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 conventional Techflow 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:
'NHE' (Automatic
Switching Negative Head)
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 |
|
| QT45-2 Twin Ended Automatic
Switching |
QT45NHE-2 |
| QT45-2 Manual Switching Air Switch
Chrome |
QT45MSA-2(C) |
| QT45-2 Manual Switching Air Switch
Gold |
QT45MSA-2(G) |
| QT45-2 Manual Switching Pull
Cord |
QT45MSP-2 |
| QT80-2 Twin Ended Automatic
Switching |
QT80NHE-2 |
| QT80-2 Manual Switching Air Switch
Chrome |
QT80MSA-2(C) |
| QT80-2 Manual Switching Air Switch
Gold |
QT80MSA-2(G) |
| QT80-2 Manual Switching Pull
Cord |
QT80MSP-2 |
| QT120-2 Twin Ended Automatic
Switching |
QT120NHE-2 |
| QT120-2 Manual Switching Air
Switch Chrome |
QT120MSA-2(C) |
| QT120-2 Manual Switching Air
Switch Gold |
QT120MSA-2(G) |
| QT120-2 Manual Switching Pull
Cord |
QT120MSP-2 |
| |
|
| SINGLE ENDED
PUMPS |
|
| QT45-2 Single Ended
Automatic Switching |
QT45SE/NHE-2 |
| QT45-2 Single Ended Manual Air
Switching Chrome |
QT45SE/MSA-2(C) |
| QT45-2 Single Ended Manual Air
Switching Gold |
QT45SE/MSA-2(G) |
| QT45-2 Single Ended Manual
Switching Pull Cord |
QT45SE/MSP-2 |
| QT80-2 Single Ended Automatic
Switching |
QT80SE/NHE-2 |
| QT80-2 Single Ended Manual Air
Switching Chrome |
QT80SE/MSA-2(C) |
| QT80-2 Single Ended Manual Air
Switching Gold |
QT80SE/MSA-2(G) |
| QT80-2 Single Ended Manual
Switching Pull Cord |
QT80SE/MSP-2 |
| QT80-2 Single Ended Automatic
Switching |
QT80SE/NHE-2 |
| QT120-2 Single Ended Manual Air
Switching Chrome |
QT120SE/MSA-2(C) |
| QT120-2 Single Ended Manual Air
Switching Gold |
QT120SE/MSA-2(G) |
| QT120-2 Single Ended Manual
Switching Pull Cord |
QT120SE/MSP-2 |
| |
|
| 'MSA' Extension Kit |
MSAEXT |
|
