amp question

ronvos

hello. i have some rope lights and tested the ampere.

it draws 0.25 amp on my 240 volt ac supply.

this would mean 60 watt hour usage which i feel is a lot.

am i correct in thinking that the higher the current (amp) the cheaper it is to run?

also if i run ropelight for 4hours a day, what would that aprox cost me in 2 months

thanks

ron

brightspark

Are they filament lamps? How did you measure it?

The more watts the more expensive it is, current isn't relevant.

ronvos

its a clear ropelight i used a multy tester to check ampage


so the higher the amps the less watts ? is this correct?

brightspark

Cost is approx 20c per unit (KwH)

60w x 4hrs x 60 = 14400 = 14.4 KwH

14.4 x .20 = €2.88

brightspark

ronvos wrote: »

its a clear ropelight i used a multy tester to check ampage


so the higher the amps the less watts ? is this correct?

No

If the voltage stays constant and the current increases then the wattage also increases

ronvos

thank you very much. ropelight is only 5 foot long and wanted it under a garden bench to light up the ground underneath as a feature. i can live with the cost of running that. thank you

brightspark

Is there a transformer? from a quick search incandescent rope lights are about 3-5 watts per foot, so your wattage should be about 25w not 60.

Also is it designed for outdoor use?

LEDs would be cheaper!

Robbie.G

Most 240v rope lights I've come across are 16.4w per metre.

brightspark

Robbie.G wrote: »

Most 240v rope lights I've come across are 16.4w per metre.

You are probably right. I was only getting figures from a quick google search.

However a 240V ropelight would not be suitable for outdoor use, esp under a bench!

You can get IP rated ropelight for outdoors.

Zen65

ronvos wrote: »

hello. i have some rope lights and tested the ampere.

it draws 0.25 amp on my 240 volt ac supply.

this would mean 60 watt hour usage which i feel is a lot.

The power consumption of any a.c. connected device is derived from the formula P = V * I * cosØ

The term cosØ is called the "power factor", and it is a measure of the degree to which current and voltage pass in-phase through the load (the max value that cosØ can have is 1). Only the in-phase product of voltage and current contribute to actual load wattage. A good set of rope lights will have a power factor of above 0.9, so let's say 0.95.

By measuring the current only you leave some uncertainty around the actual power consumption. Depending on where you live the mains voltage can be above or below 240V, but usually is below 240V in Ireland. A better estimate is 230V, but voltages as low as 220V are common.

So let's say your measurement of current is accurate in which case the power consumption P = 230 * 0.25 * 0.95 = 54W (which is a bit closer to what I would have expected for a fairly modern set of rope lights)

Taking VAT into account you could estimate the energy costs including VAT as €0.17/kWH so for 4 hours per day the consumption would cost you

0.054kW * 4Hr * €0.17/kWHr = €0.036 per day, or €1.10 per month.

If you plan to use mains - voltage rope lights outdoor make sure they have the correct IP rating (the box you bought them in should say "for outdoor use"), and that the socket you are using is properly rated for outdoor use.

Cheers,

Bruthal

brightspark wrote: »

The more watts the more expensive it is, current isn't relevant.

Current is not relative? Thats a new one.

brightspark

Bruthal wrote: »

Current is not relative? Thats a new one.

Not exactly what I meant to say, in terms of wattage and running costs the value of the current is meaningless without knowing the voltage on the lights.

And running costs are based on wattage, not current. A 12V 50w lamp has a current flow than a 230V 50w lamp, but they both use the same amount of power.

10A @ 230V is 2.3Kw but 10A @ 12V is only 120w
(power factor isn't an issue with filament lamps!)

But of course the current is still relative to the wattage.

Bruthal

brightspark wrote: »

And running costs are based on wattage, not current.

The OP measuring amps to conclude a running cost is not a bad method. After all, using current wont give an under estimate of running cost, and with led lights, it wont be far wrong using simply amps, as he knows the voltage.

A 12V 50w lamp has a current flow than a 230V 50w lamp, but they both use the same amount of power.

10A @ 230V is 2.3Kw but 10A @ 12V is only 120w
(power factor isn't an issue with filament lamps!)

Clearly in this case though, the voltage is a known 230v. Obviously watts is better than amps as amps and voltage only give VA, but it is good enough for a cost measuring method. Besides all that, most if not all items will have their wattage written on them.

Maybe something in a sticky explaining how to get a cost per hour/day/week etc from the wattage of items might help, as running costs of items seem a common enough question.

Zen65

brightspark wrote: »

10A @ 230V is 2.3Kw but 10A @ 12V is only 120w
(power factor isn't an issue with filament lamps!)

I didn't see the OP confirm that these were filament lamps. Not wishing to be unkind, but based on the question I'd guess OP is not sure what type of lamps they are.

Bruthal

Zen65 wrote: »

I didn't see the OP confirm that these were filament lamps. Not wishing to be unkind, but based on the question I'd guess OP is not sure what type of lamps they are.

Makes little difference, although I would assume they are LED.

OP measured 0.25 amps. So about 60VA

He wanted rough cost for 4 hours a day. 60va max cost = 60 watt cost, which he has seen calculated already.

ted1

Zen65 wrote: »

The power consumption of any a.c. connected device is derived from the formula P = V * I * cosØ

The term cosØ is called the "power factor", and it is a measure of the degree to which current and voltage pass in-phase through the load (the max value that cosØ can have is 1). Only the in-phase product of voltage and current contribute to actual load wattage. A good set of rope lights will have a power factor of above 0.9, so let's say 0.95.

By measuring the current only you leave some uncertainty around the actual power consumption. Depending on where you live the mains voltage can be above or below 240V, but usually is below 240V in Ireland. A better estimate is 230V, but voltages as low as 220V are common.

So let's say your measurement of current is accurate in which case the power consumption P = 230 * 0.25 * 0.95 = 54W (which is a bit closer to what I would have expected for a fairly modern set of rope lights)

Taking VAT into account you could estimate the energy costs including VAT as €0.17/kWH so for 4 hours per day the consumption would cost you

0.054kW * 4Hr * €0.17/kWHr = €0.036 per day, or €1.10 per month.

If you plan to use mains - voltage rope lights outdoor make sure they have the correct IP rating (the box you bought them in should say "for outdoor use"), and that the socket you are using is properly rated for outdoor use.

Cheers,

Do you not think that's a bit long winded explanation?
Power= volts * amps
Your voltage remains constant , do a higher current will result in more power being used

Zen65

ted1 wrote: »

Do you not think that's a bit long winded explanation?
Power= volts * amps
Your voltage remains constant , do a higher current will result in more power being used

It probably is long-winded, yes, but it was intended to explain the calculation that somebody else did here already. I did not expect posters who already knew how to calculate power to bother reading it.

Z

SpaceTime

Just to clear up one thing: Only Britain and possibly Australia, NZ and Malta and Cyprus ever used 240V systems.

Ireland and continental Europe all used 220V historically (going right back to the earliest days of AC power).

To allow for easier distribution of appliances and remove a hinderance to the single market, CENELEC and the EU decided to change the nominal voltage to 230V +/- 10%.

Both 220V and 240V systems fall into this range (207-253V) so it meant a single appliance spec of the whole EU (and countries complying to CENELEC standards).

ESB uses 230V +6%, -10% which is 207 to 244V.

You'll usually find your supply is somewhere between 220 and 230V in normal circumstances. If it's down below 207V you should be getting onto them about low voltage issues.

The biggest issue you have nowadays is that the UK is actually using 240V +/- 6% which is a tad high at the top end of the tolerance range and you can occasionally risk frying things in a UK spike a lot more easily than will occur in Ireland or on the continent as equipment's often still spec'd for 220-230V in reality.

Neither British, Irish or European power companies actually necessarily had to adjust their supply voltages as both 220V and 240V systems are comfortably within the allowed tolerances. They may be spec'ing new transformers to 230V but these days but they certainly didn't go around tweaking perfectly healthy old ones.

A 220-230V supply is absolutely ideal though for appliances. You shouldn't be experiencing any problems at all.

Incidentally, Northern Ireland actually always distributed power at 230V ! This was a deliberate fudge to ensure that appliances from the Republic and the UK worked in NI back in the old days.
So, basically the rest of Europe (including Britain and the Republic of Ireland) is now fully compliant with long-standing Northern Ireland Electricity standards

As a rule of thumb concerning max. loading I use 250v as the multiplier and 210v as the denominator when I'm too lazy to meter the outlet.

sawdoubters

you will only have 220 volts unless your in the uk


AC single phase volts to watts calculation formula

The real power P in watts is equal to the power factor PF times the current I in amps, times the RMS voltage V in volts:

P(W) = PF × I(A) × V(V)

So watts are equal to power factor times amps times volts:

watt = PF × amp × volt

or

W = PF × A × V

Resistive loads like heaters and incandescents will have a power factor of 1 and 1 is a safe bet for anyone who would ask what a power factor is.
I see grid outlets @ 240v+ quite regularly.

Generators & inverters are not necessarily Irish grid compliant.
Voltage drop on over-zealous extension leads can result in much lower values too.

SpaceTime

Roughly 207 to 244V is within the specified allowable limits.
It's nominally 230V though (and more likely 220-230V).

The Irish grid is using the world's most common voltage as its design base 220V (230V nominal).
It's the standard Europe (entire continent from Western France to Eastern Russia), China, India etc. In fact, almost the entire Eurasian supercontinent use 220-230V 50Hz - Only exceptions are Japan (100V 50 and 60Hz) and South Korea (220V 60Hz)
So, about 4.618 billion people use our voltage.

Then throw in most of South America (387m) and almost all of Africa (1bn).
and a few minor population places like NZ, Australia, etc.

It'd be difficult to find things *NOT* specified for the Irish voltage/frequency.

Only other significant system is North American 110V-120V 60Hz and Japanese 100V 50/60Hz.

Nothing at all unique, or unusual about Ireland's voltage/frequency. We just use weird plugs.