisticated panels, maybe it's possible to configure an alarm to tell you when Power Boost works more than some set interval. That would be really useful.

[captstu]

Seems unlikely that a 2KW inverter will support even one a/c due to starting load.

I ran my catamaran a/c on a 3 kW inverter with a 1200 aH battery bank and 4 strands of "00" wire to support the ~300 Amp starting surge. It just doesn't seem possible to support this load with a 2kW inverter.

What am I missing?

[wathey]

A couple of thoughts based on the reality to include with the spreadsheet math. We run a Quattro 5k/200a but same applies to the multi, we just have the inverter wired into ac2 that isn't present on the multi. The victrons will overload and crash when running to much load (more than a few minutes at max load). When they crash the touch panel can sometimes reset but sometimes you have to use the switch on the front of the unit. It's a pain but it keeps it from catching fire so there's that. The math usually missing in the spreadsheet is the charger. The multi has a 120a charger. If wired optimally all 120a of bulk charging goes into the battery bank. This number must be subtracted from the available inverting capacity. If your battery bank is full and in float mode then you have full 3kw capacity to use. Usually when we crash the inverter the loads exceed when the charger is cranking out 180a+. Eventually, hitting the crash point multiple times will break the hardware. A couple of things, a 5kw unit or a second multi wired in parallel is more aligned with a system that supports air conditioning on the inverted bus. Soft starts are a must with a multi especially if you are running dometic ACs which pull down huge amps when the compressor hits. One ac unit won't need a soft start with a multi. Again, the spreadsheet says it can handle it but two compressors on a warm day will frequently be running and therefore starting at the same time enough for that to be the target to support. If you have ac systems it's likely an advanced electrical demand (fridges, freezers, stereo etc) so add another 18 to 22ish amps of other stuff and without the charger on your capacity is nearing full utilization. Using it everyday I have found it really should not be loaded past 80% for long periods of time. My guess is your family isn't going to be down with running the ac for 20m intervals. Just some food for thought, avoid overloading electric items and your chance of a fire is significantly less. 2500 bucks for a second multi will go a long way for piece of mind.

[Dockhead]

Originally Posted by captstu

Seems unlikely that a 2KW inverter will support even one a/c due to starting load.

I ran my catamaran a/c on a 3 kW inverter with a 1200 aH battery bank and 4 strands of "00" wire to support the ~300 Amp starting surge. It just doesn't seem possible to support this load with a 2kW inverter.

What am I missing?

The Victron inverters can power short term loads of about double their rated capacity.

The ratings are exaggerated, however, with regard to continuous loads. The 3000 Multiplus, in my experience will barely pull 2kW continuously, less in hot weather.

[Dockhead]

Originally Posted by wathey

A couple of thoughts based on the reality to include with the spreadsheet math. We run a Quattro 5k/200a but same applies to the multi, we just have the inverter wired into ac2 that isn't present on the multi. The victrons will overload and crash when running to much load (more than a few minutes at max load). When they crash the touch panel can sometimes reset but sometimes you have to use the switch on the front of the unit. It's a pain but it keeps it from catching fire so there's that. The math usually missing in the spreadsheet is the charger. The multi has a 120a charger. If wired optimally all 120a of bulk charging goes into the battery bank. This number must be subtracted from the available inverting capacity. If your battery bank is full and in float mode then you have full 3kw capacity to use. Usually when we crash the inverter the loads exceed when the charger is cranking out 180a+. Eventually, hitting the crash point multiple times will break the hardware. A couple of things, a 5kw unit or a second multi wired in parallel is more aligned with a system that supports air conditioning on the inverted bus. Soft starts are a must with a multi especially if you are running dometic ACs which pull down huge amps when the compressor hits. One ac unit won't need a soft start with a multi. Again, the spreadsheet says it can handle it but two compressors on a warm day will frequently be running and therefore starting at the same time enough for that to be the target to support. If you have ac systems it's likely an advanced electrical demand (fridges, freezers, stereo etc) so add another 18 to 22ish amps of other stuff and without the charger on your capacity is nearing full utilization. Using it everyday I have found it really should not be loaded past 80% for long periods of time. My guess is your family isn't going to be down with running the ac for 20m intervals. Just some food for thought, avoid overloading electric items and your chance of a fire is significantly less. 2500 bucks for a second multi will go a long way for piece of mind.

Sorry, but the Quattro/Multiplus doesn't work like that. It EITHER charges, or inverts, not both at the same time. When Power Boost is working, it's taking power out, not putting it in.

What you are probably observing is the effect of voltage drop. There are less watts of power available if the batteries are down and voltage drops.

[more]

Originally Posted by jc1409

1/ So when I'm not connected to shore power, if I turn on the air conditioner units (have 3 of them) - the inverter would try to supply enough power (and fail).

To use the MPII in this way and get the benefit of supplementing show power with the inverter, my conclusion is that I will just need to manage use of the air conditioners, while not on shore power - e.g., turn them off at circuit breaker to avoid anyone 'accidentally' turning them on and overloading inverter.
Jeff

first ask 1 by one question.
answer for q1.
first buy automatic/or manual transfower switch only for AC(example)
shore power 1 line to ATS (master side) and from inverter to ATS (source B side) from ATS to AC unit all 3.

Normaly shore power connect to Victron to charging and also connect generator to victron.

Also use current limiting device before go in ATS from shore power XX A
from generator XX A,From victron XXA
current limiter find locally mini shop like this
https://www.etigroup.eu/products-ser...iter-6a-k-10ka

https://www.youtube.com/watch?v=babtv00R-Nc

[rslifkin]

Originally Posted by Dockhead

The Victron inverters can power short term loads of about double their rated capacity.

The ratings are exaggerated, however, with regard to continuous loads. The 3000 Multiplus, in my experience will barely pull 2kW continuously, less in hot weather.

They're rated in VA rather than watts, which is part of the issue. My Multiplus 2000 is rated for 2000VA / 1600 watts continuously, but that's in a 25* C environment with optimal airflow to the unit. Raise the ambient temperature to 40*C and you're down to 1450 watts continuous output. For the 3000, it's 3000VA / 2400 watts at 25* C, 2200 watts at 40* C. They do have quite a good short term overload capacity, however.

[Dockhead]

Originally Posted by rslifkin

They're rated in VA rather than watts, which is part of the issue. My Multiplus 2000 is rated for 2000VA / 1600 watts continuously, but that's in a 25* C environment with optimal airflow to the unit. Raise the ambient temperature to 40*C and you're down to 1450 watts continuous output. For the 3000, it's 3000VA / 2400 watts at 25* C, 2200 watts at 40* C. They do have quite a good short term overload capacity, however.

That's it, exactly. It's important to read the fine print.

[fxykty]

Originally Posted by Dockhead

Sorry, but the Quattro/Multiplus doesn't work like that. It EITHER charges, or inverts, not both at the same time. When Power Boost is working, it's taking power out, not putting it in.

What you are probably observing is the effect of voltage drop. There are less watts of power available if the batteries are down and voltage drops.

Ummm, our Quattro charges and inverts at the same time all the time. The amount of power available to charge is reduced by the amount of power required by the inverter. If the inverter power exceeds the charge power then all the charge power is passed through to the inverter.

[rslifkin]

Originally Posted by fxykty

Ummm, our Quattro charges and inverts at the same time all the time. The amount of power available to charge is reduced by the amount of power required by the inverter. If the inverter power exceeds the charge power then all the charge power is passed through to the inverter.

They only charge or invert, never both. When on shore power with both the current limiting and power assist enabled, it does the following: charge at full speed until you hit the shore current limit, then reduce charging power to avoid going over the limit. If charge current hits 0 and you're still pushing the limit, it will invert (drawing power from the batteries) to supplement the shore supply to hold you down to the limit. When power demand drops, inverter output will decrease until it's doing nothing, then as you drop below the limit again it'll start charging again.