Pursuant to ACCA Manual Zr, install the Bypass Hand Damper in a
convenient location on the bypass duct
before or after
the actual bypass
damper. Allow at least 6 inches of clearance between both dampers.
Secure the assembly with sheet metal screws and seal all connections.
Insulate the entire bypass duct if necessary. Loosen the thumb screw on
the manual quadrant and test to make sure the blade moves freely in
both directions, then set the Bypass Hand Damper to the full open
position. Follow the instructions below.
•
If you have a Manometer
proceed to
“Adjusting
the Bypass Hand Damper”
Follow the directions for
setting the Bypass Hand Damper Delta P, based on
the Delta P (Total ESP) across the HVAC system.
•
Setting the correct bypass differential pressure
will
prevent the Bypass Duct from becoming the path of
least resistance and helps to:
*
Eliminate DX coil freeze-up
*
Eliminate Over-Heating
*
Eliminate System Short Cycling
*
Eliminate ECM Fan Motor Hunting
*
Eliminate Bypass Damper Hunting
•
If you don’t have a Manometer,
simply adjust the
hand damper to the ½ closed position. EWC Controls
recommends at least ½ closed because setting some
value pressure drop is better than none at all.
See Figure 1.
•
If during bypass mode,
the Zone system Trips
excessively on the Supply air Sensor, you observe
Excessive Condensation on the bypass duct or Air
Handler, or you measure unusually low Differential
Temperatures,
then close the Hand Damper some
more. If there is excessive noise through the bypass
duct, then open the Hand Damper a little.
•
If you accidentally close
the Hand Damper,
approximately 30% of the design bypass volume will
still flow through the Hand Damper due to the
truncated blade design. This unique design prohibits
adversely affecting the blower motor curve.
Adjusting the Bypass Hand Damper:
Before adjusting the hand damper, the installer should confirm the following:
(1) The zone system and all zone dampers are functioning properly.
(2) The HVAC System is functioning properly in highest (CFM) speed.
(3) Make sure all zone dampers are open and the Barometric or Electronic
Bypass damper is fully closed.
(4) Make sure the air filter is new or clean.
See Figure 2:
EXAMPLE - Measure the HVAC system Differential Pressure
(Delta P) with
all zones calling and the bypass fully closed.
1. Measure the static pressure at the Supply Plenum (0.16”wc)
2. Measure the static pressure at the Return Plenum (-0.35”wc)
3. Observe the Delta P readout on the Manometer.
(0.51”wc)
4. Or solve for Delta P = 0.16 - (-0.35) =
0.51”wc
(Delta P Target to Match)
See Figure 3:
EXAMPLE - Measure the HVAC system Differential Pressure
(Delta P) in the
worst case scenario (smallest zone calling and all other zones closed).
Bypass damper is forced open and the Hand damper is open.
1. Measure the static pressure at the Supply Plenum (0.29”wc)
2. Measure the static pressure at the Return Plenum (-0.15”wc)
3. Observe the Delta P readout on the Manometer.
(0.44”wc)
4. Or solve for Delta P = 0.29 - (-0.15) =
0.44”wc Delta P
(NO MATCH)
Adjust the Hand Damper (towards the closed position) and keep adjusting
until the Delta P readout on the Manometer reads the same or close to the
0.51”wc target above.
EXAMPLE - Measure again.
1. Measure the static pressure at the Supply Plenum (0.22”wc)
2. Measure the static pressure at the Return Plenum (-0.29”wc)
3. Observe the Delta P readout on the Manometer.
(0.51”wc)
4. Or solve for Delta P = 0.22 - (-0.29) =
0.51”wc Delta P
(Matches Target)
You are finished.
Lock the Hand Damper in place. Release all forced Zone
dampers and place the Zone system and Thermostats back to normal operation.
NOTE: Values provided above are examples only. Your actual pressure readings will vary, but
the procedure will always be the same.
385 Hwy. 33 Englishtown, NJ 07726
Ph: 800-446-3110 - Fx: 732-446-5362
CONTROLS INC.
Excellence Without Compromise
EWC
Model
RD-HD, SID-HD, ND-HD
Bypass Volume Control Hand Damper
APPLICATION NOTE
Forced Air Zone Controls
®
P/N 090376A0169 REV. F 03.05.13
Copyright © 2011 EWC Controls Inc., All Rights Reserved.
Note: This EWC drawing of the Bypass damper, Hand Damper, Static Pressure control and Related duct work is intended to serve only as a guide.
Your actual duct work layout may differ. Use the graphic as a guide when planning or designing a Zone system regardless of the Equipment type,
Duct layout and Airflow configuration.
HVAC
UNIT
Return Air
from
All Zones
Supply Air
to
Zone Dampers
Pitot Tube
Ultra-Zone
™
PS4
Static Pressure Control
Ultra-Zone
™
Zone Control
Panel
EBD
Motor Actuated or Barometric
By-Pass
Damper
3/8” O.D.
Reference Tubing
24vac Power
Control Wiring
Ultra-Zone
™
Supply
Air
Sensor
(required)
RD-HD
SID-HD
ND-HD
Hand
Damper
Return
Air
Sensor
(optional)
M
P
Ultra-Zone
™
Ultra-Zone
™
Figure 1
