hi all

I am new so don't flame me if I do something daft!

I was asked the power consumption of an old (1996?) burglar alarm system with 4 PIRs. The customer has one of these 'Owl' devices that measures realtime household electricity usage and reckons the alarm uses

hi all

I am new so don't flame me if I do something daft!

I was asked the power consumption of an old (1996?) burglar alarm system with 4 PIRs. The customer has one of these 'Owl' devices that measures realtime household electricity usage and reckons the alarm uses

I don't understand how you seem to correlate maintenace fee to the cost of electricity drawn by the system.

A bit like saying my car service cost

Point taken. I assumed that annual electricity cost should be much cheaper than the cost of skilled British labour. But petrol and service fee analogy makes sense.

But how about this alarm that makes up 30% of this domestic customer's annual electricity bill? Can't be right shurely?

it could be 70w i suppose if its very old and not very efficient.

Those meters arnt very accurate though.

Best way is to meter (with a calibrated meter) the current draw on the ac input side.

id say a modern panel should draw around 10-20w

but if its running warm, has old high current use components and an inefficient transformer etc then yes its possible. But id still say its too high (ie the reading)

also how have you calculated that is

70 watts X 24hours X 365days = 613.2KWhrs per year

Electricity price varies, but estimate 14p per KWhr charged for first 900 units per year. Burglar alarm is one of the few things that can't be switched off ever, so you need to use this higher electricity price for it.

613.2kWhrs X

it could be 70w i suppose if its very old and not very efficient.

Those meters arnt very accurate though.

Best way is to meter (with a calibrated meter) the current draw on the ac input side.

id say a modern panel should draw around 10-20w

but if its running warm, has old high current use components and an inefficient transformer etc then yes its possible. But id still say its too high (ie the reading)

also how have you calculated that is

An old optima (eg) panel only has 125mA mains fuse = 30W max (hence need fully charged batt to deliver 1A @ 12v). Wouldnt expect the panel to draw that unless charging a flat/knackered bettery. Modern PSU's work differently.

Hi all.

Must admit, I thought that the figures sounded too high.

But based on 10p per kwh, a single 100W bulb uses a tenth of a kilowatt per hour and therefore costs 1p an Hour to run.

So if it

Hi all.

Must admit, I thought that the figures sounded too high.

But based on 10p per kwh, a single 100W bulb uses a tenth of a kilowatt per hour and therefore costs 1p an Hour to run.

So if it