house light fuse 8amp blowing

[F Murtz]

fritz wrote:

"F Murtz"<haggisz@hotmail.com> wrote in message news:4d625a4d@dnews.tpgi.com.au...
fritz wrote:

"F Murtz"<haggisz@hotmail.com> wrote in message news:4d622c15@dnews.tpgi.com.au...
kreed wrote:


In Australia in most cases an active and neutral go from light to light
and a twin drops to the switch (active and switch wire)
So you may have to disconnect downstream wiring at the light socket.



That is rare in QLD, but have seen this once.

In this one case there was an active and a neutral at both light and
switch, and a single
dual sheathed cable (switched active) ran from switch to light.


I do not know if things have changed but in nsw they used to loop a twin+e (active neutral + earth to every lighting point or
group of lights then drop a twin to each switch,except for two way or intermediate switching when a twin strap went between
switches.
very rarely did neutral end up behind a switch except in special circumstances.
I have not looked recently so maybe they do things differently now

Just had a look at 'Australian Electrical Wiring' Pethebridge& Williams
and several possibilities for basic single-switching are shown :
1) looping-in at batten holder - twin (A+N) with earth between batten holders
and twin drop to switch
2) looping-in at switch - twin to switch, twin to batten holder with
separate earth to batten holder
3) looping-in at switch - twin and earth to switch, twin and earth to
batten holder (but a protected straight-through earth OR an approved
earth joint at the switch is required)
4) looping-in at junction box with twin and earth to batten holder and twin
to switch
5)surface conduit system - actives are looped at switch, neutrals and
earths at the batten holder.

The important thing is that all batten holders must have an earth
available - old installations did not do this.

Other possibilities are allowed as long as they comply with the SAA
wiring rules. For example, when adding a new light and switch to an
existing installation it may easier to use two junction boxes etc.




I was not discussing what is legal,I was discussing common practice.

The quoted source was (is?) widely used as a textbook for the Electrical
Trades. I provided it to indicate the common practise as electricians
are taught to do.
Electricians do not make it a practice of doing everything the rule book

allows.
every thing in the rule book is not necessarily common practice the
rules are there to cover all sorts of eventualities not only common
practice

I assume the installation was done legally, are you suggesting the faulty
installation was not compliant ?

No

Economically they did not take wires where they were not needed.

They still should have complied with the rules.

Did not say they did not

The discussion was about fault finding and the place to isolate further down the line is at the lighting fixture as most of the
connections are done there. Single switches usually have only two wires. Most fuse blowing faults are at the fixtures.

As in 1), 4) and 5) above,

In the days of split conduit,cabling was a bit different as single wires were used and cables went direct to where they were going
ie less connections.
The conduit I was referring was an historical reference it was used in

and on walls sixty years ago and has not been used for over fifty years.

That is case 5), the system is called surface conduit because that's
how it is most often mounted (not inside walls etc.). Single wires
are usually used. It is all explained in the quoted source, Pethebridge
& Williams.


I think you are trying to teach your grandmother to suck eggs

This discussion was about trying to find a recent fault occurring in a
probably normal installation

 

[F Murtz]

Sylvia Else wrote:

On 22/02/2011 12:31 AM, fritz wrote:

They still should have complied with the rules.

The rules change.

Sylvia.

No one said they did not comply with the rules

I think mr fritz lives in another country and has no first hand
knowledge of australian household electrical wiring

 

[Don McKenzie]

On 20-Feb-11 12:29 PM, coffeexxx wrote:

Q; how do I trace a damaged power line in the walls/ceiling without
breaking giprock everywere?? What do electricians do in these
cases?? rewiring the entire lighting circuit is too huge a job.

Believe it or not, I was an electrical contractor in 1964, however I know things have changed somewhat since then, but
I'll give it my best shot.

You can unscrew a switch or two, to determine if it is just actives that drop down from the lights to the switches.

Someone suggested a plug in circuit breaker for the fuse holder. Great idea for chasing this fault. I have them fitted
anyway. Who wants to keep changing a fuse wire in this day and age?

Now what you do is section isolate:
-----------------------------------
If the active-neutral pairs run from the switchboard to each lighting position in turn, you draw yourself a map of how
you would run it to save cable, if you were wiring it. This will be wrong of course, but it will be a guide to get started.

At the half way point in the cable run, unscrew the light fitting, and separate the wires. If the fault vanishes, then
you have half your house wiring working, and you know the problem is in the second half. If not, split it in half again,
until you do get it working. If you are getting early results, you can redraw the cable map.

If you are not confident enough to do this, then I strongly suggest you get a sparkie in. Getting the right sparkie may
be the secret.

Me, I got too old to wobble around on a ladder, and I couldn't see what I was doing anyway, so I would be looking for a
good sparkie.

Good luck with it.

Cheers Don...

=================




--
Don McKenzie

Site Map: http://www.dontronics.com/sitemap
E-Mail Contact Page: http://www.dontronics.com/email
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http://www.dontronics-shop.com/ics.html

Bare Proto PCB for PIC or AVR projects?
"I'd buy that for a Dollar!".

 

[keithr]

On 22/02/2011 5:48 AM, Don McKenzie wrote:

On 20-Feb-11 12:29 PM, coffeexxx wrote:

Q; how do I trace a damaged power line in the walls/ceiling without
breaking giprock everywere?? What do electricians do in these
cases?? rewiring the entire lighting circuit is too huge a job.

Believe it or not, I was an electrical contractor in 1964, however I
know things have changed somewhat since then, but I'll give it my best
shot.

You can unscrew a switch or two, to determine if it is just actives that
drop down from the lights to the switches.

Someone suggested a plug in circuit breaker for the fuse holder. Great
idea for chasing this fault. I have them fitted anyway. Who wants to
keep changing a fuse wire in this day and age?

Now what you do is section isolate:
-----------------------------------
If the active-neutral pairs run from the switchboard to each lighting
position in turn, you draw yourself a map of how you would run it to
save cable, if you were wiring it. This will be wrong of course, but it
will be a guide to get started.

At the half way point in the cable run, unscrew the light fitting, and
separate the wires. If the fault vanishes, then you have half your house
wiring working, and you know the problem is in the second half. If not,
split it in half again, until you do get it working. If you are getting
early results, you can redraw the cable map.

If you are not confident enough to do this, then I strongly suggest you
get a sparkie in. Getting the right sparkie may be the secret.

Me, I got too old to wobble around on a ladder, and I couldn't see what
I was doing anyway, so I would be looking for a good sparkie.

I had this problem a few years ago, the lights would intermittently blow
the fuse. Called a sparky in, but he was useless, he knew how to put
wiring in but had no idea about fault finding. I knew that the house had
been extended, and where the lighting for the new section tapped into
the main part, so I split it there. That fixed the problem, so I started
splitting the wires that ran from that point.

Eventually, I tracked it down to one cable which ran through the roof
under some floorboards that the previous owner had put in to make it a
storage area. Pulled up a floorboard and lo and behold lots of little
white creatures running about, the termites had come up through the wall
on the surface of the studs right into the roof without causing any
damage and then eaten through the lighting cable.

The exterminator guy told me that this is not unusual, termites seem to
like PVC cable. I'm glad they did otherwise they could have eaten the
place out before we knew they were there.

 

[Sylvia Else]

On 22/02/2011 2:57 PM, coffeexxx wrote:

thanks for the valuable tips n info, I will be splitting the cable
run as described to isolate section shorting. But first I thought I
would quickly check the closest light switches to the powerboard which
is the bathroom. I have had termite problems in this area before and
when I pulled out the switch I found ant saw dust caked around the
wires. I cleaned it off and rewired the fuse hoping this was a lucky
find but fuse blew 2 seconds later instead of instantaneously. There
may be more ant gunk on other switches which I will investigate.

BTW; the first switch has ridiculous amount of stiff wiring hanging
off the light switch. ie they are using the spare holes on switch as
a terminal connector for 5 neutral wires and 4 actives. This doesnt
look like good practice. I was thinking of buying some large screw
connectors and joining all the neutrals and another for the actives
and dropping them behind the switch to relieve all the strain and
close proximity of the actives/neutrals, and may as well buy a new
switch also.

here is a pic
http://www.alttokyo.com/test/light1.JPG

this pic is after cleaning all ant sand of exposed wires.

If it ain't broke....

Sylvia.

 

[coffeexxx]

thanks for the valuable tips n info, I will be splitting the cable
run as described to isolate section shorting. But first I thought I
would quickly check the closest light switches to the powerboard which
is the bathroom. I have had termite problems in this area before and
when I pulled out the switch I found ant saw dust caked around the
wires. I cleaned it off and rewired the fuse hoping this was a lucky
find but fuse blew 2 seconds later instead of instantaneously. There
may be more ant gunk on other switches which I will investigate.

BTW; the first switch has ridiculous amount of stiff wiring hanging
off the light switch. ie they are using the spare holes on switch as
a terminal connector for 5 neutral wires and 4 actives. This doesnt
look like good practice. I was thinking of buying some large screw
connectors and joining all the neutrals and another for the actives
and dropping them behind the switch to relieve all the strain and
close proximity of the actives/neutrals, and may as well buy a new
switch also.

here is a pic
http://www.alttokyo.com/test/light1.JPG

this pic is after cleaning all ant sand of exposed wires.

 

[Don McKenzie]

On 22-Feb-11 2:57 PM, coffeexxx wrote:

thanks for the valuable tips n info, I will be splitting the cable
run as described to isolate section shorting.

I described section isolation in another thread.

BTW; the first switch has ridiculous amount of stiff wiring hanging
off the light switch. ie they are using the spare holes on switch as
a terminal connector for 5 neutral wires and 4 actives.

It looks like your electrician has elected to do his loops at the switches and not at the ceiling lighting points.
This may actually work out better for you, if you can't readily access the ceiling wiring.

Your problem appears to be a short between a neutral and an active. Possibly even an earth and an active.

There may well be similar wiring behind most switches, stretched and many conductors crunched into a single terminal.
When the cable is new, and you are young, nimble, and confident, it is very easy to grind 4 or 5 conductors into a
twisted pattern with a pair of bull nose pliers, so they will squeeze into a switch terminal and be locked up with the
screw. I could virtually do it with my eyes shut, and I'm sure most good sparkies can.

So it may be quite a job to actually rewire and add new terminals to each point. You have opened up a switch with
multiple actives near the switchboard.

Next step would be to get an 8A circuit breaker if you don't already have one, and use it. Drop the 4 actives out of the
switch and separate them. Test it. If the breaker doesn't trip, you are getting started with section isolation.

One of the actives will be the incoming active from the switchboard, or a previous switch. Easiest way of finding it is
to use a meter to check for 240VAC between your neutrals and actives. When you find it, screw just this one active back
into the switch, and see if you can get your first light to work.

You then add actives until the breaker trips. Get the picture, and know where to go next?

Again if you aren't confident about this, get an Electrician. I would hope that you can safely use a meter in this
fashion, if you are reading this news group.

Cheers Don...


=====================


--
Don McKenzie

Site Map: http://www.dontronics.com/sitemap
E-Mail Contact Page: http://www.dontronics.com/email
Web Camera Page: http://www.dontronics.com/webcam
No More Damn Spam: http://www.dontronics.com/spam

These products will reduce in price by 5% every month:
http://www.dontronics-shop.com/minus-5-every-month.html
http://www.dontronics-shop.com/ics.html

Bare Proto PCB for PIC or AVR projects?
"I'd buy that for a Dollar!".

 

[fritz]

"F Murtz" <haggisz@hotmail.com> wrote in message news:4d627dba$1@dnews.tpgi.com.au...

Sylvia Else wrote:
On 22/02/2011 12:31 AM, fritz wrote:

They still should have complied with the rules.

The rules change.

Sylvia.

No one said they did not comply with the rules

I think mr fritz lives in another country and has no first hand knowledge of australian household electrical wiring

Wrong
I do live in another country now but lived in Australia for 44 years.
I also have a copy of Australian Electrical Wiring - Theory and
Practice, which I obtained while doing an Electrical Trades
course as a supplement to an Electrical Engineering degree.

 

[Rheilly Phoull]

On 2/22/2011 5:24 AM, keithr wrote:

On 22/02/2011 5:48 AM, Don McKenzie wrote:
On 20-Feb-11 12:29 PM, coffeexxx wrote:

Q; how do I trace a damaged power line in the walls/ceiling without
breaking giprock everywere?? What do electricians do in these
cases?? rewiring the entire lighting circuit is too huge a job.

Believe it or not, I was an electrical contractor in 1964, however I
know things have changed somewhat since then, but I'll give it my best
shot.

You can unscrew a switch or two, to determine if it is just actives that
drop down from the lights to the switches.

Someone suggested a plug in circuit breaker for the fuse holder. Great
idea for chasing this fault. I have them fitted anyway. Who wants to
keep changing a fuse wire in this day and age?

Now what you do is section isolate:
-----------------------------------
If the active-neutral pairs run from the switchboard to each lighting
position in turn, you draw yourself a map of how you would run it to
save cable, if you were wiring it. This will be wrong of course, but it
will be a guide to get started.

At the half way point in the cable run, unscrew the light fitting, and
separate the wires. If the fault vanishes, then you have half your house
wiring working, and you know the problem is in the second half. If not,
split it in half again, until you do get it working. If you are getting
early results, you can redraw the cable map.

If you are not confident enough to do this, then I strongly suggest you
get a sparkie in. Getting the right sparkie may be the secret.

Me, I got too old to wobble around on a ladder, and I couldn't see what
I was doing anyway, so I would be looking for a good sparkie.

I had this problem a few years ago, the lights would intermittently blow
the fuse. Called a sparky in, but he was useless, he knew how to put
wiring in but had no idea about fault finding. I knew that the house had
been extended, and where the lighting for the new section tapped into
the main part, so I split it there. That fixed the problem, so I started
splitting the wires that ran from that point.

Eventually, I tracked it down to one cable which ran through the roof
under some floorboards that the previous owner had put in to make it a
storage area. Pulled up a floorboard and lo and behold lots of little
white creatures running about, the termites had come up through the wall
on the surface of the studs right into the roof without causing any
damage and then eaten through the lighting cable.

The exterminator guy told me that this is not unusual, termites seem to
like PVC cable. I'm glad they did otherwise they could have eaten the
place out before we knew they were there.

I would go along with that. Had a similar case where the little workers
had found a cable to a switch in their way, they just kept coming at it.
As one died another stepped up, it was only detected since the owner
complained that the switch wouldn't turn off the light. They had
stripped a couple of inches of the cables and were somewhat agro when
exposed to the sunlight It was a potential fire hazard, probably
would have been blamed on faulty wiring by one of us useless sparkies !!

Rheilly P