The Electrical Contractor Network

ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Books, Tools and Test Equipment for Electrical and Construction Trades

Register Now!

Register Now!

We want your input!

Featured:
   

2017 NEC and Related
2017 NEC
Now Available!

   
Recent Posts
Sprinklered equipment 26-008
by bigpapa
Yesterday at 04:24 PM
On Delay Relay with Auto Reset
by Potseal
12/01/16 09:59 AM
Wow, that was close!
by jraef
11/28/16 07:06 PM
Earthquake in New Zeeland
by RODALCO
11/27/16 11:25 PM
Calling all Non-US members!! (Non-US only)
by Tjia1981
11/27/16 06:33 AM
New in the Gallery:
12.5A through 0.75mm˛ flex (just out of curiosity)
Shout Box

Top Posters (30 Days)
gfretwell 15
HotLine1 10
Trumpy 8
Texas_Ranger 8
sparkyinak 7
Who's Online
0 registered (), 215 Guests and 4 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#141988 - 11/21/04 05:35 AM Heat Conduction or Fault?
LiveWireUK Offline
Member

Registered: 07/29/04
Posts: 15
Loc: Berkshire + London + Norfolk, ...
Guys, maybe one of you can allay my concerns somewhat?

In my student house, we have both a washing machine and a tumbledryer plugged into an extension lead, which I made (A double metal clad socket, with a compression gland and 5m of 1.5mm PVC(3183Y)) as our “utility room” has no powerpoints. My concern is over a frequent occurrence of the dryer plug, extension lead plug and the flex becoming “noticeably” warm during operation of the tumbledryer, regardless of the use of the washing machine. I noticed this, where no one else in the house did, mainly as I am, naturally, more conscious of these things.

The dryer plate states 2050W Loading. So, for the sake of argument, lets say 10A. So the loading on the extension lead (fused at 13A), with the washing machine off, is fine. I’ve disassembled the extension lead, checked all my wiring, and checked all the leads for any damage. I’ve checked the plug and connections on the dryer. All are tightly and correctly connected and no signs of damage, corrosion or poor/intermittant connection. My multi meter confirms no shorts or leaks to earth or P/N in the wiring up to the dryer, which should operate one of the fuses in this assembly anyway. No earth fault in the dryer either.

So what is causing this heating effect? I am far too suspicions of this to believe that the heat of the elements is conducting all the way back to the extension lead plug? I don’t see how it can be a prolonged overload on the extension lead, not without blowing the fuse.

I am more suspicious of this situation as, when I was younger and at my parents, I got burnt by the plug pins on our 18 year old tumbledryer. The neutral wire had totally burnt it self out throughout most of the flex, and the fuse had never blown.

For now we only use either the washing machine or the dryer at one time and the extension is on an RCD. ANY ideas or solutions?

Ash (LiveWireUK)

Top
Test Equipment:

Large Selection of Test Equipment For Electrical, HVAC, Test & Measurement
Large Selection of Test Equipment For Electrical, HVAC, Test & Measurement

#141989 - 11/21/04 12:42 PM Re: Heat Conduction or Fault?
djk Offline
Member

Registered: 12/26/02
Posts: 1269
Loc: Ireland
Unlike a lot of other heavy appliences tumble dryers will draw close to their max rating for most of the cycle (this could be 80 or 90 mins)

So, if that dryer's rated 2050 W you can assume that it is actually consuming that much power for almost all of the cycle.

I just had a look at our Miele dryer and it's also a 1.5 X 3 flex and it's slightly warm, but not hot just noticably warm.

The plug is also slightly warm, but not dangerously so.

Your washing machine will only draw the max rating during the heating part of the cycle which might only last 15 mins or so. The element will be intermittently turned on and off for short times to maintain that temp during the wash.

However, there is no way that you can run both of those appliences together on a single 13A plug! The fuse *SHOULD* blow.. I'm amazed it's not blowing.
Running both of those appliences on an extension cord from one socket is a potential fire hazard.

2050W dryer + about 1850W for a washer is considerably more than 13A

I've seen a BS1363 socket catch fire and it's not something you want to have happen!

Regarding the pins heating up:

British plugs and sockets are not recessed, so to prevent electric shock most of the surface area of the pin is sheathed in plastic and the sockets are designed only to make contact with the tip of the pins. The surface area of the pin that actually makes contact is supprisingly small given the size of the plug.

(European schuko plugs don't really have this problem as they're recessed)

Anyway, for heavy appliences like tumble dryers I think it's very important to ensure that the plug and socket are of good quality and are making proper contact. Repeated plugging in and plugging out will eventually loosen the contacts in the socket. Personally, I would always make sure that the outlet for dryers, washers etc is a good brand like MK (likewise for the plug).

I honestly don't think that BS1363 plugs are a very good design. They're far too prone to overheating and rely on far too many add-on safety devices (sheathed pins, fuses etc). A modern recessed schuko plug / socket system is just fundementally safer.

There are a number of things that could have caused that 18 year old dryer to burn you / over heat the plug.

1) Older dryers didn't have very good temp controls so tended to draw more power as they just kept the heaters on constantly throughout the cycle. Modern ones would tend to switch in out thermostatically.

2) The plug or socket could have been making poor contact.

3) Given that it was 18 years old, it could have been designed for the rest of Europe (where sockets / plugs can provide 16A) or with the older BS546 15A round pin plugs. So could easily have been drawing close to 13A all the time.

Any of the above, or a combination of the above could have caused the problem.

When BS1363 is used in Ireland, on 220-230V systems this problem can be even more pronounced. There are plenty of instances where 15A BS546 plugs and sockets, schuko in older installations, or direct hardwired connection into a 16A circuit is used.

Top
#141990 - 11/21/04 02:13 PM Re: Heat Conduction or Fault?
LiveWireUK Offline
Member

Registered: 07/29/04
Posts: 15
Loc: Berkshire + London + Norfolk, ...
DJK, many thanks for your considered and detailed reply. It's greatly appreciated.

to quote: "there is no way that you can run both of those appliances together on a single 13A plug!"

Just to add to my earlier post, as I may have not made it clear. We only use one appliance at a time. Using both at the same time "should" overload the lead even as an intermittent load, say the spin cycle on the washer.

The point that is concerning is that the tumble dryer ALONE, on full-heat for a period of, say, a 30 minute cycle, is enough to cause this heating effect. That is, a load of ~10A drawn on the lead for that period.

Unless i am wrong (and i may very well be) the flex used, 1.5mm PVC 3183Y, has a native current carrying capacity of 16A, rated so upto 65*C. So, logically, there should be no "apparent" heating effect due to either intermittent or prolonged overload, for that flex type and CSA. The plug is then fused with a 13A fuse. I accept there are other variables; I just find it rather odd and a little concerning (as does much of the wiring in our house, per my other posts!).

I agree DJK, that good components are always best used. As far as I can recall, the socket is an MK standard socket, the styling is that of say 20 years ago, and the plug is a duraplug "tough plug" and is quite new as I only made the extension a year or so ago. I never use components that don't obviously display the relevant BS no, or kitemark. I will try replacing the plugs on both the extension lead and the dryer, and see if that makes any difference (?)

It has to be said, that I have never really considered the design of our 1363 plugs and sockets. I guess it's all to easy to assume that your national standard is "best" or "safest" as a matter of some nationalistic pride. I have seen some awfully cheap looking plugs and sockets about and do try to stick to the better-known brands. I personally like MK and Crabtree wiring accessories, but that’s another discussion!

To rally up some defence, I think our 1363s have some merits to them also: 1) Shuttered sockets. 2) Incorporated fusing, something that as far as I am aware no other county/national standard plug adopts (Why is that? Are we just being “British” and going that bit further? Is there a story there, anyone know?) 3) Polarisation, as you can only put it in one way …. there must be more ??

What’s the consensus? Are our 1363s that bad?

Ash (LiveWireUK)

edited for typo

[This message has been edited by LiveWireUK (edited 11-21-2004).]

Top
#141991 - 11/21/04 02:17 PM Re: Heat Conduction or Fault?
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
At 2050W the current should be well within the capacity of a 13A plug (about 8.5 amps). As Dave said though, many of the cheap plugs get worringly warm on even a moderate load.

You might not notice it on, say, an electric kettle because it's only runing a few minutes at a time. But that dryer is running continuously for an hour or more. I would echo the comment about making sure that heavy/long-term loads such as this are wired through good quality connectors (MK is an excellent choice) rather than no-name bargain basement types.

And most definitely do not run the dryer and washer simultaneously on that extension!

Top
#141992 - 11/21/04 02:30 PM Re: Heat Conduction or Fault?
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
Ash,
Looks like we crossed posts.

Is the heating along the cord even, or is it warmer at one end? If the latter, then it's suggestive of the heat being conducted back along the wire from the plug or socket at that end.

One common source of heat is the fuse and clips in a BS1363. You can sometimes track this down if the load has been on a while by unplugging and then:-

(a) feeling the face of the plug -- If the area directly above the line pin is noticeable warmer than the rest, then the fuse and/or clips are suspect

(b) quickly removing the cover and feeling the line/neutral terminals and fuse/clips inside.

 Quote:
To rally up some defence, I think our 1363s have some merits to them also: 1) Shuttered sockets.

In may be in a minority here, but personally I think the shutter aspect is often overrated here.

 Quote:
2) Incorporated fusing, something that as far as I am aware no other county/national standard plug adopts (Why is that? Are we just being “British” and going that bit further? Is there a story there, anyone know?)

The story is that the fused BS1363 plug was introduced with the ring circuit arrangement in the late 1940s. The plug fuse is necessary because OCPD on the ring is rated at 30A. Because the ring is a peculiarly British way of wiring a home, I guess you could say that fused plugs are just we British going our own way!

Top
#141993 - 11/21/04 02:43 PM Re: Heat Conduction or Fault?
djk Offline
Member

Registered: 12/26/02
Posts: 1269
Loc: Ireland
Also, shutters are pretty much standard on modern european fittings too. They're operated by applying equal pressure with the two pins simultaniously, just like the way MK & a few other brands do it in the UK.

Top
#141994 - 11/21/04 02:46 PM Re: Heat Conduction or Fault?
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
Hi there Ash!,
Personally, I would say that this sort of heat in a flex is quite normal, with a dryer on the end of it and also considering that the flex is 5m long.
 Quote:
What’s the consensus? Are our 1363s that bad?

The pins on the 1363 plug certainly look a lot heavier than our Aus/NZ plugs.
Just as a note, I'm not sure how things go over in the UK, but here, running an extension cord from one room to another is very much frowned upon.
_________________________
Let's face it, these days if you're not young, you're old - Red Green grin

Top
#141995 - 11/21/04 02:46 PM Re: Heat Conduction or Fault?
LiveWireUK Offline
Member

Registered: 07/29/04
Posts: 15
Loc: Berkshire + London + Norfolk, ...
Thanks PaulUK, I thought there was a sudden rush of posts haha!

As far as I can recall, the heating effect is noticeable throughout most of the flex. It is quite prominent in the plug though, so it may indeed be tracking back from there. I did remove the fuse and pass it to one of my housemates, who remarked on how warm it was!

I have ordered two new MK toughplugs from TLC and I'll see how they go. Why can't there be a branch closer to Norwich!! Grrr. All the other components are, in my opinion, good ones. A contactum socket on the extension and CCC flex. I checked the kitchen socket, its is some unknown branded one, looks like those horrid economy ones you can get from screwfix. Oh how is despair with the wiring in this house!! :'( Still waiting on the fusebox remodel

I feel a bit deflated that there should be such plugs and sockets that proudly boast the kitemark on them if this is how warm they get with just 8.5A!

Trumpy, I am sure many of my contemporaries over here would frown on it also. But given in the context of the wiring of our student house I think I may JUST be forgiven... Maybe . I guess I could just wire the dryer to the FCU that’s just two inches from the sink top LOL. Don’t Ask!! Grrr.

Thanks guys!

Ash (LiveWireUK)

edited to include Trumpy's comments

[This message has been edited by LiveWireUK (edited 11-21-2004).]

Top
#141996 - 11/21/04 04:02 PM Re: Heat Conduction or Fault?
n1ist Offline
Member

Registered: 02/13/02
Posts: 176
Loc: Malden MA
I might be doing the math wrong, but here it goes...

I looked up the resistance of 1.5mm wire - it is about 1.15 ohms/100m, so the 5m cable has a resistance of 0.06 ohms * 2 = 0.12 ohms (counting both wires). At 8.5A of current draw, it is dissipating 8.7 watts. That comes to 1.7 W/m, slightly warmer at the connections since they are probably higher resistance than the wire.

/mike

Top
#141997 - 11/22/04 04:16 PM Re: Heat Conduction or Fault?
uksparky Offline
Member

Registered: 07/06/04
Posts: 199
Loc: UK
n1ist has hit the nail squarely I would think.

And given that the calculations he cites would apply to 'ideal conditions', I suspect the warming effect would be slightly greater.

It will certainly be due to the resistance of the cable though - a 15m length supplying flc constant for a 2050W device will definitely warm up.

Why not hang any surplace around 2 sticks and chuck your smalls on them to dry!
_________________________
If hindsight were foresight, we'd all be millionaires!

Top



ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals