HISTORICAL NOTE
For a period during the late sixties and early seventies there was a tendency to do away with the open fire by building up the opening and depending on one boiler source for heating the dwelling.
In recent years the move has been to re-open the fireplace as an alternate source of heat and to give the room a focal point plus the advantage of good ventilation.
With this has come the realisation that the open fire with high output boiler or a cooker with a high output boiler would be very economical and versatile in use if it could be linked into the central heating system, or assist to supply, the entire demand for heating and domestic hot water.

TECHNICAL DIFFICULTIES
In principle the requirement to link two or more boilers into one heating system is relatively simple to arrange. In practice there are physical difficulties, possible dangers and in many cases high financial cost to the householder.
The difficulties lie in linking the boilers, so that one boiler when in operation does not supply the second boiler with hot water when it is not in operation. Attempts to link boilers in domestic situations have resulted in solutions which are either dangerous, expensive, complex or a combination of all three.

DUNSLEY BAKER NEUTRALIZER

NEUTRALIZER LOCATION
In converting an existing system most of the work is carried out within the cylinder cupboard, normally the C type Neutralizer is installed under the cylinder and the R type Neutralizer on the floor at the side of the cylinder, both work exactly the same.
Whichever Neutralizer you use the the location must be a minimum of 350mm above the solid fuel boiler to the bottom of the Neutralizer, this is to create a gravity circuit as shown in layout 2. There are nine connections on the Neutralizer, the top one is the vent, the side upper ones are the flow pipe connections and the bottom ones are the returns.
There are many configurations for linking boilers together, for example, in our Layout ref B89a, this is showing an un-vented cylinder but the system is designed so that the first floor heating circuit will work on gravity in case of a power failure or overheat situation, because an un-vented cylinder has to be pumped it can be installed on any floor above or below the Neutralizer.
Please Note: The Neutralizer will not work on a sealed central heating system.

OPERATION OF THE SYSTEM
Our layout 2 is the most popular one, the cylinder and gas/oil boiler are controlled through the special Sunvic Motorised Valve with auxiliary switch. Example: When the hot water channel only is switched on the gas boiler will heat up the cylinder to set the temperature of the cylinder thermostat, the Sunvic valve will then close and the auxiliary switch will shut down the gas/oil boiler. The gas boiler will switch on again when the cylinder is calling for hot water, this also stops the gas/oil boiler from cycling. For central heating both hot water and central heating slides require to be in the ON position.
Please note: To follow our wiring circuit a Honeywell ST699 or ST799 programmer must be used.

SOLID FUEL BOILER
The solid fuel boiler must have 28mm flow and return pipes up to the Neutralizer to create a gravity circuit. Solid fuel boilers which are controlled by a water sensing thermostat require the water accelerating shown in fig. 1 and fig 1a in our installation instructions.
To stop the solid fuel boiler reaching an overheat situation a high limit pipe stat set at 85 degrees C is strapped onto the side of the Neutralizer and wired to make on rise, this will over-ride any other control and switch on the central heating pump.

The Dunsley Baker Neutralizer System is the invention of John Baker, UK Patent No. 2113364, and is manufactured in Great Britain by DunsleyHeat Ltd.