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When either the programmer or the room thermostat stop calling for heat, the
controller senses loss of space heating demand and switches off the central heating
pump, P2.
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 SPACE HEATING MODELS 'R'
(FIGURES 2.2. & 2.4)
The space heating demand is controlled by the programmer and the room thermostat
and its operation is independant of the operation of the mCHP.
When both the space heating programmer and the room thermostat are calling
for heat, the controller senses these demands and switches on the mCHP pump, P3
and energises the 3-Port valve, V1, to open the central heating port. Therefore the
preheated water flows from the thermal store to the space heating circuit (i.e.radiators)
and returns back to the store via the mCHP unit.
When either the programmer or the room thermostat stop calling for heat, the
controller senses loss of space heating demand and it de-energises the 3-port flow
share valve to open HW port only switches off the central heating pump, P3 if mCHP
unit is not running to charge the thermal store.
The controller will also energise the 3-port valve to flow share mode (CH + HW) if the
store temperature falls below the pre-set value (see table 3.5) to provide hot water
priority and it will move the valve back to CH mode when store temperature is greater
than this pre-set value.
2.2.4 STORE HEATING WHEN SPACE HEATING
DEMAND IS NOT ACTIVE - ALL MODELS
The operation mode of the mCHP unit and the automatic electric boost (if enabled)
is controlled by the store temperature sensors S1/2, S5 and S6 and the heating
programmer. The store heating demand will only be accepted if either 'hot water' or
'space heating'demand is switched on by the programmer.If this is the case then,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.
Supplied By www.heating spares.co Tel. 0161 620 6677
SYSTEM DESCRIPTION 2.0
(d) The store heating demand ceases when both
(e) When the store heating demand ceases,the
(f ) If the store temperature exceeds 95ºC when
2.2.5 STORE HEATING'N'
MODELS-SPACEHEATING
DEMAND ACTIVE
The store heating demand will only 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.
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 if enabled.
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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.
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.
the store heating demand is active, the
controller will switch off all active heat
sources and activate the overheat safety trip
lockout.
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