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# Power usage calculations....???

Discuss Power usage calculations....??? in the Electrical Forum area at ElectriciansForums.net

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#### Sparky83

Welcome to ElectriciansForums.net - The American Electrical Advice Forum

Hi,

I have been asked a question by a client at work, and im not really sure what to do, they want to know how much money they can save by turning off a lift in there building.

The lift draws 8.1amps when traveling, and it draws 0.5amp when waiting on a floor.

They are saying that for arguments sake it goes up and back down a 3 story building 10 times a day. It takes 2 mins to get up and 2 mins to get down.

What else would i need to know to work out how much power (kw/w) it uses to get from ground to the 3rd floor and back again?

I know i can work out the kw by multipling the current and voltage (its 3phase by the way) but that doesnt take into account the time its drawing it for.

Any help would be great,

Thanks

Sparky93

#### trev

##### -
When it's moving it's X Kw. Time the travel from ground to top then multiply by the amount of trips in a day. You can work out the Kwh used easily
Do the same for what it's using while standing idle. Add the two together and multiply by the Kwh rate they are charged by their supplier. That'll give you the cost per day then you can make whatever recommendations you see fit.
Hope that makes sense mate, if not PM me and I'll explain a bit better

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#### Philpot

One of the best and most accurate ways of checking the power usage of electrical devices is to use one of the, easily available, power monitors. Like the ones that some electricity supply firms supply free of charge. I was asked the same question about some heated propagation beds that I put in a greenhouse. ( £6-£8/week)

You just clip the little current sensor onto a the supply,Live or Neutral, for the device. Then leave it for a week and check the total power used. Most of these monitors can have the tariff set so you can get a really accurate. The answer will be ....very little.....so you can tell him not to be so mean.

You then have a monitor for any other question you get asked. Have a look on Ebay they are £25 to £75 or you may be able to get one from some one who got one free but doesn't use it.

Phil

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#### Sparky83

When it's moving it's X Kw. Time the travel from ground to top then multiply by the amount of trips in a day. You can work out the Kwh used easily
Do the same for what it's using while standing idle. Add the two together and multiply by the Kwh rate they are charged by their supplier. That'll give you the cost per day then you can make whatever recommendations you see fit.
Hope that makes sense mate, if not PM me and I'll explain a bit better

One of the best and most accurate ways of checking the power usage of electrical devices is to use one of the, easily available, power monitors. Like the ones that some electricity supply firms supply free of charge. I was asked the same question about some heated propagation beds that I put in a greenhouse. ( £6-£8/week)

You just clip the little current sensor onto a the supply,Live or Neutral, for the device. Then leave it for a week and check the total power used. Most of these monitors can have the tariff set so you can get a really accurate. The answer will be ....very little.....so you can tell him not to be so mean.

You then have a monitor for any other question you get asked. Have a look on Ebay they are £25 to £75 or you may be able to get one from some one who got one free but doesn't use it.

Phil

Thanks for the replies guys, i would get one of those energy monitors but i need to know before i can get hold of one, but i might get the company to buy one for the future as it will certainly save some time.

Trev, i'll send you over a pm and you can let me know if I'm correct in what I'm saying...

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#### Philpot

I'm very sorry Sparky but I said ( the Live or Neutral ) that should have been , ( one of the phase conductors). I am reasonably shure that the reading would be x3 for total power, being a balanced load. That is because the devices assume a Single Phase voltage of 230volts.

If you are buying a device for your business it may be better to get one that will monitor all 3 phases. This would be much more expensive but would be industrial strength, as it were. Maybe you can source a 3phase meter ( ex supply Co ).

Sorry I didn't read the question correctly, thought it was single phase. You know what thought thought!!!

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#### Sparky83

No worries mate, thanks for reposting though!

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