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I am currently expanding my RE system with a third multi II inverter to 3 phase from the current 2 phase in parallel. (mulltiplus II 5000/48/70-50) I have purchased some Airpax 150A DC breakers and just wondered if I need to link them all together so if one trips, they all trip. I don't have any 3 phase motors running just 3 separate circuits on the AC side to spread the loads which get quite high when we run air con,etc..
Any help much appreciated
Hi @rithym1964
you don't have to link the DC breakers, when one trips, all units will switch off.
on a parallel system this is different there they should ideally be linked.
Also: these breakers should never trip unless there is a short-circuit somewhere, so its also a bit of a theoretical issue.
Hello Daniel thank you for answering my actual question it seems my thread has been hijacked by somebody who thinks they know what I am trying to achieve without understanding my situation. It is a straightforward question and you answered perfectly... In a 3 phase situation the DC breaker bars it is not necessary to link them... in a parallel situation it is best to link them. Thank you
To me it would be much better to Parallel all 3 units to become 1 large 15Kw system. as this way the loads can be spread evenly over all 3 inverters
then run 3 circuits off the switch board if need be.
I am presuming by your description that you are running 2 separate inverter systems , but its not really clear what you are now doing.
are you going from 1 pair of inverters to now 3 inverters setup in 3 phase.
if this is the case I would advise against that, as you are then limited to a max of 5Kv from any one inverter, (you cant share across the 3 phases) you have to then load balance the phases.
Just some thoughts to consider
Paul B Thanks for reply. At the moment I have two 5KVA multis in parallel and they are connected to the 48V bus bar via one 250A Midnite DC breaker which means both inverters go off together in the event of a trip (never happened yet) If I add a third 5KVA multi it would be asking too much to connect that to the same breaker so I have purchased three 150A DC breakers, one for each multi. My question is should I link the DC breaker on/ off switches so if one trips they all trip together?
As for the question of parallel or separate phases I hear your suggestion about spreading the loads across all three inverters in parallel but I also have a 3 phase borehole water pump 120M down which normally runs from the grid at night using cheaper rate electric and fills my water tank. This will not run off a single phase. My grid connection is 3 phase 21KVA and if that goes down and my inverters are in parallel I have no way to pump water from the borehole. Chances are that will never happen but I am trying to cover all scenarios in case it does...
it really makes no difference really which way you do it as if one trips the other inverters will shut down anyway. as it wont run on just 2 phase's
even if they were in parallel one goes down they all shut down.
yes if you have 3 phase item then thats another kettle of fish, but you did say in the orginal heading " I don't have any 3 phase motors running"
Anyway balancing the phases will be a issue I think you will find, but give it a go its always easy to convert back.
keep in mind that if any one of the phases overloads then all 3 shut down,
