Jet 120i, Installation & Servicing Instructions Manual, Page: 5 / 24

5
Installation General
Pipe Fittings
All pipe fittings are made via 22mm compression
fittings directly to the unit. The fittings are threaded
3/4”BSP male parallel, should threaded pipe
connections be required.
Cold Feed
A 22mm cold water supply is recommended, however,
if a 15mm (1/2”) supply exists, which provides sufficient
flow, this may be used (although more flow noise
may be experienced).
A stopcock or servicing valve should be incorporated
into the cold water supply to enable the cylinder and
its associated controls to be isolated and serviced.
Cold Water Combination Valve Assembly
The inlet combination valve can be connected
anywhere on the cold water mains supply prior to
the unvented cylinder. There is no requirement to
site it close to the unit, it can be located at a point
where the mains supply enters the premises if this
is more convenient (see Fig 05, page 11). The cold
water combination valve is installed as a complete
one-piece unit. The valve incorporates the pressure
reducer, strainer, expansion valve and check valve.
Ensure that the valve is installed with the direction
of flow arrows pointing in the correct direction. No
other valves should be placed between the cold
water combination valve and the cylinder. The
expansion relief valve should be installed with the
discharge pipework in either the horizontal position
or facing downwards, if fitted inverted, debris may
be deposited on the seat and cause fouling of the
seat. A Balanced cold water port available
Drain Tap
A suitable drain tap should be installed in the cold
water supply to the cylinder between the expansion
valve (see Fig. 05, page 11) and the heater at a lower
level as possible. It is recommended that the outlet
point of the drain pipework be at least 1 metre
below the level of the heater (this can be achieved
by attaching a hose to the drain tap outlet spigot).
Secondary Circulation
If secondary circulation is required it is recommended
that it be connected to the cylinder as shown
(see
Fig. 06, page 11) v ia a swept tee joint into the cold
feed to the unit. A swept tee joint is available as an
accessory (order code no. 5133565).
The secondary return pipe should be in 15mm pipe
and incorporate a check valve to prevent backflow.
A suitable WRAS approved circulation pump will be
required. On large systems, due to the increase in
system water content, it may be necessary to fit an
additional expansion vessel to the secondary circuit.
This should be done if the capacity of the secondary
circuit exceeds 10 litres.
Pipe capacity (copper):
15mm O.D. = 0.13 l/m (10 litres = 77m)
22mm O.D. = 0.38 l/m (10 litres = 26m)
28mm O.D. = 0.55 l/m (10 litres = 18m)
Outlet
The hot water outlet is a 22mm compression fitting
located at the top of the cylinder. Hot water distribution
pipework should be 22mm pipe with short runs of
15mm pipe to terminal fittings such as sinks and
basins. Pipe sizes may vary due to system design.
Figure 02: Cold Water Combination Valve Assembly
Expansion valve
(8 bar)
Cold mains
connection
(22mm)
Expansion valve
outlet (15mm)
Outlet connection
(22mm)
Direction of
flow
Balanced take
off port
Pressure reducing
valve cartridge
(3.0 bar)