N Gauge Forum

General Category => General Discussion => Topic started by: texhorse on February 05, 2018, 06:52:18 pm

Title: A word of caution
Post by: texhorse on February 05, 2018, 06:52:18 pm
This "obvious" and "basic" thread is aimed at those like me, who even at 51 years of age is obviously still very naive where electricity is concerned.

Not much is happening on my layout this evening, as I've been blowing my electricity circuit in the house through using too many amps through the layout shed!  I was using a heater in the shed, and its use has put too much current through the house supply.  I came indoors to change the fuse for the fifth time since Christmas, thinking to myself that I really should investigate the cause.

I unplugged the plug from the wall and burnt my fingers on the pins of the plug!  When I opened it up, there's even little scorch marks in there!  Now THAT is scary.

So tomorrow, the heater is going to the tip.  Then I will replace the fuse in the plug again.  We'll see if the power cuts out again.  I am guessing it won't.

The moral of the story is to remember not to try and use too many appliances through a humble household power supply.  My layout, my shed, my house could all have had a disaster.

Andy
UK
 :dunce:
Title: Re: A word of caution
Post by: ntpntpntp on February 05, 2018, 07:10:47 pm
Blimey, what rating is the heater?     A 3KW heater is about the max a plug with a 13amp fuse can handle, but that should still be well within a house ring main circuit's load capacity unless you've got a load more of them on the same circuit.
Title: Re: A word of caution
Post by: themadhippy on February 05, 2018, 07:18:39 pm
sockets are allowed to get hot
Quote
, BS1363-2:1995 requires for double socket outlets that both socket outlets have loads applied via test plugs, 1 test plug having a load of 14 amps whilst the other has a load of 6 amps, making a total load of 20 amps on the cable supplying the double socket outlet. The double socket outlet is then subjected to this loading for a minimum continuous period of 4 hours or longer until stability is reached with a maximum duration of 8 hours (stability being taken as less than 1 degC rise within 1 h). The test is passed if neither the terminals / terminations, nor the accessible external surface, increase in temperature by more than 52 degC.
However i'd throw away the plug if its showing scorching and replace with a decent mk or equivalent decent make plug.
Title: Re: A word of caution
Post by: Yet_Another on February 05, 2018, 07:44:30 pm
sockets are allowed to get hot
Quote
, BS1363-2:1995 requires for double socket outlets that both socket outlets have loads applied via test plugs, 1 test plug having a load of 14 amps whilst the other has a load of 6 amps, making a total load of 20 amps on the cable supplying the double socket outlet. The double socket outlet is then subjected to this loading for a minimum continuous period of 4 hours or longer until stability is reached with a maximum duration of 8 hours (stability being taken as less than 1 degC rise within 1 h). The test is passed if neither the terminals / terminations, nor the accessible external surface, increase in temperature by more than 52 degC.
However i'd throw away the plug if its showing scorching and replace with a decent mk or equivalent decent make plug.
That does assume the socket is wired into the ring main, though.
Title: Re: A word of caution
Post by: themadhippy on February 05, 2018, 07:55:59 pm
Quote
That does assume the socket is wired into the ring main, though.
BS1363-2:1995  doesn't cover the wiring method, thats  down to BS7671
Title: Re: A word of caution
Post by: texhorse on February 05, 2018, 07:57:15 pm
All I know is that I'll be working in the shed in Winter with a coat on in future!  Far safer.....

Andy
UK
Title: Re: A word of caution
Post by: edwin_m on February 05, 2018, 08:31:39 pm
Is the plug rated at 13A?  Occasionally you find 5A rated plugs, there is nothing to stop someone fitting a 13A fuse and using it for a high-power appliance.  This would result in it getting very hot and possibly melting or starting a fire.  The current rating should be marked on the plug. 
Title: Re: A word of caution
Post by: davidinyork on February 05, 2018, 08:40:09 pm
One of the most common issues (although it doesn't sound like it's the case here) is over-loading 4-way adapters, or even plugging one into another. The things to particularly watch out for are things with heating elements (fan heaters, kettles, etc), and things with fairly powerful motors (hoovers, drills, washing machines). These should normally be plugged into the wall socket directly, or if an extension lead is used make sure it's a heavy-duty (i.e. 13a rated) one, preferably with only one socket at the end to prevent overloading.

Also, it's advisable to check the rating of 4-way adapters - some are 10a rather than 13a, including the flex, so swapping the fuse for a 13a is a really bad idea as it could lead to the flex melting.
Title: Re: A word of caution
Post by: themadhippy on February 05, 2018, 08:49:54 pm
Quote
Is the plug rated at 13A
All BS1363 plugs are rated for 13A,when you see a  3A label it just meens its been  fitted with a  3A fuse
Title: Re: A word of caution
Post by: port perran on February 05, 2018, 08:54:58 pm
All I know is that I'll be working in the shed in Winter with a coat on in future ;)!  Far safer.....
Andy
UK
I’m with you, if it’s getting hot then I’d get rid of it.
There’s two things I don’t trust. Electricity and the wind. And you can’t see either of them  ;)
Title: Re: A word of caution
Post by: texhorse on February 05, 2018, 09:11:56 pm
I had a 5 amp fuse in the plug.  I had been assured by an expert that this would be more than adequate for what I used in the shed.  Unfortunately, he was not taking the electric heater into account.

Thankfully no harm done, and I'll be trying again in daylight, minus the heater, and checking the plug to ensure it's not getting hot.

Andy
UK
Title: Re: A word of caution
Post by: davidinyork on February 05, 2018, 09:17:26 pm
I had a 5 amp fuse in the plug.  I had been assured by an expert that this would be more than adequate for what I used in the shed.  Unfortunately, he was not taking the electric heater into account.

Thankfully no harm done, and I'll be trying again in daylight, minus the heater, and checking the plug to ensure it's not getting hot.

Andy
UK

A heater will normally have a 13a fuse.
Title: Re: A word of caution
Post by: stevewalker on February 05, 2018, 10:27:00 pm
A common reason for an overheating plug is poor contact with the socket - due to spring metal contacts weakening or corroding. It would be a very good idea to replace both the socket and the plug - the heater itself is probably fine.
Title: Re: A word of caution
Post by: texhorse on February 05, 2018, 10:29:59 pm
It wouldn't be that Steve.  The shed was only wired to the household supply in October.  I'll rethink what you've said tomorrow after I've tried it without the heater.

Andy
UK
Title: Re: A word of caution
Post by: stevewalker on February 05, 2018, 10:37:40 pm
It wouldn't be that Steve.  The shed was only wired to the household supply in October.  I'll rethink what you've said tomorrow after I've tried it without the heater.

Andy
UK

One other possibility springs to mind and is worth checking - especially with it being a new installation. A terminal screw not tightened down properly can give rise to a lot of heating and could be in either the socket or the plug.
Title: Re: A word of caution
Post by: colpatben on February 06, 2018, 07:26:22 am
Can I get this straight?

 
The shed was only wired to the household supply in October.  I'll rethink what you've said tomorrow after I've tried it without the heater.

Andy

When you say that the shed was wired into the household supply is the cable to the shed terminated directly into the main fuse/distribution board i.e. adjacent to the incoming meter?

I had a 5 amp fuse in the plug.  I had been assured by an expert that this would be more than adequate for what I used in the shed.  Unfortunately, he was not taking the electric heater into account.

Andy
 


I came indoors to change the fuse for the fifth time since Christmas, thinking to myself that I really should investigate the cause.

I unplugged the plug from the wall and burnt my fingers on the pins of the plug!  When I opened it up, there's even little scorch marks in there!  Now THAT is scary.

Andy
UK
 

Or does the shed cable start at a fused plug top somewhere inside house (kitchen) which is where the 5amp fuse is, and is it this plug top that is getting hot?
(http://www.ngaugeforum.co.uk/SMFN/gallery/61/1337-060218071614.jpeg)

It would also help is you could describe the cable running to the shed.

    1) Cable size/type ie 2.5mm2 Twin & Earth, 1.5mm2 3 core armoured etc.
    2) How installed ie burried, clipped to the fence, overhead on catenary etc.
Title: Re: A word of caution
Post by: texhorse on February 06, 2018, 08:31:07 am
Hi Colin.  The 4 way plug socket from the shed goes up to a standard light switch in there, to switch on the power.  After leaving the shed the power comes through armoured cable tacked to the garden fence and through a hole into the house.  From there, there is a cut out switch for safety.  Finally the cable goes up to the standard plug socket in the living room.

Andy
UK
Title: Re: A word of caution
Post by: ntpntpntp on February 06, 2018, 09:05:26 am
The 4 way plug socket from the shed goes up to a standard light switch in there, to switch on the power. 

hmm.... I thought lighting circuit switches were typically rated for 10A, and you've been running a 3kW heater (12.5A) through it?  What else was running in the shed as well?

Slightly worried about  this "expert" you had to do the wiring for you.  OK you may not originally have said you were going to run a heater, but even so you've have cabling and 13A sockets installed to the shed, which is rather more than just a lighting circuit. What about at some future point if perhaps you move on and someone buys the property? They would naturally expect sockets to be able to take the usual load.
Title: Re: A word of caution
Post by: LAandNQFan on February 06, 2018, 09:23:43 am
I'm not an expert, but when I installed the supply to my shed I took the following into consideration:
the length of the run of armoured cable;
the type of plug and socket that would be needed;
the total load on the circuit.
The longer the run of armoured cable, the more the resistance.  As I was running nearly 20 metres, I decided to limit the drain on the circuit to five amps.
From a RCD socket, a heavy duty plug is fitted with a five amp fuse (Why did yours not blow? - even a 1500 watt heater draws more than 5 amps). The armoured sleeve round the cable is bonded to earth through the RCD socket.
As a light switch is not rated for the amperage of a power circuit, I fitted a power isolating switch where the armoured cable enters the shed.  I still replaced its fuse with a 5 amp fuse.  I should check the light switch in your shed to see if there are any signs of overheating there.
My heater in the shed is a 40watt greenhouse tube heater drawing a sixth of an amp. LCD lighting, a CDU and two controllers draw a couple of amps, and I switch the controllers off if I am using a 40watt soldering iron or the glue gun.   Any power tools I use in the shed are battery operated.
All this may seem over-cautious, but I still have the scar from my first attempt at dismantling a light switch over 70 years ago!
Title: Re: A word of caution
Post by: texhorse on February 06, 2018, 09:24:17 am
That didn't read right.  It's not a light switch being used for a light.  It's just a switch I'm using for On / Off purposes.

Andy
UK
Title: Re: A word of caution
Post by: LAandNQFan on February 06, 2018, 09:27:16 am
It's not whether the switch is being used for a light, Andy.  A light switch should not be part of a power circuit.
Title: Re: A word of caution
Post by: Jerry Howlett on February 06, 2018, 09:31:34 am
Up here in the Italian mountains if you draw 6 Amps "Bang" the entire supply to the house drops out.
Switch on the Oven when the washing machine is on.....  Bang.  Electric showers ???  No chance.

Oh and in the old part of the house lights and the sockets ..one circuit. Some days you can see the lights dim when the village is using too much power.

Take care with your mega supplies!

Jerry

Title: Re: A word of caution
Post by: colpatben on February 06, 2018, 09:45:01 am
Hi Colin.  The 4 way plug socket from the shed goes up to a standard light switch in there, to switch on the power.  After leaving the shed the power comes through armoured cable tacked to the garden fence and through a hole into the house.  From there, there is a cut out switch for safety.  Finally the cable goes up to the standard plug socket in the living room.

Andy
UK

So where is the ‘blowing’ 5 amp fuse is in a plug top at ‘A’ or ‘B’?

Or is the cable to the cut out safety switch ‘hard wired’ from the ring circuit at the back of the living room socket?

(http://www.ngaugeforum.co.uk/SMFN/gallery/61/1337-060218094125.jpeg)
Title: Re: A word of caution
Post by: daffy on February 06, 2018, 09:52:04 am
Andy, the set up,you describe sounds remarkably similar to what used to power my shed. A wire from a plug socket in the house, protected by a basic Plug-in RCD, through a hole in the wall, then armoured cable down the fence line to the shed with a switch linking to sockets.

I say "used to" because when I moved here four years ago that was what was there. When some wiring upgrade was needed for various thing in the house, my fully qualified and certified electrician condemned the shed system in its entirety.
As he said, it works, but it's not to code, it's not safe, and he would not issue a new certificate on the house without disconnecting it completely.

As I understand it, any wiring to a shed should come direct from the main Consumer Unit, or 'Fuse Box' on a dedicated circuit. That is also where any RCD should be located.

I understand why many don't take this precaution as my electricians quote to power the shed properly was hefty, so if I want any power there now I just run an extension lead as and when I need it - which is not often - and only for low- load devices, like an inspection lamp or a drill. That way I'm pretty certain I won't burn my shed down or electrocute myself. Touch wood! ;)
Title: Re: A word of caution
Post by: davidinyork on February 06, 2018, 09:58:25 am
It sounds a right bodge, to be honest!

If it's plugged into a 13 amp socket, the absolute maximum draw for everything plugged into it (i.e. everything in the shed) is 13 amps - assuming all the wiring / switches in the circuit are also rated at 13a. As noted above this is probably not the case, so the maximum will be the rating of whatever the lowest rating cable / switch in the circuit is (seemingly the light switch which turns it on).

This sort of thing is an accident waiting to happen - get it properly wired in to the consumer unit, with its own trip switch.
Title: Re: A word of caution
Post by: BobB on February 06, 2018, 11:02:02 am
The standard outlet in South Africa is the old UK 16 amp style of three round pins. (Questioned by a visiting American - he said is that an industrial plug !) I've seen people here use the standard plug for running welders that need about 35 amps or more. Maybe the cold weather means the heater was pulling power for to long. Short interruptions such as when the fire's thermostat operates are often enough to prevent overheating but if the fuse is blowing it's almost certainly an overload.
Title: Re: A word of caution
Post by: PaulCheffus on February 06, 2018, 11:03:45 am
This sort of thing is an accident waiting to happen - get it properly wired in to the consumer unit, with its own trip switch.

Hi

Couldn't agree more. I would get an certified electrician to come and check this. Last thing you want is the house to burn down.

Cheers

Paul
Title: Re: A word of caution
Post by: texhorse on February 06, 2018, 11:04:47 am
The heater is now outside the shed waiting for the scrap men.

Been in the shed for three hours almost this morning.  No cut outs, no problems.  Came up to the house.  The plug socket is as cold as any other in the house.  All is well.

It might be a "bodge job", as you say David, but it works.  The electrician who put it in for me, did say, to be fair, that it needs its own circuit into the main house supply, with its own trip switch.  He also said that for now, as long as I didn't run too many amps through the system, it would be fine.  I guess I was trying to do too much.

Andy
UK
Title: Re: A word of caution
Post by: davidinyork on February 06, 2018, 11:07:39 am
It might be a "bodge job", as you say David, but it works.

Electrical bodge-ups do often tend to work (which is a lot of the problem), until one day they don't work an if you're unlucky they cause a fire.
Title: Re: A word of caution
Post by: texhorse on February 06, 2018, 11:17:41 am
Or you do what I did today, and stop asking so much from your power supply.

I originally put this up here to try and show people that putting too many appliances through the circuitry may have dire consequences.  I was naive, but lucky nothing has happened.

I've learned my lesson. 

Andy
UK
Title: Re: A word of caution
Post by: davidinyork on February 06, 2018, 11:23:32 am
I originally put this up here to try and show people that putting too many appliances through the circuitry may have dire consequences.  I was naive, but lucky nothing has happened.

On any extension from a standard socket (which is what this is), add together all the fuse ratings of the applicances you want to connect to it. If it comes to more than 13*, don't do it. Yes, it will probably work if it's a bit over 13 unless all the applicances are drawing close to their fuse rating, but it simply isn't worth the risk.

*assuming that any 4-way adapter used is also rated at 13amps
Title: Re: A word of caution
Post by: themadhippy on February 06, 2018, 11:32:36 am
Quote
As I understand it, any wiring to a shed should come direct from the main Consumer Unit, or 'Fuse Box' on a dedicated circuit. That is also where any RCD should be located.
No you  can  run a  fused spur off the ring final,only drawback there is your limited to 13A max load
Quote
a heavy duty plug is fitted with a five amp fuse (Why did yours not blow? - even a 1500 watt heater draws more than 5 amps). The armoured sleeve round the cable is bonded to earth through the RCD socket.
Steal wire armour is not and never was intended to be terminated into a plug. And now we open up a bigger and potential more dangerous problem,the earthing arrangement,put simple its best not to take your earth from the household supply,instead use an earth spike at the shed end.
Quote
I thought lighting circuit switches were typically rated for 10A,
plate switches rated for 20A are common enough and look just like a normal light switch,its only when you turn em round and see there double pole that the games given away

Title: Re: A word of caution
Post by: colpatben on February 06, 2018, 11:41:39 am
Or you do what I did today, and stop asking so much from your power supply.

I originally put this up here to try and show people that putting too many appliances through the circuitry may have dire consequences.  I was naive, but lucky nothing has happened.

I've learned my lesson. 

Andy
UK


On a final note from me this link should be a good starting place for all those who are Installing/using electricity in an outbuilding.

http://wiki.diyfaq.org.uk/index.php/Taking_electricity_outside (http://wiki.diyfaq.org.uk/index.php/Taking_electricity_outside)


"Be EXTRA Careful Out There'
Title: Re: A word of caution
Post by: daffy on February 06, 2018, 01:05:56 pm
Quote
As I understand it, any wiring to a shed should come direct from the main Consumer Unit, or 'Fuse Box' on a dedicated circuit. That is also where any RCD should be located.
No you  can  run a  fused spur off the ring final,only drawback there is your limited to 13A max load

Thanks for the clarification. :thumbsup: My comment was based upon my electricians conclusion for what I had initially planned for my shed, where the total amp usage could have exceeded 13amps.

 :beers:
Title: Re: A word of caution
Post by: first timer on February 23, 2018, 09:01:20 am
I,ve had a sertified electrition look at my problem to put power into my shed but I have not got a spare ring on my main consumer box but he says he can take a supply off the double socket on the wall which runs directly to the main box, is this safe? or is there another way or an add on to the main box which can be fitted?

    Les.
Title: Re: A word of caution
Post by: The Q on February 23, 2018, 09:15:43 am
Yes it is safe but it limits you to 13A total load in the shed, so NO, 3 bar fires, plus lights, plus soldering Iron, plus railway transformers.
If you can make do with a 2KW heater in the shed, would leave you 4 amps spare (roughly to run the rest).

If you want a 3Kw Fire and a kettle in the shed. Then you need an extension to, or bigger replacement of, the consumer unit. So you can have a proper ring main to the shed.

 I've had to go further, with the shed having it's own consumer unit, but then there could be a heater either end of the shed, 3 fridges to run, me soldering away and then SWMBO would put the kettle on...
Title: Re: A word of caution
Post by: first timer on February 23, 2018, 09:21:54 am
I will be using, 1 light standard bulb, 1, double track controller 1 amp per track, and a heater which is a low usage of 400 or 800 watts, what do you think?
Title: Re: A word of caution
Post by: The Q on February 23, 2018, 11:13:32 am
That will be well below the 13A amp limit on a spur.

Heater 800W = about 3.5 A.
One flourescent light bulb (big) 15W= less than 0.1A
1 dual gaugemaster (or similar) is on a 3 Amp Fuse.
Large Soldering Iron 50W = about 0.2 A

 total 6.8 Amps.

So you'd still have plenty spare for a spot light or the like if you are under the layout...