Supplied By www.heating spares.co Tel. 0161 620 6677
4.0 System Details
8
4.1
Water Circulating Systems
Water Circulating Systems
1. The appliance is suitable for fully pumped
sealed systems only.
The following conditions should be observed
on all systems:
•
The boiler must not be used with a direct
cylinder.
•
Drain cocks should be fitted to all system low
points.
•
All gas and water pipes and electrical wiring
must be installed in a way which would not
restrict the servicing of the boiler.
•
Air vents should be fitted to all system high
points.
•
All components used in the system must be
suitable for operation at 110
°
C (230
°
F).
4.2
Treatment of Water Circulating Systems
•
All recirculatory water systems will be subject to
corrosion unless an appropriate water treatment is
applied. This means that the efficiency of the system
will deteriorate as corrosion sludge accumulates
within the system, risking damage to pump and
valves, boiler noise and circulation problems.
•
For optimum performance after installation this
boiler and its associated central heating system must
be flushed in accordance with the guidelines given in
BS 7593:1992
“
Treatment of water in domestic hot
water central heating systems
”
.
•
This must involve the use of a proprietary cleanser,
such as BetzDearborn Sentinel X300 or X400, or
Fernox Superfloc. Full instructions are supplied with
the products, but for immediate information please
contact BetzDearborn (0151 420 9563) or Fernox
(01799 550 811) directly.
•
For long term protection against corrosion and
scale, after flushing it is recommended that an
inhibitor such as BetzDearborn Sentinel X100, or
Fernox MB-1 or Copal is dosed in accordance with
the guidelines given in BS 7593:1992.
Failure to flush and add inhibitor to the system
may invalidate the appliance warranty.
•
It is important to check the inhibitor concentration
after installation, system modification and at every
service in accordance with the manufacturer
’
s
instructions. (Test kits are available from inhibitor
stockists.)
•
For information or advice regarding any of the
above contact the Baxi Helpline.
4.3
Bypass Requirements
1. The boiler is fitted with a pump overrun device
which allows the removal of residual heat from the
boiler.
NOTE:
The pump overrun will operate for
approximately 8 minutes. The system design must
therefore always provide an open circuit for water
to circulate between the boiler flow and return.
Typical Systems
Arrangement
Option A
Boiler
Air Vent
Radiator
Circuit
Fully Pumped System
Air
Vent
Radiator
Circuit
Twin Zone
Valve System
Air
Vent
Radiator
Circuit
3 Port Divertor
Valve System
Option B
Radiator
Circuit
Option C
Fig. 4a
Fig. 4b
Fig. 4c
Fig. 4d
Examples of systems which require a
bypass are:-
a) A system controlled by non-electrical
valves e.g. mechanical thermostatic control
valves both on the radiators and the hot
water circuit.
b) A system using twin zone valves (e.g.
Honeywell 'S' Plan) (Fig. 4c).
c) A system using a 3 port divertor valve
(Fig. 4d) does not normally require a
bypass therefore this system is
recommended. The exception to this is
where thermostatic radiator valves are used
and then a bypass is required.
NOTE:
For
‘
S
’
Plan systems the bypass
flow circuit must be situated between
pump and zone valves as option A
shows (Fig. 4b).
The bypass circuit can be:-
a) For all boilers a minimum of 6 metres of
22mm copper pipe, (measured between the
boiler flow and return connections). It
should be fitted with a lock shield valve
opened at least 1 full turn or a proprietary
bypass valve set to give a minimum flow
rate of 8 litres/min (1.8 gal/min) (Option C,
Fig. 4a & Option A, Fig. 4b).
b) A radiator fitted with lock shield valves.
The radiator output should be a minimum of
800 watts (2,700 Btu/h). Typically a
convector type radiator with an area of
3750 cm
2
(4 sq ft) is adequate (Option B,
Fig. 4a).
c) Any circuit that provides the same
operating conditions as option A or option B
(Figs. 4a & 4b).
