Fuse too big on fridge

[John-SJW]

A small under counter AEG fridge. Instructions say it is fitted with a 13A fuse in the plug. Also states it must be replaced by a 13A fuse. The fridge is drawing 0.32 amps. A 13A fuse is ridiculously oversized. If having a mcb or RCBO at the CU for just the fridge, a 1.00mm cable can be run on a radial for it.

The instructions do say that a qualified or competent electrician must fit the appliance, so a get out for them. If the electrician say 3A will do then that is that I suppose. Do many ignore these types of instructions and say insert a 3A fuse in the plug? Safer.

 

[telectrix]

you fit what the manufacturer recommends, the flex on the fridge will be 1.5mm so a 13A fuse is correct. a 3A fuse would probably keep blowing as the compressor kicked in (inrush/surge current).

 

[loz2754]

you fit what the manufacturer recommends, the flex on the fridge will be 1.5mm so a 13A fuse is correct. a 3A fuse would probably keep blowing as the compressor kicked in (inrush/surge current).

Had one today on an EICR.
Someone had replaced the 13 amp fuse with a 3 amp fuse in a fused grid switch feeding the fridge. Of course the fuse had blown, so I replaced it with a 13 amp and it worked.
Fridges have large inrush currents every time the compressor starts up.

 

[Spoon]

If having a mcb or RCBO at the CU for just the fridge, a 1.00mm cable can be run on a radial for it.

Have a look at Table 52.3 of the BBB and see why this statement is incorrect.

 

[Lucien Nunes]

If having a mcb or RCBO at the CU for just the fridge, a 1.00mm cable can be run on a radial for it.

Except that the minimum permissible cable size for a power circuit (i.e. not lighting) is 1.5mm².

As above, the reason for the larger fuse is that starting surge current that can progressively weaken and blow a 3A fuse, possibly after a year or two. It might survive normal starts, but when somebody twiddles the thermostat while the compressor is running, stops and restarts it against head pressure, the motor stalls and the fuse has to take the stall current for a few seconds until the thermal protection trips.

Customer-fitted 3A fuses used to be a known cause of service callouts to fridges and freezers back in the day, modern compressors use less juice but it still seems to be a needless risk to fit a 3A when the appliance is designed for 13A. Neither rating will reliably protect the compressor against overheating, that's what the thermal protector is for.

Oops post crossed with @Spoon

 

[Spoon]

Except that the minimum permissible cable size for a power circuit (i.e. not lighting) is 1.5mm².

As above, the reason for the larger fuse is that starting surge current that can progressively weaken and blow a 3A fuse, possibly after a year or two. It might survive normal starts, but when somebody twiddles the thermostat while the compressor is running, stops and restarts it against head pressure, the motor stalls and the fuse has to take the stall current for a few seconds until the thermal protection trips.

Customer-fitted 3A fuses used to be a known cause of service callouts to fridges and freezers back in the day, modern compressors use less juice but it still seems to be a needless risk to fit a 3A when the appliance is designed for 13A. Neither rating will reliably protect the compressor against overheating, that's what the thermal protector is for.

Oops post crossed with @Spoon

Your post is a lot more detailed and informative than mine mate..... But then again I can't find fault with any of your posts..

 

[John-SJW]

Except that the minimum permissible cable size for a power circuit (i.e. not lighting) is 1.5mm².

As above, the reason for the larger fuse is that starting surge current that can progressively weaken and blow a 3A fuse, possibly after a year or two. @Spoon

OK a 6A fuse, not 3A. 13A appears way over the top for a draw of 0.33 amp, even taking in the surge factor and the surge rising with age.

Where does it say power has to be minimum of 1.5mm? I have not aware of reading that anywhere.

 

[telectrix]

the 13 A fuse is to protect the fridge cable/flex, which will be 1.5mm, 19A CCC. therefore the fuse needs to be <19A, so 13A fuse is ideal. end of.

 

[John-SJW]

back in the day, modern compressors use less juice but it still seems to be a needless risk to fit a 3A when the appliance is designed for 13A. @Spoon

I get the impression these Continental makers write all to suite Continent electrical systems, not rewriting for the UK market. I have see nonsense like, must have a 16A supply, etc, in appliances drawing fraction of that.

 

[i=p/u]

Follow mf instructions... selection and erection, inspection of electrical equipment say manufactures can use smaller csa and they do.

but again that 0.33 is higher when is turned on and off.

 

[DPG]

OK a 6A fuse, not 3A. 13A appears way over the top for a draw of 0.33 amp, even taking in the surge factor and the surge rising with age.

Where does it say power has to be minimum of 1.5mm? I have not aware of reading that anywhere.

Someone posted the location of that info further up this thread.

 

[John-SJW]

the 13 A fuse is to protect the fridge cable/flex, which will be 1.5mm, 19A CCC. therefore the fuse needs to be <19A, so 13A fuse is ideal. end of.

I my point it is not the end of. Only going by regs is not what competent electricians should be doing. Sometimes you have to use the electrical knowledge and training they are given.

I know 13A will protect the cable. My point is that a 6A fuse will give greater protection overall. The 6A fuse will also protect the appliance, not just the cable.

I have a rice cooker, made in China that came with 1.5mm cable and a 13A fuse. 350w consuming 1.4A. I have 250v. I replaced it with a 6A fuse. It has worked perfectly...for years. I have the impression the Chinese just think, OK, its the UK, put in a 13A fuse, with a get out in the instructions, use a competent electrician. Meaning he decides.

 

[John-SJW]

Follow mf instructions... selection and erection, inspection of electrical equipment say manufactures can use smaller csa and they do.

but again that 0.33 is higher when is turned on and off.

I tested the surge with an amp clamp that keeps the peak reading. It never got to 1A. With age, say it gets to a 3A surge. 6A still is a massive margin.

 

[i=p/u]

Fuse protects cable, just to happens protect appliance aswell

 

[DPG]

I tested the surge with an amp clamp that keeps the peak reading. It never got to 1A. With age, say it gets to a 3A surge. 6A still is a massive margin.

A clamp on ammeter will probably miss the brief high current spikes. The refresh rate of the display wouldn't even keep up with them.

 

[John-SJW]

Have a look at Table 52.3 of the BBB and see why this statement is incorrect.

I am making a point of the low current draw.

 

[John-SJW]

Fuse protects cable, just to happens protect appliance aswell

A low fuse protects better and safer. I have seen many innards of burnt out appliances that would have blew a lower rated fuse before they gave problems, giving greater protection.

Regarding surge, all fuses have a surge factor built in. That is a 6A fuse can take way over 6A on surge and not blow. A sustained say 8A it will blow.

 

[snowhead]

I tested the surge with an amp clamp that keeps the peak reading. It never got to 1A. With age, say it gets to a 3A surge. 6A still is a massive margin.

Is that with the fridge in a warm kitchen and turning it Off then back On within a few minutes?

Try putting the fridge in a conservatory or outbuilding leave it off for week in the middle of winter and then switch it on and check the switch on current.

Manufacturers have got years of experience and probably miilions of hours in test and development, if they say 13amp is needed, I'm sure they know best.
They can't write instructions for specific circumstances they have to be for worst case.

 

[John-SJW]

I have a 800w toaster. It draws 3.2 amps. It came with 13A fuse. I replaced it with a 6A fuse. For four years it has not blown the fuse. If the 6A fuse starts to blow then the appliance is in its old age, or defective, needing to be replaced, or fixed, before any serious safety problems arise.

 

[John-SJW]

They can't write instructions for specific circumstances they have to be for worst case.

That is one of my prime points. Use electrical training and knowledge then apply it, using common sense.