10 Operating information
General
How the boiler operates
The Crest uses an advanced stainless steel heat exchanger and electronic control module that allows fully condensing operation. The blowers pull in air and push flue products out of the boiler through the heat exchanger and flue piping. The control module regulates blower speeds to control the boiler firing rate. The gas valves sense the amount of air flowing into the boiler and allow only the right amount of gas to flow.
How the control modules operate
The Crest boiler is equipped with a SMART TOUCH control module. The SMART TOUCH control module receives inputs from boiler sensors and external devices. The control module activates and controls the blowers and gas valves to regulate heat input and switches the boiler, Hot Water Generator (HWG), and system pumps on and off as needed. The user programs the control module to meet system needs by adjusting control parameters. These parameters set operating temperatures and boiler operating modes.
Control inputs and outputs
Enable
This input tells the boiler to provide water for space heating.
Hot Water Generator (HWG) tank thermostat
This input tells the boiler to provide water for heating an indirect HW tank.
0 - 10V BMS input (set point or power)
The Crest can be controlled by a Building Management System (BMS) using a 0 - 10 VDC signal. The control can be configured by the installer to use this signal to either control set point or firing rate.
0 - 10V System Pump speed input
When a variable speed system pump is used, and there is a 0 - 10V signal available from the pump speed control, this signal may be connected to the boiler. Doing so will allow the boiler to anticipate changes in the BTU’s needed by the system as the system flow changes, and therefore, help the boiler to maintain the desired system temperature. Connect the - input terminal to the COM or - output terminal on the pump speed control, and the + input terminal to the 0 - 10V or + output terminal on the pump speed control. Note that the voltage on these inputs must never go below ground.
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Installation & Operation Manual
HWG priority
The SMART TOUCH control module allows connection of a HW thermostat or sensor to the low voltage connection board. When the HW thermostat or sensor calls for heat, the control module activates the HW pump, shuts down the boiler pump, and immediately sets the target outlet water temperature to 180°F (82.2°C).
This provides automatic priority heat allocation to the HW Generator for maximum response and recovery. The HW pump continues for 60 seconds after the heating cycle to deliver the most possible heat. The control module can be programmed to limit the firing rate of the boiler during a HW call for heat.
Controlling sensor
The control module is programmed to use the outlet sensor as the control sensor by default. If a system supply sensor is connected, the control automatically uses it as the control sensor. The control module may be programmed to use the inlet sensor as the control sensor instead. In this case, the control will use the system return sensor if it is connected.
Anti-cycling
After a space heating demand has been satisfied, the control will delay the next space heating call for a set time period (time is adjustable by the installer). The time delay will be bypassed if the inlet water temperature drops too far during the delay.
Boiler, system, and HW pump control
When a space heating call for heat starts and no HWG call is on, the boiler pump is turned on. The system pump will turn on also if it is programmed to do so. If a HWG call for heat is on, the boiler pump will wait to turn on until just before the HWG pump turns off. After the space heating call for heat ends, the boiler pump will run for an additional period of time.
When a HWG call for heat starts, the HWG pump is turned on. If a space heating call for heat is on, the boiler pump will turn off a few seconds after the HWG pump turns on.
Louver
When the boiler needs to control combustion air louvers, connect a 24 VAC louver relay to the two (2) Louver Relay terminals. Connect the Louver End Switch to the Louver Proving Switch input on the Low Voltage Connection Board.
Temperature control
Modulation
The Crest is capable of modulating its firing rate from a minimum of 4 - 6% (model specific) to a maximum of 100%. The firing rate is dictated by the call for heat (i.e., space heating or hot water generation), the heating load, ramp delay (if enabled), and various other temperature limitations.