Relay
An electromagnet device used in a control circuit to provide electric current to a valve or switch. Referred to as a start relay when used for a motor.

Resistor
A device to limit the current flow in a circuit.

Rheostat
A type of resistor where the resistance can be adjusted to various levels.

Safety Pilot Valve
See pilot safety valve.

Secondary Transformer Winding
Low voltage side of a step down transformer.

Series Circuit
An electrical circuit in which only one continuous path is provided for the flow of current, so that the current flows through all components in the circuit.

Solenoid
A wire wound coil that creates a magnetic field when energized.

Solenoid Valve
A valve operated by a solenoid coil.

Solid-state
Semiconductor type switching device with no moving parts to control an electrical circuit.

S.P. (Single Pole)

A switch device that opens or closes connections in a single conductor.

S.P.D.T.
Single Pole, Double Throw

A switch that opens or closes connections alternately in two conductors of the same circuit.

S.P.S.T.
Single Pole, Single Throw

A switch that opens or closes connections at one position in a circuit.

Standing Pilot
Pilot flame remains lit whether main burner is off or on.

Steam Temperature/Pressure Table

Gauge Pressure P.S.I.G.	Temperature Fahrenheit
0	212
2	218.5
4	224.4
6	229.8
8	234.6
10	239
15	249.7
25	266.8
30	274
40	286.7
50	297.7

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