SAFETY CHECKLIST
When repairing a kiln or working with electrical equipment, always remember:

Wear appropriate PPE (Personal Protective Equipment):
 Rubbersoled, closedtoe shoes
 Safety goggles or a face shield if possible
 Work gloves
 Long pants and short sleeves
 Remove all jewelry

Do not work on live equipment unless absolutely necessary:
 Unplug the power cable
 Lock out electrical power at the disconnect or circuit breaker

If working with live equipment:
 Use only one hand near the equipment
 When using a multimeter, clamp one lead in place and operate the other lead with one hand, keeping your free hand away from the equipment

Clean the area around the kiln and ensure it’s dry and free of water.

Use the proper tools and don’t improvise:
 For example, use a fuse puller to remove blown fuses instead of a screwdriver
BASIC ELECTRICITY FOR KILNS
Electricity can be measured in four ways: amps (current), volts (energy or potential energy), ohms (resistance), and watts (power).

Volts:
 Volts measure the force or pressure pushing electricity through a circuit.
 Higher voltage means higher force, which can be dangerous.
 Voltage varies by location: typically 240V in US homes, 208V or 480V in industrial settings.
 Major appliances may use 240V, while small electronics typically use 120V.

Amps:
 Amps (amperes) measure electrical current or flow.
 Higher amperage means a greater volume of electricity.
 Current represents the strain on your electrical system. Homes usually have a set amperage capacity, like 200 amps.
 Appliances should be properly fused and not all used simultaneously to avoid tripping the main breaker.

Ohms:
 Ohms measure resistance to flow in an electrical circuit.
 Materials vary in conductivity (e.g., copper vs. rubber).
 Elements in kilns are made of resistive metal alloys to generate heat.

Watts:
 Watts measure power.
 More power means faster heating and higher temperatures for kilns.
 Larger kilns need more watts to heat the larger space.
Ohm’s Law:
 Amps, volts, ohms, and watts are related by Ohm’s Law.
 Example: Kiln circuit amperage can be found by dividing volts by ohms.
Single vs. Three Phase Power:
 Single Phase:
 Electricity moves along two “hot” wires (one in, one out).
 Three Phase:
 Utilizes three “hot” wires to distribute electricity, spreading out the current and reducing the needed wire size and circuit breaker capacity.
Mathematical Relationships (Formulas):
For use with single phase only: The electrical industry has designated letters to stand for amps, volts, ohms, and watts.
 Amps = “I” (think “intensity of amperage”)
 Volts = “E” (think “energy”)
 Ohms = “R” (think “resistance”) (Ω is the symbol used to indicate ohms)
 Watts = “P” (think “power”)
THE WATER ANALOGY FOR UNDERSTANDING ELECTRICITY IN KILNS:
 Electricity is analogous to water flow and pressure.
 A kiln’s electricity supply is like a water reservoir.
 Small kilns need less power (watts) than larger kilns, similar to smaller buckets needing less water flow.
 The hotter a kiln gets, the more power it needs, like increasing water flow to fill a bucket with more holes.
Electrical Measurements in Water Analogy:
 Amps: Flow of electricity (like water flow in gallons per second)
 Volts: Pressure pushing electricity (like water pressure)
 Ohms: Resistance to flow (like pipe diameter)
 Watts: Work done by electricity (combination of volts and amps)
Series Circuits
 Single path for current flow
 Break in any part stops the current
 Current is the same throughout; components must handle the total current
 Voltage is divided across components; total resistance is the sum of individual resistances
Rules for Series Circuits:
 The value of a current (amperage) flowing in a series circuit is the same through all parts of the circuit.
 The total voltage of a series circuit is equal to the sum of the voltages across each part of the circuit.
 The total resistance (ohms) of a series circuit is equal to the sum of the resistances across each part of the circuit.
 Line voltage is divided across each component in a series circuit in proportion to the component resistance values. Referring to the schematic below, the total resistance is (25Ω + 30Ω = 55Ω). Voltage measured between points A and B is:
240 x (25Ω/55Ω) = 109 Volts.
Voltage measured between points B and C is:
240 x (30Ω/55Ω) = 131 Volts.
Note that 109 + 131 = 240 volts
If there were (2) resistances whose values were equal, the voltage would be divided equally in half, and would measure 120 Volts.
Measuring Resistance in Series Circuits
 The total resistance of a series circuit is the sum of all the individual resistances.
Parallel Circuits
 Multiple paths for current flow
 Components connected to line voltage; current still flows if one component fails
 Components must withstand full line voltage
 Current varies with resistance; more paths mean less overall resistance
Rules for Parallel Circuits:
 The total current (amperage) supplied to a parallel circuit is equal to the sum of the currents through the branches.
 The voltage across any branch of a parallel circuit is equal to the supply voltage.
 The total resistance of a parallel circuit is always less than the resistance of any of the branches.
Example of a Parallel Circuit in an L&L kiln
The following parallel circuit is typical of the DaVinci, Doll and J2900 kiln rings; there are (3) elements per ring, connected in parallel.
In this example, each element has a resistance of 49.8Ω. At 240 VAC, each element develops
(240 VAC/49.8Ω) = 4.82 Amperes
The total circuit amperes, then, is
4.82 + 4.82 + 4.82 = 14.46 Amperes.
Measuring Resistance in Parallel Circuits
The total resistance is always less than the lowest reading of a single element. Often this is difficult to measure if all the elements in the circuit are connected to two points with no way to isolate them.
If all elements are known to all have the same resistance then you can multiply the number of elements by the resistance value of the entire circuit to get one element’s approximate resistance. In the above example The resistance of the entire circuit is 49.8Ω / 3 = 16.6Ω.
Total Resistance = 1 / ( (1 / R1) + (1 / R2) + (1 / R3) )
If the elements in the circuit have different resistances, like in SchoolMaster kilns, there is no easy way to determine the individual resistances of the elements. The best way to solve an element problem with these kilns is to replace all the elements in the troublesome circuit. You can also measure the resistance on each element.
Series/Parallel (Combination) Circuits
 Combine series and parallel circuits
 Used in some frontloading kilns to manage sidewall and backwall heating elements
Rules for Series/Parallel or Combination Circuits:
Certain circumstances require the use of Series/Parallel, or Combination circuits (in which series and parallel circuits are combined). In some frontloading kilns these circuits are used to combine, for instance, sidewall heating elements and backwall heating elements (often shorter than sidewall) in a combination circuit that is controlled by one power relay.
In the above example, the total resistance can be found by first dealing with each branch circuit individually. Starting from the right, this circuit is a series circuit; add the (24Ω + 24Ω = 48Ω). The other two circuits are parallel and are equal in value (12ΩW each); therefore, the resistance value of these two circuits is equal to (12Ω/2 = 6Ω). Drawing an equivalent circuit with (2) parallel circuits, one of 6Ω and one of 48Ω, looks like the following:
Solving for this circuit:
Total Resistance = 1 / ( (1 / R1) + (1 / R2) + (1 / R3) )
Total Resistance = 1 / ( (1 / 6Ω) + (1 / 48Ω) ) = 1 / (.1666 + .02083) = 5.33Ω