Are Over Voltage Problems widespread

[matthunt]

Are any of you seeing High voltage problems in houses with Solar/PV installed in same street?

I attended a call out a few weeks ago due to the fuse board apparently smoking. When i arrived it transpired it was the shower circuit, the voltage measured was 246v and the current 36 amps meaning a 7.5kw shower drawing 8.8kw through a cartridge type Wylex db. The fuse was rated at 30amps and you just could not touch it due to the heat. We all know of the inherant problems with this type of fuse whilst continuing to operate on steady over current. Has anyone else seen this type of problem? as i am aware that multiple PV installs in a street on the same phase will obviously boost the voltage due to the nature of the invertors.

 

[Darkwood]

Have a read of this long winded survey regarding PV issues its not a uk based survey but it still addresses all the points you raise.

http://www.iea-pvps-task10.org/IMG/pdf/rep10_06.pdf

The shower issue you have may be more to do with the installation itself as the tolerences allowed are 10% either side of 230 and all items maufactured for the market should take this into account when designed, i would have thought a 30amp fuse on an 7.5kw undersized anyway.

 

[Knobhead]

Considering most distribution transformers do not give the mythical 400V it’s hardly surprising. Most distribution transformers do not have tap changers and therefore are still set to their original 415V (240V) or 433V (250V). The voltage could be dropped at the 33/11KV level by OLTC’s (On Load Tap Changers) but this would have the knock on effect of increasing current. Most of the UK’s distribution is old and decrepit and simply won’t stand the increased load.
Yet another example of a European directive that is totally impractical. I wonder if the Belgians have cranked their voltage up from 380V (220V).
You’ll be complaining about voltage dips if it was lowered.

 

[matthunt]

Thanks for your coments and link darkwood

I agree with the posibility of the install but unfortunately i do not know what if anything had been changed during the life of the install, shower size / fuse etc. The point was that the increasd voltage had caused the overheating problem due to the excess current.

 

[Rockingit]

Thanks for your coments and link darkwood

I agree with the posibility of the install but unfortunately i do not know what if anything had been changed during the life of the install, shower size / fuse etc. The point was that the increasd voltage had caused the overheating problem due to the excess current.

I think this is the wrong tree to bark up, tbh. 246V is a 'perfectly normal' voltage - 253 is the max allowed (10%) and in busier areas you might well get 230-240 during the day but come back after all the industrial units have gone home and you'll soon see it rise.

Sounds to me like you've nothing more sinister than a fault with the shower/cct (and a 7.5kw shower at 240v needs a little more than a 30A CPD).

 

[matthunt]

Thanks for the comment rockingit

Taking the shower circuit out of the equation, do you not think a supply voltage of 246v could be on the dangerous side as our disconnection times are based on 230volts? obviously the electricity companies love it as they get to charge us more money

 

[Sintra]

246 V is not a high voltage IMO more than likely when this was installed nominal voltage was 240 V anyway.

 

[matthunt]

246v is a high voltage for an appliance if it is rated at 230v, i dont think the shower was rated at 7.5kw at 240v so it must be drawing more current than it was designed for.

 

[DPG]

230V will almost never be exactly 230.00V - check out the tolerances that are allowed - you may be surprised. Daz

 

[Darkwood]

The shower manufacturers will have tested its units well beyond voltages expected in domestic supply and yes agree the higher voltage will draw an higher current on a fixed resistor device like a shower but this overheating could have been a issue developing over years as the fuse is under-rated to start with for a 7.5kw, the shower may have developed its own problems if it too is getting hot but this is usually a loose connection that causes this, manufactures crimps on the element stalks is oftrn a prone area if they are not welded/soldered in place.
I would not consider PV to be a culprit here but its more likely problems with circuit, shower or both and as we lack all the installation details we can only speculate and cant even suggest a solution without knowing cable size, length installation methods etc...

 

[SirKit Breaker]

Knackered pull switch, neutral worked loose i bet.

Cheers...........Howard

 

[matthunt]

nope, checked all connections,it was purely an overvoltage problem, just wanted to know if anyone else had come across this before?

 

[Rockingit]

Matt - think about this logically from a different angle: When do PV's produce peak output and when do most people hit the shower? The voltage down your street fluctuates like the wind, just accept it! Manufacturers are well aware of this and engineering tolerances are made.

 

[Darkwood]

Be careful you are still convincing yourself its an over-voltage problem and its not you just have a higher than average voltage and to note nearly all the supply network is still pumping out 240v this is well within acceptable voltage range, re-reading you first post all it sounds like you have had is a possible loose connection on the fuse carrier or associated termination and this has been exacerbated by a underated fuse mixed with a little higher than normal voltage.
The voltage isnt the issue its just down to incorrect fusing and a loose connection thats probably overheated and welder the termination solid, if this is the case the fuse carrier and way shouldn't be re-used at all as metal fatique from the heat damage will be a weak point.

 

[Sintra]

As a matter of interest what size of cable is on the shower circuit.