Boiler With External Controls - Keston HEAT 2 45 Installation & Servicing

2.25 BOILER WITH EXTERNAL CONTROLS

1. If the boiler circulating pump is not controlled by the boiler
then the overrun time of this pump MUST be set to a
minimum of 30 seconds. Failure to do so may invalidate
the warranty.
2. It is preferable that any pump used to circulate water
through an individual boiler is controlled by the local boiler.
Either as a 230V 50Hz supply as shown, enabled by the
Volts Free Contacts e.g. MFR1 or controlled by the option
kit for 0-10V pump control. If not then a pump overrun
function MUST be provided by the controlling system.
Input - SL1, SL2
Input - 0-10V
Sensor - Outside
Sensor - Header
Sensor - Room
Sensor - DHW Tank
Output - MFR1..4 output
Bus - OT1, OT2
Bus - VariCAN
External controls via switched live demand
Showing internal Boiler Pump controlled directly from PELV PWM control
I1
L N PE
Mains Supply
1 2 3
Fused Spur
/ Isolator
L N
Mains Supply
32
SECTION 2 - INSTALLATION
Electrical Specifications for External Connections
Voltage
230V 50Hz
0 to 10V DC
24 V DC to 230V 50Hz
230V 50Hz
230V 50Hz
External Controls via Switched Live Demand
Boiler pump controlled directly from MFR1
Mains Voltage/230V 50Hz
I2 I3
SL1 L SL2 L ~
230V 50Hz
Demand inputs Interlock
1 2 3 4 1
Switched Live
/ Volts Free
Contact
PE
External Controls
3. The pump load and switch on surge current must be within
the limits of the output if it is powered directly from the Volts
Free Contact. The limits are as specified in the Electrical
Specification Table below.
A slave contactor may be used to power the pump where
needed.
4. If the switched live is provided without a Volts Free Contact
then this MUST be taken from the same phase as the
boiler mains supply, preferable through the same isolator.
5V DC
OpenTherm V 4.0
CAN Open, proprietary protocol
I4 I5
~ L N C NO PE
230V 50Hz
Auxiliary MFR1
2 1 2 1 2 3
Internal Boiler Pump
Load
3kΩ min
5mA max
10kΩ @ 25ºC β(25/85)=3977
1.0 A max at CosØ = 0.6
Peak Surge 20A < 20ms
Peak Transient 100A < 10uS
Volts Free Contacts
I6
C NO PE C NO C NO
MFR2 MFR3 MFR4
4 5 6 1 2 3 4
PELV PWM pump connection
continued............
Installation & Servicing