User Guide

ManualsBrandsEWC Controls ManualsDampers12" RD-HD Volume Control Bypass Hand Damper

Table Of Contents

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

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

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

Zone Dampers

Pitot Tube

Ultra-Zone™PS4

Static Pressure Control

Ultra-Zone™

Zone Control

Panel

otor

3/8” O.D.

Reference Tubing

24vac Power

Control Wiring

Ultra-Zone™

Supply

Air

Sensor

(required)

-H

amp

Return

Air

Sensor

(optional)

Ultra-Zone™

Figure 1

Summary of content (2 pages)

PAGE 1
APPLICATION NOTE Model RD-HD, SID-HD, ND-HD ® Forced Air Zone Controls Bypass Volume Control Hand Damper 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.
PAGE 2
Example values Your values will vary STEP 1: Place the system into single zone scenario. Figure 2 Excellence Without Compromise EWC (All zones are calling and the bypass is closed). If necessary, use the hand damper to close-off the bypass completely. Observe the Total ESP value at the bottom of the Manometer or do the math yourself. Record the value. That value is now the target CONTROLS INC. WC P1 0.16 ESP 0.