Hi, any ideas on why this fan specifically says that an extension cord cannot be used with it? It's fairly low power at 285W, even with a really poor power factor of say 0.3 that's <1kVA and there are plenty of heaters that are higher power and don't have similar stipulations.
Extension cord not allowed, but why?
- Thread starter WhydidIstart
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I think they do it to discourage you moving it about whilst its on, generally you wheel it to a location and leave it there plugged in.
Not moving it is sensible, but why not just put "Caution: Do not move whilst operating" or similar on the label?
An extension cord is not not allowed. It is another case of manufacturers giving wrong instructions. Good job we don't have to follow manufacturers instructions especially if they are wrong. Manufacturers instructions are guidance only so can be safely ignored if wrong.
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Lol, you would think the manufacturer would know their own product... just a shame that's not always true!
What do you think could be behind them putting that on there in the first place though? Perhaps it’s what rocky said, or despite claiming CE compliance they found the motor was electrically noisy and extension leads made that worse and hence the label? Perhaps the PF is poor and they had someone overheat a low capacity extension lead, so thought it was easier to say that rather than try to explain why a larger lead is required than expected for a 285W load?
What do you think could be behind them putting that on there in the first place though? Perhaps it’s what rocky said, or despite claiming CE compliance they found the motor was electrically noisy and extension leads made that worse and hence the label? Perhaps the PF is poor and they had someone overheat a low capacity extension lead, so thought it was easier to say that rather than try to explain why a larger lead is required than expected for a 285W load?
Would anyone take any notice, plus its proberly safer the power switch near the fan, to see its safe to switch on, we put them in pubs and the punters drag them round then the leads a trip hazard, i suppose the short fitted lead also limits how far they can move it.
In a controlled enviroment i dont see a problem with a lead.
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With a fixed outlet the voltage must be no less 11.5 volt below incoming voltage (5%) but with an extension lead the voltage where RCD protection is given can drop to silly values and still comply. Most sockets needed a ELI of 1.44 now less with amendment 3 and that relates to volt drop 230 - 13A x 1.44Ω gives 211 volts. But with RCD protection an extension lead can still comply when volt drop means only 100 volt although that is being silly.
However fridges and freezers have for years had a problem, if the volts drops too much, on start before the motor has got to speed the pressure can build up to a point where the motor stalls and the overload disconnects the supply, it will retry once cooled, but if it can't start very quickly the overload is damaged, so most freezers and fridges state do not use an extension lead.
I would guess the label was for a fridge or freezer and has been stuck on a fan in error?
However fridges and freezers have for years had a problem, if the volts drops too much, on start before the motor has got to speed the pressure can build up to a point where the motor stalls and the overload disconnects the supply, it will retry once cooled, but if it can't start very quickly the overload is damaged, so most freezers and fridges state do not use an extension lead.
I would guess the label was for a fridge or freezer and has been stuck on a fan in error?
Many jet washers state the same. It is to do with volt drop. I've seen capacitors pop on jet washers used with excessive extension leads.
Hi, thanks for the info everyone, at least I have an idea of how that statement may have ended up on it.
As others have said, I think the issue is probably excessive volt drop caused by either undersized leads, or poor contact resistances on dodgy extension leads, seems to have the potential to cause issues with single phase induction motors. There was a thread on the IEE a while back about tumble dryers and extension leads.
I dare say you'd be alright with a short extension lead of a decent CSA, but that starts to become a bit difficult to convey via a small warning label aimed at a non electrically skilled person, so they leave it at "don't use extension leads"
Its the same thing as don't put metal in the microwave oven... it doesn't have to be a complete prohibition (the inside of the machine is stainless steel afterall), but trying to explain the circumstances when metal might cause a problem becomes difficult. I often leave the spoon in curry or soup while heating, which concerns the other half somewhat!. Just as well I don't have time for hobby electronics these days..... the tray of ferric chloride with a board to be etched sat in it went in the microwave to get it upto optimal working termperature....
They would have used the mini-oven instead, but there was some SMD reflow soldering going on in that...
Mine recommends leaving a spoon in a mug of liquid whilst being microwaved!
Probably to avoid superheating
Could they be concerned that if you don't have RCD protection and use a long and/or thin extension lead, the fault impedance may well be such that instead of blowing a fuse/tripping a breaker, you could have the fan sat there with it's metalwork at 120V for an extended period ?
As mentioned above, rather than try and explain what combinations may be OK, it's easier to just say to not do it.
As mentioned above, rather than try and explain what combinations may be OK, it's easier to just say to not do it.
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