13
1.6.5 Sensing
Head
The units are designed to operate using a sensing
head, supplied by Vapac Humidity Control Ltd. which
should be connected as shown below
. Other
propriety sensing heads which give a DC signal
may also be used, providing the control signal is
connected to control terminals 5 & 6, and the
sensing head is powered externally from the unit.
If “Frost Protection” is required do not connect
the thermistor input from the sensing head to
control terminals 1 & 2, which should be used to
connect the “frost protection thermistor” (part
number 1220275) instead. Frost protection is
selected via the display – Set the frost demand
above the minimum cylinder demand (LE units
>20%; LE(P) & LE(C) units >8%)
Note:
Use of the 24V supply of the VAPANET unit
to power other items of equipment will
invalidate the Vapac warranty
.
1.6.6
Security Circuit / E.P.O. Shutdown
As standard units are shipped such that terminals 9 &
10 are provided for connection of an E.P.O.
(Emergency Power Off) switch or fire shutdown
facility. Other control interlocks, such as high limit
humidistat, airflow switch and/or fan interlock and time
switches etc. should be connected to terminals 11 &
12.
Please note that if a display is connected to
the unit “DI1 Control Option” must be set to
“Shutdown”.
NB breaking terminals 9 & 10 will prevent any unit
operation including frost protection.
1.6.7 Load
Shed
Option
This can only be evoked via a display, either “hard
wired” or hand held. When this option is selected,
making the connection between terminals 11 & 12 will
activate the “load shed” software routine, which will
inhibit the operation of either the unit or in the case of
twin cylinder units unit or just the 2
nd
cylinder. This will
limit the power used during peak supply periods. If
this option is selected, the fan interlock, airflow switch
and/or high limit hygrostat should be wired into
terminals 9 & 10 with the EPO switch if fitted (as per
the drawing on the far right). It should be noted that
selection of this option will mean that frost protection
cannot be utilized.
Please note that if a display is connected to the
unit “DI1 Control Option” must be set to the
following:
Single cylinder units: “Load shed”.
Twin cylinder units: either “Load Shed Cyl 2” or
“Load Shed Both”.
Vapac’s accessory kit part numbers for sensors are
Remote Room mounted sensing head FVKIT-107
And
Remote Duct mounted sensing head FVKIT-108
1
2
4
5
6
7
8
9
10
11
12
Vapac
HUMIDITY
SENSOR
9 VOLT
POWER SUPPLY
TEMPERATURE
AND
HUMIDITY
SENSOR
Th
er
mi
st
or
Th
er
mi
st
or
+9 V
o
lt
0 V
olt
R
ef
.
RH
O
u
tp
ut
11
10
12
8
7
6
1
2
4
5
9
Load Sh
ed
Standard Operation
Load Shed Operation
9
5
4
2
1
6
7
8
12
10
11
E.P.O.
Fire Stop
Fan
Air Flow
High Limit
Interlock
Switch
Hygrostat
Hygrostat
Switch
Interlock
High Limit
Air Flow
Fan
Fire Stop
E.P.O.
