US Electrics - a question

[Desie]

guys

I've had a question from a US riend of mine. I'll cut and paste to ease my efforts.

Can I have your opinions so that I can go back to them.

Our electric bill has always been high since we've lived here, going on 14 years. High as in our average kilowatt hour reading/month on the meter runs between 3500 and 4000, here this winter its running 7500. The average is probably half that. Have had the electric co. out a couple of times, they checked from the pole back to their lines, sd. everything looks ok. We've tried to isolate the problem down, can't find anything that looks out of the ordinary (my husband has one of those clamp meter thingy-ma-bobs) -- you know what I mean!!! ) So, called the electric co. again, they come out -- this time they tell us that they are having trouble with low voltage on the line, so they put a couple of meters on so that they can see just what's happening. I guess we should have 120-125 v. coming in on average and ours has been running 107, 111, it constantly jumps around, one night the electric guy sd. his meter showed it was down to 95 v. Now, my question is..........would low voltage put a drag on everything to cause you to use more kilowatts? Some people say yes others say it wouldn't affect the kilowatts actually used. I realize you have to use the formula of volts x amps = kilowatts or whatever it is, and with low voltage it would appear that you would use less kilowatts, but is it taking more energy to turn everything when there's not enough volts?

And you thought it was going to be easy!!

Ta

 

[JohnD]

I am going to guess that most of the load will be on heating appliances (since it is winter, AirCon will I hope be off). Lighting, PCs, TVs etc use far less energy than heating/cooling appliances.

Assuming the heating appliances have thermostats to turn them off when the house or water reaches its target temperature (and they don't open the windows to let the hot air out) then the kWh used to heat the house will not change with voltage fluctuations. If it takes 28kWh per hour to keep the house warm, then a lower voltage will lead to a slightly longer heating period before the thermostat cuts out, but if heat loss is the same, no more energy required.

I would be looking for:
Space heating thermostats turned up to a higher setting than usual
Heater left running in an area that is usually unoccupied (e.g. garage or loft space)
Wasteful use; e.g. external heaters as used for smokers or over external hot-tubs
Hot-water outlet leaking and losing hot water
High-usage appliance either running more than usual, or bought a bigger one (e.g. tumble drier)
Insulation or draught-proofing is not working properly (e.g. building damage or recent alterations)
Teenager with fan heaters in their room
Person with a hash plantation in the attic using heaters and grow-lamps
Check all outbuildings for anything left running.
Watch the meter for usage and try turning off circuits one at a time to see which ones make an unexpected difference to usage.

Ordinary clamp meters only work if they are round a single core, not a whole cable.

There is a slim chance that an electrical fault is letting current run to earth, turn off all circuits and see if the meter stops.

 

[bernardgreen]

I realize you have to use the formula of volts x amps = kilowatts

volt x amps = watts kilowatts = (volts x amps) divided by 1000

First use I = V / R ( volts divided by resistance ) to find the amperage.


You cannot use I = W / V to find amperage where V is actual volts supplied. That formula is only valid when W and V are the designed values for the equipment.

resistance is the constant ( but varies with temperature )

In general half the voltage means one quarter of the wattage on resistive loads.

Motors do not have a constant "resistance" ( complex impedance with back emfs ) and may take a lot more power if running below normal speed due to low voltage,

 

[crazycanuck]

they have small household measuring reader in the usa that you plug in the wall socket and then plug your individual item into it and it has a digital reader of how much power that equipment is using.
They might try a electronic shop for one.

 

[Gees]

Why don't you have the electricity supplier change the meter?
I bet if the readings where very low they would be out like a bullet....

One other thing is to check if you have any mains isolation transformers in the building. These can sometimes rack up the power without getting very hot at all. Something to do with power factor??