Whatever lines you run external to a keg box or kegerator should be OPEN INSULATED lines…what does that mean?
It means you run 1.5″ or 2″ PVC drain type pipe between the box and tower that is open to allow air to flow from the keg box up to the tower.
The beer line is run in this enclosed “open” cold air space. The outside of the PVC is then well insulated with several layers of foil clad insulation.
This is done so you always have cold beer right up to the tap – some take the cheap route and just insulated the beer tubing, but that’s not recommended.
You can see this in detail in the EHBP-03 plan drawings, page 26 – Tapper Location & Assembly Considerations.