Baxi 35/80 IE, Installation & Servicing Instructions Manual

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1. The system should include a domestic hot water cylinder thermostat, room thermostat,
timer and zone valve(s).
2. A system frost protection thermostat is shown in each diagram. This is in addition to the
boiler frost protection thermostat that is integral to the appliance.
3. When the boiler selector switch is in the central heating and domestic hot water position
there will be a 230V supply at terminal 1 of the boiler terminal strip.
4. The boiler incorporates a domestic hot water thermostat that allows a maximum
temperature of 65°C.
For this feature to operate the boiler requires a switched live feed
to the domestic hot water relay PCB.
5. Methods of wiring several typical heating schemes are shown. In Scheme 1 the boiler does
not differentiate between central heating and domestic hot water demands. With Schemes 2,
3 & 4 the boiler utilises the benefit of the integral domestic hot water thermostat referred to
above which overrides any temperature requirements of the central heating control(s).
6. It is recommended that the central heating temperature control is always set at maximum.
Scheme 1
IMPORTANT: For wiring to the DHW Water Relay please see Section 8.10 .
b - blue
w - white
o - orange
gr - grey
g/y - green/yellow
Scheme 1
7. Scheme 1 shows the use of a 3 port mid position zone valve and is based on a 'Y' plan
system. The boiler will provide hot water to the central heating system, domestic hot water
store or both.
8. A live feed to terminal 2 of the boiler terminal strip controls the boiler. This feed is taken
from either the DHW cylinder thermostat or via the mid position valve depending upon
demand.