Precautions For The Use Of Steam - York YHAU-CW Manual

SECTION 5 - COMMISSIONING
The Chiller Pre-Start Up and Commissioning Checklist
contains specific information for the installation and
start-up of the unit. The steps and procedures MUST
be performed by a YORK/Johnson Controls Service
person prior to customer use.
All items on the checklist MUST be completed prior to
charging and initial operation. Failure to do this may
result in machine malfunction, damage, and/or injury.

PRECAUTIONS FOR THE USE OF STEAM

Absorption chillers driven by steam use corrosion-
resistant stainless steel (SUS) tubes in the High Tem-
perature Generator.
Staining and corrosion of the tubes in the evaporator,
absorber, and condenser largely depend on the quality
of the water used as chilled water and cooling water.
As a result, since the water is supplied from the boiler,
observe the following precautions for control of the
boiler water.
Water quality must be checked periodically for stain
and corrosion to prevent problems. If water quality is
not controlled and maintained properly, premature tube
failure can result. Causes of bad quality water include:
• Polluted seawater
• Polluted underground water
• Cooling tower located near a chimney or in dirty
air
Be sure to analyze the chilled water and
the cooling water within one month after
commissioning. See Table 24 on page
95.
Install strainers of 10 mesh and above to the chilled
water and cooling water inlets.
Shut off valves are installed in the chilled water and
cooling water inlets as well as the outlets. Be sure the
valves are completely open when supplying water. If
not, the water flow can become turbulent (at the shut
off valves). If that happens, the water chamber case
and tubes may be damaged. If you need to reduce the
quantity of the chilled water and cooling water, use the
valves to adjust the flow.
94
When the flow rate change of the chilled water is con-
trolled, the load change speed is limited. (The flow rate
change function must be installed first.)
• The load change condition to limit the chilled wa-
ter temperature at the outlet is ±0.9°F 1.5% mini-
mum/maximum.
• The critical load change condition to prevent an
overcooling trip of the chiller is 5% minimum/
maximum.
Set the steam feed pressure at the inlet of the steam con-
trol valve to the specified level. If the pressure is lower
than the specification, performance may be insufficient.
Limit the steam pressure fluctuation in the range of the
specification value +7/-14 PSIG. If the pressure fluc-
tuation is too big, control becomes unstable. The valve
may start to hunt for the correct chilled water tempera-
ture at the outlet. As a result, performance suffers, and
the operation may stop.
Be sure to install a strainer of 60 ~ 70 mesh before
the steam control valve. If the steam control valve is
clogged, the control valve has a problem and the steam
flow rate cannot be controlled. If the system has a non-
leak steam control valve, does not have a steam shut-
off valve, and the control valve is clogged, the steam
leaks while the chiller is stopped. The solution in the
high temperature generator may crystallize.
Adjust the pressure at the steam drain outlet to the
specified level at the specification point with the regu-
lator valve on the facility side.
If steam drain or air may flow back while the chiller is
stopped, install a check valve to the middle of the drain
return piping. If two or more chillers are installed and
their drain return pipes are joined together to return the
drain to the hot well tank, install the check valve before
the junction of the pipes.
Install a drain trap at the lowest place of the control
valve before the steam control valve inlet side to pre-
vent an inflow of drain to the high temperature gen-
erator. And install a mist separator if too much mist is
contained in the steam.
FORM 155.31-ICOM2.EN.UL
ISSUE DATE: 12/21/2018
JOHNSON CONTROLS