Which double pole double throw/ 2 way changeover relay? advice please

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MisterB

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enough to know i shouldnt touch things i know nothing about ....
Can anyone recommend a suitable DPDT relay please. I am looking to install an automatic 240v to 12v relay, so it changes automatically when the EHU is connected and defaults onto 12v (which will enable the inverter to provide the 240v supply to the circuits) and then switch back to EHU supply when back on EHU.

also, would you recommend it be housed in a separate enclosure or withing the consumer unit?




I am looking at this one, but not sure if its suitable

Thanks
 
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MisterB said:
Can anyone recommend a suitable DPDT relay please. I am looking to install an automatic 240v to 12v relay, so it changes automatically when the EHU is connected and defaults onto 12v (which will enable the inverter to provide the 240v supply to the circuits) and then switch back to EHU supply when back on EHU.

also, would you recommend it be housed in a separate enclosure or withing the consumer unit?




I am looking at this one, but not sure if its suitable

Thanks
Click to expand...
If you don’t mind me asking why do you need to do this?
 
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NicM said:
If you don’t mind me asking why do you need to do this?
Click to expand...
of course, i am fitting an inverter - primarily to power the microwave when not on EHU, several people contributed to the thread by suggesting that it might be useful to consider fitting an auto change over and having the inverter automatically provide the supply to more than just the microwave, when not on EHU.

there are different ways to achieve this inc a manual change over but the auto changeover really appeals
 
I tried something like this a few years ago. As I remember- make sure the 240v relay is suitable for ac or it will buzz all the time and bear in mind that all the time the inverter is running- whether you are using it or not, it will put a definite but small load on the battteries.
In the end I scrapped it and prefer to run low load items like phone chargers etc off the 12v side
Mike
PS Re-read your post - we dont have a microwave
 
Make sure you do your homework on the battery load presented by the microwave via an inverter!
M
 
MisterB said:
of course, i am fitting an inverter - primarily to power the microwave when not on EHU, several people contributed to the thread by suggesting that it might be useful to consider fitting an auto change over and having the inverter automatically provide the supply to more than just the microwave, when not on EHU.

there are different ways to achieve this inc a manual change over but the auto changeover really appeals
Click to expand...
Okay so how many amps do you think you will be using?
 
Oh, I guess 16amps, sorry,

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Lets say 800w at 240 = only 3.3amp but now work that from 12v ( watts are still watts) and we get 66amps plus the microwave loss and the inverter loss.
I know its not on for long but it want 'arf paste the battery
mike
 
MisterB said:
Can anyone recommend a suitable DPDT relay please. I am looking to install an automatic 240v to 12v relay, so it changes automatically when the EHU is connected and defaults onto 12v (which will enable the inverter to provide the 240v supply to the circuits) and then switch back to EHU supply when back on EHU.

also, would you recommend it be housed in a separate enclosure or withing the consumer unit?




I am looking at this one, but not sure if its suitable

Thanks
Click to expand...
This one is 12v only.
 
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I will have 2 X 130AH batteries, a 2000w pure sine wave inverter, a 30 amp B2B and next year (when I get chance to fit it) a 260w solar panel. I understand running the microwave will be a big chunk, but it won't be on for that long, and I know other people have a similar system. The microwave won't be our only source of cooking but a 'bonus' from time to time, IF it all works out
 
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Don’t think you can safely use 12v and 240v (or get one) though the Same relay, you will have to just change over the 240, as in Eu hook up or 240 from inverter.
As post #7
 
Last edited:
Works for me.
 
i appreciate all the comments - i had a previous thread running

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Hi, we have an Adria 640 SLT and i have tried to fit a 1000W pure sine wave inverter. when i connect the inverter direct to the leisure battery, it trips the electric supply into the van - even without the fuse/circuit breaker on the inverter set to 'on' - it appears that the onboard Adria...
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which may help answer some of the questions/issues being raised - and it does seem possible that what i am trying to achieve is actually achievable - i know it wont give me the ability to use an appliance in every socket to run at the same time, but the main priority of being able to use the microwave for short bursts 'occasionally' seems to be achievable and having an automatic change over switch would take it to the next level (of 'convenience gadgetry')

what i am trying to replicate is actually installed as a matter of norm on top end motorhomes, i'm not aiming for perfection, just a bit of convenience !
 
olley said:
It's a 240v relay you want as it's the ehu which is doing the switching.
Click to expand...
sorry, i had a senior moment, thinking i was switching from 240v supply to 12v supply - when in fact i am just switching from one 240v from the EHU supply to a second 240v supply from the inverter
 
MisterB said:
sorry, i had a senior moment, thinking i was switching from 240v supply to 12v supply - when in fact i am just switching from one 240v from the EHU supply to a second 240v supply from the inverter
Click to expand...
You got there in the end(y)
 
There is a thread in my signature of how I did this if it helps?

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MisterB said:
I will have 2 X 130AH batteries, a 2000w pure sine wave inverter, a 30 amp B2B and next year (when I get chance to fit it) a 260w solar panel. I understand running the microwave will be a big chunk, but it won't be on for that long, and I know other people have a similar system. The microwave won't be our only source of cooking but a 'bonus' from time to time, IF it all works out
Click to expand...
We have a pretty similar system, it works a treat but we do have 440amp battery bank and plenty of solar, yes it is high load but its only for a few minutes. I can't help with sourcing because I didnt fit it but ours is in a separate housing. I agree with the poster who said don't leave the inverter on, good idea to get one with a remote switch.
 
stage 1 complete - 2 x 130Ah batteries fitted, inverter fitted - microwave circuit identified and removed from main consumer unit. 3 pin pug fitted to circuit cable. 240v socket outlet fitted leading from consumer unit - so i can (for now) just plug the microwave circuit into the main ehu or the inverter. The inverter has a remote so i can turn it off when not in use.


if it all works out, i will at some stage fit an auto switch/relay (or manual if it is the best option), but i want to make sure its a realistic improvement before i start drilling and fixing stuff where its on view, so far everything is under the seats !!

Thanks to all those who offered an insight/information or just an opinion on the merits (in particular on the previous thread) both technical and practical !!

it certainly doesnt fall into the category of must have or essential, but it does fall into the category of 'nice to have' ....
 
MisterB said:
stage 1 complete - 2 x 130Ah batteries fitted, inverter fitted - microwave circuit identified and removed from main consumer unit. 3 pin pug fitted to circuit cable. 240v socket outlet fitted leading from consumer unit - so i can (for now) just plug the microwave circuit into the main ehu or the inverter. The inverter has a remote so i can turn it off when not in use.


if it all works out, i will at some stage fit an auto switch/relay (or manual if it is the best option), but i want to make sure its a realistic improvement before i start drilling and fixing stuff where its on view, so far everything is under the seats !!

Thanks to all those who offered an insight/information or just an opinion on the merits (in particular on the previous thread) both technical and practical !!

it certainly doesnt fall into the category of must have or essential, but it does fall into the category of 'nice to have' ....
Click to expand...
Have tried a real world test of the microwave? I've recently fitted a 1200watt inverter with a dedicated socket for the microwave, I have to unplug it from the mains socket and replug it into the adjacent inverter supplied socket. I've tried mine which is only a 600watt (cooking power) microwave and it pulls @120 amps 😳. Luckily this will only be for 60 or 90 seconds.
 
Mike800966 said:
Lets say 800w at 240 = only 3.3amp but now work that from 12v ( watts are still watts) and we get 66amps plus the microwave loss and the inverter loss.
I know its not on for long but it want 'arf paste the battery
mike
Click to expand...
800 is the cooking power output, the input will be more like 1200 watts so in excess of 100 amps
 
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