lights go dim when kettle switches on

[Ben]

We recently moved to a new house (built in the 40's with an annexe added in the 80s). The lights go dim when anything with high current drain like a kettle or electric shower is turned on. This works for all different combinations of ceiling lights and lights plugged into sockets in the house and the annexe, and happens when any high-current appliance is switched on in the house or the annexe (which are on different fuseboxes). This would suggest to me that the voltage is dropping at the point where the mains enters the house, and therefore that the cable coming up from the road is under rated. Does this sound like a reasonable conclusion, and is it something we should worry about?

[meow2222]

If the dimming is significant, as appears to be from what you say, then youre looking at an immediate fire risk.

NT

[John Rumm]

This is difficult to quantify without numbers. Some dimming is to be expected, but it depends on how much you are getting.

If you connect a voltmeter to the system and take a reading what do you get? What does it change to when you add say a 3kW load from the kettle?

Try and place the voltmeter on a different circuit to the one you are running the test load on. That way you should have your results influenced less by the resistance of the houses wiring.

[Stephen Dawson]

Don't mess about with this, phone your electricity supplier and ask for an emergency call as you may have a fault with the cutout or meter. If they can't find anything wrong then ask for a recording voltmeter to be fitted.

[meow2222]

what needs the most urgent checking is the wiring within the house, and a recording meter at the incomer will only check a small fraction of that.

But really, if the dimming is significant, then theres no need for a voltmeter, the problem is serious.

NT

[tony sayer]

In article , Ben writes

I'd expect "some" dimming when the shower is on as they take silly amounts of current, the kettle less so. It seems as if the voltage drop across the cables is too great but that can be checked with a voltmeter to see if its excessive or not. It could be possible that there is a high resistance joint somewhere thats causing the voltage drop and that can be a fire risk if it gets too hot!..

As you say it does seem that the problem might be on the supply side can't remember of the top of my head but its something like plus 6 % and minus 10% of 230 volts to be within tolerance.

Are you on an overhead or underground supply?..

Best bet is to have a competent electrician check it out......

[Ed Sirett]

If the dimming is such that you could say whether he kettle is on or not just by looking at the lights then there is a big problem. There is a high resistance on the incomer, meter connections, main switch, or main switch connections.

Measure the line neutral voltage if there is a drop of more than 10V when the kettle is used then there is a potential problem.

[The Natural Philosopher]

Yawn. Here we ho again. More bollocks from the wannabee Drivel man.

[The Natural Philosopher]

Absolute crap. Its patently obvious from his post that the issue lies outside the house.

It happens on every combination of devices on all circuits.

Its almost certainly either the incoming wires from the local substation, or, if its a personal transformer on a pole as mine was, that.

[John Rumm]

The fault as described does not really point to a house wiring fault - the same results are observed on two CUs and all circuits regardless of where the load is. This points to a fault at the incomer, or in the supply.

[js.b1]

The harmonised EU nominal supply voltage is 230V +10% -6%.

If lights merely dim *briefly* under heavy load *switching on*, this is not uncommon with high loads (13A, 40-50A shower). It more commonly noticed with large welding equipment.

If lights dim *continually* under heavy load *operation*, that indicates a **serious** defect requiring investigation.

Cause may be house-side (high resistance CU busbars due to bad connections, oxidised, corroded) or utility-side (high resistance meter/service-head/overhead connections). Overheating service heads do cause uncontainable fires.

-- JS-B.

[The Wanderer]

You need to satisfy yourself that everything is OK around the meter position for a first off. If you get someone to switch on the shower - that'll take the most - and just have a listen and a sniff around the meter position and the consumer units, that should tell you pretty quickly if you have a loose connection somewhere abouts. You'll get some arcing and/or buzzing.

Are you in a rural or urban location? Sounds very much like a problem with the distribution network that supplies your property. This can quite often be a real problem in rural areas, where distribution networks can be like wet string, particularly where there hasn't been much development for a few years.

Contact the local distribution company - they may not neccesarily be the company who sell you your electricity - and tell them you have a problem with the lights dipping whenever you put any load on. Probably be a two stage thing, first they'll get a linesman out to check connections on the system (presuming it's overhead) then if they don't find anything, they'll probabaly instal a recording voltmeter for a few days, which will quantify the problem.

Be warned, however, post privatisation, they'll probably try to make you pay for any improvements they have to make to their system. In general terms you shouldn't, but come back for more advice if they try it on.

[The Wanderer]

How do you come to that conclusion?

[Ben]

Its very much a rural area, and to answer a question from another post the dimming is continuous until the heavy load is switched off. I'll measure the voltage drop and if its excessive report it to the distribution company (and report back here of course).

[The Wanderer]

Just remember that cheap MMs are really only an indication at best. Back in the days when I used to have to check voltages I carried a (very expensive) laboratory substandard that was checked annually against a national standard. Not unknown for DMMs or cheap analogue MMs to read as much as

10-15volts different to the SS! Indeed, I also had (and still have, somewhere) an Avo8 that read different to the SS. And it had been for recalibration five or six times over the years. :-(

[tom.harrigan]

Recently, during the renovation of my house, I found that all my wiring was jammed through a hole in a wooden beam. I had to reroute it to do some work there (a full rewire is immanent). When I finally managed to extricate the various circuits from the hole ( I have no idea how they got them in there), there were clear signs of overheating. After connecting everything back up, my lights were definitely brighter, and my kettle boils quicker too.

I wouldn't rule out a problem in your house until you've made sure that your circuits are as they should be. In my house half the bathroom wiring was spurred of the cooker circuit. If your supply is affected by a kettle, you must be extremely remote.

Regards

T

[Ben]

The thing is, any light (ceiling or socket, house or annexe) dims, and the house and annexe are on different fuseboxes, so I reckon the voltage has to drop at the point where the mains enters the house.

[Ben]

It appears to be overhead as far as the bottom of the driveway and then underground up the front garden.

[Dave Fawthrop]

|!tony sayer wrote: |!> Are you on an overhead or underground supply?.. |! |!It appears to be overhead as far as the bottom of the driveway and then |!underground up the front garden.

Have you complained to whoever looks after the distribution of electricity in your area? **Not** who you pay, they are different. Being overhead there may be a problem with the supply to the house.

[Stephen Dawson]

NT,

Stand back from this and leave it to those that have the experience in this field, i.e. me. (10 years investigating voltage compliants for an REC, then

10 years running my own electrical firm.)