Jump to content

Fitting a switch to a 12 volt fridge


Featured Posts

I want to able to switch our 12 volt fridge off (an inline isolation switch?) It is our weekend / holiday boat and we have found we don't use the fridge if we're only on the boat for a couple of days.

 

I have the correct thickness of wire and have been told I need a 20 amp switch.

 

I haven't been able to find a 20 amp switch, however I have a 5 amp / 240 volt switch which the shop told me that it should be equivalent to a 20 amp / 12 volt switch.

 

So if I have the correct switch, the 2 wires from the fridge, 1 red and 1 black, can I put this switch just onto 1 of these wires? red or black? or do I need to put both wires through the switch?

Link to comment
Share on other sites

A 20 Amp switch is a 20 Amp switch, whatever the voltage.

 

You could use something like this.

http://www.screwfix.com/p/british-general-20a-1-gang-double-pole-switch-white/76090

 

This is a double pole switch, which would allow you to switch both the positive and negative wires, but for your situation, just switching the positive (red) wire would be fine.

Link to comment
Share on other sites

In theory you should not use AC rated switches on DC because DC tends to burn the contacts when the switch opens. In practice it is not such a problem in the vast majority of cases.

 

Only worry about switching the red wire.

 

The reason the cables are so large is to avoid voltdrop when the fridge motor starts and this is critical so the switch should also be specified to avoid voltdrop.

 

Knowing AC switches are somewhat vulnerable to burning when used on DC and a large switch contact area helps to minimise the burning I used a double pole "water heater" switch that is rated at something in excess of 20 amps. I stripped a fair length of insulation off the the cables, split the conductors and twisted them into two groups and sleeved them with heat shrink. I then connected them to both the line and neutral sides of the switch. Such switches are easily available and doing it this way it doubles the contact area.

 

There is absolutely no way a 5 amp 240 volts switch is equivalent to a 20 amp DC one. As the fridges normally draw around 4 amps draws such a switch may work, especially as you would tend to use the switch when the motor is not running, however I think it woudl be vulnerable to contact burning, increased resistance and thus voltdrop.

Link to comment
Share on other sites

Most likely your 'fridge is supplied by a single circuit breaker or fuse; it should be. Trip the CB or remove the fuse when you do not want the 'fridge to run.

 

If you do find that other circuits are then disconnected, rewire them into a spare CB/fuse or one that requires less current.

 

Personally, I can no longer imagine life without a 'fridge/freezer, even for a weekend.

 

Alan

Link to comment
Share on other sites

If you ALWAYS remember to turn the fridge thermostat right down to OFF before you turn the fridge off, then you'll get away with a 5A switch whether it's designed for 12v or 240v. Otherwise if it's a 240v switch I'd go for one rated at not less than 10A.

Link to comment
Share on other sites

I want to able to switch our 12 volt fridge off (an inline isolation switch?) It is our weekend / holiday boat and we have found we don't use the fridge if we're only on the boat for a couple of days.

 

I have the correct thickness of wire and have been told I need a 20 amp switch.

 

I haven't been able to find a 20 amp switch, however I have a 5 amp / 240 volt switch which the shop told me that it should be equivalent to a 20 amp / 12 volt switch.

 

So if I have the correct switch, the 2 wires from the fridge, 1 red and 1 black, can I put this switch just onto 1 of these wires? red or black? or do I need to put both wires through the switch?

If you visit Vehicle Wiring Products in Ilkeston you can get a 12v 20a toggle switch (ref # 60300) with standard blade connectors for £6.86 + VAT. Worth getting to know them as you live close by.

 

Paul

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.