What We Cover in This Article:
- What are Equipment Schedules for Electricians?
- Understanding a Piece of Equipment’s Voltage, Phase, and Ampacity
- How Do We Apply the Equipment Schedule’s Information to the Job?
What are Equipment Schedules for Electricians?
The previous articles on prints have told you where to install equipment and touched a little bit on specs + data, but an equipment schedule is calculated by the electrical engineer and tells you exactly what size of wire, phase, and voltage a piece of equipment needs and also the panel it’s fed from.
Now, electrical engineers do make mistakes, so I recommend doing a quick check over of their details of the equipment schedule. You do this by reading the nameplate on your piece of equipment which you can then compare the ratings to your charts + codes making sure everything lines up.
I want to stress the importance of feeding equipment from the right panel, as in a commercial setting, we often deal with different panels with different voltages.
On most sites, higher voltage panels are used for heavy-duty mechanical equipment like air conditioners, make-up-air units, and exhaust fans, for example, but not always! So always double check the equipment schedule and electrical prints for these details.
So this is what an equipment schedule would look like. (They can vary, I’ve made this myself):
Understanding a Piece of Equipment’s Voltage, Phase, and Ampacity
There are three very important things to look at on your equipment schedule:
- The voltage of the equipment
- The phase of the equipment (Is it single phase or three phase? – Also, this symbol means phase – Ø)
- The ampacity (load) of the equipment
- (The frequency does not matter here in Canada, as we’re on 60Hz, however, on a nameplate, frequency is also included, too!)
Here in Canada, equipment is often run on 120V, 208V, 240V, or 600V. (There are times where we have a transformer that outputs 480V, too.)
It’s very typical for equipment to be fed with a higher voltage to improve efficiency and decrease the wire size required to run the unit. (Learn more about voltages + amps with Transformers.)
Looking at voltage on an equipment schedule is as simple as it sounds. However, sometimes you may assume this bigger equipment is fed with these higher voltages when really, it’s actually powered with 120V! (You can check out why do electricians use higher voltages than 120V?)
So, double-checking the equipment schedule will indicate what voltage that particular piece of equipment requires, and eliminates any confusion.
It’s the phase section which is tricky for a lot of new apprentices because depending on the job site you’re working on, the voltages you’re working with can vary.
For example, homes in Canada operate on 120/240V because they are single phase – meaning they only have two hots and a neutral – whereas a condo is typically three phase giving us 120/208V!
It’s important for you to understand how we get different voltages to grasp the concept of single phase, three phase, and how we get 120/208V or 347/600V for example. (Line-to-phase would be 120V, but line-to-line would be 208V in the case of 120/208V.)
Now for the kicker:
On a three phase panel, you can have 208V single phase and 208V three phase! (This is why checking the equipment schedule/name plate of your equipment is very important so you pull the right amount of wires to your equipment.)
Here’s how we can get single phase and three phase out of a panel:
The types of voltages and phases you get all start from your main panel.
If your main panel is three phase with a neutral, you can have three phase with a neutral at other sub-panels fed from this panel, too. But, if you feed a sub-panel which only requires single phase from this three phase panel, this sub-panel is now restricted to single-phase which is fed from your three phase panel.
It’s a pretty simple concept to understand, but very important.
With that said, let’s say we have a sub-panel off of our main panel which is three phase with a neutral, and it’s voltage is 120/208V. This panel will provide the most flexibility to us, but we must pay even closer attention.
If a piece of equipment says it’s 120V, it’s simple. Pull one hot, one neutral, and a bond. This would be line-to-phase voltage.
If a piece of equipment says 208V single phase, then you pull two hots, no neutral, and a bond (unless your equipment schedule specifies it needs a neutral.)
And finally, if a piece of equipment says 208V three phase, you are required to pull three hots to this equipment and a bond wire. (These are your three different phases – A, B, and C- or Red, Black, and Blue.)
This again relates to the panel which is providing the equipment power.
If the panel only has two phases, then you can only power a piece of equipment with 208V single phase.
Long story short, look at your equipment schedule and look at the required phase.
It should show either a 1 for single phase or a 3 for three phase.
- 120V Single Phase – One Hot, One Neutral
- 208V Single Phase – Two Hots
- 208V Three Phase – Three Hots
Another thing to quickly mention is the number of conductors to pull to the equipment.
Typically most of this heavy-duty does not need a neutral, but sometimes it does!
So make sure to check the type of feeder required to pull.
This will typically be called Load.
You’ll also see the metric used vary as well, such as: kW (kilowatt), FLA (full load amps), and HP (horse power) for example.
I will keep this article simple and just go with Watts (as anything else gets into deeper electrical theory. Watts is simply Volts * Amps.)
Long story short, the reason we are wanting to know the ampacity of our equipment is so we can properly size our conductors.
Let’s say we’re looking at a unit heater (the fan heater image below) which is single phase, requires 208V, and its load is 2500W. (Just making up these numbers.)
To find our amps, all we have to do is: 2500W / 208V = 12.02A
We can safely run #14/2 to our example unit heater.
If this unit heater were three-phase, we’d then have to apply root 3 (1.73) – More info on calculating how to find amps in a three phase system.
How Do We Apply the Equipment Schedule’s Information to the Job?
So now, all that information is cool, but how can we actually use it?
Well, this will be a little summary of what we’ve already learned. Hopefully it will clear things up.
When looking on your panel schedule, it will tell you all the different equipment you have to supply power to from that panel. Just follow this in order and try to group your pulls together to save yourself time by tackling as many tasks in one pull.
Now after you look at your panel schedule, if you’re unsure on any equipment, you can quickly look at the equipment schedule, which will clarify any confusion on wire size or how many wires to pull to your destination.
It really is as simple as that.
To be a well-educated and useful electrician on site, it’s all about knowing how to read your prints, as well as identify any errors!
If you take the time out to learn prints, you will avoid mistakes, save your company money, and definitely be respected among your peers.
It’s not about ‘knowing-it-all’ or ‘being smarter than everyone else’, it’s about working as a team and pointing out things you’ve learned over the years or noticed on the prints.