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Connecting inverter/charger to Fuse Box

Pacemaker1000

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Jun 18, 2022
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how would I connect something like a Vitron Multiplus to a fuse box to supply whole house!
I would assume AC out via an MCB in the fuse box, no problem there but what if I also want to connect the AC in also to the fuse box to charge batteries during off peak?
havnt seen any kit with built in timers So could just use a time switch relay?
what can’t get my head around is that both AC input and output are in theory shorted out?

is this correct or how else can I achieve this

thanks
 
how would I connect something like a Vitron Multiplus to a fuse box to supply whole house!
I would assume AC out via an MCB in the fuse box, no problem there but what if I also want to connect the AC in also to the fuse box to charge batteries during off peak?
havnt seen any kit with built in timers So could just use a time switch relay?
what can’t get my head around is that both AC input and output are in theory shorted out?

is this correct or how else can I achieve this

thanks
What you are talking about is a Transfer Switch. You can't connect the grid and your inverter together at the output. That requires a grid-tied system with a Utility Interconnection Agreement, to send energy back to the power grid.
What it seems you want is a Transfer Switch. It allows you to bypass the inverter and supply the grid to your sub-panel. Most inverter/chargers have a transfer switch built-in, but if it's inverter maintenance that you want to do without interrupting power, then you need an external transfer switch. Where one input comes from the inverter, the other input comes from the grid, and the output goes to your sub-panel. So it can only ever be one OR the other, not both. The transfer switch can be automatic, or it could be manual. There are lots of options out there. Growatt has one, Tesla has one, I'm sure there are others.
 
Ok, thanks.
so I’d need an automatic transfer switch connected to the fuse box with one cable Then one to the AC in and another to the AC out?
in one position batteries or solar would power the fuse box and position two fuse box (grid) would charge batteries during a set time with hopefully a built in timer?
 
Ok, thanks.
so I’d need an automatic transfer switch connected to the fuse box with one cable Then one to the AC in and another to the AC out?
in one position batteries or solar would power the fuse box and position two fuse box (grid) would charge batteries during a set time with hopefully a built in timer?
No, not quite what I said but if that's all you want to do then, most inverter/chargers like EG4, MPP, and AIMS have that functionality built-in. If you set it to battery priority, it will run on the battery until it's discharged, then switch to the grid bypass and charge it back up. The output is practically undisturbed by this transfer.
I've attached the Victron brochure. It compares the different types available there. Every inverter has its own method and requirements.
 

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Thanks, I’ll study this later.
getting close but I only want the battery to charge at a specific time period when it’s cheap ( a four hour window) so need a timer I think.
 
An AIMS Inverter/Charger, 4kW, split-phase 120/240V output connected to a circuit panel for your small house. Put a programmable timer on the grid AC input to the inverter, and connect a large battery bank to the inverter. The inverter can be set to grid priority. When your timer connects the inverter to the grid, it will automatically switch and start charging the battery. When the timer turns off, the inverter will automatically switch back to the battery and power the load. Yes, all you need is a 20A, 240V programmable timer! I have the inverters.
 
So connection wise you would have a cable connected to AC out and fuse box and another cable teed across AC out through a timer to AC in. Battery/ solar powers house when possible and cuts off when it receives input power?
that makes sense if can’t be done with all in one unit.
looks similar to the diagram you sent of the Multiplus unit where AC out connects to AC in via a relay

any idea what kW battery charges at? Is it fixed at say 3kw?
 
The proper process to design your system is to start with the loads.
Step 1 is, to write down the Watts, Volts, and Ampere rating for everything that needs to be powered by the system, and then make a spreadsheet listing how many hours a day each item needs to be powered by the battery. This tells precisely how many kW the inverter needs to deliver simultaneously, and how many kWh the battery and the solar need to deliver.
Step 2 is, based on where you live, determine how many kWh of usable energy can be derived from the solar panels available, then multiply that until you have enough to charge back what you used at night + what you need during the day + some reserve for winter/cloudy days.
Step 3, shop for components that meet your needs.

Your questions depend on your needs. There are components that can do just about anything, you need to start by knowing exactly what is required, then we can help you design and shop.
 
I charge an EV, heat a thermal store and throw in washing machine etc during cheap electric. around 20kw and happy to pay that on cheap rate.
remaining usage is 10kw over the remaining 20 hours. So aiming for solar/battery to provide this. Would start fully charged from cheap electric until sun can takeover
 
So 30 kWh per day? An EV (Tesla) charges at 7.5kW of power and has a 60 kWh battery for energy storage. I think you mean, your using 20kWh and another 10kWh, total 30kWh/day. Correct?

I just modeled a system in central Arkansas that averaged around 35kWh per day. It is 9.72kW dc, 24 x 405W solar panels.

Screen Shot 2022-06-18 at 6.35.12 PM.png
 
Looking for something more modest just to cover the 10kw that’s outside the cheap period.
solar calculater says a 4-6 kw solar array should generate 10kw a day.

thanks very much for the help by the way. Much appreciated ?
 
I get it. "Peak-shaving and rate arbitrage". My old crew installed some 3-phase units that are designed to do exactly that. The Enphase system with the IQ Battery is designed to be programmed to do this too. So can Tesla Powerwall.
 
Just to confirm.
normal design solar charges battery and inverter AC out connects to fuse board. When no power available grid takes shortfall.
so I can connect grid (same connection AC out is connected to) via a timer to AC in to only charge during off peak?
something like an immersion heater timer would do the job

tesla power wall and gateway would do the job along with 6kw solar. Just need to find cheaper alternative as quote is £19000!!

battery and whatever solar to get through the day between 430 and 0030

or preferred first option is to start with just battery and charger inverter and use cheap rate as 10kw is all that’s needed for day use. Plus can do all this work myself without paying for Scaffolding and panel installation

thaks
 
Last edited:
Just to confirm.
normal design solar charges battery and inverter AC out connects to fuse board. When no power available grid takes shortfall.
so I can connect grid (same connection AC out is connected to) via a timer to AC in to only charge during off peak?
something like an immersion heater timer would do the job
No, the grid NEVER connects to the same connection as the inverter AC output for this type of system. The grid connects to the AC INPUT terminals of the inverter. The fuse board connects to the AC OUTPUT terminals of the inverter. When your timer turns on the grid, the Inverter automatically connects the INPUT to the OUTPUT to power the load. When your timer turns off, the inverter automatically disconnects the input and starts powering the load from the battery. I hope that's more clear.

You never want the inverter output like this to send power back to the grid. It can electrocute someone working on it miles away if there's an outage. Grid-tied inverters have protections against this, a battery backup inverter like a Victron does not.
 
Think there may be confusion over what I mean by the grid I’m referring to the mains supply to the house fuse board.
AC out is connected to the fuse board so is therefore connected to the grid
 
Think there may be confusion over what I mean by the grid I’m referring to the mains supply to the house fuse board.
AC out is connected to the fuse board so is therefore connected to the grid
I think a diagram is in order then, with all the inputs and outputs labeled. I may be confused, but the terminology you've used said that you will have the grid AND the inverter output, terminating in the same fuse box? That's a no no!
 
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