49
Optional Heat Reclaim Module —
For chillers with
the heat reclaim option,
Configuration
→
UNIT
→
RECL
should be set to YES from the factory.
This option requires the installation of an additional board.
This is the same board as used for energy management module
(EMM).
This board allows control of:
• a heat reclaim condenser pump
• a heat reclaim condenser heater
• solenoid valves to shut off the normal cooling coil (one,
two or three for each circuit, depending on the unit size)
• two solenoid drain valves for the heat reclaim coil (one
for each circuit)
• two solenoid valves to shut off the water condenser (one
for each circuit)
• two solenoid drain valves for the water condenser (one
for each circuit).
For more control details, refer to the unit low voltage con-
trol schematic.
Selecting the heat reclaim mode can be done with either the
local interface or remotely with the (
RECL_SW
) contact or by
CCN. For remote connection, Position 14 and 15 on terminal
block 7 should be used to switch to air cooled (open) or heat re-
claim mode (closed). The
RECL_SW
contact can be accessed
through (
Input
→
GEN.I
→
RECL
).
In local mode, the reclaim select must be set to “Switch
Control” (
Operating mode
→
RL.SE
= Switch Ctrl
).
In CCN mode, the reclaim select must be set to YES (
Oper-
ating mode
→
RL.SE =
YES
).
The heat reclaim function becomes active when the heat re-
claim entering water temperature is lower than the heat reclaim
setpoint (
Setpoints
→
MISC
→
RSP
), minus half or quarter of
the heat reclaim dead band (
Setpoints
→
MISC
→
RDB
). The
default heat reclaim dead band is 8° F and the recommended
dead band range is 5 to 20° F.
The difference between the reclaim entering water tempera-
ture and reclaim set point will determine if one or two circuits
are required to provide heat reclaim capacity. See Table 35 for
details.
Table 35 — Heat Reclaim Circuits
The heat reclaim function is not active when the heat re-
claim entering water temperature is higher than the heat re-
claim set point, plus half of the heat reclaim dead band.
Heat reclaim active mode is indicated by
MODE_14
= 1.
Mode_14 can be accessed through CCN.
The following is the changeover procedure from cooling
mode to heat reclaim mode. First is the start-up of the condens-
er pump. Then, verification of the condenser flow switch con-
trol contact. If this remains open after one minute of condenser
pump operation, the circuit remains in cooling mode and an
alarm will be activated. The control will then wait until the dif-
ference between saturated condensing temperature and saturat-
ed suction temperature is higher than 10° F. When this occurs,
the pumpdown sequence is activated.
During pumpdown, the control will open the water con-
denser inlet valve and close the air condenser air valves
3 seconds later. After one minute or when the subcooling value
is above 13.2° F, the heat reclaim operation is effective.
Heat reclaim entering water temperature (
HEWT
), leaving
water temperature (
HLWT
), heat reclaim pump hours
(
HR.CD
), refrigerant sub-cooling (
hr_subcx
) can be can be
accessed through following paths:
Temperature
→
HEWT
Temperature
→
HLWT
Run Status
→
RUN
→
HR.CD
Temperature
→
CIR.A
→
HRS.A
Temperature
→
CIR.B
→
HRS.B
RECLAIM CONDENSER WATER VALVE OUTPUT —
This output (0 to 10 Vdc) is used to control heat reclaim con-
denser 3-way water valve position through a variable speed
device.
The 3-way valve should be installed to facilitate the cold
water start-up (below 59 F) and maintain a stable head pressure
control during heat reclaim operation. The minimum position
of the water valve should be set at 20% and maximum position
should be set at 100%.
When the entering water temperature is below 68 F, the wa-
ter valve should remain at 20% position to allow a maximum
re-circulating of the warm water between the 3-way water
valve and heat reclaim condenser.
When the entering water temperature is above 104 F, the
water valve will remain fully open, allowing no recirculation of
the warm water.
When the entering water temperature is between 68 F and
104 F, the water valve will be adjusted between 20% and 100%
position in linear proportion to the value of the entering water
temperature.
SERVICE
Electronic Expansion Valve (EXV) —
See Fig. 25
for a cutaway view of the EXV. High-pressure liquid refriger-
ant enters valve through the top. As refrigerant passes through
the orifice, pressure drops and refrigerant changes to a 2-phase
condition (liquid and vapor). The electronic expansion valve
operates through an electronically controlled activation of a
stepper motor. The stepper motor stays in position, unless
power pulses initiate the two discrete sets of motor stator wind-
ings for rotation in either direction. The direction depends on
the phase relationship of the power pulses.
The motor directly operates the spindle, which has rotating
movements that are transformed into linear motion by the
transmission in the cage assembly. The valve cone is a V-port
type which includes a positive shut-off when closed.
There are two different EXVs. For circuits with 1 or 2 com-
pressors, the total number of steps is 2785. For circuits with 3
or 4 compressors, the total number of steps is 3690. The EXV
motor moves at 150 steps per second. Commanding the valve
to either 0% or 100% will add extra 160 steps to the move, to
ensure the value is open or closed completely.
The EXV board controls the valve. Each circuit has a
thermistor located in a well in the suction manifold before the
compressor. Suction pressure as measured by the suction pres-
sure transducer is converted to a saturated suction temperature.
The thermistor measures the temperature of the superheated
gas entering the compressor and the pressure transducer deter-
mines the saturated temperature of suction gas. The difference
between the temperature of the superheated gas and the
saturated suction temperature is the superheat. The EXV board
controls the position of the electronic expansion valve stepper
motor to maintain superheat set point.
HEAT
RECLAIM
ENTERING
WATER
TEMPERATURE
NO. OF CIRCUITS IN RECLAIM
START UP
hr_ewt>rsp+h
r_deadb/4
hr_ewt>rsp+h
r_deadb/2
hr_ewt
<
rsp-
hr_deadb
/2
Two
One
Zero
rsp-hr_deadb
/
2<
hr_ewt
<
rsp-
hr_deadb
/4
One
One
Zero
Содержание AQUASNAP 30RBA315
Страница 77: ...77 Fig 37 Control Schematic 30RB060 080 a30 4619...
Страница 78: ...78 Fig 38 Control Schematic 30RB090 150 a30 4620...
Страница 79: ...79 Fig 39 Control Schematic 30RB160 190 a30 4622...
Страница 80: ...80 Fig 40 Control Schematic 30RB210 300 a30 4622...
Страница 81: ...81 Fig 41 Heat Reclaim Control Schematic a30 4622...