HAMWORTHY HEATING LTD
25
PUREWELL VariHeat he
500001155/F
Figure 8.5.3.2 - Power Control
Figure 8.5.3.1 - Flow Temperature Control
8.5.4
Central Heating Program
To activate this mode of demand, the relevant parameter must be set to Remote On/Off or Switched Live On/Off.
The central heating demand is detected when the Room Thermostat or Switched Live input closes. If an outside
sensor is fitted, the water temperature setpoint depends on the outside sensor value and the selected heating
curve ( to be set during commissioning).
Modulation during this mode of operation is based upon the measurement of flow sensor S1. The selected heat-
ing curve will determine the control setpoint. The user can limit the maximum setpoint.
If the outside sensor is not connected, the setpoint is determined by the user.
If the outside air temperature exceeds 32°C the demand is switched OFF, and will be re-instated when the outside
temperature has dropped by the hysteresis setting –see figure 8.5.4.
As soon as the flow temperature exceeds the setpoint by the hysteresis value, the burner will switch OFF, the
pump will continue to run and the anti-cycling timer will start. As soon as the flow temperature has dropped below
the hysteresis value and the anti-cycling timer has elapsed, the burner will switch ON.
The regulation is based upon PI -control, but the maximum capacity of the boiler can be limited by step modula-
tion - refer to section 8.5.7.3.
8.5.5
Frost Protection
Individual boilers are capable of two stage frost protection by setting the relevant parameters.
If the return temperature (sensor S2) drops below the first level protection temperature, the pump is activated. If
the temperature continues to fall below second level protection temperature, the burner is switched ON and the
fan speed is held at minimum firing rate. The pump and the burner remain ON until the temperature rises above
the temperature On Offset.
Should an outside sensor be fitted, by setting the relevant parameters, the pump is switched ON if the outside
temperature is below the minimum frost setting, and it will switch OFF outside of the Hysteresis band.
Should the boiler be switched OFF on the display screen, the frost protection function is still active.
Note:
- Frost protection is
only
available on the Shunt Pump.
8.5.6
Stand-by
Logging data - the control will log data to provide information for both User and Service Engineer. This logged
data can be used to correct an error or block and consists of:
•
Total gas consumption
•
Running hours, with power equal to or less than 50% of its maximum setting.
•
Running hours with power greater than 50% of its maximum setting.
•
Total ignition attempts
•
Fault ignition
•
Last 10 errors/blocks
