Watlow's SERIES N7 Helps Deliver a Thermal Loop Solution for Meal Delivery Service


An OEM manufacturer of meal delivery systems was redesigning their equipment for a new generation of products. They were seeking a new control system to handle the functions of retherming pre-prepared meals, a process that utilizes a convection cart to keep meals cold until mealtime and then reheats a portion of each tray while keeping the rest cool.

The customer wanted a new controller that:

  • Featured easy to update programs
  • Was convenient for the end user to operate
  • Would automatically retherm meals at the right time
  • Provided expanded communications that could be migrated to wireless communications for future expansion


The meals were refrigerated on individual serving trays until mealtime and hot portions needed to be heated before employees arrived to deliver them. Therefore, the customer needed a controller that could combine precision convection heat and simultaneous refrigeration with an intelligent controller that could have the meals ready to deliver unsupervised.


Watlow provided a thermal loop solution consisting of heaters, sensors and controllers. Watlow's system approach provided a value-added solution for the customer. They were able to work with one contact to integrate the entire system and answer questions. This provided both convenience and ease of use.

The system solution included the SERIES N7 controller, E-SAFE® RELAY, tubular heaters and thermistors.

The SERIES N7 drove the bulk of the system value because it could be customized to the application. It offered the I/O capability to satisfy the customer's current needs while providing additional I/O for upcoming expansion. The modular aspect of the SERIES N7's Ethernet module also allowed the customer to add Ethernet either before or after integration of the new system.

The SERIES N7 was programmed to handle one zone of cooling and one of heat with a future option for up to three zones of heat control. The user-friendly interface, consisting of embedded switches and LED's, simplified programming and operation of the unit. The SERIES N7's customized overlay option simplified implementation for the customer as well. After supplying artwork for the control panel, they received a tailor-made overlay with custom icons, logo, LED lights, etc. The resulting controller supports with the customer's strong brand identity and bold equipment design.

Another advantage of the SERIES N7 was the wide range of output options. The customer utilized switched dc outputs, electromechanical relays and solid state relays that kept wiring to a minimum while saving space in the cabinet.

The E-SAFE RELAY provided a long-lasting solution with the benefits of rapid cycling and PID control. The E-SAFE RELAY did not burn out prematurely and eliminated the mercury concern of MDRs in the food application.

The remainder of the system included a custom tubular heater assembly with a sheet metal flange and thermistors. The customer was pleased with Watlow's solution and has future plans to use the process outputs options, available with the unit.

Key products were used for your solution:

SERIES N7, E-SAFE relay, tubular heaters and thermistors