Dumb question ? - fridges / extension leads

[Calvin Sambrook]

"Colin Wilson" wrote in message news: [e-mail]...

I often see inappropriate instructions, almost all seem to be someone making H&S up as they go along. This one falls into that category. Unless it's a big, industrial, FO fridge even the startup current can't be that much.

Of course from their POV an extension lead means: Unknown cable sizing More connections Possibly coiled cable All of those could lead to problems.

I'm sure you already do but I'll say it anyway, When cutting off a plug always remove the fuse.

[Peter Parry]

Elfin safety paranoia. If the extension lead is left coiled on a drum it will overheat at a small fraction of its rated current. Fridges go on and off by themselves so the overheating and possible subsequent combustion may take place at night or when no one is in.

[Derek Geldard]

Where do you get that amps figure from ?

What is your figure for the inrush current?

You have measured it ?

From

Typical current draw for a refrigerator?

My 20 year old upright freezer is about 10A starting, 3.27 amp running (263 watts)

My 10 year old fridge is very similar

(Figures from the US)

Derek

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Colin Wilson saying something like:

Load of bollocks. It'll be fine if it's a short lead and not coiled.

[John]

Ever seen nurses thumping in crooked plugs in a hospital.

[ARWadsworth]

Adam

[NT]

from the 60w typical rating. Admittedly I ignored power factor, which will add maybe 25% on, but makes no qualitative difference to the outcome.

US fridges are different animals to UK ones. Typical run power on a new machine here is around 60w. At 240v thats 0.25A, or a bit more considering power factor.

If we use your ratio of 3:1 for startup current, then the Vdrop during startup would be about 1.3v, leaving 238.7v for the compressor that's rated to run on 220v nominal as well as 240v nominal.

Even if we used an aggressive figure of 16x start current, 16x 0.44v =3D

7v drop, leaving the machine 233v, when its rated to run ok at a bit over 200v.

reveal the truth.

NT

[NT]

Even bell wire could cope with an intermittent quarter amp load coiled.

NT

[Derek Geldard]

Nurses are not a patch on 20 y. old female radiographers, (although we came across a few nurses who used to stand at the lab door and just throw the blood at their Blood Gas Analyser )

- enormous steel handles just "come off" in their hands.

R.N. Captain overheard at a trade exhibiton in 1970 about the (very first Philips VCRs) ...

It's not "Sailor Proof").

Derefgk

[Mike Clarke]

Latest one I came across is the warning label stuck on the side of a brand new Ikea stainless steel kitchen sink.

"This appliance must be earth bonded (IEE regulations 15th edition 1981)"

People making dogmatic H&S utterances really should try to keep up to date. I don't know if earth bonding kitchen sinks was a requirement in the 15th edition (it was in the old 13th edition that I still have a copy of) but it hasn't been needed since the 16th.

[Peter Parry]

A. You are assuming that's all that is plugged in. B You are forgetting the Elfin Safety writer had probably stopped taking the dried green frog pills.

It never pays to confuse Elfin Safety with reality.

[The Medway Handyman]

I think the term Effin Softy sums it up nicely :-)

[NT]

Not really, even a 20A load on a sensible 5m extension lead wouldn't take the fridge out of its voltage spec.

NT

[John Rumm]

Startup inrush would more likely be 5 x In, perhaps as high a 9 x In. The power factor could add getting on 50% top of that. If the fridge is genuinely only 60W or so, then its a non issue since we are talking a couple of amp tops. If its one that sucks a couple of hundred W then the number creep up quite quickly.

Well not necessarily. The truth may be the "no extension lead" advice is a stock wording they have had in the manual for years, and used to make far more sense on machines that needed 13A fuses to ensure they did not pop on motor start. Or, it might be they warn against extension leads in a kitchen on the grounds that they are known to cause trips, falls, scalds etc (i.e. all the stuff part P makes worse!) and it has nothing to do with the electrical size of it.

[John Rumm]

So do I ;-)

[Mike Tomlinson]

In article , The Medway Handyman writes

To connect to the cooker/washing machine point?

[Andrew Gabriel]

I haven't measured a fridge, but I have measured by aircon compressor. The normal power rating is 1.5kW, and I observe the consumption varies between 1.0 and 1.5kW. When the compressor fails to start with a locked rotor, the consumption is 4.5kW (for a few seconds before it gives up, and waits for the pressure differential to decay away before retrying). A fridge or freezer does exactly the same, in expecting that the compressor will sometimes fail to start, and need to wait and retry.

I haven't measured the current draw when this happens, and that might be more than the 3:1 or 4:1 ratio for the power consumption.

[The Medway Handyman]

Yup. Thats why it really confused them.

Which bit of "American floor cleaning machine company" didn't you understand?

[<me9]

My earliest copy (not to hand at the moment) is 13th edition (about 1966) and I don't recall any mention of bonding sinks. I think bonding and equipotential zones came in in the late 70s or early 80s. A lot was overdone at first as a CYA exercise.

[Mike Clarke]

In my 1963 issue there's a requirement in Regulation 404 to bond exposed baths, metal pipes, sinks and tanks with a note that it applied to bathrooms, kitchens, sculleries, laundries and milking-sheds. But it does say that this only applied where segregation from metalwork and other services is impracticable and the exemption to Regulation 214(a) was invoked. Regulation 214(a) applied where cables were drawn into the same ducts as extra low voltage circuits, the exception applied to multicore cables for lifts so perhaps it didn't apply to domestic situations. All a bit confusing but fortunately just of historical interest now.