appliance internal fusing

[Steve]

A thought just struck me. How come in open-front integral dairy fridges, there are individual breakers or fuses internally for the different parts of the fridge. for example it might have fuses for the compressor, circulation fans, condensor fans, lighting, controller, plus others for 3-phase units.

Yet in a domestic electric range cooker (and any other multi-element cooker), everything is just protected by the 50 amp MCB. There are no internal fuses or MCBs for the parts of the cooker. Any internal faults would have to draw 50 amps before the mcb/fuse trips/blows.

Why is this?

One would think the dairy fridge would need no fuses, as everything is protected by a 13 amp fuse in its plugtop!

 

[securespark]

Why does a BA panel have internal fuses? Why can't everything be protected by the 2A fuse in the spur?

BA panels have fuses to protect the aux 13V output, RKP's & bells/strobe, to protect those parts of the system.

I guess the fridge mfrs want to protect PCB's, components, etc if there's a fault.

 

[plugwash]

lets be honest if heating elements start drawing overcurrent they are probablly already f*cked and you don't really need to protect them from overcurrent for fire protection reasons since they are already getting plenty hot enough to start a fire and hence you keep stuff thats flamable away from them

motors on the other hand can draw a lot of current if stalled, this means they will get very hot in a place thats not designed to get very hot causing both fire risk and damage to the motor.

 

[TicklyT]

It's probably down to manufacturing costs, and hence the price to the consumer.
As Pugwash says, even the fanciest range cooker is only a tin box with heating elements in it. Okay, you've got a clock and a little fan or two, which may benefit from their own protection if they fail, and maybe the manufacturers have to use their judgement there on cost of replacement versus protection, but the whole box is already designed to 'contain' enough energy to pop the protection on the supply.

I have yet to find any internal fuses in a domestic 'fridge, but again, i've never had cause to look.

Are proper commercial ranges fitted with any internal protection for, say, each oven individually?

 

[ColJack]

the compressors usually have thermal overload protection built in, as do most other motors these days..

it they get warm enough to trip it, it stops the motor etc until it's cooled down, or on some, once it's overheated it doesn't reset.

on larger 3phase bits of kit, this is usually done through contactors for control.
to save the cost of contactors and thermal overloads for things that are always on, it's cheaper to just miss out the internal overload and fit breakers...