4. ADJUSTING THE WEIGHTS
A barometric damper maintains a relatively constant pressure drop across itself
until the point that the blade is fully open.
A.
Ensure all zone dampers are fully open and that the filter is clean (replace if
necessary).
B.
Screw the weights on the balancing mechanism as close to the collar as
possible.
C.
Turn on the system blower at high speed. You may need to make a cooling
call to do this. If the outside temperature is below 50°F, do not turn on the
compressor. Disconnect power to the condensing unit by switching off the
circuit breaker or removing the fuse before making a cooling call.
D.
Move the weights outward until the barometric damper blade fully closes, then
move the weights out an additional ¼” to ½”.
E.
If the damper is installed between the supply and return plenum, then the
pressure drop across the damper is approximately equal to the system
pressure.
1
The barometric damper will open and close to try and maintain this pressure
drop when individual zones are calling. The blade will open more when a
smaller zone is calling and less when a larger zone or combination of zones is
calling.
F.
To ensure that you are not bypassing too much air
2
, make a heating or
cooling call (depending on outdoor temperature conditions) from the smallest
zone (i.e. the one with the smallest zone damper). After five (5) minutes,
measure the supply air temperature and ensure it is within normal operating
limits. In the cooling mode, the supply air temperature should be above 40-
45°F. In the heating mode, the air supply temperature should be below about
150°F. Refer to the HVAC equipment manufacturer literature or contact the
equipment manufacturer to find out what the limits are. If the supply air
temperature is not within normal operating limits, move the weight further
down the threaded rod to reduce the bypass air.
©Research Products Corporation 2014
B2203198B
10006029