Assisting Electrical Contractors with Process Control Solutions

Furnace heating control
24 January 2023

ADM Instrument Engineering was approached by an electrical contractor, who provides services to many of Australia’s leading manufacturers and mining companies.

The contractor required assistance in coming up with a solution to control 4 heater loads.  

3 of the loads are switched on and off via contactors and the other is a variable load controlled by a Eurotherm EPower thyristor

Eurotherm EPower
Eurotherm EPower Thyristor


A Eurotherm 3504 series process controller was selected to ensure smooth transition between the fixed loads switching points, which will help stop spikes on the supply. 

The Eurotherm Model 3504 acts as a slave co-processor to the digital control system (DCS), utilising the 4-20 mA output to control the principal heater bank. It also adds or subtracts three auxiliary heater banks in a staged fashion. 

Eurotherm 3504 Process Controller
Eurotherm 3504 Process Controller


The principal heater bank has the variable load, which is controlled by the Eurotherm EPpower. The control signal of which is shaped to transition the output smoothly between heater banks #2, #3, and #4 as they switch in and out. 

The DCS’ control output signal is connected to the Eurotherm 3504 controllers process input effectively becoming a remote setpoint. The three additional heater banks are controlled by relay contacts (via interposing relays) which are energised at selected points on the DCS output gradient. The 3504 utilises math & logic operators to shape the control output to the Eurotherm EPpower heater controller. 

This is just one example of how ADM was able to assist an electrical contractor in proposing a technically suitable process control solution to their customer, which was affordable to the end customer. 

Please do not hesitate to contact ADM Instrument Engineering if you are seeking assistance with providing a process control solution.