7
Installation
Specifications
Trouble shooting
PumpWise
Warranty
Negative head systems
Negative head systems are where no natural
flow of water goes to the shower head
because it is above the height of the base
of the cold water tank. Most instances
of negative head systems occur in loft
conversions or where the cold water tank
sits on the joists in the loft. If the distance
between the bottom of the cold water tank
and the shower head is 2 feet or less it is also
possible that a negative head pump will be
required. The negative head range of pumps
activate the pump automatically even where
no natural flow exists.
FORCE pumps suitable for negative head
operation are the FORCE 15 TU, 15 ITU,
20 TU, 20 ITU, 20 SU, 20 ISU, 30 TU, 30 ITU,
30 SU and 30 ISU.
Figure 7. Negative head system
2 litres/min
natural flow
Other
supplies
Usable
capacity
Fit an
equilibrium
ball valve
The hot
connection
must be by
an approved
top or side
entry flange
(Figure 3)
Negative head
Other services
Cold water storage
The hot connection
must be via a
¾”
No Stop Essex flange
Inlet
Inlet
Outlet
Inlet
Vent and
other services
Outlet
Outlet
Outlet
C
H
MAX
65
˚C
MAX
65
˚C
C
H
Inlet