Anyone any electrical knowledge?

[Tinman Steels Ltd]

Watts = amps x voltage so you are getting the same power but depending how you looked at it most appliances will only draw the power they need so they should draw a little less current to give the same power(watts) but it shouldn't make much difference in running costs, when testing appliances I normally megger them at 250v which doesn't do them any damage unless they have sensitive electronics in them but that is a very rare ( i have had customers who have assured me everything has been unplugged and meggered at 500v and appliances have still worked but that dose have a good chance of frying electronics ),yes higher power will cause lights to fail earlier but even 110v lamp will run on 240v not for long and very bright but I can't see how 250v would cause them to go much earlier, I think if memory serves it would be in the region of 10% earlier if filament type, but college was many moons ago and once exams are finished if I'm being honest the only calcs that really are done by most sparks are cable sizing for loads. It would be spikes that would cause most problems but this could be due to the transform but without any testing or figures this is just a possibility and down to the supply company ( disclaimer many days have passed and alcohol has been drunk since my college days )

Regards

James

 

[TheTallGuy]

Watts = amps x voltage so you are getting the same power but depending how you looked at it most appliances will only draw the power they need

That only really applies to electronic goods, basic items such as lamps, kettles and motors rely on Current = Volts/Resistance (strictly speaking it's impedance for ac, but that's another story), therefore if the voltage is higher the current is higher and hence so is the power. Items such as TVs, computers and phone chargers use electronic power supplies (SMPSU) so will normally only take the "power" that is needed at any given time (sort of). Modern washing machines usually have an electronic supply for the computer part, but it's rare to see a SMPSU or inverter powering the motor.

but I can't see how 250v would cause them to go much earlier

I read an article a while back that suggested it was down to poor manufacture. Poorly made bulbs (as most are these days) have more "hot spots" on the filament - quite often where the filament joins to the main terminals. These hotspots will loose tungsten through "evaporation", which leads to a the spot getting hotter and evaporating more tungsten etc. Given that most bulbs are produced in china, where everything is pared down to the minimum, they are more susceptible to early hot spots forming from higher voltages. A normal bulb is able to handle spikes quite well as the pulse of energy will be dissipated throughout the bulb, leading to almost undetectable brief flashes of increased brightness, if it's a long chain of high energy spikes then damage/failure might occur.

 

[Tinman Steels Ltd]

Modern washing machines usually have an electronic supply for the computer part, but it's rare to see a SMPSU or inverter powering the motor.

Higher end machines ( not all ) tend to use a brush-less motor which are 3 phase induction motors, but only tend to be on the £400 + range of machines which can be fun to work on when trying to fault find a motor which won't kick into spin, i have seen poorly made lamps pop on the same day as installed, but I do tend to go for Philips, GE, Osram and Sylvania yes you will pay more for them but the trade off for service length does work out better in the long run. Most nominal voltage I see locally is around 244 volts so not really going to make much difference to the KWh if my maths are right it would be a factor of 2.8%, I did try to not get to technical as even most trained sparks get confused when impedance, power factors and diversification are thrown into the mix and just reference their onsite guides or regs.

Getting on my soap box I think alot of confusion was/is caused by harmonisation with Europe even though we didn't change any of the power out puts from the power stations we still have the nominal voltage of 240v +/-, I have yet to measure a voltage under 236v on a properly wired installation (not saying under this means a bad installation but just in my experience its due to volt drop on under sized cables) , Previously the UK nominal voltage was 225.6V to 254.4V. Now it's 216.2V to 253V, so 251v is still with in the tolerance, but i would be getting the on to the supplier of your power if goods keep going pop.

 

[Old Boar]

Thanks for your replies. I am getting the feeling that all the failures have not been due to my wiring. It was a faint hope....

 

[Exfarmer]

All I know about electricity is that it comes out of a plug, and is dangerous!
After the electicity board moved my mains lead to underground as it was too low above ground, I have had nothing but problems. Two freezers, a kettle, a toaster, a TV and endless lightbulbs have blown or just stopped working. They came out and tested the supply and found a reading of 22 and 249. They then came out and have put in a test box which they will leave for a week, but the reading then was 251. From them I understood that the legal limits are 215 to 251, so I was right at the top end.

So a couple of questions:-

If the power goes over the 251, would that cause the problems I have been having?

When they take the test box away, they can see the readings over the week, but would they admit it if it goes over 251?

What can I do about it?

No, my house insurance does not cover the freezers and I am loath to claim for the rest as I will be paying in premiums later. HELP!!!

In my limited knowledge of electrics a low voltage is far more likely to cause your problems than high, except in the matter of bulbs.
I wonder if you have a poor connection somewhere.
Checking voltage is only effective when you factor in max and min consumption over various periods of the day.

 

[TheTallGuy]

I have yet to measure a voltage under 236v on a properly wired installation (not saying under this means a bad installation but just in my experience its due to volt drop on under sized cables)

Varies a bit at home, but the average is 233V at the incoming fuse with the house isolated; 8pm on a dark winters night it sometimes drops down to around 220V. I suspect that the tranny is getting near it's rated power as there have been 8 additional houses put on it over the last few years & even the pigeons won't sit on it when everyone is home!

I oversaw a 3ph installation a couple of years back & when they hooked up to the fuses, one phase was 220V to neutral, where the others were 238V - the wire monkeys wanted me to sign off as all okay - I refused & insisted they investigated as I knew that the phases were in balance at the connection point, it turned out to be a bad joint & they had already filled the joint box with resin - I was not flavour of the month!