Manual Switch - Inverter to EHU?

Wissel

Wissel

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Having just ordered all my cabling to fit out my van's 12v electrics, I'm wondering about 230v.

Having asked about inverters before, I've seen a few people say they don't like the auto-switch over available on some inverters. So I wondered, can I use a double-pole changeover switch to switch between EHU and inverter power?
(I am useless when it comes to inverters)

At present, I have no inverter. The main EHU cable feeds directly into the consumer unit, has an RCD, a ring main powering most sockets and a separate trip powering the heater and another powering the EHU charger to the leisure batteries.

What i'd like to do is add the double pole change-over before the EHU feed reaches the consumer unit, with another feed from the inverter. Then (at least the way my simple brain sees it) I'd be able to power all sockets from either EHU or the inverter, with everything going through the RCD and fuses at all times.

Can I do this or is there a better way?

Also, if this is okay to do, what size switch would be ideal?

I'm thinking a double pole, 230v, 20a version should be about right?

Thanks in advance,
David
 
Have you done a search on previous threads about this? I seem to remember @Techno went into some depth with a similar project. It may have been an auto system but looked a neat job.
 
The problem doing it too early in the wiring, so to speak, is your inverter will also power the battery charger and the refrigerator as well if it is one of the automatic ones. You only want it to power the sockets normally.
I would use your double pole switch on the socket circuit only and fit a non-latching RCD on the feed coming from the inverter.
 
It will work if you fit it in the correct place to bypass the charger and fridge (or turn off the charger and select gas on the fridge) BUT....don't forget, under any circumstances, to switch it BEFORE hooking up or turning on the inverter.
If both inverter and mains are running together you will have two different phases running together and will trip the post and/or blow the inverter.
This is why an auto change over is preferable.

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DBK said:
The problem doing it too early in the wiring, so to speak, is your inverter will also power the battery charger and the refrigerator as well if it is one of the automatic ones. You only want it to power the sockets normally.
I would use your double pole switch on the socket circuit only and fit a non-latching RCD on the feed coming from the inverter.
Click to expand...

That's an excellent point @DBK (I'm not with it today - man flu lol)

So the ideal situation would be 2 rails in the consumer. One that is powered by the inverter or EHU, that powers just the sockets. And a second rail with items that I only want powered when on EHU, so only connected when EHU selected on the switch?
Both these rails would have individual RCD's.

Do I have this right?
 
I would have two separate circuits with only low amperage sockets wired to the inverter and the second circuit only for high load ecu sockets. You can easily switch plugs to the ECU sockets
 
pappajohn said:
It will work if you fit it in the correct place to bypass the charger and fridge (or turn off the charger and select gas on the fridge) BUT....don't forget, under any circumstances, to switch it BEFORE hooking up or turning on the inverter.
If both inverter and mains are running together you will have two different phases running together and will trip the post and/or blow the inverter.
This is why an auto change over is preferable.
Click to expand...

Would this be an issue with a proper changeover switch?

I thought the point of these was isolating both positive and negative from one source before connecting another?

Have I got this wrong (probably) :)
 
As for changeover switch capacity.....20a won't be high enough.
Add ALL the mains breakers capacities together and use that total capacity.....there's a potential there to use the full amperage even if you don't use it.
Or look at the fuse boards main switch capacity and use that instead.....you can't exceed that under normal use.
 
Wissel said:
Would this be an issue with a proper changeover switch?

I thought the point of these was isolating both positive and negative from one source before connecting another?

Have I got this wrong (probably) :)
Click to expand...
Correct....I have a lot on my mind at the moment and can't think straight.

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pappajohn said:
As for changeover switch capacity.....20a won't be high enough.
Add ALL the mains breakers capacities together and use that total capacity.....there's a potential there to use the full amperage even if you don't use it.
Or look at the fuse boards main switch capacity and use that instead.....you can't exceed that under normal use.
Click to expand...

My figuring on 20a was that the feed from an EHU source would be fused at 13a maximum (I think) and the inverter cable would have a plug the other end, again 13a. Am I missing something on this?
 
We have an auto change over relay, it cuts out the supply to the battery charger when on the inverter but it still power the fridge which I don't see as a problem, if we are travelling with the inverter on I will just let it run the fridge on 240v likewise when the sun is out and we want the microwave or coffee machine I will just leave the fridge on Auto and it sorts itself out, if I want to leave the inverter on all day for some reason I just put the fridge to Gas, but it does mean that you have all the options available should you want/need one day.

Martin
 
I use this which leaves 2 poles spare I know but spot on quality
https://www.ebay.co.uk/itm/32-AMP-R...384512&hash=item4d181d2982:g:k8sAAMXQXaxRITVO


IMG_0330-L.jpg

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There will be some things that you should never want to run off the inverter (such as the Fridge, Charger, Heating, AirCon, and Kettle) so don’t allow it by wiring them in. You should be thinking of separate circuits from your inverter for low wattage items (and occasional high wattage things like hair driers only if your inverter has capacity).

I’d suggest you install a modest output inverter, then you’re less tempted to try running things like microwaves from it. Wiring sockets from the inverter separately allows the use of them without the need for any switching. When on mains, the charger will have more work to do but the whole set-up is much simpler. Although a high output inverter might cope with heavy loads, I don’t think it’d be kind to the batteries so ought to be avoided.
 
Our kettle has run off the inverter for at least 3 yrs. How many batteries you have is what matters
 
Actually I fitted 3x125AH in February 2013 and I said at the time that Id give them away and replace them after 4 yrs. That hasn't happened. I increased to four after the first year but in the main they are close to 5 yrs old now and still OK.

However I have 8x125ah these days and the flexibility of two banks and being able to shift the balance if one set is low is a big help
 
Thanks guys, think I have it all sorted in my head now :)

@rogher - no kettle (gas) or m/wave (don't use one at home), but will be powering my Tassimo so need a 1500w Sine Wave inverter. Apart from that, just the occasional hairdryer usage etc as almost everything we use is 12v.

The switch for the inverter will be next to the Tassimo, so get up, switch on, coffee, coffee, switch off. I doubt we will have EHU very often, so changeover will usually be set to the inverter.

This will be powered by a 300Ah LifePO4 bank, which can deliver 150Ah constant without damage (must get this ordered)
 
LiFe batteries just like LiPo can be severely damaged if the volt per cell goes below the manufacturers specification. So make sure you know the limitations

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Techno said:
LiFe batteries just like LiPo can be severely damaged if the volt per cell goes below the manufacturers specification. So make sure you know the limitations
Click to expand...

Thanks Techno. I'm going with a fully programmable BMS that I'll set to cut out at a little over the recommended low voltage and to stop charging a little before full. I know this will cost me a bit in capacity, but should help the batteries last.

Funny really. I started planning this build a month or so ago, with a view to starting the build in March. At the rate things are progressing, we will hopefully be living in the van by March now :)
(and can't wait)
 
Techno said:
Why? hook up is only 16 amps
Click to expand...
Hook up is but what's the consumer unit main switch rated at ?
Your average domestic one is rated at either 63 amps (commonest), 80 amps or 100 amps.
The potential is there to use that amount in the same way the vans main switch may be rated at 32amps.
Any changeover switch should be capable of handling the same amperage.
 
Wissel said:
Having just ordered all my cabling to fit out my van's 12v electrics, I'm wondering about 230v.

Having asked about inverters before, I've seen a few people say they don't like the auto-switch over available on some inverters. So I wondered, can I use a double-pole changeover switch to switch between EHU and inverter power?
(I am useless when it comes to inverters)

At present, I have no inverter. The main EHU cable feeds directly into the consumer unit, has an RCD, a ring main powering most sockets and a separate trip powering the heater and another powering the EHU charger to the leisure batteries.

What i'd like to do is add the double pole change-over before the EHU feed reaches the consumer unit, with another feed from the inverter. Then (at least the way my simple brain sees it) I'd be able to power all sockets from either EHU or the inverter, with everything going through the RCD and fuses at all times.

Can I do this or is there a better way?

Also, if this is okay to do, what size switch would be ideal?

I'm thinking a double pole, 230v, 20a version should be about right?

Thanks in advance,
David
Click to expand...
This is exactly what I've done. It's a double pole changeover switch rated at 20 amps. It has 3 possible positions EHU - OFF - INVERTER so there can be no conflict. I put a fused spur on the van charger and it's usually off anyway now the solar has been upgraded.
 
Last edited:
pappajohn said:
Hook up is but what's the consumer unit main switch rated at ?
Your average domestic one is rated at either 63 amps (commonest), 80 amps or 100 amps.
The potential is there to use that amount in the same way the vans main switch may be rated at 32amps.
Any changeover switch should be capable of handling the same amperage.
Click to expand...
It only needs to handle the maximum that can be delivered and that is dictated by the available supply of 16 Amps
There is no potential to use more without tripping
 
Techno said:
However I have 8x125ah these days and the flexibility of two banks and being able to shift the balance if one set is low is a big help
Click to expand...
Without wishing to digress too far, Andy, how do you balance the use of two banks? (Wish I even had the payload for two banks.)

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I use one for the 12 volts and one for the 230 volts
A selector switch combines them if I need to balance them e.g. if my inverter batteries are very low I can stave off damage by transferring surplus from the hab battery bank until the next opportunity to recharge
 
I ended up ordering a 10way, dual RCD, split load consumer unit.

It's a little larger than I'd have liked, but will fit a 12v fuse board inside as well (fuses still accessible from outside).

I then ordered this changeover switch:
changeover.jpg

This will fill the empty bays in the consumer unit to make a nice neat job. It's a proper 125a (ott) changeover to switch from mains to a genny. Should be ideal to switch from mains to inverter power.
 
For anyone interested, here is my final consumer unit design, I say final but drew the wires in whilst half asleep and haven't double checked them yet :)
Consumer-Mine.gif

Whether using EHU or inverter, the source can be isolated before switching (EHU via main switch, inverter via it's own switch). When using inverter power, the first RCD is switched off.

I'm adding a polarity check to the outside of the box, along with a polarity changeover switch. This fits into the circuit where the "X" are.

Finally, it's all wired in 6mm cable.

Have I missed anything?

Thanks
 
Change the negative on the diagram to neutral?
My changeover switch is nothing like that but as long as it isolates mains when on inverter and vice versa it will be ok and no need to switch off the mains incoming.

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