Lights dim when cooker/appliances are on

[mattm123]

Hi

I have moved into a new (Edwardian) house and have noticed that the lights dim when the cooker/appliances come on.

the cooker is on its own 40A MCB and the appliaces are on the downstairs sockets ring. The lights are also on a seperate MCB

Can it be possible that the supply to my house is not able to cope with the demand of an electric oven and lights at the same time?

Any suggestions of things to check to isolate the issue?

Regards

M

 

[Steve]

Normal on some supplies. Nowt to worry about, unless the incoming electricity equipment looks particularly aged (cast iron cutout etc).

if in doubt put a picture up.

 

[mattm123]

consumer unit is circa 1990 and the meter etc has been recently changed.

Someone told me that the cooker MCB should be the first breaker on the buzz bar in my setup its the last the order is soket up, sockets down lights up, lights down cooker?

but not sure if this is important as the are all in parrallel i would have thought? and secondly i get the same issue when using large items off the plug sockets.

If its normal then i'll ignore it, if you have energy saving bulbs in you dont notice it as you do with the old style ones

 

[RF Lighting]

It is best practice to put the highest load nearest the main switch, but in reality it won't make much difference if any at all.

Most likely nothing to worry about.

 

[ban-all-sheds]

But it is possible that it is something to worry about.

I'm not scaremongering, but IMO to dismiss the possibility that a loose connection in the CU or cutout has created a high resistance joint with a "Nowt to worry about, unless..." or a "Most likely nothing to worry about" is dangerously complacent.

I agree that it's probably OK, but the chance that it isn't is not zero, and since the consequences of it not being OK could be a fire my advice would be to get it checked.

 

[mattm123]

thanks for the advide will check the connections in the CU to make sure they are all good.

What is the "cutout"?

M

 

[holmslaw]

..

 

[mattm123]

sure, thanks

well i guess all i can do is to check the CU connections......

thanks

 

[ban-all-sheds]

Please be very careful - even with the main switch off the incoming terminals will still be live, and they need to be checked as well.

As holmslaw said you must not attempt to open your service fuse housing, but (unless it's obviously broken) you can feel it, and the incoming cable, to see if it's getting warm, and check for any overheating-related smells.

Try to get as much running in the house at once, all lights on, appliances going, shower running if you have an electric one, large pans of cold water on the cooker so that the hob is on for a while, etc. Obviously stop all of that immediately if you do detect any overheating.

 

[mattm123]

sounds like a good test, would i be correct to expect no heat at all in the incomming cables to the CU.

Will give this a go this evening

m

 

[ban-all-sheds]

Depends on their size. It could be OK for them to get warm - all cable sizing calculations are done on the basis that the conductor temperature can be 70°C. Touch something that hot and it will burn you. Fortunately electrical cables have insulation, and the outside of that does not get as hot.

 

[LoveRocket]

If you have a multimeter (and are confident to use it on live mains), measure your mains voltage with not much on, then measure it with your heavy duty stuff on. If you post the results up here people will be able to advise whether there's something amiss or not.

 

[Steve]

If you have a clamp meter, you could even tell us how much current you're pulling with that voltage drop

If any of the cables at the mains get hot towards their end, this is something to worry about. It indicates a loose connection.

If you do decide to tighten the incoming cables in the CU, wear some heavy gardening gloves and use an insulated shaft screwdriver (but not a neon one - you cant get the torque you need on these - they twist).