Operation4.2 Sampling Hole LocationPCAThe analyzer requires that a ½" diameter sampling hole be made in thefurnace stack to accommodate the probe stop on the Probe and HoseAssembly.Locate the sampling hole downstream from the last heat exchanger,and upstream from any source of dilution, such as a draft diverter(Figure 4-1) .Important! As the distance between the last heat exchangerand sampling point increases, stack loss will falsely decreasedue to heat loss by convection from the flue or stack.For residential and light-commercial combustion-equipment applications,the following recommendations are applicable:• Oil Gun Burners – Locate sampling hole at least 12 in. (30 cm) down-stream from the furnace breaching, and at least 6 in. (15 cm) upstreamfrom the furnace side of the draft regulator.• Gas Burners – Locate sampling holeat least 6 in. (15 cm) upstream fromthe furnace side of the draft diverteron gas-converted units. For gas-designed equipment, the probe maybe inserted down into the fluethrough the draft diverter or hood.FLUE GAS FLOW(Downstream)DRAFTDIVERTER/REGULATORSAMPLEPOINT(Upstream)FURNACEBREECHINGFigure 4-1. Sampling Hole Location4-2 Instruction 0024-9219
