Tom Miller, CCIM
The Mystery of Electrical Power – A Primer from Miller Industrial Properties
Wire: Either copper (preferred and stable) or aluminum (cheaper but tends to corrode and fittings tend to loosen more due to expansion/contraction). Wire is sized to carry a designed load within the circuit and is sized inversely to its label. Wire size 24 is pretty small, whereas ‘000000’ (6 ought) is multi-stranded and monstrous. The electrons in copper wires move more easily than in aluminum, so aluminum wires need to be larger to carry the same amount of them.
DC or Direct Current: Used in automobiles, DC is associated with anything battery powered. In a DC circuit, the electrons flow in a circular path from the source through the wires back to the source and back out again
AC or Alternating Current: AC is used everywhere DC isn’t used. In an AC circuit, electrons do not flow in a circular path, but think of one electron bring shoved into the circuit, which displaces all the electrons in the circuit one spot forward and one electron pops out the end of the wire at the load. It’s like a pipe full of marbles or a hose full of water; one in, one out the other end. In the USA, our electrical grid system all runs on a specific alternating frequency. One by one, electrons are pumped into the circuit at a specific rate or frequency.
60 Hz: This is the number of times per second that the power source pumps an electron into an AC circuit.
Single Phase: This is where things get more mysterious. As AC power is source generated, it is three-phase. A power user can use a single phase of the three-phase power and use that to power his items just fine. Think of it as a single cylinder motorcycle – every time the engine goes around one turn, the cylinder powers it once, then “coasts” until the next time. Think of one wire popping out an electron once per revolution. Most ‘low’ power use items employ single phase power.
Three Phase: To understand this, think again of the engine with three cylinders. Now, every time the engine turns once, it’s powered three times; once by each cylinder every time around. You can see why this would be far more powerful, smoother and more efficient since the power used to keep the motor turning can be less for each of the three power sources per revolution with nearly no ‘coasting’ each revolution. Think of three separate wires shoving out their electron once per revolution. Equipment with higher power needs use three phase power. Most equipment runs far more efficiently in the three-phase mode, although most can be powered using both single and three phase, depending how the electrician wires the ‘power tap box’ on the equipment. Anyone paying the bills wants to use three-phase power.
MSB (Main Switch Board): This is the main power panel that the energy company serves their power into from their transformer. The MSB houses the main circuit breakers and the electrical meter sockets. This is where we prefer to get the true volts and amps into the location because this is what’s coming into the site. Getting correct power capacities in multi-tenant spaces gets trickier, as it requires being careful not to add up distribution panels downstream of the main power source into the space.
Meter Sockets: MSB’s for multi-tenant buildings have multiple meter sockets. As buildings are demised, landlords can easily segregate power consumption charges per tenant by the power provider metering all power to a suite right from the MSB location. If an MSB has all the meter sockets full, adding a new tenant’s unique meter is more challenging.
Distribution Panel: This is any panel downstream from the main power panel. It is common to have the sum of all distribution panels exceed the power rating of the main power within the space. Electrical designers have factors they use, since they know that no single distribution panel will likely ever be used 100% at any given time. So we can have, for example, five 200A panels served from an 800A main source panel. Hence the importance of getting the power rating from the source panel only.
Connected Load: This is a term referring to what a facility is really using at any given time. Looking at a power bill will show what the connected loads are, since the power is charged out by what is being used – not by what could be used. The connected load of a manufacturing plant is always less than the total power served into the MSB, and in most cases considerably less. Here’s a life application – when a client says he “needs” 4000A/480V, it’s always nice to check their power bills at NV Energy to determine the real connected load. If NVE determines it’s never been more than 1800A at their current location, that’s valuable information when you’re looking for a property.
Onto volts and amps! Returning to the water hose analogy, let’s say we had a farm with a water tank and a hose attached. We fill the water tank and connect a pump to add pressure in the tank.
Volts: The water pressure we get out the end of the hose is like the volts rating in an electrical circuit. More volts means more pressure to shove the electrons into and out of the wire. If we increase the water pressure in the tank from 60 psi to 120 psi, we get much more water from the same-sized hose. Accordingly, a 480 volt circuit can produce a lot more electron flow than a 110v circuit. Think volts equals pressure.
Amps: The amount of water that flows out of the hose or through the circuit is related to the amps (or current). Adding amps is like changing the hose from a half inch to a one inch hose. This also adds a lot more electrons flowing out of the end of the wire. Think amps equals size or amount.
Efficiency: There are formulas that kick in here but suffice it to say that any electrical device operating at higher voltages is running more efficiently than at lower voltages. It consumes less power on higher voltages. This is why everyone wants 480V power. And some high energy users (plastics guys) would love to get the 2160V systems that a few rare locations have, such as 990 Waltham way – 800A/2160V, which is actually a massive amount of power. The power company sells ‘2160’ at about 10% of the cost of 480V power. Makes you wonder why this isn’t prominently featured on the CRBE flyer, doesn’t it?
Watts: Watts is like a horsepower rating for an engine. It is a rating of electrical power. The formula is watts = volts x amps. A common hairdryer’s high setting generally use 1500 watts. Most home circuits are 15 amps and 110 volts. This means they can handle about 1,650 watts before everything goes dark and quiet. Most house circuits include a number of wall outlets. So when a woman cranks that hair dryer to flamethrower mode and another appliance is on one of the other circuits the hairdryer is also on, we know what’s next – 12:00 blinking on the clocks.
Resistance: This is the impedance to the flow of electricity through a circuit. This is what the appliance or motor causes within the circuit. It’s not especially important information to know.
Circuit Breakers: Electrical circuits have devices that open the circuit when it is overloaded. This keeps the wires from getting too hot and causing a fire when the hairdryers are running. This is what we are flipping in the dark to get the bathroom circuits running again.
110, 208, 220, 277, 440, 480, etc.: These are all voltage ratings. All we need to focus on is the voltage rating of the main power into a location. Everything else is distribution voltages after the transformers change things to suit certain applications. None of them mean anything.
Transformers: Again, nothing we need to be concerned about. A transformer takes a certain current and changes it to different currents and even different Hz. It can step power up or down. That’s the boxes that hummm all the time. No concern of ours, except to understand than when a transformer is located next to the primary power panel, there is generally a big breaker (100A) in there to serve the transformer, which probably is the power source for all the 110v outlets and lighting in the office and any 110V service in the warehouse.
Ground Fault: This is a special circuit interrupter found in areas where water is or could be present. If they work right, this device keeps the user of an appliance that comes in contact with water from running the electrical circuit through its body. This would cause a new hairdo pretty quickly that even the hairdryer won’t fix.
AC-DC: Is another matter having little to do with this subject.
This is a lot of information, and for the industrial real estate property hunter, some of it is fairly meaningless. Still, it’s good to know what matters and what doesn’t, even if it just means you have the knowledge to marvel at useless commentary on an agent’s marketing flyer. My favorite from the recent past: “more power than you would ever need.”
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