8
THE SYSTEM – Page 8
The Envoy boiler has an aluminium alloy heat
exchanger therefore all systems need to be thoroughly
cleansed and the correct treatment added to the system
water.
The only system additives recommended by Potterton
are FERNOX-COPAL or GRACE DEARBORN-
SENTINEL X 100 and should be used in accordance
with the manufacturers instructions. This will include
use of the appropriate system cleanser.
The boiler must be used on INDIRECT FULLY
PUMPED systems only, which may be sealed or open
vented.
The system should be designed so that the maximum
static head does not exceed 30.5m (100ft) and a
minimum of 150mm (6in). See FIG. 4.
On all systems the pump live should be wired to the
boiler terminal block, it will then be controlled by the
pump over-run timer. This will ensure that the pump will
continue to run after boiler shut down if the water
temperature is high, thus preventing nuisance operation
of the overheat control.
It is important that where electrically operated zone
valves are used the boiler is wired so it does not cycle
when the zone valves are closed. Also, systems fitted
with controls that close both hot water and central
heating circuits while the boiler is still hot, must be fitted
with a by-pass circuit to dissipate residual heat from
within the boiler.
If a three port diverter valve is used as shown in FIGS.
4 & 5 a by-pass is not necessary since one circuit is
always open.
Where a pair of two port valves are used, a by-pass is
necessary. The total length of the by-pass circuit taken
from the boiler connections should be greater than 4
metres of 22mm pipe. It should be fitted with a
lockshield valve and be adjusted to maintain a minimum
flow through the boiler of 4.5 litres/mm (1 gal/mm)
see FIGS. 4 & 5.
Systems fitted with controls which allow the boiler to
operate when both the hot water and central heating
circuits are closed i.e. mechanically operated
thermostatic control valves, must be fitted with a by-
pass circuit capable of:-
1.
Dissipating a minimum of 1kW (3400 Btu/h).
2.
Maintaining a minimum water flow through the boiler
of 9 litres/mm (2 gal/mm).
A suggested method of meeting these requirements by
using a bathroom radiator fitted with two lockshield valves
is shown in FIGS. 4 & 5.
Drain off taps should be fitted in the pipework close to the
boiler and in the low points of the system.
NOTE
Although the system can be emptied using the drain off
taps installed in the pipework around the system, to
empty the boiler it is necessary to remove the drain off
cap positioned within the boiler case. See FIG. 2.
SEALED SYSTEMS
Installation
The installation must comply with the requirements of
BS.6798 1987 and BS.5449 Part 1. The B.G. publication
“British Gas Specification for Domestic Wet Central
Heating Systems” should also be consulted.
SAFETY VALVE
A non-adjustable spring-loaded safety valve, preset to
operate at 3 bar (451bf/in2) shall be used. It must comply
with BS.6759 Part 1 and include a manual testing device.
It shall be positioned in the flow pipe either horizontally or
vertically upwards and close to the boiler. No shut-off
valves are to be placed between the boiler and the safety
valve. The valve should be installed into a discharge pipe
which permits the safety discharge of steam and hot
water such that no hazard to persons or damage to
electrical components is caused.
PRESSURE GAUGE
A pressure gauge incorporating a fill pressure indicator,
covering the range 0-4 bar (60Ibf/in
2
) shall be fitted to the
system. It should be connected to the system, preferably
at the same point as the expansion vessel. Its location
should be visible from the filling point.
Summary of Contents for envoy 30
Page 4: ...4 TECHNICAL DATA PAGE 4 FIG 2 GENERAL ARRANGEMENT ...
Page 28: ...28 FAULT FINDING CHART 1 Page 28 ...
Page 29: ...29 FAULT FINDING CHART 2 Page 29 ...
Page 30: ...30 BOILER INTERNAL WIRING Page 30 ...
Page 31: ...31 BOILER WIRING LAYOUT Page 31 ...
Page 36: ...36 Back Page ...