Electrical Systems: Decoding Your Panel

In upgrading or maintaining a house, there are a lot of unspoken, rarely taught pieces of information.  For new homeowners (and even some veterans), there may not have been an opportunity to learn some of the nuances beyond turning on a switch or flipping a breaker.  Hopefully, this information can help with understanding what all the little numbers mean on an electrical panel.  

Quick Disclaimer: I'm not an electrician.  I know a lot, and I have a great understanding of the basics, can open and understand the inside of electrical panels, and I know what information is important for every homeowner.  I'm also based in the US, so my experience pertains to the electrical systems we have here.  Elsewhere, systems are similar, but have different standards for voltage and amperage to power devices.

I also think it's important for fuse boxes to be upgraded to circuit breakers: both for safety and for ease of maintenance.  Upgrading our fuse box to breakers was an insurance requirement for us too.

​Safety Features

​The biggest benefit to a well-managed breaker panel is safety!  If there is a problem with an outlet, or a fixture is being replaced, it is very easy to isolate the area being worked on without limiting power to the rest of the building. Isolation also makes it easy to prevent problems in the future.  

Old houses are often wired with a lot of areas together, and cannot handle multiple appliances or functions at once.  A well-labeled panel helps to spread the load and prevent popped breakers by knowing which rooms are grouped together, so high wattage devices like a microwave and hair dryer aren't running at the same time. Breakers pop when there is a overload of current, and the breaker cannot keep up with the amount of power that is demanded across devices. 

Reading the Panel

There are a few different things to note in the panel itself: single-pole breakers, double-pole breakers, service disconnect, main ground wire, and power from the meter.

1) Single Pole Breakers
These are the narrow switches in the electrical panel.  (In the US) These are powered with 120 volts of electricity.  Typically, these are either 15 or 20 amp circuits.  Each breaker should be labelled with a 15 or a 20 on the breaker itself to indicate the amperage for the circuit.  

2) Double Pole Breakers
These are the switches that take two slots in the breaker panel.  These typically power higher amperage devices like electric dryers, stoves, and AC condensers.  These are powered with 240 volts, and amperage can range from 20 amps to 60 amps.  

3) Service Disconnect
The service disconnect shuts down power to the entire structure and any connected sub-panels.  It is labelled with the total amperage for the structure. Mine is labelled as "MAIN" but some others will be in the first slot on the panel. No matter the location, it will have the highest amperage rating of all the breakers.

4) Main Ground Wire
The main ground wire is key to the electrical system for safety. The main ground is either a bare copper wire or a green-coated wire. This runs in two places: outside to a grounding rod and/or (depending on the age of the service) to the water meter. Each circuit should have at least three wires: a hot and neutral which carry power from and back to the electrical service, and a ground wire.  This ground wire captures any discharged or lost energy and transfers it to the ground where it can be dissipated safely. 

5) Power from the Meter
The power from the meter are the main wires that bring power to the panel.  These are inside the cover of the panel and always have power, even if the main disconnect is shut off.  NEVER touch these!  

Subpanels

​Some houses have secondary or sub panels to help manage electricity more effectively across a large property.  Power is carried across a double-pole breaker to a smaller panel (smaller in amperage, not always smaller physically), and from there the power is divided over breakers similarly to the main panel.  Splitting power this way can help to manage balancing new and old wiring, and it can help divide power effectively in different areas: a basement apartment or garage can independently manage power instead of centralized management at the main panel. 

I hope this helps to demystify some home electrical systems!  I do plan to dive into this subject a little deeper, as I truly believe knowledge is power!  Understanding these systems really helps in future-proofing and planning ahead, and that is always a helpful thing.