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TVP Manual (full) March 2007 CE rev 03.doc
Caution
The interface will not accept analogue inputs e.g. Voltages. Applying a voltage to the control
pins of the interface will cause control problems. Use additional relays to produce the no-volt
contact closures required.
4.23 Basic Interface configuration and control via a single relay
Connecting pin 9 (remote enable), pin 1 (operate unit), pin 13 (operate defrost) to pin 24
(GND). This can all be achieved within the 37-pin remote interface plug supplied with the unit.
For your convenience the link between pins 9 and 2 is made this has the effect of
automatically forcing the unit into remote mode when ever the interface plug is connected. If
the interface plug is to be used purely for data logging the analog out put this link must be
removed.
On power up
Unit will be forced into remote by pin 9 being low, it will see pin 1 low and turn on the
compressor and start the PRE_COOL cycle.
When the pre-cool is competed the system will go to STANDBY and see pin 13 low, it will then
go into a defrost cycle (warm coil, this will terminate when CO reaches the Set point, the
Suction pressure goes high or the defrost timer exceeds 5 minutes).
Once defrost is complete the unit will enter the STANDBY state.
To cool
The systems needs to requires a single closure between 11 and GND, so long as pin 11 is low
the system will remain in COOL. When the relay/switch is opened pin 13 will be observed as
“low” the TVP will then automatically enter the DEFROST cycle before returning to STANDBY.
In this basic scheme the system will always do a complete cycle, i.e. It will perform COOL –
DEFROST – STANDBY.
This can be expanded by adding a second switch between pin 13 and GND to select Defrost,
here if both switches are open the system is in STANDBY, to select COOL close pin 11 to GND.
To select defrost close pin 13 and then open pin 11.
NOTE the system updates the I/O @ 70 milliseconds, if cool is removed before defrost is
applied the system will go into STANDBY momentarily. This can cause a problem for some
slow to update systems.
4.24 Full Interface
This shows the complete I/O for the twin coil TVP.
The control inputs are exactly the same as above but with two additional inputs for COOL 2
and DEFROST 2. The digital outputs are shown with either a customer supplied power supply,
the internal 24VAC (fused 2A) or the outputs can be connected to system Ground for customer
systems with open collector inputs.
Analog Out put
The analog output is will show the value of coil out, the output is in the range 1 – 10VDC
against system ground open circuit therefore indicates a sensor failure or loss of continuity.
The formula follows;
V = 3.3-(T/25)
Where
V = volts
T = Temperature
o
C