You should keep the keg cold when using a jockey box, although it is not absolutely necessary. Jockey boxes are designed to chill the beer as it enters via the beverage line and flows through the coils. The cold coils help to maintain the temperature of the beer as it is dispensed, providing a refreshing and chilled drink.
While prior refrigeration and icing of the kegs is not required, it can be beneficial, especially on extremely hot days. Keeping the kegs cold before connecting them to the jockey box helps to minimize the melting of ice inside the jockey box. This can be particularly important if you are using the jockey box in a warm or outdoor setting where the ambient temperature is high.
If the kegs are already chilled before connecting them to the jockey box, the system can work more efficiently. The cold beer will flow through the coils and maintain its temperature as it is dispensed, resulting in a better drinking experience for your guests.
I have personally used jockey boxes for outdoor events during hot summer days, and I have found that keeping the kegs cold beforehand greatly improves the performance of the jockey box. The beer stays colder for longer, and there is less ice melting inside the box, which can dilute the beer and affect its taste.
In situations where refrigeration or ice is not readily available, you can still use a jockey box without pre-chilling the kegs. The system will still work, but the beer may not be as cold as desired, especially if the ambient temperature is high. In such cases, you may need to use more ice in the jockey box to help maintain the desired temperature.
While it is not necessary to keep the keg cold when using a jockey box, doing so can greatly enhance the overall experience. The cold beer will flow through the chilling coils and provide a refreshing and chilled beverage for your guests. So, if possible, it is recommended to keep the kegs cold before connecting them to the jockey box, especially in hot weather conditions.