Circuits running out of power and high bills

[jonshutt2]

Hi, I'm trying to fix a few problems with my in-laws 18th century Scottish farmhouse. There's a lot of 'projects' here but one is electrics:

They've always had bills of over £200/month. A lot of this will be as they use convector heaters as the oil boiler + central heating broke years ago. (that's another project) But even so £200 seems a high. This weekend they had maybe 5 convector heaters running, during the week it would be less.

I also noticed this weekend that with 3 convector heaters going on the downstairs circuit, other appliances like a radio and the mircowave no longer worked, and a lamp was very dim implying there isn't enough current getting to them. Turning off 2 of the heats brought the lamp, mircowave and radio back to life.

So, does anyone have any diagnostic advice, or tools I could use to investigate what is taking all the power and making the bills high. The house wiring could be at fault, or something somewhere could be plugged in that's using a large amount of power.

Also, is it normal for a circuit to start failing with 3 convector heaters, a tv, a kettle, a fridge freezer and maybe 5 energy saving lamps turned on?

Thanks for any advice

 

[deadshort]

How old is the wiring ?

DS

 

[Echo the husky]

If high current loads are causing things to dim, it is likely due to a high resistance joint somewhere. You don't say the wattage of the heaters, but 3 heaters is could to be running the circuit near it's limit, especially if the heaters are set to full power and thermostats are set quite high.

What type of circuit is it, ring, radial? what size fuse/ MCB etc? How old is the wiring?

 

[JohnD]

you say farmhouse.

I'm guessing a long overhead supply.

How far away is the pole-mounted transformer, and what else does it run?

Farms often have quite a good supply, because of the farm machinery, especially if dairy, but it may run between the buildings on bits of flex and wet string.

£200 a month is presumably the direct debit, which is not a good guide to actual usage. It would be an average of about 2000kWh per month, but you need to check the actual meter readings.

By my reckoning, one 3kW convection heater, used 24 hours a day for 31 days, uses 2,232kWh, which would cost in the region of £250

Three heaters, eight hours a day, the same.

Energy from electricity is very expensive.

BTW energy saving lamps, and LEDs, may be more tolerant of voltage fluctuations.

 

[jonshutt2]

Hi Folks,

Thanks for your comments.

I chose the word farmhouse as it describes the house, it's not been used as a farmhouse for a while (at least 30 years) but I don't know when main supply line was installed.

The line to the house is at least 200m long.

I've just checked and the house was wired in the 60's at the latest, so yup, it's old wiring!

So, it's probably combination of things, with rewiring the ultimate answer - however with limited funds its probably best to try and get heating installed and therefore not require the convection heaters.

 

[jonshutt2]

@Echo the husky - yes, for a while the led lamps (plugged in to same circuit) in the kitchen have dimmed while turning the kettle on. I've no idea the heater kW but yes they'll be on full.

 

[bernardgreen]

If the voltage drop due to the heating load is such that radios and other appliances do not work then there is a serious problem. As mentioned this is most likely to be a high resistance joint which will become hot. With that level of voltage drop there will be a lot of heat generated in the poor joint and if this is in the house then a fire risk exists.

The first diagnostic would be to measure the voltage drop per additional kilowatt load at the appliance and at the incoming supply.

If the drop at the appliance is roughly the same as the drop at the incoming supply then the fault ( or indequate wiring ) is not in the house.

If the drop at the appliance is more than a volt or two greater than the drop at the incoming supply then the fault ( or indequate wiring ) is likely to be in the house.

Do you have a voltmeter and if so are you confident to use it to measure voltages on live circuits ?

 

[Echo the husky]

I thought the fault was only on one circuit? Or did I misunderstand the the first post?

 

[OwainDIYer]

I thought the fault was only on one circuit? Or did I misunderstand the the first post?

Maybe there is only one downstairs circuit. Lights, sockets, cooker, wet string out to the barn where the neighbour's got a pot grow on, all one one 5 amp nail.

I suggest checking the main intake and meter area for any hot patches or smells of burning.

 

[jonshutt2]

Hi there, the fault does appear to be with one circuit - the lamps are plugged into the same circuit at the kettle / heaters etc.

Problem is I don't live there! I just visit every few weekends! However, I think I'll call an electrician to come check things out

 

[endecotp]

Do you own a multimeter?

 

[ericmark]

I am told the new meters measure watts, but some older meters measure amps and assume the volts are 230. So volt drop could result in large bills due to meter being designed for 230 volt.

As others have said you need to measure the volts. But another way to work out what is going on is to measure the impedance, or prospective short circuit current. It's all down to maths, so with a 60 amp supply with supply volts open circuit at 230 for a drop of 6% (maximum allowed) then the impedance needs to be 0.26Ω using ohms law. If the open circuit voltage is over 230 then you could get away with more, so 16% i.e. starting 10% high would give 0.61Ω. These figures would drop with a 100A supply. It is also not allowing for a volt drop in the high voltage supply to the transformer. But no point looking for faults in the house wiring if the fault is in the supply.

I argued with a farmer over generator position, he wanted it away from house to keep noise down, I wanted it local so less volt drop and the engine heat could warm the house. At the cost of electric it may be cheaper to local generate and use engine heat to warm house? What would be interesting would be cost of running a generator. There are Sterling engine driven generators that use waste heat from central heating boiler, so it may be that an over all project rather than just looking at electric power.

It could be a simple cable joint at fault, on the Falklands I found power into an office block was around 1/2 the power out from the generators, it turned out years before a cable was repaired with Denso tape. That night we had light snow, in morning there was a patch of ground where snow had melted, we were lucky to find the joint so easy.

So step one measure and find if supply or local wiring at fault.

 

[Lectrician]

Does sound like a high resistance joint.

 

[JohnW2]

I am told the new meters measure watts, but some older meters measure amps and assume the volts are 230.

That may possibly have been true a very long time ago (before my lifetime), but I don't think that it has been true for at least the last 50-60 years, quite probably a lot more. Indeed, given the wide variation in supply voltages, it would be very unfair to charge people for 'energy usage' on the basis of an assumed voltage.

As far as I am aware, for those last 50-60 years (quite probably a lot more), electro-mechanical meters have had both 'voltage coils' and 'current coils', and therefore measure true VA - although probably not corrected for PF. I don't know much about the modern 'electronic' ones, but I assume that they are at least 'no worse' than those old ones

Kind Regards, John

 

[endecotp]

Tha electro-mechanical meters have had both 'voltage coils' and 'current coils', and therefore measure true VA - although probably not corrected for PF.

They measure power, not "VA", i.e. a purely reactive load will register zero.