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Technical Data
Sheet No.1
Negative Head Systems
What Is Negative Head?
A
Negative Head Situation exists where the pumped outlet is in a position level
or above the level of the cold water storage tank.
Since conventional Techflow pumps
require some gravity flow to activate the pump switching mechanisms, they
cannot start under these circumstances and will require some form of external
switching to initiate pump start up. This can be achieved in a variety of ways
as  explained in
The Techflow Products Solutions.
You will note from the diagram
opposite which shows a typical automatic switching installation (AS) that the
pump still has to be installed in a positive head position in order to ensure
that the inlets of the pump are flooded.
There are other situations that can
exist where conventionalTechflow pumps cannot start without external
assistance. These situations exists where the outlet devices, taps, mixers,
valves, etc. are too restrictive to allow sufficient gravity flow to lift the
float switches. In these circumstances a Negative Head System is
required.
When fitting a Techflow Negative Head
System dedicated hot and cold supplies are required using the appropriate
anti-aeration flange and 22mm inlet pipe work.
The Techflow
Products Solutions
All SINGLE and TWIN Pumps are available with one
of the following switching systems:
'AS' (Automatic
Switching)
This is a fully automated switching
system which senses pressure drop when a tap, shower valve, etc. is opened.
Each pump is supplied complete with a sensing unit which is fitted to the pump
outlet and offers the following features:
| o |
** |
Unique system
ensuring that both hot and cold outlets can be operated independently using a
single switching unit. |
| o |
** |
Integral by-pass
system to protect pump when one side runs against a closed outlet. |
| o |
|
Suitable for whole
house pumping applications. |
| o |
|
Compact pre-wired
system. |
| |
|
** Applicable to twin ended
Pumps only. |
'MSA' (Manual
Switching - Air Switch)
The Pump is supplied with a flush
mounted push-button air switch which is operated once the shower valve or tap
is opened to 'kick-start' the pump. The system includes the following
features:
| o |
|
Pump stops once
shower valve is closed without further need to operate air-switch |
| o |
|
Flush mounted
push-button switch available in chrome or gold finish |
| o |
|
Intrinsically safe
switching in bathroom environment without need for a power supply |
| o |
|
Pump supplied
complete with 5 metres of air-line pre-assembled |
| o |
|
Optional 5 metre
extension kit available providing 10 metre operating range |
'MSP' (Manual
Switching - Pull Cord)
The Pump is operated from a ceiling
mounted pull-cord switch which is used to 'kick-start' the pump once the shower
valve or tap is opened. The following features are included:
| o |
|
Pump stops once
shower valve is closed without further need to operate switch |
| o |
|
Minimum disruption
to bathroom environment and no requirement to break into tiles
surfaces |
| o |
|
Pump pre-wired for
ease of installation |
Negative Head
Systems
| PRODUCT TYPE |
 |
CODE |
| TWIN
PUMPS |
|
| QT45 Twin Ended Automatic
Switching |
QT45AS |
| QT45 Manual Switching Air Switch
Chrome |
QT45MSA(C) |
| QT45 Manual Switching Air Switch
Gold |
QT45MSA(G) |
| QT45 Manual Switching Pull
Cord |
QT45MSP |
| QT80 Twin Ended Automatic
Switching |
QT80AS |
| QT80 Manual Switching Air Switch
Chrome |
QT80MSA(C) |
| QT80 Manual Switching Air Switch
Gold |
QT80MSA(G) |
| QT80 Manual Switching Pull
Cord |
QT80MSP |
| QT120 Twin Ended Automatic
Switching |
QT120AS |
| QT120 Manual Switching Air
Switch Chrome |
QT120MSA(C) |
| QT120 Manual Switching Air
Switch Gold |
QT120MSA(G) |
| QT120 Manual Switching Pull
Cord |
QT120MSP |
| |
|
| SINGLE ENDED
PUMPS |
|
| QT45 Single Ended
Automatic Switching |
QT45SE/AS |
| QT45 Single Ended Manual Air
Switching Chrome |
QT45SE/MSA(C) |
| QT45 Single Ended Manual Air
Switching Gold |
QT45SE/MSA(G) |
| QT45 Single Ended Manual
Switching Pull Cord |
QT45SE/MSP |
| QT80 Single Ended Automatic
Switching |
QT80SE/AS |
| QT80 Single Ended Manual Air
Switching Chrome |
QT80SE/MSA(C) |
| QT80 Single Ended Manual Air
Switching Gold |
QT80SE/MSA(G) |
| QT80 Single Ended Manual
Switching Pull Cord |
QT80SE/MSP |
| QT80 Single Ended Automatic
Switching |
QT80SE/AS |
| QT120 Single Ended Manual Air
Switching Chrome |
QT120SE/MSA(C) |
| QT120 Single Ended Manual Air
Switching Gold |
QT120SE/MSA(G) |
| QT120 Single Ended Manual
Switching Pull Cord |
QT120SE/MSP |
| |
|
| 'MSA' Extension Kit |
MSAEXT |
|
