TFP1450
Page 7 of 28
to energize the Solenoid Valve to
open. After the ten minute duration, at
which point should the Solenoid Valve
become de-energized and close (espe-
cially while operating under battery
back-up), the MRA-1 will have already
automatically opened, thereby prevent-
ing the DV-5a Diaphragm Chamber
from becoming re-pressurized, and
preventing an inadvertent closing of
the DV-5a during a fire event.
WARNING
If the delay between electric actua-
tion and subsequent sprinkler activa-
tion is anticipated to be greater then
10 minutes, adjust the battery back-up
calculation accordingly. Inadequate
battery back-up may result in failure of
the system to operate in the event of a
fire during a power failure.
Releasing Circuit
The releasing circuit must be equipped
with a Potter RCDS-1 Releasing Circuit
Switch, or equivalent. The RCDS-1
provides for a temporary disconnect
(de-energized) of the Solenoid Valve
during Step 9 of the Valve Resetting
Procedure.
System Air Pressure Requirements
The recommended system air pres-
sure for the Double Interlock Preaction
System with Electric/Electric Actuation
is nominally 15 psi (1,0 bar), irrespective
of the water supply pressure. The use
of a higher system air pressure may or
may not adversely affect water deliv-
ery time, and the use of a lower system
air pressure may prevent clearing the
alarm of the Low Pressure Switch on
increasing pressure. The Low Pressure
Switch is field set to alarm at nominally
12 psi (0,8 bar) on decreasing pres-
sure when using a nominal system air
pressure of 15 psi (1,0 bar). It is recom-
mended that the system air pressure
be maintained by either of the follow-
ing methods:
• A maximum 200 psi (13,8 bar) plant
air supply in combination with the
Model AMD-1 Air Maintenance
Device described in Technical Data
Sheet TFP1221
• A maximum 3000 psi (206,9 bar)
nitrogen cylinder in combination with
the Model AMD-3 Nitrogen Mainte-
nance Device described in Technical
Data Sheet TFP1241
NOTES:
It is recommended that the pressure
maintenance device be of a type that
maintains a constant system pressure,
i.e., a pressure maintenance device
that utilizes a pressure regulator versus
a pressure switch (e.g., the AMD-1 or
AMD-3). Use of a pressure switch oper-
ated pressure maintenance device with
a cut-in/cut-out differential may result
in a delay in the operation of the system
due to a fire, because of the cut-out
pressure being higher than the recom-
mended nominal system air pressure.
The dew point of the air or nitrogen
supply, for a system exposed to freez-
ing conditions, must be maintained
below the lowest ambient tempera-
ture to which the system piping will be
exposed. Introduction of moisture into
the system piping can create ice build
up which could prevent proper opera-
tion of the system.
The Air Pressure Relief Valve is typi-
cally field set to crack open at a pres-
sure of about 20 psi (1,4 bar) when
using a nominal system air pressure of
15 psi (1,0 bar).
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