Capacitors – Series and Parallel

Knowing how to combine capacitors in series and parallel properly is a great practical field skill to employ when you need to get a customer up and running, but you don't have the exact size.

Increasing in size is easy. Just connect in parallel and add the two sizes together. For example, if you needed a 70MFD capacitor, you could easily connect a 50 and 20 in parallel, which will add up to 70MFD. Connecting in parallel is as easy as making two jumper wires with connectors, jumping one side of each capacitor to the other, and connecting one side as usual.

Connecting in series is a little more tricky. It goes like this:

Total Capacitance is 1 ÷ (1÷C + 1÷C) = Total MFD When Wired in Series

The result is that the total capacitance will always be less than the smallest capacitor. Let's imagine a real-world scenario where you need a 3MFD capacitor, and all you have is 5 & 7.5 MFD on your van.

The math would be:

1 ÷ (1÷5 + 1÷7.5) = Total MFD

_

1 ÷ (0.2 +.13) = Total MFD

_

1 ÷ (0.33) = Total MFD

_

3.03 = Total MFD

It's definitely not something you will run into every day but a nice knowledge tool to have in the noggin toolbox.

—Bryan

 

One response to “Capacitors – Series and Parallel”

  1. This is awesome, I just had a call where this would have saved me a few hours and not having to go to supply house to grab cap! Appreciate all you do for industry see you at AHR if it happens!

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Related Tech Tips

The Unexpected Result of Series Circuits
When I teach electrical basics, we do this exercise where we sit down and connect a 10-watt bulb to a power supply and through a switch. It's a SUPER SIMPLE circuit—the kind you might have learned about in a high school science class. But then I grab another 10-watt bulb and tell them to connect […]
Read more
Giving Static for Failing to Take Static 
This article was written by Christopher Molnar, a licensed Florida mechanical contractor. While I'm not personally a practitioner of the “check static every time” doctrine, I certainly appreciate Chris and his passion for this topic. Thanks, Chris! Why Check Static Pressures on EVERY call You wouldn't go to the doctor’s office and walk away without […]
Read more
Does the Voltage or the Amperage Kill You?
I hear the following phrase a lot: It's the amperage that kills you, not the voltage. While there is truth to the statement, it is sort of like saying, “It's the size of the vehicle, not the speed that kills you when it hits you.” OK, so that's a pretty bad example, but hopefully, it […]
Read more
loading

To continue you need to agree to our terms.

The HVAC School site, podcast and daily tech tips
Made possible by Generous support from