PF correction

Andrea B.

Would anybody have any documentation or links relating to power factor correction on an Irish commercial complex.

Basically, unit has a lot of pumps (can't be specific as I am inquiring on behalf of someone) and their energy assessor reckons a €600 pa saving on pf correction.

Really looking for what metrics are needed in deciding correction and what commercial components are available for correction.

fishdog

Aprox how many VAR are you talking about?

Andrea B.

Can't even guess, but will get more info as I have never even been at site.

Hoagy

I wouldn't get into the PF calculations at all unless you want to do it as an exercise.

What you really need is their last three ESB bills, which will tell you how many wattless units they're actually being charged for.

Wattless units are not charged for until they exceed one third of the general units used.

The charge for wattless is less than 1 cent per unit. (See ESB Tariffs)

It must be a large customer if there's a possible saving of €600 per year.

Correction only needs to reduce the wattless units to below the one third limit, there's no benefit to the customer to correct towards unity at the meter position.

If you get copies of the last three ESB bills and give them to someone like Barb Electrical they'll tell you what size capacitor bank you need.

Andrea B.

Folks, many thanks for concise replies. Hoagy, I will pass on your post.

fishdog

there's no benefit to the customer to correct towards unity at the meter position.

In this case possibly not as it is an existing installation, but sometimes there is an enormous benifit. A smaller cable (much cheaper and physically smaller) with a lower current capacity can be used form the point of power factor correction to the equipment being supplied. This is due to the load current being reduced. If the PF is very poor this can make a dramatic difference.

Power factor correction also reduces losses in the cable, I^2 R.

I have never bought a capacitor bank, but AFAIK it is very expensive, if it will save €600 pa it may take a long time to pay for itself.

Just out of interest do you have any idea what the phase angle is?

Hoagy

fishdog wrote: »

A smaller cable (much cheaper and physically smaller) with a lower current capacity can be used form the point of power factor correction to the equipment being supplied. This is due to the load current being reduced. If the PF is very poor this can make a dramatic difference.

Not strictly correct, the benefit you get from PFC on load current only occurs upstream of the correction.
The load current between the point of correction and the equipment remains the same.

If you can apply your correction at the equipment location then you may indeed be able to reduce the cable size.

fishdog

Hoagy you are correct! I was was thinking the total current being reduced, but I forgot that the total current is upstream of the capacitors.
Thanks!

LeBash

If you want send me your email and ill forward you a full powerpoint presentation and a list of units.

It contains everything you need for the calculations etc. There is also a trade list in it i think, to make sure its worth while.

I just got it all installed in my own place.

Steve

I'd second the Barb Electric suggestion.

Bear in mind that the bills must have 'max-demand' figures or they're not much use and a survey will be required.
Also the bills should be for the period of highest use (if it's seasonal) - 12 months worth at a minimum.