22
Indirect system
Boiler Selection
The Andrews water heater, indirect models are suitable for use with most gas or oil fired boilers compatible with
unvented systems i.e. fitted with a temperature control thermostat and thermal cut-out. If in doubt consult the boiler
manufacturer. Solid fuel boilers or any other boiler in which the energy input is not under effective thermostatic control,
unless additional and appropriate safety measures are installed, SHOULD NOT be used. The boiler used can either be
a sealed system or open vented type, maximum primary circuit pressure 10 bar. The primary flow from the boiler MUST
be pumped. Gravity circulation will not work due to the special design of the primary heat exchanger. It is recommended
that an air bleed point or automatic air vent is incorporated in the primary return pipework close to the cylinder. The
boiler flow temperature should usually be set to 82ºC (maximum flow temperature to primary heat exchanger 89ºC). The
boiler cannot be vented through the cylinder.
Indirect thermal cut-out and 2-port motorised valve
To comply with building regulations, and to prevent the Andrews water heater from overheating the 2-port motorised
valve supplied MUST be fitted to the primary flow to the indirect coil. It must be wired such that in the event of the
cylinder over heating it will close the primary circuit.
Wiring
All electrical wiring should be carried out by a competent electrician and be in accordance with the latest I.E.E. Wiring
Regulations BS 7671 , current edition.
IT IS RECOMMENDED THAT ALL WIRING TO THE IMMERSION HEATERS IS OF A FIXED TYPE.
DO NOT OPERATE THE IMMERSION HEATER(S) UNTIL THE CYLINDER HAS BEEN FILLED WITH WATER.
Safety
DO NOT BYPASS THE THERMAL CUT-OUT(S) IN ANY CIRCUMSTANCES
DISCONNECT FROM THE MAINS SUPPLY BEFORE REMOVING ANY COVERS
NEVER ATTEMPT TO REPLACE AN IMMERSION HEATER OTHER THAN WITH THE RECOMMENDED SPARE PART
Temperature control
clockwise to increase,
counter-clockwise to
decrease
Thermal cut-out
reset under cap
0
30
40
50
60
70
°C
Figure 8: Indirect controls
