Radiant Coil Design. Many older furnace designs have radiant coil guide support
pins penetrating the floor, as shown in Figure 9.9. It is important to seal and insulate these
openings properly to prevent cold air leaks that increase fuel consumption and reduce
furnace efficiency. In modern furnaces, the guide support pins either have been
eliminated or the pins go into a trough on the floor, with no floor penetration, to reduce
cold air infiltration and energy loss.