Input or Output Wattage

NoIdeaWhatImDoing · 14 Jun 2011

Hi Folks
I have searched the forum but can't find the answer I'm looking for.
I know that I need to find the wattage rating of an appliance to work out what fuse needs to fitted in the plug however, I have just been looking at my microwave rating plate which says Input Power 1200W, Output Power 700W 2450MHz. Which one do I need to use to calculate; the Input or Output wattage?

DetlefSchmitz · 14 Jun 2011

Short answer - the input.

NoIdeaWhatImDoing · 14 Jun 2011

DetlefSchmitz said:
Short answer - the input.

Thanks. That was fast. I wont ask why it's Input

Hagarbloke · 14 Jun 2011

Input power is what is actually drawn from the mains supply, and hence what the appliance needs to be fused for. Output power is what it actually puts out in terms of RF power. The difference between the two indicates the efficiency of the appliance. Also some power is obviously also required to power the light, motor and losses in control electronics etc. If you fused it based on its output power the fuse would blow every time you used it.

riveralt · 14 Jun 2011

NoIdeaWhatImDoing said:
Hi Folks
I have searched the forum but can't find the answer I'm looking for.
I know that I need to find the wattage rating of an appliance to work out what fuse needs to fitted in the plug however, I have just been looking at my microwave rating plate which says Input Power 1200W, Output Power 700W 2450MHz. Which one do I need to use to calculate; the Input or Output wattage?

1.2kw input is just over 5amps which would suggest you would need a 13amp fuse - but you would best be guided by the manufacturers instructions - do you have a copy? Can you obtain one online? Failing that speak to their customer services department.

bernardgreen · 14 Jun 2011

riveralt said:
1.2kw input is just over 5amps which would suggest you would need a 13amp fuse

Or 10 amp

aptsys · 14 Jun 2011

or 7A

JohnW2 · 14 Jun 2011

riveralt said:
1.2kw input is just over 5amps which would suggest you would need a 13amp fuse - but you would best be guided by the manufacturers instructions ...

Indeed. What no-one seems to have mentioned is that the maximum acceptable rating of fuse depends upon the cable fitted to the appliance - which is why one needs to look at the instructions. Although very probable, there's theoretically no guarantee that a 1.2kW appliance will have a cable rated at 13A.

Kind Regards, John.

STI · 16 Jun 2011

Agree with what has been said about the cable, but every Microwave i have ever looked at comes with a 13a fuse fitted. Especially since the accepted range of fuses to be used for devices has become 3,5 and 13. The dear old 10A although still available to buy is rarely used by manufacturers now except IT equipment and TV's but the latter is fast becoming a standard 5A fitted fuse.

ban-all-sheds · 16 Jun 2011

http://www.tlc-direct.co.uk/Main_Index/Necessities_Index/Plug_Top_Fuses/index.html

ericmark · 17 Jun 2011

There has for some time been a problem getting 1, 2, 5, 7, and 10 amp fuses at non electrical outlets. 3A and 13A seem to be the options preferred.

As already said the fuse is only to protect the cable and because in rest of Europe the 16A un-fused outlet has become a standard and we must make equipment suitable for whole of Europe if the appliance requires a fuse it will be inside the appliance and we do not rely on the fuse in the plug.

But our cable is rated 3, 6, 10, 13 amp for 0.5, 0.75, 1, and 1.25mm sq so one would expect fuses to be sized to suit. However I have never seen a 6A fuse for a plug.

All microwave cookers I have opened have contained an internal fuse. People don't seem to realise how they work and try doing silly things like dry aggregate in domestic microwaves which once the water is removed is just like switching it on with nothing in and it then blows the fuse. Having worked with concrete I have renewed many internal fuses where the lab techs have used too long of a time.

What I can't understand is how in rest of Europe one can use 0.5mm flex on bed side lamps when all they have is 16A sockets. But I suppose they don't follow the same rules. After all German sockets are not allowed here.

JohnW2 · 17 Jun 2011

ericmark said:
There has for some time been a problem getting 1, 2, 5, 7, and 10 amp fuses at non electrical outlets.

Agreed, in general, but Mr eBay always has plenty! For reasons we've discussed before, I use quite a lot of 1A and 2A ones.

ericmark said:
As already said the fuse is only to protect the cable and because in rest of Europe the 16A un-fused outlet has become a standard and we must make equipment suitable for whole of Europe if the appliance requires a fuse it will be inside the appliance and we do not rely on the fuse in the plug.

A reasonable point but, as you imply, in UK-think a fuse in the appliance has a different purpose from one in a plug. The regs do grudgingly allow a cable to be protected by a downstream OPD to some extent, but that isn't really part of the 'UK-think'.

ericmark said:
What I can't understand is how in rest of Europe one can use 0.5mm flex on bed side lamps when all they have is 16A sockets. But I suppose they don't follow the same rules.

Clearly not - and their rules presumably don't have the same attitude to cable protection as we do.

Kind Regards, John.

ban-all-sheds · 17 Jun 2011

The question is does a 16A breaker (not a fuse, remember) provide adequate fault protection for the flex?

JohnW2 · 17 Jun 2011

ban-all-sheds said:
The question is does a 16A breaker (not a fuse, remember) provide adequate fault protection for the flex?

That's one question, but I think the more fundamental one (which I suspect is what was being implied) is whether a 16A OPD of any sort can provide adequate protection for a flex rated at 3A!

Kind Regards, John.

ban-all-sheds · 17 Jun 2011

In free air? (-ish).

One would need to do the sums, but I don't believe that German (for example) safety culture is intrinsically more lax than ours.

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Input or Output Wattage

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