Power Factor Correction

[Lighty]

Hi All

As some of you may know we here in South Africa are being hit with heavy electricity bill increases, something like 40% about 2 months back, and now there is talk of another 45% beginning of 2010

I was chatting to someone recently and he was telling me about Power Factor Correction and how it can save you money.... it this true and can it be used in a home (220V single phase) or will it only be efficient on 3 phase supplies?

Thanks

 

[Diver300]

It depends what you are charged for. Is it kWh or kVAh?

If you are charged for kWh then you won't save much if anything for power factor correction.

 

[RadioRon]

I don't think it is worthwhile in residential applications. Here is a link with some analysis.
**broken link removed**

I copy an excerpt from that link here for summary:

"
The **broken link removed** above provides estimations as to the number of hours per day and month that various motor-driven appliances are used. It also contains computed power losses in the cables supplying the appliances for a unity PF and 0.75 lagging PF condition. The purpose of developing this **broken link removed** is to demonstrate the power losses under both PF conditions and to illustrate the small increase in cost involved in not using the equipment being offered for PFC.
Note that the top three cells in the far right column of the **broken link removed** total $0.09. If one estimates that the monthly electric bill — with the inclusion of the cost of appliances that do not affect the PF (i.e., unity PF devices such as lighting, entertainment equipment, electric stoves, toasters, hot water heaters and the heater elements of electric clothes dryers) — is $60 to $80, then the $0.09 is negligible at approximately 0.1% of the total monthly electric bill."

 

[Alexsgarage]

I don't think that it will make much difference in a house, most household appliances are a resistive load or already have power factor correction built in. Also, are you being billed in Kilowatt Hours or Kilo Volt Amp Hours, that is really the big difference.

 

[Lighty]

thanks for the replys,

We are charged in KWh, I understand if I'm correct PFC only helps with inductive loads?

Although most appliances are resistive I do have a quite a bit of inductive load I power:

-Metal Halides - 150W & 2* 400W (for my Marine tank)
-Fluorescent lighting about 400W (including energy saver bulbs)
-Pool pump - 650w
-Plus all other Inductive devices....

I do understand that I'm not going to save alot, but every little bit helps!

Does a PFC unit just consist of Caps?

 

[Diver300]

PFC is usually just capacitors. I don't know how automatic PFC equipment decides how much capacitance to add.

If you are charged for kWh, then the only saving is for a reduction in losses in the cables. It won't save you more than a tiny fraction. See Radio Ron's reply

 

[Lighty]

Thanks guys

 

[Sceadwian]

Mind you if you're not sure of exactly what you're doing the loss in the capacitors themselves will cost more than the power correction factor they help with.

 

[Andrew Leigh]

Hey Lighty,

a couple of suggestions

a) for ± R 600 buy and install a timer switch for you geyser. We have found that it takes no more than 3 hours to heat up a 150l geyser. Work out a system where you all use the hot water at the same time. It saved us about R 300~400 per month.

b) buy a thermal blanket for your geyser.

c) change all your light bulbs for the high efficiency ones.

d) your pool pump motor is more like 1kW, try shortening the cycle.

e) install a gas cooker.

f) fit "Think Pink" insulation in your roof for keeping the heat in in winter.

g) see if cold water washing is acceptable to your wife

h) switch lights off and learn to have only the lights on that are necessary.

i) don't fill your kettle boil only what you need / get a small kettle

Cheers
Andrew

 

[Lighty]

Hey Lighty,

a couple of suggestions

a) for ± R 600 buy and install a timer switch for you geyser. We have found that it takes no more than 3 hours to heat up a 150l geyser. Work out a system where you all use the hot water at the same time. It saved us about R 300~400 per month.

Inquired today about a timer, about R250-R300 just for the unit

b) buy a thermal blanket for your geyser.

will do

c) change all your light bulbs for the high efficiency ones.

90% done, but the metal halides sre thirsty

d) your pool pump motor is more like 1kW, try shortening the cycle.

Mine is a BADU® Porpoise 10, only 0.67kw

e) install a gas cooker.

Though about this, but could be dangerous with my other half

f) fit "Think Pink" insulation in your roof for keeping the heat in in winter.

Ok

g) see if cold water washing is acceptable to your wife



h) switch lights off and learn to have only the lights on that are necessary.

i) don't fill your kettle boil only what you need / get a small kettle

Good point!

Cheers
Andrew

Thx for the advise Andrew