Mitsubishi Electric PURY-WP200 Service Manual page 108

[ VII Control ]
Defrost Operation Control
-5- Defrost Operation Control
(1) Defrost cycle type
The defrost cycle has following two types: Bypass defrost that is the same method as that used in a CITY MULTI series sys-
tem and heat recovery defrost (default) that the heat is collected from the water circuit and the defrost cycle ends early.
The following figure shows the refrigerant flow for the bypass defrost. In the bypass defrost method, LEV1 and 2 are closed
and the heat is not exchanged between the refrigerant and water. In the heat recovery defrost method, the defrost cycle ends
early because the heat is caught from the water.
The basic defrost method is the heat recovery defrost with the dip switch 3-10 on the HBC turned OFF (default). The bypass
defrost may be performed depending on the water temperature. Setting the dip switch 3-10 to ON performs the bypass defrost.
HBC refrigerant system
Low-pressure
pipe
TH16
High-pressure
S
pipe
(2) Starting the defrost operation
The defrost cycle will start when all of the three conditions (outside temperature, cumulative compressor operation time, and
pipe temperature) under <Condition 1>, <Condition 2>, or <Condition 3> are met.
Outside temperature
(TH7)
Cumulative compressor
operation time
Pipe temperature
(TH6)
1) Pipe temperature(TH6)
SW3-3 OFF
SW3-3 ON
If 10 minutes have passed since compressor startup or since the completion of a defrost cycle, a forced defrost cycle can be
started by setting DIP SW2-7 to ON.
Even if the defrost-prohibit timer is set to 90 minutes (or 150 minutes for "Condition 3" to be met), the actual defrost-prohibit
time for the next defrost cycle is 50 minutes if the last defrost cycle took 12 minutes.
HWE1113B
21S4Mb
Cooling-main Heating-main
TH14
heat exchanger
heat exchanger
Water Water Water Water
TH12
TH15
LEV2
LEV3
S
HIC
SVM1
Refrigerant flow
Condition 1
-5ºC [23ºF] or above
50 minutes or more
90 minutes or more if the defrost prohibit timer is set to 90.
The pipe temperature has
stayed below the temperatures
in the table below (Note1) for
three minutes.
-8ºC
-5ºC
HBC water system
Water pressure
21S4Ma
protection valves
TH13
TH33
PS
PS1
TH11
Refrigerant Refrigerant
LEV1
Condition 2
-5ºC [23ºF] or below
The pipe temperature (TH6)
has stayed at or below the val-
ue obtained from the formula
"Outside temperature (TH7) -
10ºC [18ºF]" for three minutes.
or the 63LS reading has stayed
below the value obtained from
the formula "1.5 + 0.02 x
(20+TH7)" for three minutes.
- 99 -
TH34 TH37
S
Water pump WP2
TH32
Refrigerant Refrigerant
TH36
TH35
S
Water pump WP1
Water pressure
protection valves
Water vent Expansion Water
valve tank supply
Condition 3
250 minutes or more
The pipe temperature has
stayed below the temperatures
in the table below (Note1) for
three minutes
GB