How to connect inverter to 240v system?

Alice1

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23
Ok. We would like to connect an inverter to the leisure batteries and to the built in 240 volt system in our 2004 Burstner T-Star 680. Every inverter I have seen has a 240v socket on it for the outlet and I cannot work out how to do it. Would like to have it permanently connected to the 240v circuit. We already have a built-in inverter fitted which just runs the air con unit, but this doesn’t run the sockets. Is there a simple or easy way of connecting this inverter to the 240v system on the m/h? Will I have to buy a second inverter, and if so where canI get one (fitted or diy - we are near Thirsk) Or have I missed something?
 

Minisorella

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1,449
I just have a small extension lead running from my inverter, which is in a tricky spot so this helps make it handier. Not sure I'd want to have the inverter serve the mains sockets because it would blur the lines too much for me but I seem to remember being told that you'd need a separate box with breaker switches. Mind you, I know nothing... the experts will be along soon I'm sure :ROFLMAO:
 

Alice1

Full Member

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23
I just have a small extension lead running from my inverter, which is in a tricky spot so this helps make it handier. Not sure I'd want to have the inverter serve the mains sockets because it would blur the lines too much for me but I seem to remember being told that you'd need a separate box with breaker switches. Mind you, I know nothing... the experts will be along soon I'm sure :ROFLMAO:
Yes we've already got one with a plug socket but its a faff to connect it and use it as it isn't in the right place. Still we'll wait for the experts to respond!
 

Okta

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495
I believe there are systems that involve an automatic changeover that ensures there is no conflict between mains and inverter. I have my inverter in an exterior locker and run the ehu cable under the mh from it to the input socket on the other side. However, I disconnect everything except the sockets and make sure I use only low demand appliances that will not overload the inverter. I daresay there are arguments against this method and you need to be careful that there is nothing hidden running, such as the mains charger.
 

Wully

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1,608
Jeff how dose that work with the battery charger ? I’m a bit thick when it comes to electric stuff and thought about doing this and thought it must be wrong because it’s too easy.
 

jeffmossy

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Jeff how dose that work with the battery charger ? I’m a bit thick when it comes to electric stuff and thought about doing this and thought it must be wrong because it’s too easy.
Wully turn off the inbuilt 240v battery charger and also make sure the fridge / freezer are switched to running on gas , then that should just leave your sockets live , but remember not to overload the inverter / batteries by plugging in heavy usage appliances
 

Wully

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I’ll give that a try my invertor is 2500 pure sine wave with a remote had it lying around for ages just fitted it before henly mainly used like 99% of invertors for drying the wife’s hair I know it’ll kick he’ll out the batteries if abused but I’ve got that wee alien contraption that I darent mention to charge batteries?
 

jeffmossy

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1,713
I’ll give that a try my invertor is 2500 pure sine wave with a remote had it lying around for ages just fitted it before henly mainly used like 99% of invertors for drying the wife’s hair I know it’ll kick he’ll out the batteries if abused but I’ve got that wee alien contraption that I darent mention to charge batteries?
Make sure you earth the van Wully , I use a steel heavy duty tent peg hammered into the ground , then use a jump starter lead from the chassis to the peg
 

alwaysared

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328
Ok. We would like to connect an inverter to the leisure batteries and to the built in 240 volt system in our 2004 Burstner T-Star 680. Every inverter I have seen has a 240v socket on it for the outlet and I cannot work out how to do it. Would like to have it permanently connected to the 240v circuit. We already have a built-in inverter fitted which just runs the air con unit, but this doesn’t run the sockets. Is there a simple or easy way of connecting this inverter to the 240v system on the m/h? Will I have to buy a second inverter, and if so where canI get one (fitted or diy - we are near Thirsk) Or have I missed something?
You could always use something like this

Regards,
Del
 

Tony Lee

Full Member

Messages
70
I just plug my EHU cable into the invertor , but make sure the van is earthed . Simples
Good idea to make sure the battery charger is disabled otherwise the electrons get dizzy going round and round in circles all the time.

There can also be problems getting earth leakage circuit breakers (if fitted - and advice here needs to apply to motorhomes wired ti both British and EU standards) to work properly because of a lack of MEN point. Making sure the van is earthed (how?) doesn't solve the problem.

Actually the best and most responsible advice to these sort of questions is if you need to ask in these sort of fora, then you should leave it to licensed experts to do the work.
 
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Okta

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495
If the test button trips off the supply I had assumed all was well. Is this not the case?
 

wildebus

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2,677
Ok. We would like to connect an inverter to the leisure batteries and to the built in 240 volt system in our 2004 Burstner T-Star 680. Every inverter I have seen has a 240v socket on it for the outlet and I cannot work out how to do it. Would like to have it permanently connected to the 240v circuit. We already have a built-in inverter fitted which just runs the air con unit, but this doesn’t run the sockets. Is there a simple or easy way of connecting this inverter to the 240v system on the m/h? Will I have to buy a second inverter, and if so where canI get one (fitted or diy - we are near Thirsk) Or have I missed something?
I'd be a little surprised if there is a built-in Inverter dedicated to an air-con unit, given how much power they draw. But it is possible if you have a large enough battery bank.

If you want to have 240V sockets 'live' when not plugged in, then I would think a second inverter might be the better option then messing with the existing one as it is possible that is a customised inverter designed for AC use to deal with start-up surges and the like.
The point about having an inverter feeding the 240V outlets which then feed a battery charger and you end up going in a loop is an interesting one and is possible depending how the system is setup but best avoided as a possibility really.

The approach I prefer over messing around with cables when I want to use the inverter is to use a Contactor, which is essentially just like a relay, that feed the 240V sockets. When the Contactor detects no power from hookup, it connects the sockets to the Interver; when there is power from hookup, the contactor gets enabled and the sockets are connected to mains power. This is all automatic and the switching happens so fast power does not get interrupted to the devices plugged in.
I've attached a PDF showing how this is all wired up on my van (I've actually got a number of different 240V circuits, same as you would do in a house, and one of those circuits is on this Hookup/Inverter Contactor auto-switching system).
 

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SimonM

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554
I’ve got 4&110ah leisure batteries hooked up to a 2000w inverter that lives just 2 feet from the batteries and so has a very short cable run. If I need to run anything off the inverter that won’t plug into its socket I simply use a short dedicated extension lead, nothing too long the inside of the MH isn’t that big.
 

StreetSleeper

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1,851
You might find this thread interesting, My Latest Project in Motorhome Chat: especially the last bit.

Rae
 

Tony Lee

Full Member

Messages
70
Proper changeover systems ususlly include extra contacts for switching the earth as well so that eart leakage breakers work properly.

In many elcb, the test button simulates an imbalace by connecting a resistor between L1 and L2 to bypass 40mA around the sensing system and that is not yhe same as 40mA flowing to earth. The test button tests the breaker, but not the system it is installed in
 

cliveandann

Full Member

Messages
70
Proper changeover systems ususlly include extra contacts for switching the earth as well so that eart leakage breakers work properly.

In many elcb, the test button simulates an imbalace by connecting a resistor between L1 and L2 to bypass 40mA around the sensing system and that is not yhe same as 40mA flowing to earth. The test button tests the breaker, but not the system it is installed in
A system supplying 230v AC from both the mains and an inverter should ideally have a centre off changeover switch to switch both the live and neutral circuits. This can be achieved simply by moving a plug from one socket to another, by a manually operated switch or as suggested earlier using an automated system with a contactor. Whatever the power source the load circuits need to be protect by some form of trip.

Tony has suggested using an ELCB (earth leakage circuit breaker). These ceased to be recognised by IET Regulations in 1981 although manufacturers still seem to provide devices described as such. For best protection I would suggest using a RCBO which is a Residual Current Breaker with Overload protection for the mains and a separate RCBO for the inverter both installed in the circuits before the changeover switch. It is possible to design a circuit to use a single RCBO but this requires an 8 pole changeover switch. Use a MCB for each circuit after the changeover switch. Specifying the RCBO and MCBs depends on the circuit parameters.

The wiring diagram pdf provided by Wildebus does not include any protection in the inverter circuit which is potentially dangerous. The incoming mains is protected by an RCB and circuit overload protection by MCBs. It would also be helpful to show the neutral circuits.

As always get everything checked by a qualified electrician.
 

cliveandann

Full Member

Messages
70
No Protection? really? are fuses not regarded as a protective device in your opinion?
Fuses are indeed a protective device.. Your circuit diagram shows a fuse in the 12v dc supply to the inverter which I agree is good protection. However I cannot see any form of protective device on the AC output side of the inverter. The power goes from the inverter to the contactor and then to the sockets with no RCBO or similar in the circuit.
 

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