Basic Electricity

Basic Electrical Terms Voltage: the driving force, potential symbol is V, units are Volts Resistance: resistance to flow symbol is R, units are Ohms Current: a measure of flow symbol is I, units are Amps Power: rate energy is produced or used symbol is P, units are Watts

Voltage Water makes a great analogy for electrical systems. Higher voltage is just like running a pump at higher pressure.

Current (amps) The fish are swimming in current (water). In a piece of copper wire the electron moves from orbital ring to orbital ring of adjacent atoms.

Resistance (ohms)

Resistance differences

The analogy V R I

Ohm’s Law relates these terms E = I • R I = E ÷ R

Distribution system components Transformer Subpanel with circuit breakers Heating cable 120, 208, 277 Vac 480, 600, 1K, 10K Vac Utility Transmits at high voltage to reduce line losses Reduces voltage to useable levels Distributes current and protects circuits Uses electricity to generate heat

Standard Voltages Commercial and industrial facilities 120, 208, 277, 480, 600 Volts, 3 phase Residential buildings 120 and 240 Volts We differentiate our products by voltage 120 Volt vs. 240 Volt 120 Volt products are designed for 100 – 130 Volts 240 Volt products are designed for 200 – 277 Volts

Standard circuit breakers Provide over-current protection for short circuits only Trips if current flowing exceeds breaker rating Typical ratings for heat-tracing applications: 15, 20, 30, 40 and 50 amp Manufacturers: Square D, GE, Cutler-Hammer

Ground fault circuit breakers In addition to over-current protection, these breakers trip if a small fault current flows to ground 5 mA level for personnel protection (GFCI) 30 mA level for equipment protection (GFEPD) Required for all heating cable circuits by NEC, CEC and by Tyco Thermal Controls Tyco Thermal Controls recommends 30 mA level equipment protection to avoid nuisance tripping Selection Guide on Web site shows breakers available for different voltages; available in Tyco Thermal Controls price list

Ground fault breaker operation Circuit Breaker Heating Cable Line A Line B Fault Ground Sensor If currents in Line A and Line B are not equal, some current is going to ground through a fault. The ground fault circuit detects this imbalance and trips the circuit breaker.

Electrical Issues in Heat-Tracing Maximum circuit lengths Self-regulating cables draw more current at start-up temperature than at steady-state temperature Thus, maximum circuit lengths are based on start-up current, not steady-state current Tyco Thermal Controls calculates maximum circuit lengths to ensure current draw does not exceed breaker rating Always use the design guide or TraceCalc for circuit lengths Transformer sizing Safe transformer sizing is based current draw at start-up temperatures rather than at steady-state A conservative solution is: transformer load = breaker rating x 0.8 x voltage