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PCA
Instruction 24-9351
4-2
Operation
Figure 4-1. Sampling Hole Location
4.2 Sampling Hole Location
The analyzer requires that a 13 mm (½ in.) diameter sampling hole be
made in the furnace stack to accommodate the probe stop on the Probe
and Hose Assembly.
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 ex-
changer and sampling point increases, stack loss will falsely
decrease due 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 30 cm (12 in.) down-
stream from the furnace breaching,
and at least 15 cm (6 in.) upstream
from the furnace side of the draft
regulator.
• Gas Burners – Locate sampling hole
at least 15 cm (6 in.) upstream from
the furnace side of the draft diverter
on gas-converted units. For gas-
designed equipment, the probe may
be inserted down into the flue
through the draft diverter or hood.
FLUE GAS FLOW
(Downstream)
DRAFT
DIVERTER/
REGULATOR
SAMPLE
POINT
(Upstream)
FURNACE
BREECHING