Detailed recommendations for the water circulation
system are given in BS. 5449: Part 1 (for smallbore and
microbore central heating systems) and BS. 6700.
Draining taps must be located in accessible positions
which permit the draining of the whole system, including
the appliance and hot water storage vessel. Draining taps
should be at least 1/2in BSP nominal size and be in
accordance with BS. 2879.
The appliance boiler section should be connected to a
cistern water supply, subject to a maximum head of
18.25m.
A suggested fully pumped system is shown in Fig. 4.
However when deciding on the type of system -
NOTE
the
following requirements:-
1. The circulating pump
MUST
be running when the
boiler burner is
ON
.
2. The system MUST be capable of gravity feed to the
domestic hot water tank without the pump running.
This allows the cooker burner to provide domestic hot
water without the aid of the pump for summer use,
and in case of electrical failures.
FAILURE TO DO THIS WILL INVALIDATE THE
WARRANTY.
Refer to boiler section pressure loss curve - Fig. 3.
Circulation Pump
It is recommended that the selected pump be of a
proprietary type and manufacture, and be adequate to
give the required temperature differential between the
flow and return.
The pump should be able to meet the requirements of the
system design and be fitted in a readily accessible
position.
It may be positioned either on the boiler section flow or the
return depending on the system design.
The boiler section pressure loss curve, see Fig. 3
indicates the loss of head across the boiler section and
should be considered when selecting the correct pump
size.
Gravity Domestic Hot Water and Pumped Heating
The 28mm O.D. primary flow pipe must rise continuously
from the boiler section to the cylinder to ensure good
gravity circulation and extended to provide an open vent.
The 28mm O.D. primary flow and return pipes must not
exceed 10m in length. Pipe runs in excess of 5m must be
lagged.
To obtain Domestic Hot Water gravity circulation with the
circulating pump on, the special injector tee (supplied with
the appliance) must be connected to the heating/cylinder
return pipes with the outlet of the tee connected directly to
the boiler return pipe within 600mm.
NOTE: THIS PROVIDES DOMESTIC HOT WATER
FROM THE COOKER BURNER ONLY - WHEN THE
BOILER IS GOING THE PUMP MUST BE RUNNING.
UNDER NO CIRCUMSTANCES SHOULD THE BOILER
BURNER OPERATE WITHOUT THE PUMP RUNNING.
Fully Pumped System
The domestic hot water flow pipes may be pumped
provided that domestic hot water gravity circulation can
take place in the event of pump failure or loss of electrical
power or when the pump and boiler burner cuts out, either
due to circuit satisfaction or end of programme. See Fig.
4 for system schematic. The boiler section is suitable for
use with most types of central heating control systems.
Isolating Valves
Isolating valves (preferably of the keyless type) must be
fitted to the inlet and outlet of the circulating pump to
facilitate service and replacement of pump without
draining the system.
Hot Water Storage Vessel
It is recommended that an indirect 190 litre (40 gallon) hot
water storage cylinder of the double feed type e.g.
(Manufactured by Albion Cylinders) complying with the
BS. 1566 Part 1: DF Type 10.
WATER CIRCULATION SYSTEMS
Boiler Output
17.6kW (60,000 Btu/h)
10°C - 14°C
(18°F - 25°F)
Temperature differential across
the boiler
Water Flow Rate
1091 - 1515 litres/h
(240 - 333 galls/h)
4
Fig.3 - Pressure Loss Curve