12
Installation and Servicing
Section 1 - General
1.15 OPEN VENT SYSTEM REQUIREMENTS
1.16
S
CHEMATIC PIPEWORK AND SYSTEM BALANCING
The boiler does not normally need a bypass but at least
some radiators on the heating circuit, of load at least 10%
of the minimum boiler output, must be provided with twin
lockshield valves so that this minimum heating load is always
available.
Balancing
1. Set the programmer to ON for both CH and HW. Turn
the cylinder thermostat down. Close the manual or
thermostatic valves on all radiators, leaving the twin
lockshield valves (on the radiators referred to above)
in the open position. Turn up the room thermostat and
adjust these lockshield valves to give boiler flow and
return temperatures not more than 20
o
C apart. These
valves should now be left as set.
2. Open all manual or thermostatic radiator valves and
adjust the lockshield valves on remaining radiators to
give around 20
o
C temperature drop at each radiator.
3. Turn up the cylinder thermostat and adjust the cylinder
balancing valve so that the cylinder achieves a maximum
flow consistent with adequate flow to the radiators.
Check that with only the domestic hot water loop in circuit
a differential temperature of 25
o
C across the boiler is not
exceeded.
4. Adjust room and cylinder thermostats and programmer to
NORMAL settings.
System
Return
Auto
Air
Vent
The system should be vented directly off the boiler flow pipe,
as close to the boiler as possible. The cold feed entry should
be inverted and MUST be positioned between the pump and
the vent, and not more than 150 mm away from the vent
connection.
Note.
Combined feed and vent pipes may also be fitted.
There should be a minimum height 450 mm of open vent
above the cistern water level. The vertical distance between
the highest point of the system and the feed/expansion
cistern water level MUST not be less than 450 mm.
The pump must be fitted on the flow side of the boiler.
A suitable pump is a domestic circulator capable of providing
a maximum 20
o
C temperature differential across the boiler
with the whole of the heating circuit open (e.g. Grundfos
UPS 15/50, 15/60 or equivalent). With the minimum flow
circuit allowed by the controls the differential must not
exceed 25
o
C.
The vertical distance between the pump and feed/expansion
cistern MUST comply with the pump manufacturer’s
minimum requirements, to avoid cavitation. Should these
conditions not apply either lower the pump position or raise
the cistern above the minimum requirement specified by
Ideal Heating.
The isolation valves should be fitted as close
to the pump as possible.
It is recommended that an automatic air vent should be fitted
to the return connection.
Refer to Section
1.18
Refer to Section
1.14 & 2.11
