Start-Up Direct Gas
• 50/50 Recirculation
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.
4b. Set the Burner Air Pressure Differential
With the fan running and discharging 70°F air, connect a
Outer Sensing Probes
8 
7 
0.5 - 0.8 in. WC
6 
5 
Measuring the Pressure Drop
Top Baffle
5. Set the Low Fire Time Delay
Set the low fire time delay to 75% of its maximum setting. See below for location of the time delay setting.
6. Set the Maximum Firing Rate
Monitor the unit’s actual temperature rise by placing a thermocouple in the unit’s inlet and a second in the discharge, three duct diameters downstream of the burner.
Send the unit to maximum fire by disconnecting and isolating the proper wire on the Maxitrol 14 amplifier.
While monitoring the units temperature rise, set the maximum firing rate by adjusting the separate regulator or combined regulator (shown on page 13) until the designed temperature rise is achieved. After setting the maximum firing rate, reconnect the wire to the amplifier.
Remove the wire from the #3 terminal |
| Low fire | |
to send the unit to maximum fire | setting (LFST) | ||
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| dipswitch | |
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Set the discharge temperature: Typical 140°F
Minimum | Maximum |
Typical: 90°F | Typical: 140°F |
Airflow 
Burner
The proper static pressure should be between 0.5 and
0.8 inches wc. On units with |
motors 15 hp and less, adjust |
the fan rpm by means of the |
adjustable drive pulley. For |
units with motors greater |
than 15 hp, the drive pulley is |
fixed. To change the fan rpm, |
a new pulley will have to be |
Maxitrol Series 14 |
note
Do not set the burner maximum firing rate based on gas pressure. It should be set based on the unit’s designed temperature rise shown on the direct gas label.
Bottom Baffle
acquired. |
MAX BTU/HR
BTU/H MAX
NORMAL MANIFOLD
MIN BTU/HR
BTU/H MIN
MIN GAS PRESSURE
Burner and Baffles
Note
When required pressure is obtained, be sure to reconnect the outer sensing probes.
Note
To increase the static pressure, increase the fan rpm. To decrease the static pressure, decrease the fan rpm.
PRESSURE“ W.C.
PRESSION D’ADMISSION 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 |
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 | ||
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| EXTERNAL STATIC PRESSURE | |
“ W.C. |
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| PRESSION STATIQUE EXTERIEURE |
12DGX Industrial Space Heating
Direct Gas Nameplate
®