power meter confusion, please help

Cardew

Have you got a link to the technical data on this device?

malc_b

It's probably worth explaining power factor. Some thing like a kettle has a power factor of 1. All the power going in is used. So if the volts measures 240 and current 10A then you are using 2400W. Other things, PCs, washing machines, florescent lights etc. are not purely resistive like a kettle. If you like they take power in and give it back. Then you could have 10A but only be using 1200W.

The 10A is important as it means you need >10A fuse, but your meter only measures real power so you pay for 1200W. In a home that is. Industry pays more if they don't keep a power factor of 1 and they have big bits of kit to correct power factor to keep their bills down.

Plug in meters I have will measure V, A, W so I'd be surprised if this doesn't. BTW new PC or new PC power supplies are often PFC, power factor correction, so don't show this effect so much.

mbeast

Cardew wrote: »

Have you got a link to the technical data on this device?

http://www.energenie4u.co.uk/ener007_powermeter.html

http://www.greenenergyoptions.co.uk/our-products/energy-monitors1/domestic-stand-alone-displays/minim

These are the two I'm using.

Thank You

Cardew

Both appear to measure watts.

Have you tried setting both meters to 10p/kWh(for Tier 1 and Tier 2) and see what results you get.

The minim should roughly give the same cumulative kWh consumed as your mains meter - carry out a check.

moonrakerz

mbeast wrote: »

I thought these energy monitors where ment to show us how much power we're using.

I was trying to see why my bills where so much and thought it would help show me but its not much use if it saying I'm using x.xxKW and its not correct.

There is only one accurate thing that shows how much energy you are using - your main meter ! That is what is read - that is what you get charged on..............

mbeast

moonrakerz wrote: »

There is only one accurate thing that shows how much energy you are using - your main meter ! That is what is read - that is what you get charged on..............

I agree but I did believe that these energy monitors where meant to be correct to within 1-2%.

I read the house meter yesterday and reset my minim energy monitor and have just read it now.
my minim says I have used 19.09kwh however my house meter says I've used 8.50kwh.

I amazed how much of a difference there is between the two :O

terry2

mbeast wrote: »

My minim only shows KW, Co2 and £ph.

when I times's V x A it does not match the Watt reading which from my day as a car mechanic with electrics if memory serves me right it should do.

You are right BUT only for Direct current.
When you have alternating current then it ain't necessarily so. If the voltage and current are in phase, ie the peak volts happen at the same time as peak amps (eg with a kettle) then V*A=W. However if they are out of phase, ie peak voltage does not happen at the same time as peak current, then V*A does NOT = W. You have to sum the instantaneous V*A for each point in a full cycle to work out the power consumed. Now in order to cater for this, people use something called a power factor, which relates to the extent to which they are out of phase. so to get the power on AC the formula is V * A * PF.

terry2

mbeast wrote: »

I read the house meter yesterday and reset my minim energy monitor and have just read it now.
my minim says I have used 19.09kwh however my house meter says I've used 8.50kwh.

I amazed how much of a difference there is between the two :O

Sounds to me like the minim is faulty, I would get back to whoever supplied it and ask for a replacement.