18
Mexico Slimline RS 3/40 & 3/50 -
Installation
INST
ALLA
TION
INSTALLATION
20 HONEYWELL 'C' PLAN
Gravity HW & Pumped CH
Notes.
1.
Some earth wires are omitted for
clarity. Ensure proper earth
continuity when wiring
2.
Numbering of terminals on
thermostats is specific to the
manufacturer.
21 FROST PROTECTION
LEGEND
w
white
r
red
bk
black
br
brown
or
orange
b
blue
gy
grey
g/y
green/yellow
Central heating systems fitted wholly inside
the house do not normally require frost
protection as the house acts as a 'storage
heater' and can normally be left at least 24
hrs. without frost damage. However, if parts
of the pipework run outside the house or if
the boiler will be left off for more than a day
or so then a frost 'stat should be wired into
the system.
This is usually done at the programmer, in
which case the programme selector
switches are set to OFF and all other
controls MUST be left in the running
position.
The frost 'stat should be sited in a cold
place but where it can sense heat from the
system.
Wiring should be as shown, with minimal
disturbance to other wiring of the
programmer.
Designation of the terminals will vary, but
the programmer and thermostat
manufacturer's leaflets will give full details.
Diagram A
shows a double pole frost thermostat, which should
suffice for all systems which do not use the OFF terminals of the
programmer.
Diagram B
shows a 'change-over' frost thermostat, which will cover
most systems which do use CH OFF. If, however, on such a system
the HW pipework is in an isolated part of the house, a second frost
thermostat may be used to protect it.
If in doubt, ask your installer for advice.
