BYPASS Setup & Sizing
Static Pressure Controlled Bypass (MODULATING)
TUBING INCLUDED
REMOVE CAP from
LOW-PRESSURE INLET
Modulating Bypass
Configuration
The goal is to calibrate the bypass damper so that it is barely staying
closed when all zones are open. This will cause the bypass damper to
open if supply dampers close and the plenum pressure increases.
WORKS WITH
3-WIRE
POWER CLOSE
POWER OPEN
ROUND OR
RECTANGULAR
2
1
3
C
W2
O/B
W1
EH
Y1
Y2
G
E
Q
U
IP
M
E
N
T
ecojay
P
C
P
O
C
O
M
Static Pressure
Controller (ASPC-2)
USE 18 Gauge Solid
Core wire & Matching
spade connectors
(included)
NC
NO
COM
1
2
3
Wiring
Mounting
Mount with the sample line connections
in the “
down
” position
. Use screws &
standoffs through at least two of the four
mounting feet holes. (As shown below)
Air Probe (Pitot Tube)
Sm
ar
tZ
on
e
EQ
UI
PM
EN
T
DO NOT allow
supply air
pressure to blow
directly into the
pitot tube
PITOT
TUBE
To test if bypass is sized and
configured properly, make a call ONLY
from the smallest zone for cooling with
the fan at the HIGHEST speed and the
BYPASS Damper should fully or almost
fully open within 1 to 2 minutes
Turn knob clockwise SLOWLY until the
bypass damper motor starts closing
(ECOJAY damper RED light will flash)
If damper starts opening again before
fully closing, turn the knob clockwise
SLOWLY until it starts closing again.
Repeat this process until the damper is
fully closed.
(ECOJAY damper RED light will be solid)
VERY Slowly turn
the knob counter-
clockwise until the
bypass damper
motor starts to run
open.
(ECOJAY damper
GREEN light will
flash)
Just as soon as the motor starts to
run open, turn the knob back
clockwise just enough that the
damper motor stays closed.
(ECOJAY damper RED light will be
solid)
ecojay
P
C
P
O
C
O
M
ecojay
P
C
P
O
C
O
M
ecojay
P
C
P
O
C
O
M
1
2
3
Connect the flexible tubing
to the HIGH-PRESSURE
INLET as shown
Pressure inlets
pointing down
Make a call from ALL zones for cooling so all zone
dampers are fully open AND the equipment fan
(blower) is running at the HIGHEST speed.
4
AIRFLOW
Locate the air probe (pitot
tube) at least
2 FEET
downstream from the air
source, preferably as close
to the center of the
airstream as possible
High
Pressure
Inlet
Low
Pressure
Inlet
2 -2.5
10"
3 -3.5
12"
4 -4.5
14"
5
14 -16"
Unit Size
Round Damper
(Tons)
Size (Inches)**
BYPASS DAMPER “RULE OF THUMB”
Below chart assumes 400 CFM per Ton
**USE next size UP round bypass damper for any
system with a single zone less than 200 CFM.
BYPASS DAMPER (Pressure Relief)
A bypass system
consists of a short duct connecting the supply plenum to the return
air plenum.
A “bypass” damper is installed in this duct that opens
/
closes automatically to maintain constant pressure inside the duct
when zones open and close. When the correct size bypass damper
is installed and adjusted correctly, it will be fully CLOSED when all
zones are calling (no air bypassing) and will OPEN proportionately
as more zone dampers close.
BYPASS DAMPER SIZING:
Select a round damper size with a Max CFM greater than the CFM-
Needed to bypass. Use the formula below to calculate CFM needed
to bypass and the ROUND DAMPER CFM CHART to check Max CFM.
T
YPICALLY
400
CFM
PER
TON
U
SE
“N
ORMAL
CFM”
FROM
THE
CFM CHART
(P
AGE
: 8)
U
SE
A
BYPASS
D
AMPER
THAT
HAS
LARGER
“M
AX
CFM”
800 = 2
1200 = 3
1600 = 4
2000 = 5
Bypass SIZE
E
QUIPMENT
A
IRFLOW
C
APACITY
IN
CFM (
HIGH
SPEED
)
CFM
OF
S
MALLEST
ZONE
CFM-N
EEDED
TO
BYPASS
EXAMPLE: 4-T
ON
EQUIPMENT
WITH
10"
SMALLEST
ZONE
:
1600 CFM
(
EQUIPMENT
)
–
400 CFM
(
SMALLEST
ZONE
–
N
ORMAL
CFM
ON
P
AGE
: 8)
= 1200 CFM N
EEDED
SO,
FROM
THE
R
OUND
D
AMPER
MAX CFM
ON
P
AGE
: 8,
A
14"
ROUND
DAMPER
SHOULD
BE
USED
FOR
BYASS.
Mounting & Setup
It is critical that the Bypass Damper is adjusted properly for the Zoning system to work properly.
1.
Remove the Weight arm from the damper at the shaft collar and move the weight to the end of head of the weight arm bolt.
2.
Follow drawings to the right to install the damper and choose the proper
initial weight arm position
based on the
direction of airflow.
3.
Make a call for cooling from ALL zones & verify that all zone dampers are open.
4.
Make sure the bypass damper remains closed. If it is opening already, add more weight (ABDW).
5.
Once the bypass damper is remaining closed, slowly move the weight toward the shaft (½ inch at a time) until the
bypass damper starts to open slightly.
6.
Move the weight back about ½ inch so the bypass damper remains closed with all Zones open.
7.
Close one or more zones by removing the cooling calls and ensure that the barometric bypass damper opens.
Barometric Bypass
Initial Weight-Arm Positions
depend on
AIRFLOW
and
ORIENTATION
of the bypass damper. Below are the four (4)
initial weight arm positions. Select AIRFLOW & ORIENTATION for specific application.
NOTE: Extra weight may be required for
upflow applications. (Order ABDW)
Up-Flow
4
o’clock Position
Left to Right
4
o’clock Position
Right to Left
8
o’clock Position
Down-Flow
4
o’clock Position
10
11
