Balancing Airflow - Aprilaire 8100 Installation Instructions Manual

bAlANCING THE SySTEM

bAlANCING AIRflOW

1 . Drill a 7/8" hole in the return and supply ducts .
2 . Install the two airflow measuring devices in the duct using the drilled holes and seal with tape . Verify the airflow arrows are pointed in the
direction of airflow . The measuring devices should be a minimum of 2-1/2' from the damper in a 5' section of straight duct . (See figure 19 .)
3 . Set up the pressure gauges so that they are vertical and level and adjust to zero .
4 . Connect the tubing from the airflow measuring devices in the ducts to the pressure gauges (see figure 19) . The high pressure tap on the
airflow measuring device must be connected to the high pressure tap on the pressure gauge . Similarly, connect the low pressure tap on the
measuring device to the low pressure tap on the pressure gauge .
fIGURE 19 – Set-up for balancing Airflow
FRESH AIR
TO HOUSE
STALE AIR
TO OUTSIDE
AIR FLOW MEASURING
DEVICE #5158
5 . Verify the dampers are in the fully open position .
6 . Turn off the HVAC system blower and any other exhaust fans .
7 . Plug in and turn on the unit .
8 . Read the pressure gauges . If the gauge readings are the same,
the system is balanced and does not require further adjustment .
Proceed to Step 10 .
9 . If the readings are different, slowly close the damper on the duct
with the higher gauge reading until the two readings are identical .
When the readings are the same, the system is balanced .
10 . See Table 1 for approximated airflow based on pressure gauge
readings .
11 . Secure the damper positions to prevent them from changing
during operation .
12 . Disconnect the tubing and pressure gauges and remove the
airflow measuring devices . Seal the duct openings where the
measuring devices were located .
(CONTINUED)
5 FT. MIN.
DAMPER
2-1/2 FT
PRESSURE GAUGES
DAMPER 5 FT. MIN.
2-1/2 FT
Table 1 – Airflow Approximations
Airflow in a 6" Duct as Measured using
Airflow Measuring Device #5158
Gauge
Readings Airflow
(in. w.c.) (cfm)
30
0 .005
44
0 .010
55
0 .015
0 .020 64
0 .025 72
0 .030 80
0 .035 86
0 .040 93
0 .045 98
0 .050 104
0 .055 109
0 .060 114
NOTE: If airlow is restricted by more than 20% (see bold values in
Table 1), check ductwork and connections to increase flow .
STALE AIR
FROM HOUSE
FRESH AIR
FROM OUTSIDE
AIR FLOW MEASURING
DEVICE #5158
90-1746
Gauge
Readings Airflow
(in. w.c.) (cfm)
0 .065 119
0 .070 124
0 .075 128
0 .080 132
0 .085 137
0 .090 141
0 .095 145
0 .1 149
0 .105 152
0 .110 156
0 .115 160
0 .120 163
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