MultiPlus II and Powerline EMS

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Matthew Shea asked May 24, '21

MultiPlus II and Powerline EMS

I am planning an install of a MultiPlus II in a Winnebago RV that has a "Powerline EMS" The idea behind the device is it manages current draw to make sure the appliances don't draw to much power when connected to 20 or 30 amp service. has anyone installed a multiplus where a powerline or similar EMS system was in place? do you keep it or remove it? my thought is the multiplus will provide similar functionality and the EMS might confuse the multiplus so it should be removed but I would like to hear other opinions.

Multiplus-II installation

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Answer 1 · 2021-05-24T16:15:40Z

Kevin Windrem answered · May 24, 2021 at 04:15 PM

The Powerline EMS appears to be a load management system which is not handled by the Multi. I think it would be possible to put the Powerline downstream of the Multi but it's logic to sense 120 volt single phase vs 120/240 volt split phase may be fooled by the Multi.

Your best bet at a working system would be to use the new MultiPlus II designed for split-phase with a single inverter. In split phase mode, the inverter is inserted in only one leg. The other leg gets shore power direct so no power assist. When shore power isn't present the inverter does feed both legs.

An alternative is to run two Multis configured as split-phase so each leg runs off a separate inverter. This approach has limitations also in that it isn't happy with single phase shore power (both Multi's fed in phase). The best workaround if you have the space and weight is to install an transformer upstream of the Multis to create split phase power from single phase.

With two Multis, the Powerline would still detect 120/240 and not shed loads. But maybe that's OK especially since the Multis provide "power assist".

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Matthew Shea commented · May 25, 2021 at 03:21 AM

I am planning on using the the split phase multi-plus. My concern is in inverter mode or single phase mode I'm afraid the Powerline EMS will detect 30 amp service and start cutting power to things in order to keep the draw under 30 amps which will effectively make the power assist feature useless.

OPERATION WHEN CONNECTED TO 240VAC, 50 AMP SERVICE: If 240 VAC, 50 Amp service is present at the L1, L2 and neutral inputs, the energy management feature is disabled and the Control Module sends a signal to the Display Module which causes the load meter to go blank, the 50 AMP service indicator to light, and all power status indicators to light.

OPERATION WHEN CONNECTED TO 120VAC, 30 AMP SERVICE: If 120 VAC is present at the L1, or L2 and neutral inputs and no +12 VDC signal is present at J4, pin 8 on the Control Module the EMS will assume that 120 VAC, 30 Amp shore power is available and the energy management feature will be enabled. The Control Module sends a signal to the Display Module, which causes the load meter to display actual load current and the 30 Amp service indicator to light. The power status indicators will light when power is available to run its corresponding load. Initially, all relay contacts are closed. The total current is monitored. If the total current should exceed the service limit, the system will turn off the first load in the shedding table. As it does this, it calculates the amount of current that was removed, which is the value for that load. This value is placed in memory. If the current remains above the service limit, the system will turn off the next load in the shedding table. Again, it calculates the amount of current that was removed and places this value, which is the value for that load, in memory. In like manner the system turns off loads until the total current falls below the service limit or all of the four controlled loads have been shed. In this process the system has "learned" the amount of current that each particular load draws. This feature compensates for the differences in current draw over a range of line voltage and ambient temperature, by re-learning the load each time it is turned off or "shed". The system now waits until the total current is lower than the service limit and enough current is available, as compared with the amount in memory for the last load shed, before it will turn that load back on. This assures that there is sufficient current to operate the load. There is a two minute minimum delay period after a load is shed before the load will be turned back on again to prevent air conditioners from turning on with a head of pressure.

I think the only option would be to move the current sensor off the main and onto a feeder line so it isn't aware of the full load or completely gut the powerline system out which doesn't seem like an easy approach.

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