fuse rating

[Thomas123]

i've had two questions on a similator,

An 800w electric iron should have a fuse rated at...

I said 5 amp as 800/230 = 3.47a

it said i was wrong and said the correct answer was 13a


another question asked basically the same just it was a 1.5kw heater, i said 7a it said 13a.

is this correct?

 

[malcolmsanford]

If it is on a UK plug 13amp BS 1363 you really can only nowadays get a 3amp or a 13amp BS 1362 fuse for them. Though you can get 1amp, 5amp 10amp types the majority of places will sell just the 3 amp and 13amp for domestic use.

That is why you got the 13amp answer for that 800watt load.

 

[Thomas123]

another question,

if manufactures information is not available for IT equipment what of the following tests should not be conducted

i put insulation reistance,

it said earth continuity?

 

[IQ Electrical]

Generally, the manufacturers instructions take priority but this is the recommended practice:

Appliances up to 700 Watts should have a red 3 Amp fuse fitted.

Appliances over 700 Watts should have a brown 13 Amp fuse fitted.

Start up inrush can change these recommendations.

I believe the correct answer is that the IR test would be omitted, thinking about it, what damage would a continuity test do?

 

[Thomas123]

great! thank you

 

[MarkieSparkie]

Generally, the manufacturers instructions take priority but this is the recommended practice:

Appliances up to 700 Watts should have a red 3 Amp fuse fitted.

Appliances over 700 Watts should have a brown 13 Amp fuse fitted.

Start up inrush can change these recommendations.

I believe the correct answer is that the IR test would be omitted, thinking about it, what damage would a continuity test do?

Just to add to IQ's reply. Certain types of IT equipment have a 5A fuse and that should not be replaced by one of a different value.

I think in the real world both tests are unwise without consulting the IT manufacturer. A standard IR test at 500V is likely to cause damage to sensitive IT components. Even an 'Soft' IR test at 250V may still cause damage. A substitute leakage test may also not possible if the IT equipment has electronic switching, relays or active circuitry which influences the measurement. A standard Earth continuity test at high current (>1.5x fuse rating) may well damage IT equipment connections and/or internal protective devices. Even a 'Soft Test' (20-200mA) maybe inappropriate for certain IT equipment.

 

[72-van]

All these fuses are available at the wholesaler although sometimes its better to stock up on 10A as they seem to be the harder one to find in local stores.I usually leave a couple of each type of fuse with the client after testing .