THE REALLY SIMPLE WAY TO LINK A STOVE TO CENTRAL HEATING -
Heat your home with renewable, carbon-neutral, logs. Keep your automatic control, keep your combi boiler and instant hot water... and save money
The Fire-Owl unit is a device which allows two (or more) central heating boilers operating at different pressures and temperatures to work together.
The Fire-Owl looks like a tiny, insulated, hot-water cylinder. It is actually a 'neutral-point manifold' - a specially sized and shaped water chamber with connections for pairs of flow and return water pipes. No matter what volume and pressure each flow pipe displaces into the unit, its matching return pipe must always displace the exactly negative amount out. No matter what temperature water arrives at the unit, natural convection will always balance the temperatures - hot at the top and cooler at the bottom.
Inside the Fire-Owl is a coil heat exchanger capable of withstanding a pressure of up to 4 Bar, this allows a pressurised boiler - like most combi boilers - to heat up the unit without its water impinging on other sources.
How it works:
With the stove unlit, the combi boiler works normally to supply heating - controlled by timeclock and room thermostats - and hot water normally. The only difference from normal operation is that the boiler first heats the Fire-Owl Unit before supplying heat to radiators.
When the stove is lit, a thermostat detects the hot water in the stove boiler and turns on a pump to circulate the heated water to the Fire-Owl unit. As soon as the Fire-Owl gets hot inside, its thermostat turns on the pump to move water to the radiators. Then, the thermostat built-in to the combi boiler will shut off, or reduce, its fuel consumption. OR, if a whole-system room thermostat is located where it can detect heat from the stove, it will completely shut-off the combi boiler, leaving the stove boiler to do all the work by itself. In most installations, where stove boilers have a relatively large room-heating output, and small boiler output, this will leave the stove room fully heated and the rest of the house provided with background heat only, giving a very substantial energy saving. Hot tap water will still be supplied on demand by the combi boiler.
IMPORTANT: This document explains the function of the Fire-Owl unit, any installation is still required to conform to all local, national and European rules.
INSTRUCTIONS, ILLUSTRATIONS AND EXAMPLES ARE INCOMPLETE OUTLINES FOR GUIDANCE ONLY - THE INSTALLER IS EXPECTED TO BE A COMPETENT HEATING ENGINEER ABLE TO ADAPT THE SUGGESTIONS TO INDIVIDUAL CIRCUMSTANCES. PLEASE REFER TO Standard EN 12828:2003.
For use on indirect, open-vented, systems only up to 35kW. Maximum pressure: 2bar (4Bar in pressure coil only)
To install the Fire-Owl Unit to a combi boiler and a hearth boiler stove you will need, in addition to the Fire-Owl Unit and piping:
A pipe thermostat - A cylinder thermostat - Two (2) circulating pumps - A feed and expansion tank and fittings
CLICK TO ENLARGE...
FEED AND EXPANSION PIPE: There must be an absolutely clear, continuously rising, pipe of at least 28mm diameter from the top connector on the Fire-Owl Unit to an open 20 litre (or more) expansion vessel. The Fire-Owl unit acts as a a heat sump, there is no need to fit a 'heat-leak'.
COMBI BOILER TO Fire-Owl: The flow and return pipes from the combi boiler, the pumped supply to radiators, connect to the pressure coil on the Fire-Owl Unit. This connection may require a bleed valve to ensure no air is trapped.
STOVE TO Fire-Owl: The stove flow pipe is connected to any one of the upper connectors on the Fire-Owl Unit, and the return pipe to any of the lower connectors. The pipe MUST rise continuously and have no obstructions, valves or dips of any sort. A pipe thermostat is fitted to the flow pipe near to the stove boiler to switch ON a pump to circulate this circuit above about 50°C
HEATING CIRCUITS TO Fire-Owl: Up to four heating circuits can be connected to the Fire-Owl Unit, each with its flow pipe to any one of the upper connectors on the Fire-Owl Unit, and the return pipe to any of the lower connectors. A cylinder thermostat detects the temperature at the top of the Fire-Owl Unit (remove a section of insulation) and always turns ON a pump to circulate this circuit above about 60°C
SYSTEM CONTROLS: Connect time-clock and room thermostat to the combi boiler only, in the usual way. If the room thermostat senses temperature in the stove room, it will close down the combi boiler when the stove is lit, leaving the heating to be operated by the solid fuel stove alone. In most installations this will give full heat in the main room and background only elsewhere - the best combination for cost-saving.
SAFETY: Any solid fuel boiler can boil if a fault occurs - there MUST be permanent clear route to release steam and pressure from the boiler to the expansion tank.
Telford Copper Cylinders & Stainless Ltd.
Furrows Business Park, Haybridge Road,
Telford TF1 2FE Tel: 01952 257961