4. 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 wire connected to Terminal 4 on the Maxitrol 14.
While monitoring the units temperature rise, set the maximum firing rate by adjusting the regulator until the designed temperature rise is achieved. After setting the maximum firing rate, reconnect the wire to the amplifier.
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.
Regulators and Modulating Valves
Remove cap to access |
| Remove one wire to |
maximum firing rate |
| send the unit to the |
| ||
adjustment |
| minimum firing rate |
Minimum
firing rate 
adjustment
Separate Regulator and Modulating Valves
5. Set the Minimum Firing Rate
Disconnect and isolate one of the wires running to the modulating valve to send the unit to its minimum firing rate. Set the minimum firing rate by adjusting the
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 |
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 |
needle valve shown above.
After setting the minimum firing rate, shut off the pilot to ensure that the flame safeguard can still read the main flame signal. Reconnect the wire to the modulation valve and open the pilot
note
The minimum setting for the maximum firing rate may be higher than required. This is acceptable. The
Direct Gas Nameplate
Maxitrol Series 14 — 7 terminals
Remove the wire from terminal #4 to
send the unit to maximum fire
Low fire time delay setting (75% of maximum)
Important
Setting the maximum firing rate during mild weather conditions may cause the high limit to trip out during extreme conditions requiring manual resetting.
note
Gas trains are equipped with either separate regulators and modulating valves or with a combined modulating valve.
note
Clockwise rotation increases the temperature rise, counterclockwise rotation decreases the temperature rise.
burner will modulate as needed.
IMPORTANT
The proper minimum firing rate setting results in a small ribbon of continuous flame which covers the flame road and runs across the entire burner.
Important
Do not allow the disconnected wire to come in contact with a potential ground. Damage to the amplifier or transformer could result.
NOTE
Gas trains are equipped with separate regulators and modulating valves.
NOTE
Adjusting the maximum and minimum firing rate requires the inlet air sensor to be set higher than the outdoor air temperature in order to start the burner(s). Once high and low fire have been set, the inlet air sensor should be set to the desired temperature.
NOTE
Counterclockwise rotation increases the minimum fire rate setting, clockwise rotation decreases the setting.
Model VSU
®
