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Start-up - direct gas, Check the supply gas pressure, Important – Greenheck DG / DGX with Direct Spark (470652) User Manual

Page 16: Set the burner air pressure differential, Burner and baffles, Measuring the pressure drop, Direct gas nameplate

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Direct Spark Ignition Make-Up Air

16

®

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 (see below). The
nameplate is located on the outside of the unit on the
control panel side.

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.

IMPORTANT

The purpose of the high and low gas pressure
switches is to automatically shut down the burner
if the inlet gas pressure is too low for the burner to
safely light, or if the manifold pressure is too high for
the burner to operate properly.

3. Set the Burner Air Pressure Differential

With all access panels in place, 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.

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.

NOTE

The pressure drop was set at the factory and may not
need adjustment.

NOTE

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.

NOTE

To increase the static pressure decrease the opening.
To decrease the static pressure increase the opening.

2. Check the Optional High and Low Gas

Pressure Switches

The high pressure setting is typically 8 in. wg (2 kPa)
and the low pressure is setting is typically 3 in. wg (0.7
kPa). The switches are set at the factory and should not
need adjustment. Adjust the setting only if needed. See
the Gas Train Layout diagram in the Reference section
for the high and low pressure switch location.

The proper static pressure should
be between 0.625 and 0.675 inches
wg (155.68 and 168.64 Pa). If
needed, evenly adjust the baffles
above and below the burner,
keeping the burner centered in the
opening until the required pressure
is obtained.

Adjustable
Top Baffle

Airflow

Burner

Adjustable
Bottom Baffle

Burner and Baffles

7

6

0.625 - 0.675 in. wc

Measuring the Pressure Drop

Outer Sensing Probes

U-Tube Manometer

Pressure Switch

Direct Gas Nameplate

“ W.C.

“ W.C.

“ W.C.

F

PSI

“ W.C.

“ W.C.

MAX BTU/HR

BTU/H MAX

NORMAL MANIFOLD

PRESSURE

PRESSION DÕADMISSION

NORMALE

MIN GAS

PRESSURE

PRESSION DE GAZ

MIN BURNER

PRESSURE DROP

PERTE MIN DE PRESSION

DANS LE BRULEUR

TYPE OF GAS

NATURE DU GAZ

MIN BTU/HR

BTU/H MIN

MIN GAS PRESSURE

FOR MAX OUTPUT

PRESSION DE GAZ MIN

POUR PUISSANCE MAX

MAX BURNER

PRESSURE DROP

PERTE MAX DE PRESSION

DANS LE BRULEUR

MAX GAS

PRESSURE

PRESSION DE GAZ

MAX

DESIGN ΔT

ΔT NORMALE

EQUIPPED FOR

CONCU POUR

SCFM

“ W.C.

EXTERNAL STATIC PRESSURE

PRESSION STATIQUE EXTERIEURE

AGAINST

CONTE

Minimum and maximum gas
pressures for maximum output

Type of gas