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if the store temperature falls below the pre-set limit (see table 3.5), the controller will
either switch off the space heating pump or run it at minimum speed if modulating
pump is fitted. The normal space heating pump operation will resume when the store
temperature is greater than this pre-set limit. This is to provide a degree or priority
to domestic hot water during high space heating demands.
The modulating central heating pump can be specified as an option. When this option
is specified, the pump will modulate to control the space heating return temperature
to a pre-set value.
2.2.3 STORE HEATING WHEN SPACE HEATING
DEMAND IS NOT ACTIVE
The operation mode of the mCHP unit and the automatic electric boost is controlled
by the store temperature sensors S1/2, S5 and S6 and the heating programmer. The
store heating control logic depends upon the status of the space heating demand
and is described below. The control set points are shown in table 3.5.
(a) When the store temperatures T5 and T6 measured by sensors S5 and S6 are less
than the S5 ON and S6 ON set points, the controller switches on the mCHP pump,
P3 and sends the start /run signal to the mCHP unit.
(b) When the store charging demand is active and the average top store temperature
(T1 + T6)/2 is less than 'T_hw_boost_on' set point, the controller switches the mCHP
unit to the boost run mode.
(c) When the store charging demand is active and the average top store temperature
(T1 + T6)/2 is greater than 'T_hw_boost_off' set point, the controller switches the
mCHP unit to its normal run mode.
(d) The store heating demand ceases when both store temperatures T5 and T6 are
greater than S5_OFF and S6_OFF set points or if the programmer switches off the
'hot water' demand.
(e) When the store heating demand ceases, the controller will send the stop signal to
the mCHP unit and switch off the mCHP pump after the overrun period determined
by the mCHP appliance.
(f ) if the store temperature exceeds 95ºC when the store heating demand is active, the
controller will switch off all active heat sources and activate the overheat safety
trip lockout.
2.2.4 STORE HEATING - SPACE HEATING
DEMAND ACTIVE
The store heating demand will only operate be accepted if either 'hot water' or 'space
heating' demand is switched on by the programmer.
When both store temperatures T5 and T6 measured by sensors S5 and S6 are less than
the S5_ON and S6_ON set points, the controller will switches on the mCHP pump, P3,
and sends the start signal to the mCHP unit.
When both store and space heating demands are active and the average store
temperature is less than 'T_CH_boost1_On' set point and the rate of temperature rise
in the store is less than the R_CH_boost1 set point, the controller will send the signal
to the mCHP to run in boost mode.
SYSTEM DESCRIPTION 2.0
Page 9
When both store and space heating demands
are active and the average store temperature
is greater than 'R_CH_boost1_Off' set point
and the rate of temperature rise in the store is
greater than the R_CH_boost1 set point, the
controller will send the signal to the mCHP to
run in normal mode.
When both store and space heating demands
are active and the average store temperature is
less than 'T_CH_boost2_On' set point and the
rate of temperature rise in the store is less than
the R_CH_boost2 set point, the controller will
switch on the electric boost heater.
When both store and space heating demands
are active and the average store temperature
is greater than 'T-CH_boost2_Off' set point
and the rate of temperature rise in the store is
greater than the R_CH_boost 2 set point, the
controller will switch off the electric boost.
The store heating demand ceases when both
store temperatures T5 and T6 are greater than
S5_OFF and S6_OFF set points.
When the store heating demand ceases, the
controller will send the stop signal to the mCHP
unit and switch off the mCHP pump after the
overrun period determined by the mCHP
appliance.
if the store temperature exceeds 95ºC when the
store heating demand is active, the controller
will switch off all active sources and activate
the overheat safety trip lockout.
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