Is Replacing a 25 kVAr Unit with Two 12.5 kVAr Units More Efficient?

[AbdullahS]

TL;DR Summary

Advice needed on Power Factor Correction Unit upgrade

Hi all,

The power factor correction unit for one of the buildings that I am working on needs maintenance. The service report recommends replacing the existing 25 kVAr unit with 2 x 12.5 kVAr units as "the demand on your site according to the data supplied shows us that at most there is only 30kVAr required at peak demand and quite often only requires 12.5kVAr".

This has been recommended after the analysis of interval data. The following graph shows the KVAr at the site for a period of 3 months.

Could you please advice if replacing the larger bank with two 2 smaller capacitor banks justified? If so, what is the reason? Shouldn't the old one do the job even when the kVAr requirement is low?

A bit of background about myself:
I am a mechanical engineer who is working in sustainability industry. I do have basic knowledge of reactive power but not detailed enough to answer questions such as these.

Thanks in advance.

Regards,
Abdullah

 

[Dullard]

Whether the change is a good economic decision (or not) depends primarily on how your energy supplier bills for Power Factor. In the simplest case, Power Factor correction systems add capacitance to 'offset' the inductive character of most loads. A 'too large' correction will leave your power factor 'too capacitive.' 2 smaller systems would allow closer to ideal (net zero) correction for a range of loads. As I understand it, some utilities charge for capacitive PF, and some don't - if yours does bill for capacitive PF, you'll need to compare the 'do nothing' cost to the cost of the new arrangement. If they don't bill for capacitive PF, you probably can't (economically) justify the change.

 

[AbdullahS]

Thanks @Dullard!