Electrical Systems 101

The further I get into working on houses, the more I start to understand the systems inside them.  The big systems definitely need skilled tradespeople to work on them, and homeowners and users still need access to understanding the basics.  So, with this, I'm bringing it all the way back to how home electricity works.  What exactly are amps and volts?  

I do need to preface this by also writing that I am NOT an electrician.  I know the basics: and I firmly believe that everyone should have access to the basics.  So, I'm adding them here.  I've learned a lot from reading the Black and Decker Complete Guide to Wiring, helping run wire for a master electrician before his retirement, and asking a lot of questions.

I wrote a little about this last year in LED Lighting 101, but I wanted to break it down a little more and have some of the info in one place.  This is also a good place to start if electrical panels are still tricky.  And of course, we haven't been without our own electrical issues in this house.  For me to really understand something, I need to understand both how it works and why it works.  Sometimes those answers are the same, and sometimes they aren't.  Having a good handle on some of this makes future-proofing and long-term planning (and speaking with contractors!) a lot easier.

Voltage and Amperage

Both of these are measurements for how electricity flows.  Voltage is the pressure that pushes electrons.  Amperage is the volume of the electrons.  Note: My numbers from here on out will reflect what I have in the US.  In many parts of the world, circuit capacity is higher.  The concepts are transferable.

Much like water, electricity essentially flows through a pressurized system. Most circuits have 120V circuits or 220V circuits.  The pressure through wiring is constant.  It is always 120V in a 120V circuit. Because this is constant, we have a lot of other devices that help regulate that voltage and reduce the pressure. The block on a laptop charger or a USB connection reduces voltage to levels that are safe for the device.  The AC adapter on my computer reduces the voltage to 19.5V from 120V.  Outside the home, this all happens at transformers such as the big green boxes in the ground or the metal cylinders on power poles.

Amperage measures the volume of the electrical current.  Amperage varies.  Because amps vary, this is the part that I had the hardest time understanding.  Think of a hose spigot; the water pressure from the main water line is constant.  But the volume that comes through the spigot can vary based on how narrow or wide the valve is opened.  The amperage is like the amount of water that comes through the valve. 

With the spigot opened all the way, the water is flowing at maximum capacity. This is similar to how circuit breakers work to limit power to safe levels for the devices and wiring attached.  With larger wires, higher amperage is able to move through it.  Most home circuits are either 20amp or 15amp, with variation for appliance circuits.  The higher amperage circuits can safely provide electrical current (120V on a single-pole circuit, 220V on a double pole) with larger  wiring.  

​There is so much more to write on this topic!  So, I'm dropping it here for now, since the goal was to make this information digestible.  Please drop questions in the comments!  I've come to realize I know a lot about how these things work, and want to help fill in the blanks!