The traditional way of milk cooling and is still used throughout New Zealand, dx (direct expansion) units are the workhorses of milk silo refrigeration.
For the majority of farms in Canterbury the piping design we recommend is based on one high capacity refrigeration unit connected with solenoid valve control to one or two milk silo base pads, and a smaller refrigeration unit connected to the side wall of the larger milk silo. This satisfies requirements for all of the morning milking to be put into the larger milk silo and all of the afternoon milk in to be put into the smaller silo, and applies all of the refrigeration capacity to the milk silo containing the fresh milk at the time the maximum capacity is required.
We have found this configuration to be very effective on Canterbury farms. While the traditional one refrigeration unit per milk silo concept sometimes provides more overall Kilowatts capacity, only 50% to 60% of this capacity is typically available to cool the milk at each milking, unless each milking is split between the two milk silos.
This concept also has the advantage of allowing heat recovery systems to produce very inexpensive hot water from virtually all of your milk cooling, reducing overall electricity usage by up to 60% over the more traditional one refrigeration unit, one silo concept.
Dairycool stock the most common sizes of dx units found on Canterbury farms as well as a full range of parts and components, such as compressors, condensers and fan motors to get you back up and running quickly, should any faults occur, without loss of your valuable product.