21
6.2 - Scroll compressor rotation
It is important to be certain compressor is rotating in the proper
direction. To determine whether or not compressor is rotating in
the proper direction:
1.
Connect service gauges to suction and discharge pressure
fittings.
2.
Energise the compressor.
3.
The suction pressure should drop and the discharge pressure
should rise, as is normal on any start-up.
If the suction pressure does not drop and the discharge pressure
does not rise to normal levels:
1.
Turn off power to the unit. Install disconnect tag.
2.
Reverse any two of the unit power leads.
3.
Reapply power to the unit and verify pressures are correct.
The suction and discharge pressure levels should now move to
their normal start-up levels.
When the compressor is rotating in the wrong direction, the
unit makes more noise and does not provide cooling.
After a few minutes of reverse operation, the scroll compressor
internal overload protection will open, thus activating the unit
lockout. This requires a manual reset. To reset, turn the thermo-
stat on and then off.
NOTE: There is a 5-minute time delay before the compressor
will start.
6.3 - Unit start-up cooling mode
1.
Adjust the unit thermostat to the warmest position. Slowly
reduce the thermostat position until the compressor activates.
2.
Check for cool air delivery at unit grille a few minutes
after the unit has begun to operate.
3.
Verify that the compressor is on and that the water flow
rate is correct by measuring pressure drop through the heat
exchanger using P/T plugs (see Table 8). Check the eleva-
tion and cleanliness of the condensate lines; any dripping
could be a sign of a blocked line. Be sure the condensate
trap includes a water seal.
4.
Check the temperature of both supply and discharge water.
Compare with Table 9. If temperature is within range,
proceed. If temperature is outside the range, check the
cooling refrigerant pressures in Table 9.
5.
Check air temperature drop across the coil when compressor
is operating. Air temperature drop should be between 8.3
and 13.9 K.
Table 8 - Water temperature change through heat
exchanger
Water flow rate l/s
Cooling rise K
Heating drop K
Min.
Max.
Min.
Max.
For closed loop: ground
source or cooling/boiler
systems at 0.054 l/s per kW
5
6.7
2.2
4.4
For open loop: ground
water systems 0.027 l/s per kW
11.1
14.4
5.6
9.4
6.4 - Unit start-up heating mode
NOTE: Operate the unit in heating cycle after checking the
cooling cycle. Allow five minutes between tests for the
pressure or reversing valve to equalise.
1.
Turn thermostat to lowest setting and set thermostat switch
to HEAT position.
2.
Slowly turn the thermostat to a higher temperature until
the compressor activates.
3.
Check for warm air delivery at the unit grille within a few
minutes after the unit has begun to operate.
4.
Check the temperature of both supply and discharge water.
Compare with Table 9. If temperature is within range,
proceed. If temperature is outside the range, check the
heating refrigerant pressures in Table 9.
5.
Once the unit has begun to run, check for warm air delivery
at the unit grille.
6.
Check air temperature rise across the coil when compressor
is operating. Air temperature rise should be between 11.1
and 16.7 K after 15 minutes at load.
7.
Check for vibration, noise and water leaks.
6.5 - Flow regulation
Flow regulation can be accomplished by two methods. Most
water control valves have a flow adjustment built into the valve.
By measuring the pressure drop through the unit heat exchanger,
the flow rate can be determined (see Table 10). Adjust the water
control valve until the flow of 0.027 to 0.054 l/s per kW cooling is
achieved. Since the pressure constantly varies, two pressure
gauges may be needed in some applications.
An alternative method is to install a flow control device. These
devices are typically an orifice of plastic material designed to
allow a specified flow rate that are mounted on the outlet of the
water control valve. Occasionally these valves produce a velocity
noise that can be reduced by applying some back pressure. To
accomplish this, slightly close the leaving isolation valve of the
well water set-up.
WARNING: To avoid possible injury or death due to electrical
shock, open the power supply disconnect switch and secure it
in an open position before flushing system.
