UK Manufactured Unvented Hot Water Cylinder Installation Guide
13
Cold Mains Pipework
Run the cold main through the building to the place where is to be installed. Take care not to run the cold
pipe near hot water or heating pipe work so that the heat pick-up is minimized. Identify the cold water
supply pipe and fit an isolating valve (not supplied). A 22mm BS1010 stopcock can typically be used but
a 22mm quarter turn full bore valve would be better as it does not restrict the flow as much. Do not use
“screwdriver slot” or similar valves.
Make the connection to the cold feed of the cylinder and incorporate a drain valve. Position the inlet control
just
above
the Temperature & Pressure Relief Valve (TPRV) mounted on the side of the cylinder. This ensures
that the cylinder does not have to be drained down in order to service the inlet control set. Ensure that the
arrow points in the direction of the water flow. Select a suitable position for the expansion vessel. Mount it to
the wall using the bracket provided.
Balanced Cold Connection
If there are to be showers, bidets or monobloc taps in the installation then a balanced cold supply is neces-
sary. There is a 22mm balanced connection on the inlet control set.
Fitting The Inlet Control Group
Excess pressure can lead to the cylinder bursting. The inlet control set supplied has an expansion relief valve
with a 15mm connection to allow it to be connected to the tundish. Make sure that there is sufficient space
for future maintenance and also for connection of the discharge pipe for the expansion relief valve.
It is essential that this connection is not covered or closed. The hot water expansion vessel should be hard
fixed into pipework and insulated.
Hot Water Pipework
Run the first part of the hot water distribution pipework in 22mm. This can be reduced to 15mm and 10mm
as appropriate for the type of tap etc. Your aim should be to reduce the volume of the hot draw-off pipework
to a practical minimum so that the time taken for the hot water is as quick as possible.
Do not use monobloc mixer tap or showers if the balanced cold connection is not provided. Outlets of this
type can back pressurise the unit and result in discharge.
Expansion Vessel
The expansion vessel receives the increased water volume when expansion takes place as the system heats
up and it maintains a positive pressure in the system. The expansion vessel contains a flexible diaphragm,
which is initially charged on one side with nitrogen, but can be topped up with air when required.
Select a suitable position for the expansion vessel. Mount it to the wall using the bracket provided and hard
fix into pipework and insulate. Ensure that the top of the vessel is accessible for servicing. The pipe connect-
ing the expansion vessel to the system should have a diameter of not less than 15mm and must not contain
any restrictions.
