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I have a multiplus 12/3000/120 and a roof top Dometic A/C that will trip my 300A breaker when the compressor would want to start. I’ve installed an “easy start” it helped when connected to a 15A shore power but if I try running only the inverter it will trip the breaker. I have 1 2/0 wire going into the multi + and - I don’t know if I should increase the breaker? Is my wire safe? Is my multi safe if I go to a 400A fuse? Thanks.
We have run several Dometic Air-conditioners off 12V. The typical peak current on startup was between 400 and 457A for around 1-2 seconds as seen on the scope. A 400A fuse will sustain that. The bigger current draw is not on initial startup but on re-start after they are very hot. We have no difficulty with the Multiplus 12/3000 and (non Victron) Lithium batteries that are capable of a 500A minimum surge. The BMS in the Lithium will knock out the system faster than the fuse if they cant sustain this surge.
Hi, @Daniël Boekel (Victron Energy Staff)
I am currently using a 300A breaker. If I replace this 300A breaker (which is from the batteries to the inverter) does this also mean I need to change the fuse from the batteries? It’s currently on a 300A battery terminal from blue sea.
Hi @Mariorda91
Please consult an electrician to check your system (components, wiring, connections) to make sure it is up to the task.
If it were me, I would get rid of the 300A breaker and use a 400A fuse. I would also move up to larger size cables from battery to inverter.
Most breakers larger than 250A are not DC rated and don’t have a good trip curve. If your breaker isn’t DC rated for what you are using it for, it is a big time hazard.
Your inverter is definitely capable of starting and running that AC unit. But I don’t think your cabling and fusing are up to par yet.
Hi, @solardude
I am currently using 2/0 for the whole system. I have some extra 2/0. Do you think if I add another 2/0 + and - with a 400A fuse (that will be a new 400A fuse and another 400A fuse that will replace the 300A breaker that's currently in place) so 2 positive and 2 negative 2/0 cable going into the inverter/charger and each with a 400A fuse in between will suffice? or should I rather get 4/0 to go in the inverter/charger with a 400A fuse in between? Also, what about the 300A battery terminal fuse I currently have in place? should I bump that to 400A as well?
I really appreciate taking the time to help me figure this out.
Talk to the folks at Micro-Aire there is a firmware update required on the Easy Start when using a 12 volt inverter.
Seems like the unit I purchased (Feb/2020) has the latest firmware. So I a good in that aspect! Thanks for pointing this out! Could be helpful for anyone who purchased the micro-air easy start before Dec/2019.
I run 15k btu AC in RV with easy start and same inverter. I use 400 amp fuse and 4/0 from battery/ Do you have anything else turned on that is using inverter?
No! I was testing only my 13.5 BTU A/C. But the issue at the moment is the 300A fuse I have going from batteries to inverter/charger. I have purchased a 400A fuse to replace this and also replacing the 2/0 cable with 4/0 and trying it again. fingers crossed!
