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5.3 Signal wiring notes
An earth current loop is created if a wire or screen is connected between two earth points
that are at different potential (voltage). If the wiring diagram is followed correctly, the screen
will only be connected to the earth at one end.
The earth terminal is a functional earth rather than a protective earth.
A protective earth provides protection from electric shock under a single fault condition. This
product has double insulation and therefore does not require a protective earth. A functional
earth is used in order for the product to operate. In this application, the earth is used as a
sink or drain for any electrical interference. The earth terminal must be connected to a local
earth in order to conform to the EMC directive.
Front
Back
Notes:
E = Functional earth - Connect these pins to a clean earth local to the panel.
Switch battery back-up switches ON to activate battery.
Fig. 7 Signal circuit
Connect to
clean earth
local to the
panel
Signal circuit
(view from the top)
E 97 96 95 94 93 92 91 90 75 74 73 72 71 70
LockoutBB switch
On
Off
Battery
back-up
switch
Link to
other bottom
blowdown
timers
Bottom blowdown
switch (shown with valve
closed)
COM SCN Tx- Tx+ Rx- Rx+ H / D H / D
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