Nobu NBFS-48IDU Service Manual page 29

Defrosting (only applicable to the heating mode)
1. the intelligent defrost
In the heating mode, the electric control board checks and compares the temperature of indoor room and indoor
coil pipe after the compressor works for a while; judge whether the outdoor heat exchanger part is frosted or not
according to conditions such as the change of indoor coil pipe temperature; if it is judged as frosted, it automatically
enters defrosting process. When defrosting, close the indoor and outdoor blower fan and four-way valve.
2. Outdoor PCB for defrost.
In the heating mode, the unit defrost by outdoor control board ：
① unit start defrost shall all meet the following conditions ：
a 、 compressor continuous running over 7 minutes ；
b 、 defrost relay shut off ； （ -5 ℃）
c 、 compressor cumulate running time over 50 minutes. ；
② first defrost interval time is 50 minutes, later defrost interval time decided by last defrost time.
Defrost time(minute)
15
10--15
7--10
3--7
≤ 3
（ 2 ） end defrost condition(meet one of follows)
a 、 defrost time have fifteen minutes.
b 、 defrost relay turn on ； （＞ 8 ℃）
c 、 press ON/OFF key in defrost process.
c o m p r e s s o r
o u t d o o r
b l o w e r f a n
■ Sequence chart in defrosting mode
Next defrost interval time(minute)
30
40
60
70
80
Tr
TP2