Bypass Sizing - Ecojay SmartZone ZS4X-2.0 Installation & Operation Manual

DESIGN & PRE-INSTALL
SMARTZONE DUCT SYSTEM
A ZONING SYSTEM CAN TYPICALLY USE THE SAME DUCT SIZING AS A TRADITIONAL SINGLE-THERMOSTAT SYSTEM IF THE PRESSURE RELIEF
IS INSTALLED CORRECTLY AND THE SYSTEM IS 4 OR LESS ZONES. TO MINIMIZE BYPASS AIR FLOW, INCREASE THE DUCT CAPACITY BY ONE
SIZE FOR EACH ZONE LESS THAN 25% OF THE TOTAL SYSTEM AIR FLOW CAPACITY FOR SYSTEMS WITH MORE THAN 4 ZONES, INCREASING
THE DUCT & DAMPER SIZES OF THE SMALLER ZONES (OR ALL THE ZONES) WILL MINIMIZE THE AMOUNT OF PRESSURE RELIEF NEEDED
WHEN ONLY THE SMALLEST ZONE IS OPEN.
NOTE: CONNECT DAMPERS DIRECTLY TO THE PLENUM WHEN POSSIBLE AND BRANCH OFF SMALLER DUCTS GOING TO DIFFERENT AREAS
WITHIN THE ZONES. USING THIS TRUNK/BRANCH DUCT DESIGN WILL MINIMIZE COST AND REDUCE AIR NOISE.
BYPASS - PRESSURE RELIEF
A PROPERLY SIZED BYPASS DAMPER AUTOMATICALLY MAINTAINS CONSTANT PRESSURE INSIDE THE SUPPLY AIR
DUCT WHEN ZONES OPEN AND CLOSE. WHEN THE CORRECT SIZE BYPASS DAMPER IS INSTALLED AND ADJUSTED
ACCURATELY, IT WILL BE FULLY CLOSED WHEN ALL ZONES ARE CALLING (NO AIR BYPASSING) AND WILL OPEN
PROPORTIONATELY AS ZONE DAMPERS CLOSE.

BYPASS SIZING

SELECT A 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.
TYPICALLY 400
CFM PER TON
800 2
1200 3
1600 4
2000 5
ROUND CFM CHART
DAMPER NORMAL MAX
SIZE CFM
6" 100
7" 150
8" 200
9" 300
10" 400
12" 600
14" 900
16" 1400
A 4-T
SSUME ON EQUIPMENT WITH
1600 CFM
– 400 CFM
= 1200 CFM N
SO, R
FROM THE OUND
14"
A ROUND DAMPER SHOULD BE USED FOR
3
EQUIPMENT AIRFLOW
CAPACITY IN CFM (HIGH SPEED)
CFM OF
SMALLEST ZONE
CFM-NEEDED
TO BYPASS
RECTANGULAR CFM
SURFACE AREA IN SQ. FT.
*
("HEIGHT" X "WIDTH") / 144
CFM
NORMAL CFM =
200
(SURFACE AREA IN SQ. FT.*) X 600 FPM
250
MAX CFM =
300
(SURFACE AREA IN SQ. FT.*) X 900 FPM
450
600
900
1400
2000
10"
ROUND SMALLEST ZONE
( )
EQUIPMENT
( – N
SMALLEST ZONE ORMAL
EEDED
D MAX CFM,
AMPER
BYASS.
USE "NORMAL CFM"
USE A BYPASS DAMPER THAT
HAS LARGER "MAX CFM"
=
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.
UNIT SIZE
EXAMPLE
(TONS)
2 -2.5
3 -3.5
4 -4.5
CFM )
5
BYPASS
DUCT
ROUND DAMPER
SIZE (INCHES)*
10"
12"
14"
14 -16"