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Instruction 24-94484-4
Operation
4.4 Sampling Point
FORCED AIR FURNACE – For atmospheric burner
or gravity vented, forced air heating equipment
with a clamshell or sectional heat exchanger de-
sign, test each of the exhaust ports at the top of the
heat exchanger. The probe should be inserted back
into each of the exhaust ports to obtain a flue-gas
sample, before any dilution air is mixed in.
HOT WATER TANK – Domestic hot water tanks
with the ‘bell’ shaped draft diverter can be ac-
curately tested by inserting the probe tip directly
into the top of the fire tube below the diverter.
80% EFFICIENCY FAN ASSIST OR POWER VENTED
– Combustion testing of fan assist or power vented,
furnaces/boilers should be done through a hole drilled
in the vent immediately above the inducer fan.
90% EFFICIENCY CONDENSING – Condens-
ing furnaces/boilers can be tested through a hole
drilled in the plastic vent pipe (when allowed by
the manufacturer or local authority of jurisdiction)
or taken from the exhaust termination.
ATMOSPHERIC OR GRAVITY VENTED BOILER
– Boilers, which have a ‘bell’ shaped draft diverter
on top, should be tested directly below the diverter
through a hole drilled in the vent connector.
Forced Air Furnace
Hot Water Tank
Atmospheric or Gravity
Vented Boiler
80% Eff. Fan Assist or
Power Vented
90% Eff. Condensing
O2,
CO,
Stack Temp.
Undiluted Flue
Gas Sample Taken
Under Draft
Diverter in Top
of Fire Tube
O2, CO,
Stack Temp.
O2, CO,
Stack Temp.
Combustion Air
Sampling Point
O2, CO,
Stack Temp.