Select the features you need for your SCR and this handy selector tool will take you to the correct model SCR for your application. At the bottom of this page are explanations for each selection as well as a handy current calculator should you need it. Answer the 4 questions below. If you are unsure there is a help selection below.

Phase Selection:

Please select which type of Phasing you require. This will be dependant upon the elements you are using. Need more information?


The current is the total amperes plus a safety margin. You do not want to run your SCR at 100% to keep max power. We recommend a safety margin. If you are unsure how much current is needed please use our handy calculator below to help you figure it out.

Mode Selection:

This is dependant on the type of load you have. We have a chart below that will allow you to determine which is the best type of phase control for your specific application. Need more information?

Voltage Selection:

This is the voltage of the device that you will be controlling. Select the maximum voltage your application will be using. Need more information?




Single and three-phase are the forms of power distribution used. Three phase has 3 "hot" lines and a neutral. Three phase is used in commercial and industrial applications and is more efficient when used with motors. Three-phase has three lines sharing the load allowing higher current capabilities. Three phase is seldom if ever seen in residence and is more difficult to come by as well as being more costly.

Single Phase has one "hot" line and one neutral. This is the type of power distribution seen in residences throughout north America. It is the easiest and also is available everywhere. It is the standard two wire power system.


The current is the amperes needed to power your application at full power plus a safety margin. You do not want your SCR working at 100% output continuously. Your application will only use as much current as it needs, so you will not have to worry about overpowering your elements . We recommend going 50-100% over your highest expected need.

To calculate your what size SCR you need, use our calculator. Add in your percentage of margin, the heater wattage and voltage and find out exactly what size SCR you need.

Power Calculator

How many watts is your heater rated for? Watts   
How many volts is it rated for? Volts     
Put in a margin that allows your heater to run at 100% but your SCR only at 50-75% % Safety margin
Minimum SCR needed Ampere



Type of load Comments Recommended
Constant Resistance Loads

Medium wave infrared, Most ceramic and Cartridge heaters. Immersion heaters, Wire/Coil  Heaters including Nichrome, Calrod heaters.

Resistance Nominally

Less than a 50% change versus temperature.
PA Resistance Load

Phase Angle Fired

Variable Resistance Loads:

Tungsten (T-3) lamps and heaters,
Quartz IR tubes,
Some infrared
panels,       Molybdenum heaters.

Fastest, most precise response needed

When the elements are cold there is a hi-inrush current upon start up.

High hot to cold resistance ratio Tungsten 14:1
Molybdenum 20:1
Graphite: 20:1

PA Current Control

Phase Angle Fired with Current Control

Silicon-Carbide Heaters and GLO-BAR heaters Resistance increases as elements age. Very Hi Temperature applications. PA Current Control

Phase Angle Fired with Current Control

Inductive Loads:

Isolation Transformers, Motor Loads   

Inductive loads can have a high initial current inrush. PA Inductive Load

Phase Angle Fired for Inductive loads.

Mercury Relay and SSR replacement. On/Off Control of
Constant resistance
Zero Cross over



This is the voltage of the device that you will be controlling. Select the maximum voltage your application will be using. Ranges are available up to 120VAC