Four-Way Valve Control; Electronic Expansion Valve (Exv) Control - Lennox MCFA Service Manual

24.7.2. Heating Mode
Normally the system will choose the running fan speed according to ambient temperature:

24.8. Four-Way Valve Control

In heating mode, four-way valve is opened. In defrosting, four-way valve operates in according to defrosting action. In other
modes, four-way valve is closed. When the heating mode to other modes, the four-way valve is off after compressor is off
for 2 minutes. Failure or protection (not including discharge temperature protection, high and low pressure protection), four-
way valve immediately shuts down.

24.9. Electronic Expansion Valve (EXV) Control

a. EXV will be fully closed when turning on the power. Then EXV will be standby with 350P open and will open to target
angle after compressor starts.
b. EXV will close with -160P when compressor stops. Then EXV will be standby with 350P open and will open to target
angle after compressor starts.
c. The action priority of the EXVs is A-B-C-D.
d. Compressor and outdoor fan start operation only after EXV is initialized.
24.9.1. Cooling mode
The initial open angle of EXV is 250P, adjustment range is 100-350p. When the unit start to work for 3 minutes, the outdoor
will receive indoor units( of capacity demand) T2B information and calculate the average of them. After comparing each
indoor's T2B with the average, the outdoor gives the following modification commands: If the T2B>average, the relevant
valve needs more 16p open; If the T2B= average, the relevant valve's open range remains; If the T2B<average, the relevant
valve needs more 16p close.
This modification will be carried out every 2 minutes.
24.9.2. Heating mode
The initial open angle of EXV is 250P, adjustment range is 100-350p. When the unit start to work for 3 minutes, the outdoor
will receive indoor units (of capacity demand) T2 information and calculate from subject received, size and categories.
After comparing each indoor's T2 with the average, the outdoor gives the following modification commands: If the
T2>average+2, the relevant valve needs more 16p close;
If average+2≥the T2≥ average-2, the relevant valve's open range remains;
If the T2<average-2, the relevant valve needs more 16p open.
This modification will be carry out every 2 minutes.
T4
E DC_FAN_SSLOW_SPD_ADD
21℃
19℃
D DC_FAN_SLOW_SPD_ADD
18℃
16℃
C DC_FAN_MIN_SPD_ADD
15℃
13℃
B DC_FAN_MID_SPD_ADD
12℃
10℃
A DC_FAN_HI_SPD_ADD
100