Control Outputs [A And Iv/Pr (H8)]; Sequence Of Operation - Daikin MicroTech III Installation And Maintenance Manual

Control Outputs [A and IV/PR (H8)]

The control outputs are Alarm Fault (A) and Isolation
Valve / Pump Request {IV/PR (H8)} . The operation of the
control outputs during occupied mode is as follows:
■ The thermostat alarm output: Will be energized when
there are fault conditions presently active . Without any fault
conditions active, the alarm output shall be de-energized .
■ Isolation Valve / Pump Request [IV/PR (H8)]: is
selectable to be energized when the compressor
is off (normally closed), or when the compressor is
on (normally open), by moving the wire lead to the
appropriate terminal .
Figure 4: H8 terminals on MicroTech III board
■ Reversing Valve: 24V signal that is energized upon a
call for heat mode .
■ Compressor Relay: Line or low voltage output used
to control compressor . (On/Off)

Sequence Of Operation

Fan Only
On a call for fan the fan starts immediately thru the
activation of the G terminal .
Note: If jumper JP2 on the main control board is open
the fan will run continuous whenever there is a
power supply to the unit. For cycling fan opera-
tion jumper JP2 needs to be shorted.
Cooling
On a call for 1st stage cooling from a thermostat or
network setpoint, the H8 output on the MicroTech III board
is activated to open the motorized valve to allow water
flow thru the heat exchanger. The fan starts immediately
(unless it is already on thru activation of the G terminal
by the thermostat fan switch "ON" or a wall sensor
command) at "FAN ONLY" setting . The compressor starts
after 45 seconds to make sure the motorized valve has
fully open for proof of water flow and the fan CFM output
increases . The compressor minimum on timer of 180
seconds starts . The reversing valve will de-energize 5
seconds after the compressor starts . The fan CFM output
is now determined by the Fan Setting switch, position 1,
2, 3 or 4 and the corresponding stage 1 CFM . If a two
stage thermostat is used, a further demand for cooling will
change (increase) the CFM output of the EC fan motor .
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When the room setpoint conditions are satisfied, the
compressor will shut off and the fan will either shut off
(fan switch "AUTO") or continue to run (fan switch "ON" or
jumper JP2 open). The compressor minimum off timer of
360 seconds will start .
Heating
On a call for 1st stage heating, from a thermostat or
network setpoint, the H8 output on the MicroTech III board
is activated to open the motorized valve to allow water flow
thru the heat exchanger . The fan starts immediately (unless
it is already on thru activation of the G terminal by the
thermostat fan switch "ON" or a wall sensor command) at
low CFM . The compressor starts after 45 seconds to make
sure the motorized valve has fully open for proof of water
flow and the fan CFM output increases. The compressor
minimum on timer of 180 seconds starts . The reversing
valve will energize 5 seconds after the compressor starts .
The fan output is now determined by the Fan Setting
switch, position 1, 2, 3 or 4 and the corresponding stage 1
CFM . If a two stage thermostat is used, a further demand
for heating will change (increase) the CFM output of the EC
fan motor. When the room setpoint conditions are satisfied,
the compressor will shut off and the fan will either shut off
(fan switch "AUTO") or continue to run (fan switch "ON" or
jumper JP2 open). The compressor minimum off timer of
360 seconds starts .
Boilerless Electric Heat Mode
Units equipped with the boilerless electric heat option
include an entering water temperature sensor . On a call
for heating the fan starts immediately (unless it is already
enabled through activation of the G terminal from the
thermostat fan switch "ON" or a wall sensor command .) at
"FAN ONLY" setting . The H8 output on the MicroTech III
board is activated to open the motorized valve allowing
water flow thru the heat exchanger. If the entering water
temperature is below set point, (55°F standard units or
28°F for geothermal units), the MicroTech-III controller
will disable the compressor, increase the fan speed to
electric heat CFM and energize a 24VAC output to the
electric heat control circuit . When the room setpoint
conditions are satisfied, the electric heater will turn off and
the fan will either cycle off (fan switch "AUTO") or continue
to operate (fan switch "ON" or jumper JP2 open). If the
entering water temperature is above setpoint, the unit will
operate in compressor heating mode . The setpoints are
adjustable by the BAS . .
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ICro eCh nIt ontroller
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