York Millennium YDAS 410, Установка, эксплуатация и обслуживание

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YORK INTERNATIONAL
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High Discharge Pressure Unload Point
The Discharge Pressure Unload point is used to avoid
a high pressure cutout shutdown by unloading a com-
pressor if its discharge pressure approaches the cutout
value. The chiller can then continue to run automati-
cally at reduced capacity until the cause of the exces-
sive pressure is attended to (e.g. dirty condenser coils)
or ceases naturally (e.g. high ambient temperature).
For the first 60 seconds of operation discharge pressure
limiting is disabled. After this time, if discharge pressure
exceeds the programmed limit, a 1 second unload pulse
will be sent to the slide valve of the affected compressor
every 5 seconds until the discharge pressure drops be-
low the programmed limit. The message will be removed
and reloading take place when discharge pressure has
dropped 60 PSIG below the threshold.
Typically, the unload point should be set 20 - 25 PSI be-
low the discharge pressure cutout setting. The micro will
accept a range of programmable values between 200 -
390 PSIG for R22 models, 128 - 270 PSIG for R134a
models. This programmable value is password protected.
To program the Discharge Pressure Unload, key in the
required setting and press the Enter key to store the
value into memory and scroll to the next display.
High Average Current Unload Point
The Average Current Unload point is used to avoid a
high motor current safety shutdown by unloading a com-
pressor if current draw approaches the maximum limit
cutout value. The chiller can then continue to run auto-
matically at reduced capacity until the cause of the ex-
cessive current is attended to.
The micro will accept between 30 - 115% for the unload
point. The motor current safety will shut the compres-
sor down whenever current exceeds 115%.
If the programmable limit is set between 100% and 115%
of full load current, this safety will protect against exces-
sive current causing compressor shutdown due to ex-
tremely high ambient, high chilled liquid temperature, and
condenser malfunction caused by dirt or fan problems.
If the programmable limit is set below 100% of full load
current, this feature can be used for “demand limiting”.
This is important when demand limiting is critical due to
power requirements or limitations in the building (See
also Section 1.7).
For the first 60 seconds of operation, the unloading
safety is disabled. After this time, if motor current ex-
ceeds the programmed limit the SYS x CRNT LIMIT-
ING message will appear and a 1 second unload pulse
will be sent to the slide valve of the affected compres-
sor every 5 seconds, until the motor current drops be-
low the programmed limit. The message will be removed
and additional loading will take place when motor cur-
rent drops below 90% of the programmed threshold.
Typically, this setpoint should be set at 100 - 105%.
It is not recommended to program a value greater
than 105%. For maximum motor protection, pro-
gramming for 100% is advisable. When programming
values below 100% use of a leading “0” is required, e.g.
085%.
To program the Average Motor Current Unload, key in
the required setting and press the Enter key to store
the value into memory and scroll to the next display.
Anti-Recycle Timer
The Anti-Recycle Timer controls the minimum time be-
tween starts for each compressor. This is the time avail-
able for the heat build-up caused by inrush current at
start to be dissipated before the next start. Insufficient
cooling time between starts can cause heat build-up
and motor damage. A fast compressor start response
is needed in some applications and not in others. Al-
though the minimum setting allowed on this timer will
avoid excessive heat build-up, adjusting the timer for
the longest period acceptable in each application will
reduce cycling and maximize motor life. 600 seconds
is recommended.
The micro will accept a range of programmable values
between 300 - 600 seconds.
To program the Anti-Recycle Timer, key in the required
setting and press the Enter key to store the value into
memory and scroll to the next display.
Low Leaving Water Temperature Cutout
The Low Leaving Water Temperature Cutout protects
the evaporator from damage due to ice build-up caused
by operation below the chilled liquid freezing point.
L E A V I N G W A T E R T E M P
C U T O U T = 3 6 . 0 ° F
A V E R A G E C U R R E N T
U N L O A D = 1 0 5 % F L A
A N T I R E C Y C L E T I M E R
= 6 0 0 S E C S
D I S C H A R G E P R E S S U R E
U N L O A D = 3 6 0 . 0 P S I G