Voltage Problem

[Darkness]

I was at a guy's house at the weekend and he was telling me about the problems he is having regarding dropping voltage.

In his garage were he fixes cars etc he got some new equipment which has a motor (4hp). When he runs the new kit, it runs fine. Now the guy has a well, which has a pump that works around 3000w and when it kicks in to deliver water while this new kit is working and for example he switches on the kettle, the well control kit cuts out after a while. On the display screen of the well control kit, displays a voltage of 200v which causes the cutting out.

He had an electrician out who said he needed a bigger cable going to his garage so he install a large new cable. However, the problem is still the same. The electrian now came to the conclusion that the transformer on the pole outside his house is not big enough and requested him to get a bigger one installed from the electric supplier.

It is gonna cost him atleast £3500 to fit a bigger transformer. Now using my multimeter, it appears that no matter if he switches on the shower in the house, the immersion heater or the hot powerwash outside etc, his voltage drops upto 10v per item switched on.

Surely if he was using too much power, the main fuse etc would trip and should the outside transformer be capable of supplying 230v if he has a 100a supply fuse fitted? I was just wondering if there is a chance that there is more of a fault at the transformer and instead of him paying thousands to fix, the electic supplier should instead test and repair the transformer? The supply says he has a 16 (kva is it?) transformer.

Any help would be grateful.

 

[westie101]

You do not say if he actually got permission to connect the two motors to the supply, if he did not he is on his own.
On top of that he should have complained or his electrician should have advised him to about the voltage problems.

You talk about his electricity supplier, the transformer belongs to the local DNO. A 16kVA transformer should just supply 100A (it's within the overload rating) but with a noticeable voltdrop.

 

[electronicsuk]

I guess it all comes down to what size supply the DNO are contractually obliged to supply him with. The first electrician obviously wasn't worth his salt, as if he'd measured supply voltage at the intake, it would soon have become obvious that the problem was not solely due to an undersized submain supplying the garage.

The best thing is for him to contact the DNO and have them investigate, perhaps they will install a voltage logger for a couple of weeks. It could be due to a high resistance neutral on the supplier's or consumer's side, or an undersized/overloaded transformer.

 

[ban-all-sheds]

Or undersized cables anywhere between the transformer and the garage - it's not just the final link in the chain that needs to be right.

 

[Darkness]

In the garage, he has a reading of 229/230v and if I disconnect the supply to the garage, the voltage is the same. If things are turned on in the house, the voltage drops to.

The supplier took a reading of the voltage and said he is reading 230v so it's not their fault and insisted on a transformer upgrade.

 

[ban-all-sheds]

What does the voltage at the incomer to the CU drop to when items in the house are turned on?

 

[Darkness]

When items are turned on, the voltage keeps dropping i.e. 225, 220, 210, 200.

You really notice the voltage drop when items with large wattage are turned on.

 

[westie101]

When items are turned on, the voltage keeps dropping i.e. 225, 220, 210, 200.

The voltage where? At the consumer unit near the meter, in the garage, at the water pump. I'm sorry but that information is useless without a location.

 

[ban-all-sheds]

There was no quote of any other post, so it can't be anything other than a reply to my question, i.e. voltage at the incomer to the CU is dropping under load to 200.

So either there's something amiss with the supply, or the owner should get some fire extinguishers.

 

[westie101]

so it can't be anything other than a reply to my question, i.e. voltage at the incomer to the CU is dropping under load to 200.

Possibly but I've been at this game too long to assume anything.

If it is then it could be a DNO issue, but if there has been unapproved load connected they can, to some degree, walk away until those issues are resolved (a 16kVA would normally only be used to supply one customer) so the cause could be the customer

 

[ban-all-sheds]

Possibly but I've been at this game too long to assume anything.

You could be right, but if after this sequence:

if I disconnect the supply to the garage, the voltage is the same. If things are turned on in the house, the voltage drops to.

What does the voltage at the incomer to the CU drop to when items in the house are turned on?

When items are turned on, the voltage keeps dropping i.e. 225, 220, 210, 200.

he's still not talking about the voltage at the incomer as loads in the house are turned on, then I guess we'll never be able to get any sense out of him.

 

[Darkness]

My reply was to ban-all-sheds since his was the last post.

I took the reading at the CU in the house.

At the end of the day, the supplier should be giving the customer a supply of 230v if they install a supply fuse of 100a should they not and also, one doesn't expect the voltage to drop so much if they boiled a kettle?

I am going to get the guy to tell his suppliers to get out and do a proper test when a load switched on.

EDIT.

Voltage at incomer is around 230/231v before switching CU on.

 

[westie101]

I am going to get the guy to tell his suppliers to get out and do a proper test when a load switched on.
Back to top

Nearly, but no coconut.He needs to get his DNO out to check this NOT his supplier, it is not a supplier issue

Check this site to find out who!

http://2010.energynetworks.org/electricity-distribution-map/

 

[ban-all-sheds]

If you're seeing drops like that with loads as small as a kettle, (and presumably the drop to 200 with large but still normal loads like a hob or shower?) then either there's something amiss with the supply, or the owner should get some fire extinguishers.

Any signs/smells of overheating in the vicinity of the CU or cutout?

 

[Darkness]

Our DNO is our Electricity Supplier.

No signs of burning etc but he is not taking a shower while boiling the kettle at the same time if you know what I mean.