Few weeks ago, we received this debate from Martin M., one of the visitor of the blog. So here is his interesting opinion on Power Factor Correction…
You too can send us a mail if you want to create a debate on the topic of your choice.
You may have come across a nice, clear video on the importance of purchasing Power Factor Correction (PFC), also known as KVAR units for residential consumers. You may be luckier and actually met a salesperson, all verbose on how you can save a lot of money by installing a simple device between the power supply and the home appliances.
The selling point implicitly relies on people’s ignorance, as well as well laid-out misinformation and skewed facts. The main selling points for the scammers include the following
- Home appliances such as refrigerators and washing machines are induction equipment and thus draw reactive power from the system.
- Many industries use the PFC units to save energy, and so should you.
- There are a number of positive ‘testimonials’ from satisfied clients.
In my opinion, this is just a huge swindle. For starters, in most residential buildings, the power supply is split into two distinct sections, the tenant power supply, and the house service supply. The former supplies power to the individual units for regular home use such as lighting, home appliances and supplementary air conditioning.
The house service section on the other hand powers the central air conditioning unit, escalators and external lighting. The items are residential grade, and therefore do not draw any significance reactive power. Do note the following:
- The power factor for this section is already past 0.90 so no need to improve
- Most of the housed appliances are resistive rather than inductive loads. These include heaters, ovens, and refrigerators.
- Tenant power costs are billed by the kWh used, or real power, thus reactive power never comes into play. The residential meter is designed to ignore the reactive power drawn from the system, by virtue of the fact that is negligible. This means that the PFC units are useless additions.
- Most of the home appliances already have integrated PFC units for compliance with industrial standards and energy efficiency
To expound more on this point, it is a fact that some home appliances have small motors, for example washing machines. Motors are inductors, and thus draw reactive current from the system.
However, considering that the amount is negligible, and the meters are designed to ignore this value, there is absolutely no need to purchase the PFC units. In essence, when you purchase the unit, all you are doing is helping the power supply company by relieving extra load current from the system.
There are a number of residential loads that significantly decrease the power factor. This includes the HVAC unit, refrigerators, and washing machines due to the integrated motors. Do note that these are not used continuously, like would motors in continuous line manufacturing industries.
Installation of a PFC unit will increase the power factor, thus leading to reduced current draw from the system. However, do note that the residential bill amount is a product of the voltage, current, and pf.
Cost=Current X Voltage X PF
Thus by reducing the current drawn form the system and increasing the pf, the product essentially remains the same, as highlighted in the figure.
To further develop my point, there is a need to briefly highlight why industries using LV and MV systems require the PFC units. The commercial meter is different from the residential meter. It has two dials, one for the kWh, and the other for kVA. The kVA is the reactive power.
Induction motors and other industrial equipment require reactive power to run. The power utility company requires more current to sustain the standard load in the presence of significant reactive power. Thus, if the reactive power exceeds a third of the real power, the industry accrues a charge.
In my opinion, and based on the above information, PFC units are worthless for regular residential consumers. Perhaps the manufacturers should change their pitch, and instead focus on the effects on the environment from resources used to manufacture the PFC units, and thus impress on the residential clients to purchase the units, just to help reduce the power supply company’s carbon print.
This was my opinion on this subject but I’d really like to know what’s yours. So tell me below what do you think about it?