F
Operating instructions
cod. 1592001330
1592001330 XC642C GB r1.0 07.06.2004.doc
rel. 1.0
Pa. 13 / 21
14. Thermostat for liquid injection
The second probe (term. 4-7), is used to detect the temperature of the head of compressor and inject cooling
liquid when the temperature Is too high. The 5th relay (25-26) is designed for this purpose.
Parameters involved are:
Lit
:
Set point ( °C) for liquid injection thermostat
(0 ÷ 150°C)
Lid
:
Differential for liquid injection thermostat
(0.1 ÷ 10.0)
15. Type of regulation
15.1 NEUTRAL ZONE
This kind of regulation is available only for compressors. The neutral zone (Pbd) is symmetrical compared to
the target set point, with extremes: set+Pbd/2 ... set-Pbd/2. If the pressure (temperature) is inside this zone
the controller maintains the same number of loads switched on and off, without changing anything.
When the pressure (temperature) go out from the zone, regulation starts. If the pressure is greater than
SET+Pbd/2, the loads are switching on with timing given by parameters: don and doF.
A load is turned on only if the his safety times
onon, oFon, donF
are over.
Regulation stops when the pressure (temperature) come back into the neutral zone.
In the following a simplify exemplum that explains the regulation in neutral zone for compressor
homogeneous with 1 step for each compressors. The safety times onon, oFon and donF are not considered.
In the real regulation the a load is entered or turned off only if these times are over.
Ex
.
Neutral zone control
oA1 = cMP; oA2 = StP; oA3 = StP; oA4 =nu
rty = db
neutral zone regulation
FdLy = no
“don” delay not enabled at first calling after an equilibrium condition.
dLF = no
“doF” delay not enabled at first calling after an equilibrium condition.
Relay 1 - Compressor
Relay valve 1 (33%)
Relay valve 1 (66%)
33%
ON
ON
OFF
66%
ON
OFF
ON
100%
ON
OFF
OFF
Set
oA3(66%)
Loads state
Time
Pression
On
oA2(33%) On
oA1(Compressor) On
Compressor at 100%
Neutral Zone
don
doF
don
doF
doF
don
Delay evolution
Time
Time
Set + (Pbd/2)
Set - (Pbd/2)
Compressor disabled
