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joeccv avatar image
joeccv asked

Understanding Multiplus "Inverter" function - with power assist off

When running the multiplus in "inverter" mode, with power assist turned off, does the inverter ever function when connected to shore power?


For example, if the loads are drawing too much power to charge the battery and supply the inverter output, does the inverter take over to supply the output, without adding to shore power?


To phrase differently, let's take the example of a multiplus being retrofitted in a 30 amp RV:


The shore power inlet is a 30 amp inlet. The main distribution panel has a 30 amp main breaker and the box is rated at 40 amps max or so. If the 30 amp main breaker and 10awg wiring is left in place, power assist is not desireable when connected to a full 30 amp service, as this could overload distribution panel/wiring.


However, if connected to a 15 amp service, and the input current limiter is reduced, perhaps to 12 amps or lower even, will the inverter take over, without assisting the shore power input? Or are you simply restricted to pass through power with the input current limit you have now set?

MultiPlus Quattro Inverter Chargerpowerassistshorepower
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snoobler avatar image
snoobler answered ·

Unless virtual switch or assistants specify to ignore AC in based on user criteria, the inverter is always in pass-through mode when AC-in is live.

Shore limit is misleading as it only applies to two situations:

  1. PowerControl function where the CHARGER will not output more than is allowed by the input current limit.
  2. PowerAssist function where the inverter boosts power from batteries if the input limit is exceeded due to loads.

It does not prevent you from drawing more than the limit when in pass-through mode.

Regardless of any input limit setting, if you exceed shore power rating in pass through mode and powerassist is disabled, you will trip the shore power breaker.

If you seek to prevent overdrawing the shore power, you must have powerassist enabled OR you need to make sure you don't exceed input limit by manually managing your loads.

Your questions:

When running the multiplus in "inverter" mode, with power assist turned off, does the inverter ever function when connected to shore power? - NO

However, if connected to a 15 amp service, and the input current limiter is reduced, perhaps to 12 amps or lower even, will the inverter take over, without assisting the shore power input? - NO

Or are you simply restricted to pass through power with the input current limit you have now set? - NO. You are only restricted from the charger side. If 12A is set, the loads + charger will never exceed 12A; however, if your loads exceed 12A, you will overload the source as input limit only applies to the charger powercontrol and inverter powerassist.


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joeccv avatar image joeccv commented ·
I see. So without having access to a PC and a multiplus at the moment (I will in a few days), is there a way to use the ignore AC assistant to get the inverter to output it's full capability while staying below the 30 amp breaker rating of the output?


Or is there another way to use the assistants to limit the output of the inverter to a set value (let's say the output breaker's rating) but still be able to use a DMC or smart dongle to change the input current limit?


In my second example above using the 15 amp service, what would happen if the power assist function was turned on but the factor was set to 1? I'm assuming power control would function to keep the breaker from tripping, but the inverter + ac input would still not provide more than the 12 amp limit set for this scenario, correct?

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Kevin Windrem answered ·

I look at this differently. The inverter/charger core connects the AC and DC sides of the system. It can transfer power either direction. It can move power from the DC side to the AC side; or move power from the AC side to the DC side.

The AC side of the inverter/charger core is always connected to the AC output. If the AC input is within the acceptable voltage and frequency range, the AC input is also connected to the AC output. So power can flow from the AC input to the AC output or flow into the inverter/charger core.

The inverter/charger core will move power from the DC side to the AC side if the incoming AC power does not satisfy the AC load. This is called "power assist" if the AC input is connected. It is called "inverting" if the AC input is not connected.

If the incoming AC power satisfies the AC loads, then the inverter/charger core can move power from the AC side to the DC side. This is called "charging" but may also be supplying DC loads.

The AC input current limit restricts how much AC input power is available for either the AC loads or for charging/supplying DC loads. If the total load power (DC and AC) exceeds the AC input current limit, the remaining power will come from the batteries (or other DC charging sources).

In an energy storage system, one additional power flow is allowed: from the DC side OUT the AC input to the grid. This is known as "feed in". Feed in power will generally come from solar charge controllers also connected to the DC bus but could come from the batteries to assist the grid during peak times of the day when solar energy isn't available.

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snoobler avatar image snoobler commented ·

The AC input current limit restricts how much AC input power is available for either the AC loads or for charging/supplying DC loads. If the total load power (DC and AC) exceeds the AC input current limit, the remaining power will come from the batteries (or other DC charging sources).


Only if powerassist is enabled. OP indicated powerassist is disabled.

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