Wiring for new Engel Fridge

[stevemac Lurker Find all posts View Profile Close stevemac]

Hi,

New Engel fridge (MT45F-G4D-V) in preparation for cross country journey later this year (if interstate travel restrictions ease)

Read the manual before using in the car & there is a diagram and instructions on connection to the vehicle electrical system. It reads Any switches and lead wires for other electrical equipment should not be shared with the wiring between the refrigerator and the battery. Other equipment can generate high voltage pulses which may cause transistor damage to the refrigerator power supply. See attached image

So a little confused / concerned as this is not how the vehicle is wired. The vehicle is wired as follows (sorry could not find a diagram)

Dual Battery setup with redarc SBI

• Aux battery is under the bonnet
• 200A circuit breaker fitted between each battery and the SBI
• 60A circuit breaker between the Aux battery and Load

Connection from the engine bay to the rear of the vehicle is via 2 cables (1 ea for positive and negative). From memory they are 2B&S, In the rear of the car these connect to

• ABR Sidewinder Battery Protector (60A) which connects to
• Blue Sea systems fuse block with individual fuses for
  • Fridge,
  • Car PC & screens,
  • USB outlets,
  • Anderson Plug (for air compressor)

All cables, fuses /circuit breakers are appropriately sized (cables are oversized)

Note - I know the battery protector is not required for this fridge (as it has an inbuilt solution). I might separate the fridge circuit from the ABR unit

Would like to hear from others on how they wired up for their Engel and if it is really necessary to run another pair of cables from Aux battery to the rear for the fridge?

thanks,

Steve

[404pug Avid PP Poster! Find all posts View Profile Close 404pug]

Don't see why you can't use the existing wiring you have. I have a 30 year old Engel the wiring for which comes off the wiring going to the camper trailer Anderson plug. No problems. Hot tip: put an anderson plug on your fridge lead to stop it coming loose on corrugations.

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

If you think about it, you run it directly to the cars cranking battery for instance, you have all the cars electrics including the starter hanging
off it. I can't think of anything apart from a winch that can generate anywhere near that sort of noise.

If it can't handle being connected to a sub fuse box then it is not fit for service.

[RPP Senior Member Find all posts View Profile Close RPP]

These new fridges have soft electronics in them. Notice in Engel's preferred wiring diagram the twisted cable from the fridge.
Apart from that there is little electrical difference in the two figures.
The twisted cable provides a small inductance (a few loops in the power cable) that will filter, to some degree, any power spikes from equipment on the same battery.

The same can be achieved in the first circuit diagram with a small coil (or Ferrite Balun) capable of handling the amps drawn by the fridge.

BTW: There is a similar issue when running 240V power tools, and fridges, off an inverter.
These devices generate reactive spikes when first switched on that can overload an inverter.
The fine print in the documentation that comes with inverters should provide advice on that matter.


Hope that helps.

[stevemac Lurker Find all posts View Profile Close stevemac]

thanks for the responses. Will look at fitting a small coil

[Brett1979 Avid PP Poster! Find all posts View Profile Close Brett1979]

The only issue arises and this can be an issue when you have 2 or more 12v outlets running off the same positive cable that may not be up to the task. The problem is called voltage drop. Let’s say you’ve run 6B&S for example to the rear and over allowed the length of the cable by a meter with excessive slack in places. And you’ve got a fridge running off this cable the same time as one other higher power draw item. This can cause the voltage to temporarily drop below the minimum required to power your fridge which will cause it to cut in & out. The fridge being in a closed up hot car with a barely adequate + cable can cause voltage drop. The higher a temp 12v electrical cabling is subjected to causes voltage drop too. If you have 2B&S cable as you mentioned then trust me when I say you have nothing to worry about. This cable is thick and would have minimal voltage drop from the battery to the rear of the car. It is a lot thicker than what 98% of people would be using. This specific cable must’ve been requested from the auto electrician when the job was booked. It probably runs under the car to the boot as it’s be too thick to feed through the allocated cabling channels in the interior of the car. You could hook 4 plug outlets to this cable in the boot with no probs. If you had 6B&S I would say don’t run it to any more than 2 plugs in your boot. I have 4B&S running to the boot to power 2 @ 12v plugs & it’s more than adequate to provide enough power for the potential draw. 6B&S is the absolute thinnest cabling you’d want to use. I don’t use 6B&S to the boot any more myself. Found out the hard way.