Johnson Controls York YCRE 040, Руководство пользователя

Страница: 22 / 68

If relief pipework is common to more than one valve its
cross sectional area must be at least the total required
by each valve. Valve types should not be mixed on a
common pipe. Precautions should be taken to ensure
that the exit of relief valves/vent pipe remain clear of
obstructions at all times.
4.7 Condenser Cooling Liquid Systems
(YCSE Only)
For primary cooling of units, condensers are usually
piped in conjunction with a cooling tower, well water or
dry coolers. Ensure the water is suitable for the stainless
steel heat exchanger.
With liquid cooled units it is necessary to control coolant
flow and / or temperature into the condenser to maintain
refrigerant pressure as constant as possible to ensure
satisfactory operation of the expansion valves.
Direct Pressure Control (By others)
With YCSE units it is possible, if desired, to control the
condenser cooling liquid inlet temperature / flow directly
from the unit refrigerant pressure.
The refrigerant pressure can either be used to control
cooling tower / dry cooler effectiveness by controlling
fans or dampers on the tower, or to control condenser
flow using a three way bypass valve.
The aim is to maintain a stable discharge pressure as
low as possible, but at least 5.0 bar above suction
pressure. This can be done at a fixed value above the
highest expected suction pressure, or by also
measuring suction pressure and using differential
control. In either case condenser cooling liquid flow and
temperature limits must also be observed.
Inlet Temperature Control (By others)
For a cooling tower / dry cooler system, the simplest
forms of control are to use fan cycling, fan speed control,
or air damper control, with the tower having a thermostat
in its sump. This will ensure stable condenser cooling
liquid temperature sensing at design conditions and
should be adjusted to ensure a condenser cooling liquid
entering temperature of not lower than 22°C at lower
ambient conditions.
If these methods are not available, or a cooling tower is
not the source of cooling water, then a three way valve
recirculation system can be used with control based on
condenser inlet liquid temperature. In this case the
objective is to maintain the inlet cooling liquid
temperature as low as possible, although still observing
the minimum limit of 22°C.
4
-
4
035-21786-100 Rev. 1 (0909)