Super Hot AAA-3000 series, Installation And Service Manual

Page: 16 / 36

AAA Series Gas Boiler – Installation and Service Manual
16
3.3 CONTROLLER OPERATION
When the controller is powered, the controller enters the operating mode if there are no sensor or high
limit errors present. The user should select one of the following modes from the controller adjust menu:
Mode 1 - Setpoint operation using parallel piping: Operates boiler stages to maintain fixed
temperature at boiler outlet sensor when a heat demand is present.
Mode 2 - Setpoint operation using primary/secondary piping: Operates boiler stages to maintain
fixed temperature at boiler supply sensor when a heat demand is present.
Mode 3 - Dedicated DHW Generation: Operates boiler stages to maintain fixed temperature at the
boiler outlet sensor when an internal demand for DHW is generated based on the DHW sensor. An
indirect hot water tank must be used to separate the AAA from an open system.
Mode 4 - Outdoor reset with reset override using parallel piping: Operates stages to maintain an
outdoor reset temperature at the boiler outlet sensor. When there is a call for “reset override” from
the DHW aquastat (i.e. ST&R is closed), the control operates the stages to maintain a setpoint
temperature at the boiler outlet sensor. If both heat demand and setpoint DHW demand are present
at the same time, the controller targets the higher of the two requirements.
Mode 5 - Outdoor reset with reset override using primary/secondary piping: Operates stages to
maintain an outdoor reset temperature at the boiler supply sensor. When there is a call for “reset
override” from the DHW aquastat (i.e. ST&R is closed), the control operates the stages to maintain a
setpoint temperature at the boiler supply sensor. If both heat demand and setpoint DHW demand are
present at the same time, the controller targets the higher of the two requirements.
Mode 6 – External boiler control : This mode can be used when connecting multiple boilers to an
external boiler control or an energy management system (EMS). The BTC series is used to provide
boiler pump control and operates stage 1 and pump when a heat demand is present. The stage 1
terminals on the external boiler control must be connected to the heat demand terminals HT & R of
terminal block TB4 on the boiler. Next, the 5 & 6 jumper wire of terminal block TB1 on the boiler must
be removed, and the stage 2 terminals on the external boiler control connected to 6 and 24Vac (R).
See wiring diagram for details.
When there is a heat demand or DHW demand the controller will switch on the system pump. If the
sensor is not satisfied, the controller will switch on additional stage(s), in sequence, and based on PID
(proportional, integral, derivative) logic. The controller continuously monitors the sensors and examines
the difference between the target temperature and the sensor temperature. Depending on the difference
in temperature (proportional), the time (integral), and how fast or slow the temperature is changing
(derivative), it will determine when to switch a stage on or off. This feature prevents "short cycling", which
can quickly wear out contactors and cause rapid temperature fluctuations.
The heating routine will operate until the water temperature reaches the user-defined temperature setting.
Once reached, the control will automatically cycle the stage(s) of the boiler on or off, as necessary, to
maintain the supply water temperature. The required number of stages which are activated is determined
by the controller. After the call for heat has been satisfied, the stage(s) of the boiler will switch off, in
sequence, followed by the pump.
3.4 RESET OVERRIDE
WARNING
If both Heat Demand and Setpoint DHW Demand are present at the same time, the controller
targets the higher temperature of the two requirements. This may result in higher than intended
water temperatures in either space heating loop or domestic hot water (DHW) heating loop. Use
pipe rated for use at the highest possible water temperature.
The BTC Series Controller has one pump relay which is normally open and will close (i.e. pump
energized) when either a Heat Demand or Setpoint DHW Demand is present. When using Reset
Override, a
switching external pump relay (e.g. tekmar Relay 003) should be utilized to stop hot water