Multiplus II with generator/shoreline switching and current limit setting

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iand asked Oct 12, '22

Multiplus II with generator/shoreline switching and current limit setting

Due to unavailablity of the bigger Quattro II in time, it looks like I'll end up using a Multiplus II 48/10000 for my boat build. This means having an external switch between generator and shoreline, so I'm looking for ideas about how to do this and how to change the AC current limit.

I could use a relay controlled by the Cerbo GX to do the switchover, if the MP II can be used to detect whether AC is present at the input or not, with an assistant to switch over -- for example, have the relay default to shoreline, then if there is demand for AC power (e.g. to charge batteries) and there is AC present use this, if not flip the relay over to the generator and start it, then reverse all this when AC demand is over (I won't always need an AC source, boat has solar panels fitted).

Is this possible, and if so has anybody tried it?

A second issue is how to change the AC current limit, the generator can supply 38A but the shoreline will typically be 16A -- but could also be 32A if the bollard allows this (not common on UK canals). Can the Cerbo GX change the MP II current limit depending on whether shoreline or generator is selected?

If none of this works then I'll have to fit a manual changeover switch, and manually change the AC current limit, either by just entering a new value (prone to error) or providing soft buttons to select the correct value -- again, can this be done by an assistant?

Yes a Quattro would be much easier, but for various reasons I don't want to use the old model... :-(

Multiplus-II

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Modifications Space

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Answer 1 · 2022-10-12T10:44:37Z

Paul B answered · Oct 12, 2022 at 10:44 AM

For me I would use 2 cont-actors and then use there internal N/o N/C switchs so that only one at a time can be on - then the gen is connected to one cont-actor and the Shore power to the other cont actor, thus if the gen starts then that contractor closes and also auto locks out the shore power contractor from closing if shore power is provided.

there also cont-actors around that have two inputs and one common output and one set are N/C and the other N/O then use the activation coil to close the N/O connection if say the generator starts. I have found these on ebay in the past.

Sample Ebay listing https://www.ebay.com.au/itm/394273827625?epid=1757722735&hash=item5bcc8d2b29:g:JXoAAOSwn1JjPR6f&amdata=enc%3AAQAHAAAA8Fee2pDzuVio%2F4iYV%2BMl16dlkPL%2Be7bZDEauzpvv%2FkLVftxrGaVx2QTVEOaYPws6EXK6VBg6jggo97FYqUSe4hMW%2FSjEG0%2F4AK3E7U4r%2BupTB1yORy0lEMF1I0T6aAwGgegcChyAKwbjMz2Hg0gDqbKr%2BO8lMQ2yXK%2FUf%2FU%2FJK1Zhzm%2BkvJ8fIAb4vsOo%2ByeJNweWqTw5BQfeKMWfbYOfAjt8crZCqKnMw5XOeZifzs0T8w6bHxtvUYa9Vy004WAvCFvxTK4gaJ6kb9TtBnjRCuSI%2F4RlgiIGCAm3f3aKKJYgsT%2BXJrYNCZHHRvqYeWbjA%3D%3D%7Ctkp%3ABFBMwLnxvPlg

as to the current limits these would have to be manually adjusted

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iand commented · Oct 12, 2022 at 11:50 AM

If the current limit has to be changed manually then I might as well also use a manual changeover switch since the user is involved anyway. Was hoping to avoid this to make it more idiot-proof, but probably won't have to change over very often so anything complicated isn't worth the effort...

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Answer 2 · 2022-10-12T11:35:54Z

JohnC answered · Oct 12, 2022 at 11:35 AM

Hi @IanD

Really general..

Hows about a pair of linked Quattro II 5000's.

Or an external ATS (automatic transfer switch). These are available standalone.

If you can roust a simple signal from the ATS, then there is indeed an Assistant that can change the Input Limit.

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iand commented · Oct 12, 2022 at 11:45 AM

A pair of Quattro II 48/5000 will cost at least £1000 more, are a pain to install/debug (parallel wiring/configuration), and won't fit in the available space :-(

Standalone ATS are also quite expensive and basically duplicate the "intelligence" that the Cerbo already has, which seems pointless if the Cerbo can do the job.

This sounds like one of those things that the Cerbo and MP II hardware should be perfectly capable of doing (with just a simple cheap 40A DPDT 230Vac relay), if only the software permits it -- which is what I was hoping someone would suggest... ;-)

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knissone commented · Oct 19, 2022 at 02:14 AM

I'm in a similar boat (ha... ha... ha...) with an RV. I have the Cerbo and MP II 2x120, with an ATS to go between shore power and generator. I can easily get a 120V signal voltage from the generator, pre-ATS, to the Cerbo. Can you elaborate on the Assistant to change input limit based off of that signal voltage? This is exactly what I'm looking for but based on other threads here I'd thought it couldn't be done.

In a perfect world, I'd love for it to "remember" the shore power limit setting, so that generator always goes to 50A but return to whatever the prior shore power limit was when generator shuts off. I'd also like there to be a ~60 second delay or so before it switches to the generator limit, but return to shore power limit immediately after generator shutdown.

Also, apologies for being a total noob with Assistants! I'm decently technical so if you could just confirm what I want is possible and nudge me in the right direction, it'd be greatly appreciated!

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Answer 3 · 2022-10-18T23:53:43Z

johnsmith answered · Oct 18, 2022 at 11:53 PM

Im using a MP II 10k for main supply and then a. MPIi 3K as a dedicated battery charger with genny and using the AC out on the MPII 3K for my welder. Relay on MP 10K or Cerbo starts genny that is connected to AC in on MP II 3K.

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Answer 4 · 2022-10-19T04:15:10Z

derrick thomas answered · Oct 19, 2022 at 04:15 AM

I am using Venus large and node red to automatically set input current limit according to generator or shore power. The ats triggers a digital input on the cerbo when the Genny is running and proving power. Node red flow sets input current limit to 50 amps with a delay of 30 seconds for the generator, and 20 amps for shore power without delay. I also use a flow to enable or disable a relay for ac water heater according to shore power being available or not.

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