When solid fuel only has been selected. The link-fuel valve will be closed and the solid-fuel valve will be open and the system will operate as follows:
1. No demand within the system slumber valve open to allow full bore gravity circulation to the slumber circuit. Safe operation of solid-fuel appliance without overheating of space or domestic hot water. Heating valve and domestic hot water valve closed, pump off.
2. Heating only: pump on, slumber and hot water valves closed, heating valve open to allow heating to be provided.Water pumped around the slumber circuit through adjustable gate valve.
3. Hot water only: pump on, slumber and heating valves closed, hot water valve open to allow circulation to the domestic hot water. Water pumped around the slumber circuit through adjustable gate valve.
4. Both heating and hot water: pump on, slumber valve closed, heating and hot water valves open to allow circulation throughout the whole of the system. Water pumped around the slumber circuit through the adjustable gate valve.
5. If the temperature of the water exceeds the high-limit setting at any time the safety controls will take effect. Then pump on, slumber valve closed whilst either heating or hot water valve will open to allow for excess heat to be dissipated into either the hot water or heating and slumber circuits, as selected. The high-limit thermostat will automatically reset when the temperature of the water has reduced and the system will return to normal operation.
When the link-fuel has been selected the system operates in conjunction with the limit thermostats:
1. When flow temperature from solid-fuel appliance is below the mid-limit, the linkfuel boiler is brought into use.The slumber valve is closed, link-fuel and solid-fuel valves open and either heating, or hot water, or both, valves open to satisfy demand of the system.Water is supplied to the slumber circuit through the adjustable gate valve and both the pump and link-fuel boiler are on. Operation of the system is switched between the solid-fuel and link-fuel by the mid-limit thermostat.
2. When flow temperature from solid-fuel appliance is between the mid- and high-limit temperatures then the link-fuel boiler is switched off. Full use is made of the output from the solid-fuel appliance only, hence achieving maximum use of the solid-fuel appliance and economizing on other fuels. Link-fuel valve closed.
3. If the flow temperature from the solid-fuel appliance exceeds the high-limit setting then the link-fuel boiler is switched off. Slumber and link-fuel valves close, solidfuel valve opens as well as either heating or hot water valve, depending upon selection of either heating or hot water for dissipation for excess heat. Pump is on to remove excess heat through the chosen circuit and also through the slumber circuit via the adjustable gate valve.
4. The low-limit thermostat provides control of the solid-fuel appliance at low temperature.
(a) Temperatures below the low-limit setting, solid-fuel valve will be closed.
(b) Temperatures above the low-limit setting, solid-fuel valve will be open.
(c) Any requirement for heating or hot water will be met by the link-fuel boiler exactly as Item 1 above.