8
Negative head systems
Negative head systems exist where insufficient natural flow of water goes to the outlet
because either the outlet or the pipework to the outlet are above the height of the base of
the cold water cistern. Most instances of negative head systems occur in loft conversions
or where the cold water cistern sits on the joists in the loft. If the distance between the
bottom of the cold water cistern and the highest point in the system after the pump is 2
feet (610mm) or less, it is also possible that a universal pump will be required. Salamander’s
universal range of pumps activate the pump automatically even where insufficient natural
flow exists.
UK CT pumps suitable for negative head operation are:
CT FORCE 15 TU, 20 TU, 20 SU, 30 TU and 30 SU, and CT Bathroom 60BU & 80BU.
Irish CT pumps suitable for negative head operation are:
CT FORCE 15 ITU, 20 ITU, 20 ISU, 30 ITU and 30 ISU, and CT Xtra 64HU, 69HU & 84HU.
Outlet
Outlet
Vent and
other services
Usable
capacity
Fit an
equilibrium
ball valve
Inlet
MAX
60°C
The hot connection
must be by an
approved top or
side entry flange
(Figure 3)
Negative
Head
If any pipe work to an outlet
is taken to within 610mm
of tank, the installation will need
to be fitted with a universal pump
Inlet
610mm
(2 feet)
Figure 6. Negative head system
The prefered hot
connection is an
appropriate flange
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