Greenheck VSU 457831 Installation, Operation And Maintenance Manual page 10

Start-Up Direct Gas
IMPORTANT
For proper unit function and safety, follow the start-
up procedure in the exact order that it is presented.
IMPORTANT
This start-up should begin after all of the installation
procedures and the blower start-up have been
completed.
1. Check the Supply Gas Pressure
Check the supply gas pressure and compare it with
the unit's nameplate pressure requirements. Adjust
the supply regulator as needed until the supply gas
pressure is within the specified range. The direct gas
nameplate is located on the outside of the unit on the
control center side.
Minimum and maximum gas
pressures for maximum output
MAX BTU/HR
BTU/H MAX
NORMAL MANIFOLD
PRESSURE
" W.C.
PRESSION DÕADMISSION
NORMALE
MIN GAS
PRESSURE
" W.C.
PRESSION DE GAZ
MIN BURNER
PRESSURE DROP
" W.C.
PERTE MIN DE PRESSION
DANS LE BRULEUR
TYPE OF GAS
NATURE DU GAZ
EQUIPPED FOR AGAINST
SCFM
CONCU POUR CONTE
Type of gas
Direct Gas Nameplate
2. Check the Pilot Gas Pressure
Check the pilot gas pressure. The recommended
gas pressure is 3 in. wc. Adjust the pilot regulator as
needed. See the Gas Train Layout in the Reference
section for the location of the pilot pressure test port
and pilot regulator.
IMPORTANT
Proper air velocity over the burner is critical on direct
fired gas units. If the air velocity is not within the unit
specifications, the unit will not operate efficiently,
may have sporadic shutdowns, and may produce
excessive carbon monoxide (CO) or other gases.
10
Model VSU Make-Up Air
MIN BTU/HR
BTU/H MIN
MIN GAS PRESSURE
FOR MAX OUTPUT
" W.C.
PRESSION DE GAZ MIN
POUR PUISSANCE MAX
MAX GAS
PRESSURE
" W.C.
PRESSION DE GAZ
MAX
MAX BURNER
PRESSURE DROP
PSI
PERTE MAX DE PRESSION
DANS LE BRULEUR
DESIGN ∆T
F
∆T NORMALE
EXTERNAL STATIC PRESSURE
" W.C.
PRESSION STATIQUE EXTERIEURE
3. Set the Burner Air Pressure Differential
With the fan running and discharging 70ºF (21ºC) air,
connect a U-Tube manometer to the outer sensing
probes (see below) and measure the static pressure
across the burner.
Outer Sensing Probes
U-Tube
Manometer
Measuring the Pressure Drop
The proper static pressure should be between 0.625
and 0.675 inches wc (155.68 and 168.64 Pa). If
needed, evenly adjust the baffles on both sides of the
burner, keeping the burner centered in the opening
until the required pressure is obtained.
Burner
Adjustable
Baffle
Airflow
Burner and Baffles
The pressure drop was set at the factory and may
not need adjustment.
When required pressure is obtained, be sure to
reconnect the outer sensing probes.
IMPORTANT
This process may need to be repeated until the
proper pressure is achieved. This adjustment
will change the air quantity delivered by the unit
and therefore the air quantity delivered should be
rechecked. Refer to the Blower Start-Up section.
To increase the static pressure decrease the
opening. To decrease the static pressure increase
the opening.
9
8
7
0.625 - 0.675 in. wc
6
Adjustable
Baffle
Airflow
NOTE
NOTE
NOTE
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