1.6 System D Heat Bank Thermal Stores operate with the standard Sealed Y-Plan layout, using a Motorised Valve(s) to divert the Boiler Flow to either the Heat Bank Thermal Store or to the Radiator Circuit, or to both simultaneously. The Heat Bank Thermal Store remains unpressurised.
1.7 The Heat Bank Thermal Store uses an Indirect Primary Heating Coil to transfer heat to the stored water.
1.8 The Heat Bank Thermal Store is fitted with an Expansion Vessel (8 litre standard) for the Primary Circuit, which is sealed and pressurised. All standard Sealed System Controls are fitted including a Pressure Relief Valve with Pressure Gauge & Filling Loop.
1.9 The unit is also fitted with a Primary Pump, Cylinder Thermostat, Flow Controls, and backup Immersion Heater. A Room Thermostat and Electronic Programmer are supplied loose for site fixing. Fitted controls are pre-wired to a System Wiring Centre.
1.10 This Heat Bank Thermal Store unit is manually filled. There is no ball valve to automatically top up the store. This has the advantage of removing the requirement for an overflow.
1.11 The wiring centre on the front of the unit is fitted with a neon warning light that tells the house-holder when to top up the unit with water. Hot water will also be unavailable until the unit is topped-up.
1.12 The Feed and Expansion Tank is fitted with a low absorption polystyrene disk, that floats on the surface of the water, preventing evaporation.  It is important that this is not removed as increased evaporation will result in more frequent top-ups.

The Vent Pipe is fitted with a lock-shield valve, and a level indicator (drain cock).  The lock-shield valve has a drilled hole to allow air to vent when the valve is shut, but will prevent surges of hot water into the F&E Tank. During filling the lock-shield valve is to be opened to allow air to vent quickly.  Also during filling,  the level indicator should be used to set the correct water level in the F&E Tank.  It is important that excess water is drained off, as overspill may occur when the unit first heats up and the water expands.