Electrical Power System Types in the Houston Texas Area
In the Houston Area, Center Point Energy is the provider of electrical Distribution. They also maintain overhead and underground Primary Service. The secondary or stepped down voltages utilized by most Businesses and Residential Customers are as follows:
Commercial Voltages:
480Y/277volt 3 Phase 4 Wire
240/120 Delta 3 Phase 4 Wire
(High Leg is “C” on Meter, “B” on Load)
(High Leg is 208v to Ground )
208Y/120volt 3 Phase 4 Wire
240/120volt 1 Phase 3 Wire
Residential:
240/120volt Delta 3 Phase 4 Wire (This is supplied to some Older homes in the Houston Metro Area )
240/120volt 1 Phase 3 Wire (This is the most common voltage for residential customers in Houston )
Higher voltages will mean smaller conductor sizes may be utilized for similar loads.
For example:
Forty 400 watt High Bay Fixtures with a ballast rating of 1.0 will require 16000 watts plus continuous duty rating of 125% or a total of 20000 watts. At 480 volts the demand is 42 amps ( 20000 / 480 = 41.67 ) or (3) Three 20 amp 480 volt circuits. Each requiring (generally) a # 12 THHN Copper Conductor. If the applied Voltage was 120 volts, then the 20000 watts would be divided by 120. ( 20000 / 120 = 166.67 ) or 167 amps! That would take (11) Eleven 20 amp 120v circuits and more than 3 times as much copper # 12 conductors. The savings then for the higher voltage systems is in the installation and the resulting savings in material and labor.
MYTHS ABOUT ELECTRICITY
Myth No. 1
In Houston, many times I heard people say that with higher voltage systems their electric energy bill will be less.
This is FALSE. You pay by the KILOWATT HOUR or per thousand watts per hour. An example is a simple appliance, a Hair Dryer. Let's say it operates at 1000 watts. Let's further say you pay 14 cents per Kilowatt hour. If you run your 1000 watt Hair Dryer for one hour it will consume 1 kilowatt of energy and you will be billed for 14 cents. If your Hair Dryer or Appliance operates at 120 volts and uses 1000 Watts, then the formula is 1000 / 120 = 8.33. The Hair Dryer or Appliance uses 8.33 amperes at 120v and therefore Uses 1000 watts of energy. If that same appliance were to operate at 240 volts, then the following would be true:
1000 / 240 = 4.16 amperes
Yes, fewer amps but the consumption of WATTS, (WHAT WE PAY FOR) remains the same.
One more example: LOW VOLTAGE LIGHTING.
Low Voltage Lighting Does NOT save you Money on your Electric Bill. Here’s why:
Lets say you have (20) Twenty , 50 watt lamps operating at 120 volts. And using 1000 watts at 120 volts.
1000 / 120 = 8.33
8.33 Amps at 120 volts but still 1000 watts.
Now lets use (20) Twenty, 50 watt lamps operating at 12 volts.
20 x 50 = 1000 / 12 = 83.33 amps.
Quite an increase in amps MUCH larger conductors will be requires for this LOW VOLTAGE system.
But what about the Watts?
Well 83.33 amps x 12 volts = 1000 watts.
So by utilizing a transformer to reduce the Voltage, you will INCREASE the required conductor size(s), and you will have NO EFFECT on the Wattage. You will still pay for the 1000 watts or 1 kilowatt.
