Lights Dimming When Using Shower.

[charliegolf]

This from a pal, thought I'd ask here...

I've just bought/moved to a new house, built circa 2002, very rural and exposed and we're pretty much the last in line as far as the power lines go. there's a transformer one or two poles away and then us.

When the electric shower or the kettle is turned on if the lights are on the lights dim appreciably, but come straight back up when the kettle/shower go off. The shower and kettle are on different circuits (as they should be) and so I don't think it's an issue with either unit having a fault, they'd trip the circuit breaker if they did I'd imagine.

Is this a sign that I've got a low supply capacity to the house form the grid?

The likelihood is I'll get a qualified sparks in to have a look but forearmed is forewarned etc.

Any thoughts? Ta.

 

[bernardgreen]

Is this a sign that I've got a low supply capacity to the house form the grid?

That is the most likely explanation, in which case you should call to your District Network Operator ( DNO ) to alert them about the weak supply.

https://www.energynetworks.org/operating-the-networks/whos-my-network-operator

It may be excessive voltage drop along the cables from meter to consumer unit. This would be due to under sized cable and would need to be investigated by an electrician and if necessary the cable replaced as soon.

 

[conny]

Couldn't help but smile at this when I read it.
About 40 years ago my MIL's neighbour asked me if their lights were supposed to dim when one of them got a shower. They had recently had an electric shower, (7.5kW), installed by someone her husband had met in the pub. (You can see where this is going). I took a look at the shower and it had been wired with 6mm T&E and, what I believed, was fused at 30A rewireable. Looking at the 'fuse box' closely I discovered there was a red going to the only 5A white fuse carrier. Turned on the lights, pulled the 5A and the lights went out. Suddenly there was a shout from upstairs by her son that the lights had gone out and the shower had stopped! By torchlight I looked at the 5A carrier to find a 30A fuse wire fitted. Putting it back in there was a rather large arc flash and suddenly the lights were working and so was the shower! After her son had finished his shower I climbed into the loft to trace the shower cable. It was wired into a terminal block wrapped in PVC tape and from the other side a length of 1.5mm T&E went to the bathroom light fitting. When I felt this piece of cable it was quite warm and soft. Went back down to the fuse box and immediately pulled the 5A fuse. Looking at the light fitting I then discovered the lighting circuit was was old VR cable. The 30A shower circuit fuse had a short length of 6mm red fitted and the loose end tucked into the wiring 'loom' with no fuse wire in the carrier. Needless to say the husband couldn't remember the guys name and hadn't seen him since they paid him. I ended up rewiring the whole house, (including the shower), for them and fitted a new 8 way CU with appropriate MCB's.

 

[SUNRAY]

Couldn't help but smile at this when I read it.
About 40 years ago my MIL's neighbour asked me if their lights were supposed to dim when one of them got a shower. They had recently had an electric shower, (7.5kW), installed by someone her husband had met in the pub. (You can see where this is going). I took a look at the shower and it had been wired with 6mm T&E and, what I believed, was fused at 30A rewireable. Looking at the 'fuse box' closely I discovered there was a red going to the only 5A white fuse carrier. Turned on the lights, pulled the 5A and the lights went out. Suddenly there was a shout from upstairs by her son that the lights had gone out and the shower had stopped! By torchlight I looked at the 5A carrier to find a 30A fuse wire fitted. Putting it back in there was a rather large arc flash and suddenly the lights were working and so was the shower! After her son had finished his shower I climbed into the loft to trace the shower cable. It was wired into a terminal block wrapped in PVC tape and from the other side a length of 1.5mm T&E went to the bathroom light fitting. When I felt this piece of cable it was quite warm and soft. Went back down to the fuse box and immediately pulled the 5A fuse. Looking at the light fitting I then discovered the lighting circuit was was old VR cable. The 30A shower circuit fuse had a short length of 6mm red fitted and the loose end tucked into the wiring 'loom' with no fuse wire in the carrier. Needless to say the husband couldn't remember the guys name and hadn't seen him since they paid him. I ended up rewiring the whole house, (including the shower), for them and fitted a new 8 way CU with appropriate MCB's.

I thought this was going to be one of those 30A fuses in a FB fed with 7/0.029 on a 15A fuse stories.

 

[Jackrae]

It may be excessive voltage drop along the cables from meter to consumer unit. This would be due to under sized cable and would need to be investigated by an electrician and if necessary the cable replaced as soon.

If that's the case those short cables will get 'quite warm' as they'll be dissipating around 300+watts ! (say 30A x 10v)