We moved into a new place last December and our surveyor warned us to get an
electrical inspection done.

The outcome of the report showed a number of areas that needed attention,
but one thing that did not come up on the report is that if any high power
device is switched on (e.g. electric shower, drill, oven, etc.) the lights
dim slightly. The dimming is not huge, but definitely noticeable.

I've done a quick survey of each of the MCB's off the consumer unit and
confirmed that the lights (with one exception) run off dedicated fuses.

Am I right to worry about this, and if so, can anyone suggest what is
happenning?

Cheers,
Chris

On Wed, 5 May 2004 20:58:32 +0100, Can2002 wrote:

We moved into a new place last December and our surveyor warned us to get an
electrical inspection done.

The outcome of the report showed a number of areas that needed attention,
but one thing that did not come up on the report is that if any high power
device is switched on (e.g. electric shower, drill, oven, etc.) the lights
dim slightly. The dimming is not huge, but definitely noticeable.

I've done a quick survey of each of the MCB's off the consumer unit and
confirmed that the lights (with one exception) run off dedicated fuses.

Am I right to worry about this,

Probably not; If you had an inspection carried out, it would be worth
asking the electrician who did the work if he checked that there weren't
any loose connections on the meter tails.

and if so, can anyone suggest what is
happenning?

Are you in a rural location? Do you have overhead cables to feed you or
is everything underground? Do you notice the dip in the lights when
you're not switching on something in your house? Are there perhaps any
light industrial units nearby?

It could be a loose connection on the mains. If it is noticeable, then
give your local electricity company a call - the ones who maintain the
system - they may not necessarily be your energy supplier and tell them.
There are limits for acceptable step variations in voltage on the
distribution system. They will investigate, usually by installing a
recording voltmeter for a few days. That will show if there's a problem
on the incoming mains and whether it's in acceptable limits.

Can2002 [email protected] wrote:
We moved into a new place last December and our surveyor warned us to get an
electrical inspection done.

The outcome of the report showed a number of areas that needed attention,
but one thing that did not come up on the report is that if any high power
device is switched on (e.g. electric shower, drill, oven, etc.) the lights
dim slightly. The dimming is not huge, but definitely noticeable.

Are you capable of safely connecting up a voltmeter to the line, and
measuring the voltage while a shower is turned on, and how much it drops
from when it's off?
Combined with the loads nominal wattage, this gives a very good idea
of how much resistance the line has.

Some dimming is normal.
It's probably going to be perceptible on most houses.

In article ,
Ian Stirling writes:
Can2002 [email protected] wrote:
We moved into a new place last December and our surveyor warned us to get an
electrical inspection done.

The outcome of the report showed a number of areas that needed attention,
but one thing that did not come up on the report is that if any high power
device is switched on (e.g. electric shower, drill, oven, etc.) the lights
dim slightly. The dimming is not huge, but definitely noticeable.

Are you capable of safely connecting up a voltmeter to the line, and
measuring the voltage while a shower is turned on, and how much it drops
from when it's off?
Combined with the loads nominal wattage, this gives a very good idea
of how much resistance the line has.

Some dimming is normal.
It's probably going to be perceptible on most houses.

Filament lamps produce an amplified change in light output for
small changes in voltage supply. Changing to compact fluorescents
might make the effect unobservable.

--
Andrew Gabriel

Hi there,

Thanks for all the info, very helpful!

Chris

Hi Ian,

Thanks for the tip, I'll test it out tomorrow.

Regards,
Chris

Can2002 wrote:

We moved into a new place last December and our surveyor warned us to get an
electrical inspection done.

The outcome of the report showed a number of areas that needed attention,
but one thing that did not come up on the report is that if any high power
device is switched on (e.g. electric shower, drill, oven, etc.) the lights
dim slightly. The dimming is not huge, but definitely noticeable.

I've done a quick survey of each of the MCB's off the consumer unit and
confirmed that the lights (with one exception) run off dedicated fuses.

Am I right to worry about this, and if so, can anyone suggest what is
happenning?



You have a crap incoming supply.

I used to have this till I paid a firtune to have a kilometer of
overhead 11KV line taken underground (it ran slap over the back garden)

In the process a piddly little car battery sized transformer up a pole
went, and was replaced with a huge transformer the size of a small
garden shed in the garden corner.

No more dimming lights when teh microwave kicks in. Period.



Cheers,
Chris

I used to have this till I paid a firtune to have a kilometer of
overhead 11KV line taken underground (it ran slap over the back garden)

Why did you have to pay? I would have thought that if the supply wasn't up
to standards the supplier would have to pay?

Following a tip from Ian last night I measure the drop in voltage when
switching on a higher power device.

Prior to running an electric shower I was seeing 247 volts (it fluctuates
quite a lot up to 248V). With the shower on it dropped to 234V. This
seemed like quite a large drop, does anyone agree?

I'm not dure of the rating of the shower, so I repeadted the test with a
2.4KW fan heater. This time the voltage dropped from 247V to 240V.

I'm going to give the electricity board a call, but would welcome any
feedback.

Cheers,
Chris

On Thu, 6 May 2004 16:58:54 +0100, in uk.d-i-y "Can2002"
[email protected] strung together this:

Following a tip from Ian last night I measure the drop in voltage when
switching on a higher power device.

Prior to running an electric shower I was seeing 247 volts (it fluctuates
quite a lot up to 248V). With the shower on it dropped to 234V. This
seemed like quite a large drop, does anyone agree?

I'm not dure of the rating of the shower, so I repeadted the test with a
2.4KW fan heater. This time the voltage dropped from 247V to 240V.

I'm going to give the electricity board a call, but would welcome any
feedback.

Problem is, although it's quite a fluctuation it's still within the
limits so they won't be overly bothered. Worth a shot though.
I still don't know what type of supply you have, what size it is and
how old it is but if it's an oldish overhead then what you're seeing
is the norm. The only way to solve it is run in a new 100A underground
supply but that could be costly. Even then it depends on how far from
the substaion you are.
--

SJW
A.C.S. Ltd.

Ric wrote:

I used to have this till I paid a firtune to have a kilometer of
overhead 11KV line taken underground (it ran slap over the back garden)


Why did you have to pay? I would have thought that if the supply wasn't up
to standards the supplier would have to pay?




I paid becuase I didn't acually want a bigger transforner up an even
uglier pole. I wanted to get rid of a 600 meter section of 11KV line
that crackled and buzzed over the patio, and was in the way of the house
I susbesquently erected...the transformer they threw in for free :-)

Prior to running an electric shower I was seeing 247 volts (it fluctuates
quite a lot up to 248V). With the shower on it dropped to 234V. This
seemed like quite a large drop, does anyone agree?

216v is the lower end of the limit so you`re well within the boundaries.

Are you fed by a rural network, or are you in an urban area with mainly
undergrounded cables ?

It could be that a fuse has blown in a substation feeding one end of the
cable, so in effect you are now fed radially (one way) rather than from
both ends.

Many overhead lines are radial by design, so if you are more rural you
may well be stuffed unless you get something a little more damning.

--
Please add "[newsgroup]" in the subject of any personal replies via email
--- My new email address has "ngspamtrap" & @btinternet.com in it ;-) ---

Problem is, although it's quite a fluctuation it's still within the
limits so they won't be overly bothered.

You were right, although I was fairly impressed as they were willing to make
an appointment if I really wanted to. I decided to hold off for now.

I still don't know what type of supply you have, what size it is and
how old it is but if it's an oldish overhead then what you're seeing
is the norm.

It's not an overhead, it appears to come from underground. I don't know
whether this is relavent, but when we first moved in the meter and main fuse
were exposed to the outside air (albeit under a small porch). I managed to
get the board to fit a plasit enclosure a while back, but one of the items
picked up by the electricians report was that the fuse looked quite worn. I
still have a slight problem here as the isolator switch is still exposed -
I'm trying to find a lockable replacement.

The only way to solve it is run in a new 100A underground
supply but that could be costly. Even then it depends on how far from
the substaion you are.

Thanks again for your advice. I guess the main thing is that I know it's
not dangerous. I may ask them to come out and check it to play safe.

Cheers,
Chris

On Thu, 6 May 2004 16:58:54 +0100, "Can2002"
[email protected] wrote:

Following a tip from Ian last night I measure the drop in voltage when
switching on a higher power device.

Prior to running an electric shower I was seeing 247 volts (it fluctuates
quite a lot up to 248V). With the shower on it dropped to 234V. This
seemed like quite a large drop, does anyone agree?

I'm not dure of the rating of the shower, so I repeadted the test with a
2.4KW fan heater. This time the voltage dropped from 247V to 240V.

I'm going to give the electricity board a call, but would welcome any
feedback.

Hi,

If CFL's can't be used and the power company won't do anything, then
maybe running the lighting circuit through a power conditioner would
do it:

http://www.apc.com/resource/include/techspec_index.cfm?base_sku=LE600I

cheers,
Pete.

On Thu, 6 May 2004 21:31:29 +0100, in uk.d-i-y "Can2002"
[email protected] strung together this:

It's not an overhead, it appears to come from underground.

It could just be the last run from the pole to your house that is
underground, it could be overhead for miles across the country.

I don't know
whether this is relavent, but when we first moved in the meter and main fuse
were exposed to the outside air (albeit under a small porch). I managed to
get the board to fit a plasit enclosure a while back, but one of the items
picked up by the electricians report was that the fuse looked quite worn. I
still have a slight problem here as the isolator switch is still exposed -
I'm trying to find a lockable replacement.

Possibly, it wouldn't hurt to get them out to have a look. If the fuse
holder is a bit on the loose side then that could be contributing to
the problem and could get very serious over time.

I may ask them to come out and check it to play safe.

I'd get them out to look at the fuse at least.
--

SJW
A.C.S. Ltd.

On Thu, 6 May 2004 21:31:29 +0100, Can2002 wrote:

Problem is, although it's quite a fluctuation it's still within the
limits so they won't be overly bothered.

You were right, although I was fairly impressed as they were willing to make
an appointment if I really wanted to. I decided to hold off for now.

Don't be put off by the comments about it being within limits. The
supply voltage can be as low as 216volts, but what you are experiencing
is a step change in the voltage giving rise to flickering lights. There
is a statutory limit on the size of this step change. I can't remember
what the figures are now, been out of the industry too long.

It won't cost you anything for the leccy company to check the supply
voltage, in your position I'd get 'em to check.

Can2002 wrote:

but one of the items
picked up by the electricians report was that the fuse looked quite worn.


Any high resistance in the incoming mains can cause this.

Following my last post I tried measuring my voltage with more high power
devices attached (both showers, over, microwave & kettle) and this time the
voltage dropped to around 215-216V.

I rang EDF energy again and they sent someone out yesterday afternoon.
Strangley all he did was disconnect the main fuse and measure the voltage
coming in to the meter, which was 247V. He drew a conclusion from this that
their line was OK and it must be my wiring!! When I pointed out that when I
measured the voltage with minimal load it showed 247V too, and that it was
only when under load that the voltage dropped, he basically shrugged his
shoulders. The only suggestion he could make was that the high and low
power devices must be running off the same MCB, but I've already confirmed
this is not the case.

I'm not sure what they're going to do next, but it basically seems as though
some link between the substation and my internal wiring has higher
resistance. Earlier postings from others seem to suggest it's the supply to
my house, but I guess I should try to test the resistance between the main
isolator and my consumer unit. Does this sound like a reasonable idea?

Cheers,
Chris

----- Original Message -----
From: "Can2002" [email protected]
Newsgroups: uk.d-i-y
Sent: Saturday, May 08, 2004 10:44 PM
Subject: Lights dimming


Following my last post I tried measuring my voltage with more high power
devices attached (both showers, over, microwave & kettle) and this time
the
voltage dropped to around 215-216V.

I rang EDF energy again and they sent someone out yesterday afternoon.
Strangley all he did was disconnect the main fuse and measure the voltage
coming in to the meter, which was 247V. He drew a conclusion from this
that
their line was OK and it must be my wiring!! When I pointed out that when
I
measured the voltage with minimal load it showed 247V too, and that it was
only when under load that the voltage dropped, he basically shrugged his
shoulders. The only suggestion he could make was that the high and low
power devices must be running off the same MCB, but I've already confirmed
this is not the case.

I'm not sure what they're going to do next, but it basically seems as
though
some link between the substation and my internal wiring has higher
resistance. Earlier postings from others seem to suggest it's the supply
to
my house, but I guess I should try to test the resistance between the main
isolator and my consumer unit. Does this sound like a reasonable idea?

Cheers,
Chris


I'd insist (as best you can) that they install a recorder to monitor your
supply voltage over a period of time.

From your previous comments (fan heater, oven) I'd say you're looking at a
supply impedence of between 0.4 and 0.8 ohms. I'd consider this "on the
high side" and be concerned therefore about any impact on the earth loop
impedence. If your report highlighted any earthing issues I'd hope that
they've been remedied.

I'd not be surprised if your supplier didn't want to do much about this volt
drop! What actual problem does it cause you?

JR

On Sat, 8 May 2004 22:44:28 +0100, Can2002 wrote:

snip


I rang EDF energy again and they sent someone out yesterday afternoon.
Strangley all he did was disconnect the main fuse and measure the voltage
coming in to the meter, which was 247V. He drew a conclusion from this that
their line was OK and it must be my wiring!!

Their first attempt will be to try and fob you off.

When I pointed out that when I
measured the voltage with minimal load it showed 247V too, and that it was
only when under load that the voltage dropped, he basically shrugged his
shoulders. The only suggestion he could make was that the high and low
power devices must be running off the same MCB, but I've already confirmed
this is not the case.

The intial contact from them is usually a craftsman. He won't know that
much about the technicalities of the supply from the substation to your
main fuse. What he should definitely have done was to put a screwdriver
on the terminals of the main fuse, just to make doubly certain that
there was no loose connection there.

I'm not sure what they're going to do next, but it basically seems as though
some link between the substation and my internal wiring has higher
resistance.

'Phone them back again - make sure you get a name - tell them that the
problem persists and please could you have a recording voltrmeter
installed.

Earlier postings from others seem to suggest it's the supply to
my house, but I guess I should try to test the resistance between the main
isolator and my consumer unit. Does this sound like a reasonable idea?

Can't remember how much info you've given - are you in a rural or urban
location? I seem to think you said you thought you had an underground
supply coming in, but do you have overhead cables out in the street?

I'd leave it alone now, and tell EDF that you think there's a loose
connection somewhere on their system and what are they going to do about
it.