Adding a switch to isolate the fridge...

[BlueStringPudding]

I'm tempted to wire in a separate switch for the pending fridge arrival, because at the moment the only way to isolate the power from anything hardwired in like a fridge would be to pull the continental fuse out of the fusebox (or turn off at the main isolation switch in the bilge). And we would want to switch it off during the winter months, etc.

Firstly: Is adding a wall-mounted switch a sensible thing to do?

 

Secondly I have a sturdy metal clad switch (the fused kind you get for 240v stuff) - would that be useable for 12v or should I go and buy someting specific? If so how would I wire the red and black cable of my 12v electrics into the live/neutral/earth screw terminals of the switch?

 

What are your thoughts please?

[bottle]

This bit I can answer:

 

Firstly: Is adding a wall-mounted switch a sensible thing to do?

 

Yes, it will also make a convenient place to connect the fridge 'flex' with the permanent wiring.

[churchward]

I'm tempted to wire in a separate switch for the pending fridge arrival, because at the moment the only way to isolate the power from anything hardwired in like a fridge would be to pull the continental fuse out of the fusebox (or turn off at the main isolation switch in the bilge). And we would want to switch it off during the winter months, etc.

Firstly: Is adding a wall-mounted switch a sensible thing to do?

 

Secondly I have a sturdy metal clad switch (the fused kind you get for 240v stuff) - would that be useable for 12v or should I go and buy someting specific? If so how would I wire the red and black cable of my 12v electrics into the live/neutral/earth screw terminals of the switch?

 

What are your thoughts please?

 

I think it is useful to isolate these kind of devices with a switch or possibly better still a switch via a circuit breaker. We have a small circuit breaker panel (all switched) with the main services on there including the fridge on its own breaker and switch, 15A if I recall correctly.

[magpie patrick]

Firstly: Is adding a wall-mounted switch a sensible thing to do?

 

Yes, we have one, it means that we can turn it off without getting to the fuse box, handy when leaving the boat for a few days but wanting other things powered, also for when someone is sleeping near the fridge and finds it disturbs their sleep, and a life saver when coming back from Huddersfield with no alternator and trying to minimise power consumption...

[RLWP]

Our fridge has a switch inside it.

 

Richard

 

Still a good idea to have a separate isolator though. And fuse in the fusebox, and dedicated cable to the fridge.

[the grinch]

OP on my old boat the fridge circuit was part of the ignition system this ensured that the fridge went off at the same time as the engine. with the fridge set high the temperature maintained over night and we could still start the engine in the morning (lister HA2) the whole boat ran off 1 x 120AH battery!

[BlueStringPudding]

Cool, thanks everyone. So it's definitely a good idea then!

 

So to the second part of my question: what sort of switch. It'd be handy if I could use the one I've already got, but like I said it's designed for live/neutral/earth. Is that safe to use with the two 12v cables I have and if so which do I connect to what!? I'd guess at red to live, but black to earth or neutral or just buy a different switch!?!?!?

[DHutch]

We have a switch, both for the 240vac and 24vdc input (dual votage fridge) and we use both.

-Deffonatly fit a switch of some sort. As said, if nothing else, it acts at a termiation between the 'fixed' wiring of the boat and fridges lead.

 

The switch in the fridge its self awfull.

 

 

Daniel

[Justme]

Cool, thanks everyone. So it's definitely a good idea then!

 

So to the second part of my question: what sort of switch. It'd be handy if I could use the one I've already got, but like I said it's designed for live/neutral/earth. Is that safe to use with the two 12v cables I have and if so which do I connect to what!? I'd guess at red to live, but black to earth or neutral or just buy a different switch!?!?!?

 

No.

 

The switch will have a (like a light switch)

live

switched live

earth

& IF its a double pole switch (like a shower switch)

neautral

switched neutral

 

In case one you wire the poss feed to the live & the poss to the fridge to the switched live & the neutral feed & fridge together.

 

In case two you wire the feed poss to the live neg feed to the neutral

then

fridge live to the switched live & the fridge neutral to the switched neutral.

 

 

Justme

[RLWP]

Technical question - what current does your fridge draw?

 

Richard

[Keeping Up]

It's a good idea to have a switch somewhere. One reason that hasn't been mentioned, is that when you aren't using the fridge it's best to leave the door open and if the fridge has a light which comes on when the door is open you can't switch that off by the fridge's own switch.

 

Is there wiring to the fridge already, from a previous fridge for example? If so, it may have its own switch back at the fuse-box, or at least its own fuse which you could remove when you don't want to use the fridge. If not, are you putting new wiring in? Remember most fridges need thicker wiring than would me already there for a 12v socket for example.

 

A 240v switch would be just fine. Just regard positive 12v (red) as if it were Live and negative (black) as if it were neutral. You can ignore the "earth" connection in this case.

[BlueStringPudding]

Thanks everyone.

 

Apart from the the ye olde fuse box at the back of the boat, there's just a loose cable at the front of the boat where the fridge needs to be wired in. It's quite a fat cable so should be fine re: voltage drop.

The old fridge was simply hard-wired in with no switch. But as it didn't work anyway and smelt like Kev's socks after the Stratford Marathon (4 hours 35 mins by the way, nearly 15 mins faster than last year. He is a happy bunny, despite now walking like an elderly Cyberman who's forgotten his Sanatogen) it didn't matter too much coz it went straight into a skip.

 

So I'll have a play with my switch tonight in preparation for imminent fridge arrival. Incidentally the fridge we're getting draws a max of 4A, average of 1A.

Edited April 28, 2009 by BlueStringPudding

[Tony Brooks]

Cool, thanks everyone. So it's definitely a good idea then!

 

So to the second part of my question: what sort of switch. It'd be handy if I could use the one I've already got, but like I said it's designed for live/neutral/earth. Is that safe to use with the two 12v cables I have and if so which do I connect to what!? I'd guess at red to live, but black to earth or neutral or just buy a different switch!?!?!?

 

 

Voltdrop when starting is a killer to 12v fridges so whatever switch you use would ideally minimise this danger. Although DC switches and AC switches should be designed differently I decided the best I could do was a 30 or 40 amp, double pole switch intended for the likes of immersion heaters at home.

 

This will have 4 holes for connections plus an earth one which you ignore. Your negative cable should not be switched but I suppose it could be if you insisted, but its normally not done, so you have a big red positive lead coming from the fuse/battery. I stripped this back and split the conductors into two bundles and insulated most of each bundle. These went into both "bottom" holes. I did similar with the cable running to the fridge and put each bundle into a "top" hole. Remember both leads should have a conductor area of 1 sq mm for each metre run between battery and fridge so an 8m run would require 8sq mm cable (mine needed 13 sq mm!)

 

Some would say this is overkill but if one of my contacts failed or one connection became lose I have redundancy built in. Is been OK for nearly 10 years now.

Edited April 28, 2009 by Tony Brooks

[BlueStringPudding]

Thanks - excellent advice everyone. I didn't get to tinker with the switch last night because there was an almighty thunder storm and I didn't fancy poking my a*se out of the bilge in the rain and lightning trying to turn off the isolator switch for the electrics!

 

But I might do it tonight instead.

 

Cheers all.

 

[frangar]

One thing I have found is that some 240v switches (esp "high current" rated ones) can have quite a high inbuilt resistance which isnt too much of a problem at 240v but a bugger at low DC voltages....I think it may be how the contacts "mate" as they dont show any signs of overheating at 240v but do have a voltage drop at low DC currents.

 

 

Gareth

[Naughty Cal]

Why would you want to switch off the fridge?

 

Think of all the beers Poor buggers will get warm.

[Tony Brooks]

One thing I have found is that some 240v switches (esp "high current" rated ones) can have quite a high inbuilt resistance which isnt too much of a problem at 240v but a bugger at low DC voltages....I think it may be how the contacts "mate" as they dont show any signs of overheating at 240v but do have a voltage drop at low DC currents.

 

 

Gareth

 

 

That's interesting but all I can say is that knowing the problems voltdrop seems to give these fridges I checked the resistance of each part of the circuit and the switch showed 1.5 ohms which it does on my meter when you make sure the probes are clean and join them. They will certainly tend to burn if used frequently when current is flowing.

 

In a similar vein I had an instant of a large, good quality master switch suddenly appear to be open circuit after a winter turned off but the contacts looked perfect, a rub with Scotchbright and away it went again. Odd.

[frangar]

That's interesting but all I can say is that knowing the problems voltdrop seems to give these fridges I checked the resistance of each part of the circuit and the switch showed 1.5 ohms which it does on my meter when you make sure the probes are clean and join them. They will certainly tend to burn if used frequently when current is flowing.

 

In a similar vein I had an instant of a large, good quality master switch suddenly appear to be open circuit after a winter turned off but the contacts looked perfect, a rub with Scotchbright and away it went again. Odd.

 

 

 

I noticed it with a "cam" type changeover switch (the type that are normally used for industrial motor controls and the like)

 

The manufacturers (Kraus & Naimer) did a version which was specifically designed for low voltage but unfortunately was also low current as well so they must realise there is a weakness as well.

 

 

Any more thoughts welcome....(I solved it my rewiring my boat and losing the need for the switch!)

 

Cheers

 

Gareth

[BlueStringPudding]

Although DC switches and AC switches should be designed differently I decided the best I could do was a 30 or 40 amp, double pole switch intended for the likes of immersion heaters at home.

 

 

Well, I had a good day of electrical jiggery pokery yesterday. As well as replacing the old and very corroded 12v socket that Black Prince kindly installed 12 years ago, I added a few extra in other cabins, repaired the stern cabin speaker cables and most importantly, added the fridge isolation switch.

 

That went really well, the wiring seemed easy as each terminal was clearly labelled Supply and Load, and I set it up in an adjacent alcove to where the fridge will go, so it's hidden but easily accessible. (And having discovered the joys of conduit piping it all looks nice and neat too... new favourite toy. Anything that stands still long enough is going to get wallmounted in plastic conduit... inspection elbow anyone?)

 

Anyway, what I wanted to check is in reference to Tony's comment above, the switch I used is one like this: (except without the neon light).

 

 

It's metal clad but comes with a 13A fuse - it's certainly nothing as exciting as a 30 or 40A one! Am I going to regret that - is the 12v fridge going to send my switch into meltdown!?!?

 

Secondly, I know we talked about not needed anything connected to the Earth terminal, however the destructions for wiring the switch said that the metal casing MUST be earthed - in addition to the usual earth terminal inside the switch. Can I still ignore that or am I going to get zapped if I touch the casing one day..?

[alan_fincher]

If you are using a switch designed for 240 volts AC in a 12 volt DC application, then it's absolutely fine not to earth the case, or use any of the earth terminals.

 

You can't get electrocuted with 12 volts, but silly errors with wiring can still cause a fire, so it needs treating with respect.

[BlueStringPudding]

If you are using a switch designed for 240 volts AC in a 12 volt DC application, then it's absolutely fine not to earth the case, or use any of the earth terminals.

 

You can't get electrocuted with 12 volts, but silly errors with wiring can still cause a fire, so it needs treating with respect.

 

 

In which case... does any of the above sound like it might constitute a fire risk?

[frangar]

Dont worry this type of switch will be fine.....just use a 13A fuse cos the fridge may "pop" a lower rated one.

[Keeping Up]

Everything is fine like that. No meltdown, no zapping, no fire risk, no thermonuclear explosions (well not many) and no worries.

[BlueStringPudding]

Everything is fine like that. No meltdown, no zapping, no fire risk, no thermonuclear explosions (well not many) and no worries.

 

 

 

Now there's a man who's never tried a bowl of my Tom Yum soup. (Take one chilli out of the packet and put to one side, then add the rest of the packet of chillis to the pan!) Kabloooooey!

 

Thanks all.

[BlueStringPudding]

The fridge finally came!!!!!! Yay! It's only taken three bloomin' months to get from the manufacturer to the wholesaler to the retailer to us!

 

And it's fableeous. I wired it in on Saturday, (new switch works a treat) and I filled it up with nosh. So much so that I can't fit any beer in it. So Kev and I are frantcially eating as much as we can as quickly as we can until we get our priorities right!

 

It's an Isotherm Cruise 100, it's really quiet and we're quite excited about it. After two years without a fridge, Kev having a cup of tea with non-lumpy milk or me grilling fish fingers from frozen have seemed unlikely... till now.

 

Oh, hoorah.