GB.GOLDSKFPX.210324
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3.2 Adjusting the Duct System
and air diffusers
In order to prevent the fans from consuming more power than
necessary, it is important to keep the pressure drop in the system
at the lowest possible level. It is also important that duct sys-
tems and air diffusers are correctly commissioned to provide the
comfort expected.
When commissioning air diffusers and the duct systems for the
GOLD, it is appropriate to follow the proportionality method.
This means that the ratio between the airflows in branch ducts
remains constant even if you change the airflow in the main
ducts. The same ratio applies to the air diffusers in the installa-
tion.
When commissioning the duct system there is provision for
locking the speed of the fans in the air handling unit to provide
a specific preset flow rate, see Section 4.1.7 in the Function
Manual, Installation.
3.2.1 Adjustment Sequence
The system should be adjusted in the following order:
1. Adjust of the air diffusers in each branch duct.
2. Adjust the branch ducts.
3. Adjust the main ducts.
3.2.2 Commissioning procedure
1. Set all the air diffusers and dampers to the fully open position.
2. Calculate the quotient between the airflow reading and the
design airflow of all the air diffusers, branch ducts and main
ducts. The air diffuser in every branch that has the lowest
quotient should be fully open. Use this air diffuser as an
INDEX AIR DIFFUSER. The same applies to branch dampers
and main dampers.
When you’ve finished commissioning, one air diffuser in every
branch, one branch damper and one main damper should
consequently be fully open.
Example on how to make an adjustment
– Start adjusting duct branch B, since this one has the
highest quotient.
– The last air device, B3, has the lowest quotient and
should be fully open.
Adjust the other air devices, B1 and B2, so that these
will have the same quotientas air device B3 (see item 5
above).
– Now adjust the air devices in branch duct C. Air
device C4 should be fully open; throttle the others to
the same quotient.
– Adjust the air devices in branch duct A. The index air
device here is air device A3, which means that you first
throttle air device A4 (the reference device) to device
A3:s quotient. Then adjust the others to the same quo-
tient as air device A4.
– Throttle branch damper B to the same quotient as
branch damper A, throttle branch damper C to the
same quotient as branch damper A.
Check that all dampers have the same quotient.
When commissioning has been completed, 3 air devices
and one branch damper should stand fully open to
obtain the lowest possible pressure in the system.
qp = design airflow (l/s)
qm = flow reading (l/s)
qm
K (Quotient) =
qp
3. Start adjusting the main duct that has the highest quotient
and the branch duct in the main duct that has the highest
quotient. Starting from this point enables you to then "press"
the air in front of you toward the sections of the system that
have the least air.
4. Adjust the last air diffuser on the duct branch so that it will
have the same quotient as the index air diffuser. This air
diffuser becomes the REFERENCE AIR DIFFUSER. The last air
diffuser on the branch is often the one that has the lowest
quotient and this air diffuser should be open. In this case, the
index air diffuser and the reference air diffuser will be one
and the same.
5. Throttle the other air diffusers in the branch to the same quo-
tient as the reference device.
NOTE! The quotient in the reference terminal will change
every time another air diffuser is throttled, so in practice
the quotient for the reference air diffuser can be set slightly
higher. The reference device must be measured in between
each air diffuser throttled.
6. Go to the branch that had the next highest quotient and
adjust the air diffusers there, etc.
NOTE! All branch dampers should be fully open until all air
diffusers have been adjusted.
7. Throttle the branch damper that had the highest quotient to
the same quotient as the branch that had the lowest quo-
tient.
NOTE! Keep in mind that the index damper changes quotient;
proceed as described in item 5.
8. When all branches have been commissioned, throttle the main
dampers in the same manner.
See also Adjustment example below.
