Is it that low on all of them?
I did blow a 5A fuse on a modern Bosch larder freezer. The fuse was in a 1.2m 1.5mm extension lead used to supply it overnight, and it blew sometime the following morning. The manual does warn to only use a 13A fuse, so perhaps significant stall is expected at some point. The 5A fuse might had been bouncing in boxes of screws for a couple of decades.
Thats not quite a 100% overload. I think the average BS plug top fuse would last longer than that(*). Wether the plug top could take the heat generated is another matter...
(*) Wonkypeida says for a 13A fuse 1-400s @ 30A (6.9kW). My experience of urns and kettles on the same 13A plugtop is that it take quite a number of minutes for the fuse to blow and the plug top melts as well.
A strictly 3kW kettle, 3000W, is 12.5A at 240V. I think most are quoted as a range such as 2960-3180W etc.
Coopers BS1362...
- 1.6*In (20.8A) MIN of 30min - 5000W
- 1.9*In (24.7A) MAX of 30min - 6000W.
Assuming it's not the first time this has been done, the fuse could well be rather weaker than spec.
When I was looking for some suitably rated Arctic cable for my arc welder I came across this site:
"Arctic cable is only designed for outdoor use at 110v, we recommend using HO7 RN-F rubber cable for temporary 230v outdoor use including marquees."
Any thoughts?
Richard
No it is not.
It is a PVC cable, 300/500V rated, a bit skimpy for a rough industrial environment where it may be subjected to not only clumsy feet, high heels and mineral oils. It does however use colour coding to match the assumed BS4343 connectors, for example yellow indicates 110V and blue indicates 230V and black indicates you are using it in a theatre :-) There are white, orange, yellow, green, blue, purple etc.
H07RNF is chosen for rough industrial environments because it is oil resistant, thicker sheath & insulation, and in particular "07" means
500/700V rated. The higher voltage rating is important if you have a 3 phase supply (generators or commercial hookup) to a BS4343 distribution board consisting of lots of blue 1 phase sockets. It can be used at any voltage re 110V, 230V, 415VAC. N is Neoprene which is UV/Rot resistant unlike R which is not.If a cable is going to get a lot of abuse, it is worth considering H07RNF.
Unfortunately a few years ago whilst Arctic was 43-47p/m & H07RNF just
59-62p/m, the price difference now is much greater. I think H07RNF is about double if not triple the price of Arctic, so I would prefer to put the money on a spare plug in RCD - or just limit H07RNF to where it is either needed or could be useful. An example is I would put H07RNF on an often left outdoor extension lead, but a casual "vacuum cleaner extension" could be Arctic.A note is H07RNF does vary around the world, the cheap Asian cables can be rigid as hell because the rubber compound assumes a warmer climate (I think). The UK stuff such as Drakaflex is extremely flexible even at freezing conditions.
The variation probably covers resistance variation as well - it is only a kettle.
For example of the four otherwise identical 700W heaters I have had, the element wattage measured by plug in energy meter vary from 707W to
823W. The precise figure may be wrong, but as a resistive load there is clearly quite a variation.I think I remember a 600W kettle once... it might be boiled by now, must find it!
You could warm it up by running 2 kettles of it:-)
Leave it outside, powered up, and the neighbours will soon warm it up...
I really dont know, I gather thats fairly typical for induction motors. I've done more work with other types, which have much higher startup current.
who knows, too many possible reasons why.
NT
Unfortunately your average lay person has no clue about the different current consumptions of different appliances, and the significance thereof.
Even if they (often only vaguely) understand that a 3-bar electric fire is more expensive to run than a 100mA phone charger, they have no concept of what the different currents involved actually mean, and what the safety implications are.
David
I was going from the graph in BS1362:
Also worth keeping in mind that with low resistance items like notional
3kW heaters, they are often quoted as 3kW at 240V (which suggests an element resistance of 12.5 ohms) but that is only 2875W at 230V. So small shifts in voltage make a noticeable difference. Factor in the effect of the load on the actual voltage drop on the lead and you can get quite substantial amount of load shedding.Say its a 1.5mm^2 flex and assume 24mOhm/m round trip resistance. Try and draw 20A through 20m of that, and you have just dropped another 600W of load.
I would have expected it to be much larger on a fridge due to the induction motor in the compressor. 5 to 9 times nominal is the range for inrush on that sort of motor IIRC.
So even a couple amp normal draw, could suck 18A on startup.
as an aside, I added some details to the end of the flex article the other day for breaking down those harmonised codings:
(still needs some work to make it a bit easier!)
It's correct. You might like to read the two articles about this that were published in the IET's /Wiring Matters/ fairly recently.
Firstly:
- 3183A 'arctic' cable made to BS 7919 Table 44 is suitable for handling down to -25 deg. C, but is only intended for use on 110 V ('reduced low voltage') systems. This cable type is explicitly described as not suitable for outdoor use at "standard voltages" (meaning 230/400 V), nor for use in industrial or agricultural buildings. [Ref. BS 7540-3 Guide to use ...]
- The 'blue stuff' is not actually an arctic cable at all. It's an ordinary duty cord to BS 6500, i.e. 3183Y or H05VV-F. It's fine for 230 V but shouldn't be handled at temperatures below +5 deg. C. It is not a heavy duty cable.
- For heavy duty, use H07RN-F, as already mentioned.
- make "Understanding Harmonised Cable Codes" a separate article, (a) shorter pages are better, (b) codes also apply to non-flexible cables;
- it might not be immediately obvious that to describe the insulation and sheath needs two codes from your table 2a, insul'n first, then sheath;
- I wonder if the big table is really necessary. Might it be simpler just to quote a few examples. This would lend itself to also quoting the British CMA code (6242Y, etc) to make a useful cross reference (i.e.
3 cols: har code, brit code, description - or similar)
(a)
Indeed - I worked that out as I was going through dodgy translations of the spec... Having only seen them used on flex specs prior to that I had assumed they only applied there - but since I had started, I though I may as well finish!
Yes will add that... table 3 could also use some examples because although that looks simple the real world uses seem to take multiple trips through it to describe size of main conductors, then CPC etc where they are different. There are some examples in the spec we can lift.
So did I after fighting with the OCRed output of it to HTML and then running it through a HTML to wiki code conversion!
Yup, like that idea... Might just stick that on as an extra quick lookup table.
See if the new note and example helps...
Table started:
Look inside the plug and socket for loose connections first.
Flexible cable after a while can get breaks inside the cable, They can be a PITA to find but are usually near the ends. Plug a light into the extention and work along it bending and flexing it. You can usually determine where the break is. Cut the break off and reconnect/replace the plug/socket.
Hi Andy
It's interesting to note that you and js-b1 disagree entirely about the Arctic cable.
At the moment the cable to my arc welder is extended with ordinary (white) flex - bought in order to get a job done in a hurry - which is far from flexible in cold weather and, while attached to the welder, a bugger to coil up for easy storage . I was weighing up the costs of replacing it with H07 and a Commando plug/connector at the welder end to make the whole lot easier to transport. However, 15m of 4.0mm H07 and a 32A Commando plug/connector pair costs more than I paid for the welder!
I've found the BS refs for Arctic and H07:
THE USE OF 'ARCTIC' CABLE
It is common to see blue sheathed flexible cables, sometimes referred to as 'arctic' cable used on temporary installations.
Manufactured to BS 7919 (not harmonized), this type of cable was designed and is suitable for use on reduced low-voltage systems only, e.g. construction site installations, e.g. 110 V centre tapped transformers at 55 V - 0 - 55 V and often seen on temporary road works traffic lights.
Cables for outdoor use should be rubber insulated and sheathed as specified in BS 7919
Richard
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