1. Basic Electricity

2. 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

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

4. 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.

5. Resistance (ohms)

6. Resistance differences

7. The analogy V R I

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

9. 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

10. 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

11. 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

12. 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

13. 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.

14. 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