Before we get into electrical panel schedules, it’s important to know that this relates to both single-phase and three-phase panels, and you will learn how to read a panel schedule in this article below.
Now, on a commercial job site, the electrical engineer has already done the panel load calculations. We electricians simply look at electrical panel schedules to determine the circuits pertaining to that individual panel. We then look at our electrical prints to figure out where these circuits are meant to be pulled in the field.
Note, while a panel schedule does include the breaker size for the circuit, it should not be fully relied on for how large of a wire to pull to that electrical load. For general equipment like basic plugs and lights, this is fine, but for certain equipment like motors and such, we should be using our Equipment Schedules, which the engineer makes clear the voltage, phase, number of conductors, wire-size, and load the equipment draws.
Further, a panel schedule is not a panel load calculation. As commercial electricians, the electrical engineers do all that stuff for us. It is our job to double-check that everything meets code, then we pull the wires as given to us on the prints.
Finally, residential electricians may have to do an electrical house calculation to determine how much ampacity an electrical panel is rated for, but a panel schedule in basic terms just shows what circuits pertain to what devices from that particular panel.. as on a commercial jobsite we may be dealing with 4-5 different panels.. like HA Panel, X1 Panel, HB Panel, and the like.
Sometimes these different panels are used for critical and non-critical loads. For example, a hospital may need to have a generator backup power in case they lose power. These separate panels are used to power different types of equipment pertaining to those cases, and we just use the panel schedule to determine what equipment is being powered off these different panels, and what circuit and ampacity they require.. which is all done by the electrical engineer!
What We Cover in this Article:
- What is a Panel Schedule
- Why are Panel Schedules Useful to Us Electricians?
WHAT IS A PANEL SCHEDULE
As an electrician, a panel schedule is pretty much our guide on what equipment needs power.
Not to be confused with an equipment schedule – that tells us what type of power and wires a certain piece of equipment needs! (Voltage, Phase, and Ampacity.)
On a typical commercial job site we have many panels, which means there will be many panel schedules to pay attention to!
It tells us the equipment name, circuit number, circuit breaker size, and the amount of poles (phases), and sometimes a phase letter designation (A, B, or C) of each device.
Here’s a panel schedule I quickly drew up:
One major thing I overlooked and did not mention, is you also need to check the NAME PLATE of the actual equipment AS SOON as you get it. Make sure that equipment’s name plate is the SAME as on the Equipment Schedule above. If it isn’t, IMMEDIATELY call your electrical engineer.. you may have prevented a big mistake!
For more info on a name plate, view what is a name plate.
I will cover each column individually:
- Description – Simply the name of the equipment/device.
- Breaker – This is the breaker size which lets us know the minimum size wire to be used.
- Poles – You can have single-pole, double-pole, or three-pole breakers. (As mentioned in the equipment schedule article, these are the number of phases required for the piece of equipment; either single-phase or three phase.)
- Circuit – This tells us the exact circuit numbers for the equipment/device. (It’s important to know how circuit numbers work in an electrical panel.)
Some panel schedules will have some more information like a symbol beside the description, which we saw in our equipment schedule article, or even include the load/demand of the equipment, too.
Equipment Schedules vs. Electrical Panelboard Schedule
It’s EXTREMELY important we use an equipment schedule to make sure we’re pulling the right number of wires, and their size, properly to the panel.
Also, in addition to this equipment schedule, we also have something called a spec sheet (or data sheet), which will tell us even MORE details about that piece of equipment, like its height, width, depth, color, or other very useful features electrician’s must prepare for BEFORE that equipment arrives on site.
WHY ARE PANEL SCHEDULES USEFUL TO US ELECTRICIANS?
This is simply what we follow as an electrician.
Once our rough-in stage of boxing, piping, and pulling branch circuits is done, we then start pulling the home runs back to the panel which give our branch circuits power.
As we continue to pull these home runs, we can keep following the panel schedule to make sure we are not missing anything!
Long-story short, panel schedules guide us on what to do next when we are in our wire-pulling stage.
A wise electrician will try to figure out all the devices they can pick-up in the least amount of pulls.