HELIX VX-050 Installation, Operation & Maintenance Manual page 78

APPENDIX A - CONTROL MODULE
User Interface Display
4. Central Heating (CH) modes available:
• CH Mode = 0 'CH with Thermostat'
• Boiler will attempt to satisfy CH demand while CH
thermostat input is closed.
• Boiler will modulate its firing rate to maintain CH set
point and match system heat load.
• CH set point adjusted in 'Settings' submenu under 'User
Menu'
• CH Mode = 1 'CH with Thermostat and Outdoor Reset'
• Boiler will attempt to satisfy CH demand when CH
thermostat input is closed.
• Boiler will modulate its firing rate to maintain CH set
point and match system heat load.
• CH set point calculated as function of outdoor
temperature using outdoor reset curve. See figure A-2
• CH Mode = 2 'CH with Full Outdoor Reset'
• CH demand is determined by outdoor temperature and
Warm Weather Shutdown temperature.
• Boiler will permanently attempt to satisfy CH
demand, when CH demand is available.
• CH thermostat input is ignored.
• CH set point calculated as function of outdoor
temperature using outdoor reset curve. See figure A-2
• CH Mode = 3 'CH with Permanent Demand'
• CH demand is prermanently on.
• Boiler will permanently attempt to satisfy CH
demand.
• CH thermostat input is ignored.
• CH set point is adjusted in 'Settings' submenu under
'User Menu'
Note:
• Once CH demand is satisfied (i.e. CH thermostat opens or
boiler determines its minimum firing rate exceeds system
heating load):
• Burner shuts off, boiler enters post purge.
• CH pump continues to run for 30 seconds.
• Control will wait until Anti-cycle time of 180 seconds
elapses before boiler fires again. Prevents short-
cycling.
• The internal heat exchanger pump is energized anytime demand
exists regardless of Pump Mode setting or type of demand (CH or
DHW).
78
Explanation