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

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

7

0.625 - 0.675 in. wc

6

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

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

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 DROPPSI PERTE MAX DE PRESSION

DANS LE BRULEUR

DESIGN ∆T

F

∆T NORMALE

 

 

 

 

EXTERNAL STATIC PRESSURE

“ W.C.

 

 

PRESSION STATIQUE EXTERIEURE

burner, keeping the burner centered in the opening until the required pressure is obtained.

 

 

Burner

Adjustable

 

Adjustable

Baffle

 

 

Baffle

 

 

 

 

Airflow

Airflow

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.

10Model VSU Make-Up Air

Burner and Baffles

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.

®

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Greenheck Fan VSU manual Start-Up Direct Gas, Check the Supply Gas Pressure, Set the Burner Air Pressure Differential
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VSU specifications

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