Feed and Expansion Tank | 22mm Open Vents | |
Cold Water Tank | ||
|
Overflow |
|
| Overflow |
|
|
| |
|
|
| Domestic Hot Water Draw Off |
Gravity Radiator |
|
|
|
| Gravity Return 28mm | Gravity Flow 28mm | Drain Cock |
| Indirect Hot Water Cylinder | ||
| High Limit Thermostat | ||
Low Limit | Central Heating Flow | ||
Thermostat |
|
| Circulating Pump |
|
|
|
Central Heating Return
Drain Cock at Lowest Point
Fig. 4. Typical Central Heating & Hot Water System
Using 4 Boiler Tappings
22mm Open Vents
inches) each side and 300mm (12 inches) above the appliance should give sufficient air circulation. If a wooden mantelpiece or beam is used in the fireplace it should be a minimum of 460mm (18 inches), and preferably 600mm (24 inches) from the appliance. In some situations it may be necessary to shield the beam or mantelpiece to protect it.
CENTRAL HEATING
SYSTEM
The central heating system must comply with BS:5449 part 1.
If the system is to be a combined heating and domestic hot water system then a double feed indirect hot water storage cylinder to BS:1556 part 1 should be used. In order to prevent the build up of scale and corrosion a suitable inhibitor should
Feed and Expansion Tank
Overflow |
|
|
Gravity Radiator | Return 28mm | Flow 28mm |
| ||
Low Limit Thermostat | Gravity | Gravity |
Circulating Pump |
|
|
Central Heating Return |
|
|
Drain Cock at Lowest Point |
|
|
Cold Water Tank
Overflow
Domestic Hot Water Draw Off
Drain Cock
Indirect Hot Water Cylinder
High Limit Thermostat
Central Heating Flow
be used. The system must be correctly vented as shown in Figs. 4 and 5. The height differential between the header tank and the appliance must not exceed 15.2 metres (50 feet).
If all four boiler tappings are used then, if possible, diagonal pairs should be connected for domestic hot water and central heating. Where a common return is used an injector tee must be incorporated into the system as shown in Fig. 6. This will ensure that a good domestic hot water supply is maintained when the central heating pump is operating.
The system must incorporate a gravity circuit which will normally
Injector Tee
Fig. 5. Typical Central Heating & Hot Water System
Using 3 Tappings
Gravity Return
(28mm Pipe)
Central Heating Return | Common Return to Boiler |
| (28mm Pipe) |
Fig. 6. Injector Tee.
Page 7
heat the domestic hot water and an unvalved radiator with an output of at least 1 kW. When the appliance is not connected to a domestic hot water system the unvalved radiator(s) on the gravity circuit must have an output of at least 1.25 kW. This is to prevent boiling in case of pump failure. All pipework in the primary circuit must be 28 mm diameter and the gravity flow pipe must rise continuously from the boiler to the open vent. Two typical systems are shown in Figures 4. and 5.
Country 8B WB 10/00
