Power

[Electroglow]

hello just a quick Q....

A customer has called up saying that when she turns on a hair dryer the shower goes cold. she said nothing trips just either the hair dryers go cold or the shower does. 

They have recently been put on to the house supply as the have had panels fitted. 

any ideas??

This is in a salon BTW (small)

 

[NozSpark]

Sounds like an intermittent connection somewhere..... Maybe the bus bar isn't within the MCBs cage on a circuit or two (or RCD)

 

[SPECIAL LOCATION]

Do all circuits comply with volt drop regs..???

 

[Robin Spark]

Is she using the hair dryer in the shower ?  :innocent

That shower is getting hotter already ]   ]

Perhaps start by checking all connections in the consumer unit for tightness and correct location of conductors in the terminals.

 

[Electroglow]

this is a 25mm SWA feeding the salon from single phase 100A. fused down to 80A switch fuse.

The room is small and consist of one lighting cct, one ring main and a shower. They say when the shower is in use the lights dim and shower goes cold. as well as the hair dryers going off now and again. 

Volt drop is not an issue i wouldn't have thought

I will check all connections for tightness ect. the rest of the house is feed from the supply and is all ok with no dimming lights ect. so must be a loose connection. 

 

[Andy™]

if the lights go dim there is a volt drop problem. its either caused by bad design or a loose connection

 

[Electroglow]

run is max 20m in 25mm SWA. then goes into the salon board. the salon is about 4m x 6m so very small. must be a loose connection 

 

[Electroglow]

when show is turned on volt drop to 120V as soon as its off the goes to 230v 

 

[Andy™]

well there's your problem

at that drop, i would expect a very badly damaged terminal somewhere. dont forget to take a pic of it

 

[Electroglow]

Wll do. When we find it 

 

[Electroglow]

cant find loose connections or burnt out terminals. 

still confused as to why the drop is so much just over 20m max

 

[SLIPSHOD & SLAPDASH]

Test it at the feed whilst shower is on.

You have more chance of finding the fault. It could even be an external fault  (suppliers)

Feed meaning at the source of the whole supply

 

[Electroglow]

just got back and found the following. 

supply V = 240

SWA cable feeding salon V = 166

SWA 25mm at approx. 35m clipped direct & in mid air. 

But the is joined on to a 16mm SWA half way through. 

So volt drop it is. but how come its so much? 

9.5KW shower everything working fine when its not turned on. 

32mm SWA required me thinks

 

[Andy™]

with shower on, whats voltage at start of SWA & end? if there is a large different, its probably at the join half way

even without doing any calcs, 9.5kw on 25mm cable will not have a volt drop that much. and if it does, 35mm (not 32mm) would not solve it either

 

[apprentice87]

Why not do some proper calcs???? no good guessing, that is what a lot of people do which is why a lot of installations simply do not work properly

When you say 16mm half way along, do you mean the 25mm changes to 16mm, or that there is a branch connection coming off your submain.

Have you worked out what the connected load is or what diversity if any you can apply. You say about showers, but how many they got?? What about other water heaters or electric heating in the place?? Anyway, at a rough guess at 14kW, a 16mm would be fine at that run length anyway.

LOADS more info needed!!! [and some pictures, hairdressers mind,, not boring electric cables!!!!]

Why not measure supply impedance at the origin of the supply and then at the salon and see if it seems sensible....

Cannot see it being a bad connection, as according to my quick calcs, the bad connection would have too be dissapating well over 7kW to give that volt drop at a load from the salon of 60A. You would not have to find the bad connection, because the fire brigade would have done it already....

john.....

 

[ProDave]

when show is turned on volt drop to 120V as soon as its off the goes to 230v 

so use your meter and find out WHERE the other 110V are being dropped.

It won't be hard, as something somewhere will be getting very hot.

 

[Electroglow]

the SWA front end reads 240V at the consumer unit it reads 160V 

yes it changed half way from 25mm to 16. then into the consumer unit. it is joined about 3/4 along the cable. 

AMP test on the salon unit was 44A with everything on including shower. 

Can you shed some light on how to find the hot bit of cable with your meter lol ??? 

one shower and a few hair dryers.  

 

[steptoe]

:shakehead

 

[Andy™]

not going to work out exact power lost but it will be very high. so should be easily detectable by either a warm cable or a warm point

maybe wait until winter and its snowing / icy and se what part of the cable isnt frozen...

or you could always do the cable calcs yourself to see what it should be. thats if you can figure out how long it is, since you did state 'just over 20mtr max' and then 35mtr...

or you could call an electrician to find the problem

 

[Electroglow]

didnt do the install only got called yesterday when shower dimmed lights ect. there for i was only told it was 25m when arrived it was 35 at a rough guess. 

even the 16mm cable at that lengh would be fine for the load. so i cant see why it drops so much. the connections are sound and tight.  i checked to see if the cable was hot but it wasn't. didnt go through the whole cable tho as it hard to get to.