Auto changeover relay for inverter

[Techno]

First picture is a selection of relays from RS components. The one on the right is my choice as it is 10 amp rated through the normally closed contact set which will be used for the inverter when off hook up.
The normally open contact set is 30 amp rated and will be used to power a skt/skts as normal when on hook up

I've mounted the relay in a "really useful box" and fitted a 25mm thread stuffing gland big enough to grip 3x1.5mm flexes all together

Power IN flex lugged up to go on the N/O contacts and the 230volt relay coil

Power out connected to the common pair of terminals and inverter feed connected to the N/C terminals

All that remains is to customise the flexes to required lengths
fit a 13 amp plug top to the inverter feed but with a 10amp fuse!!!
Fit two pairs of 10 amp rated connectors being carefull to fit the female halves to the ends that will be live i.e. the flex from the 10 amp breaker that you are going to cut that normally feeds the skt and the power out lead from the changeover.
The male ends go on the feed in to the relay box and the other part of the flex cut earlier that continues on to the socket.
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Now I just need an inverter, probably a 1.8K for my needs but I'll see what's on special.

I've already been using this setup with the other relay in the first picture but with a 350watt pure sine inverter for the entertainment and gizmo charging area "lounge"

 

[scotjimland]

neat installation .. :thumb:

a schematic diagram would handy for those who are less knowledgeable .

 

[Techno]

Thanks
There is enough information there for anyone competent to undertake the task if they find it useful. The pictures of the relay have a contact schematic :thumb:
No have a go hero/heroines please oh:

The modus operandus is
The socket radial circuit is now routed through the normally open contacts of the relay, as soon as the hook up is made this makes those contacts close to feed the socket as normal.
Without hook up you just switch the inverter on and the socket is now fed through the normally closed contacts of the relay

 

[scotjimland]

Thanks
There is enough information there for anyone competent to undertake the task if they find it useful. The pictures of the relay have a contact schematic :thumb:
No have a go hero/heroines please oh:

fair comment..
but it wasn't for my benefit, with over 45 years electrical and instrumentation experience, I'm more than capable.

 

[Techno]

Good lets keep it that way :thumb:

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[Techno]

I started out some long time ago by copying Clive Mott's auto changeover system which used a contactor. Unfortunately this has an annoying hum while ever on hook up.
The search for a suitable QUIET relay took some time and I believe I struck gold with this latest offering

 

[pappajohn]

what's an INERTER please

 

[vwalan]

sshh .you werent supposed to notice that . sonly a smelling pistake .ha ha ,.

 

[Techno]

Where can I get this cheaper?
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Don't start at outdoor bits

 

[Wildman]

what's an INERTER please

Its a non working (Inert) inverter

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[Techno]

Its a non working (Inert) inverter

Absolutely as I've not bought it yet :Cool:

 

[hilldweller]

It has the potential to go pear shaped if your inverter cannot supply the same current as the mains hook-up.

How is it for reverse polarity ?

 

[Techno]

It has the potential to go pear shaped if your inverter cannot supply the same current as the mains hook-up.

How is it for reverse polarity ?

It's double pole so no different whether it's fitted or not

If you read my guide it is limited to 10 amps by the fuse you fit in the plug top.
Inverters also have their own protection against overload and undervoltage.
Personally I'm not looking to supply 10 amps just my microwave occasionally and 1000watt hairdrier whether she like it or not

 

[Techno]

what's an INERTER please

oh:

 

[vwalan]

hi techno those other inverters may take a remote .certainly the ring one can . one of my mates put one on his . just plugs in .

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[Techno]

hi techno those other inverters may take a remote .certainly the ring one can . one of my mates put one on his . just plugs in .

Cheers Al
My 350 watt inverter has no remote but I installed it next to the batteries under the lounge seat and drilled a 25mm hole in line with the switch. I just give it a poke when we want power to the away from home entertainment devices

 

[vwalan]

i mounted mine on the upright of a seat unit then i can sort of monitor the lights . plus its got a chance of more air passing over it . my mate hid his away and contacted ring and got the plug in remote bit .
i keep saying i will get a smaller one but never do.
its handy if you cam switch it off if it starts squealing in the night in darkest winter.

 

[hilldweller]

If you read my guide it is limited to 10 amps by the fuse you fit in the plug top.
Inverters also have their own protection against overload

Probably faster than your fuse.

But the point is, if you have 3kW load and 1.8kW inverter, you are boiling your kettle, mains goes off followed by "clack", whine, nothing. It's a good plan but with a built in gotcha.

Even if you did it properly, 3kW inverter there is still a gotcha, kettle is boiling mains fails, kettle keeps boiling but not for much longer and all the lights go out.

This business of 240V in a motor home is one big can of worms. One sure solution is no 240V inside.

I'm just rambling on, frame of mind of someone designing this into a new MH, because someone is bound to say "They should build that into all of them".

 

[Techno]

You simply have to know your limitations? we never have a 3kw load even on hook up even in winter.
Kettle is always gas
Yes I have Gaslow but no gas microwave yet lol.

Yes it is feasible to fit at source but vans are complicated enough for dealers already to cope with what everyone expects.
I've designed this to be transferable as we're changing vans before long but it will be our final van and I'll do a more permanent job in the Rapido

 

[vwalan]

yes it would be nice .when i first did my trailer it was built not to use alot of leccy . but as solar came down plus i realised a gas fridge didnt work in the hot climates i changed to 240v . still cant put up with the 12v ones . my inverter etc really just runs the fridge . ,food mixers ,washing machine and the computer.
but will power drills etc if need be .
i still say gas lights use less leccy than led,s .
i did fit a ehu .but have never used it except for during the build . never use sites so indepancy is the way

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[Techno]

BTW Brian it doesn't matter if the inverter reacts faster than the 10 amp fuse the 1.5mm flex is good for 19 amps, the purpose of the fuse is to limit current for the benefit of the relay contacts but short periods in excess should be no problem.
My 800watt microwave should certainly not exceed 5 amps under any circumstances given a working load circa 1100watts

Also having read your post again
The kettle wouldn't continue on inverter after a hook up failure if that's what you meant?
switching the inverter on is a conscious decision, the circuit is automatic but turning it on is not

 

[Wildman]

you obviously know what you are doing and my brain is not functioning properly tonight so where am I going wrong 1100W at 220 v is as you say 5amps , but the inverter supply is from 12v presumably so would be seeing 90 odd amps. Sorry fuddled brain too many tablets and wine bound to be something I overlooked

 

[Techno]

you obviously know what you are doing and my brain is not functioning properly tonight so where am I going wrong 1100W at 220 v is as you say 5amps , but the inverter supply is from 12v presumably so would be seeing 90 odd amps. Sorry fuddled brain too many tablets and wine bound to be something I overlooked

Only the AC voltage current is going through the relay. The DC side of it is a completely different story and obviously you need a healthy battery capacity and a means to keep them recharged.

I've hit 13 amps from my solars under load on good days

 

[Techno]

80p Asda container upgrade and ready to go

 

[Techno]

PART II may help with understanding

Side locker floor removed and there is the flex from the mains board coming up through the floor and on its way to the nearside kitchen sockets

I managed to obtain spare length by re routing the converters choice of cable run.
Fit the 10amp through connector Female to mains side male to socket side

unit plugged in between the open ends

No holes to drill in my case, feed from inverter flex passed through gap into vicinity of batteries.

Plugged into my 350watt inverter just to test

Microwave lights on

Kitchen sockets live

When my new inverter arrives it has 2 sockets so the 350watt could be redundant.

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[Techno]

Everything working a treat now with new inverter, microwave and all first class

 

[Reallyretired]

Mine is much simpler, 1.5Kw charger/inverter/UPS. It switches over automatically.

WE do use an electric kettle (low wattage) as it only uses around 10AH to boil half full and our solar gives up to 20A in full sunlight so recharges in less than an hour. Use the kettle on gas in Autumn?winter of course.
I accept that the kettle requires 100A from the batteries but only takes a few minutes to boil so quite practical, likewise hairdryer as again only on for a few minutes.

 

[Techno]

Mine is much simpler, 1.5Kw charger/inverter/UPS. It switches over automatically.

WE do use an electric kettle (low wattage) as it only uses around 10AH to boil half full and our solar gives up to 20A in full sunlight so recharges in less than an hour. Use the kettle on gas in Autumn?winter of course.
I accept that the kettle requires 100A from the batteries but only takes a few minutes to boil so quite practical, likewise hairdryer as again only on for a few minutes.

Does that power all the sockets in your van?
Using two of my change over relays which cost me about £26 each I have power everywhere as if on hookup

 

[Reallyretired]

Does that power all the sockets in your van?
Using two of my change over relays which cost me about £26 each I have power everywhere as if on hookup

Yup powers all the sockets but not fridge or boiler.

 

[Ralph-n-Bev]

Just fitted one of these Link Removed

Great bit of kit, Inverter /Charger in one unit. The unit is fed direct from the mains in and then feeds all the sockets.

One great feature is the Power assist.....The inverter will work in parallel with the incoming mains to provide more power.

This feature works well with our small Honda EU-10i supplying up to 2.2 kw if needed.

900w from the Genny + 1300w from the Inverter.

Works well for running a 1800w hairdryer from a 900w Genny.

Not cheap..... but stacked with useful features :thumb:

Ralph.

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