MACH® Series
Gas-Fired Boiler
36
8. The control modulates the firing rate between low and high fire to maintain the desired outlet water temperature.
9. The burner will continue firing until the outlet water temperature reaches set point plus hysteresis (Off Differential).
At this temperature the fuel supply is shut off and the combustion air fan continues to run for a 30 second post-
purge.
10. When the water temperature is reduced by the load on the system, a heat request is generated. The operating
sequence will recycle to step 4.
0
1
2
3
4
5
6
7
Spark
Gas Valve
Flame Detection
Seconds
Fan
*
Flame must be detected at T = 6 seconds
*
Ignition Sequence Timing
0
1
2
3
4
5
6
7
Spark
Gas Valve
Flame Detection
Seconds
Fan
*
Flame must be detected at T = 6 seconds
*
Ignition Sequence Timing
NOTICE!
Once the boiler begins the ignition sequence, the firing sequence will continue until main flame is
reached regardless of heat request. The sequence can be interrupted by turning the power switch off.
5.6 T
ROUBLESHOOTING
If any “Manual Reset” limit device trips,
DO NOT
reset without determining and
correcting the cause. (Manual Reset Limits include: Flame safeguard, high or low gas pressure, high temperature
limit, stack temperature, low water level.)
The ENVI™ boiler control will display text based error descriptions to indicate any problems with the boiler. There are
two types of lockouts the control may experience: manual reset lockouts requiring an operator to press the reset
button, and automatic reset lockouts that will self reset when the error condition clears. A listing of errors and their
service codes is included at the end of this section.
Should the unit fail to operate, call a qualified service technician to troubleshoot the problem and implement corrective
actions.
5.6.1
The Loss of Power
In the event of a power failure, the display panel is not illuminated and the entire system is de-energized, closing all
automatic valves and halting all boiler operations. When power is restored the sequence of operation will resume at
Step 4. If any error/lockout is present when the power is lost, the control will retain that error/lockout and display the
error/lockout when the power is restored.