Superior truck refrigeration: holdover plates and mechanical blower system combine for optimum refrigeration

Dairy Foods, June, 1998

More and more frozen dessert companies are using dual refrigeration systems in their direct store delivery trucks.

Combining the reliability of holdover plates and the versatility of mechanical blower refrigeration, dual refrigeration systems combine the best of both worlds.

Holdover plates, which consist of hollow plates containing a eutectic solution mounted on interior walls and/or ceiling of the truck, have traditionally been used for daily runs up to 10-12 hours. With these systems, deep frozen products that leave the plant at -20 [degrees] F will be maintained in the acceptable temperature range throughout as much as a 12-hour route period.

The eutectic solution in the plates is frozen each night by a refrigeration compressor that is mounted on the truck and is an integral part of the system. The compressor is plugged into an electric outlet at night to freeze the solution to recharge its capacity for the next day.

Holdover plates and compressor systems are reliable, relatively inexpensive to install and with a very low maintenance requirement, the cost of operation is substantially reduced. They will last the life of the truck.

"Holdover plates are the most cost efficient, because you don't need diesel fuel to run them. You just plug them into an electric outlet," says John Aldred of Hiland Dairy. "Another advantage is that most people know how to work on them if there any problems."

Mechanical blower refrigeration is designed for medium and large truck bodies and trailers. During operation, cold air is circulated around the product to pick up heat, which is transferred to the outside. Consistent uniform air flow around the product is essential.

Mechanical blower refrigeration is excellent for long, high volume routes with numerous stops where the cooling capacity of holdover plates would fall short. Used with plates, it maintains constant temperatures within the body for long periods.

Dual refrigeration systems are ideal for extreme route conditions, such as hot, humid climates; extended route times, double routes and two-day routes; and heat infiltration resulting from numerous and lengthy door openings.

"Another advantage of the dual system is it provides backup in case one system malfunctions or fails," says Dave Wagner of Haagen Dazs.

Scroll compressors

Years of research and field testing have demonstrated that scroll compressors are less expensive to operate and more reliable for use with the eutectic solutions than their old counterparts and last as much as 50% longer.

With 80% fewer moving parts and no tip seals that wear away, the scroll compressor sets the industry standard for reliability. It is more tolerant of liquid refrigerant and debris, has less vibration, and lower failure rate.

It is also more efficient to begin with and actually becomes more efficient with use as it wears in.

"We've only had scroll compressors on a few trucks for a short time, but I don't see any drawbacks to them. They weigh less and have fewer moving parts," says Aldred.