Carrier 16JB User Manual

16jb, Carrier, Application data

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Carrier

Application Data

Application Detail

16JB

5 qP£È.S<£ù£ 5 ¡sy

Hermetic Absorption Liquid Chillers

GENERAL

Application details in this publication cover

various methods of applying the 16JB absorption
machine to meet liquid chilling needs. Throughout
this publication, the chilled liquid will be water.

Subjects covered are chilled water temperature

control, condenser water temperature control,

system design for steam and hot water machines,
and general information.

CHILLED WATER TEMPERATURE CONTROL

The absorption machine is basically a water

chiller that can be connected to any conventional

open or closed system. However, circulation of

chilled water must be continuous during operation
of the machine and during the shutdown dilution
cycle. Chilled water flow may be restricted at
partial load.

For fine chilled water temperature control

within narrow limits, such as required in precision

control of industrial processes or maintenance of

laboratory conditions, the chilled water system
may require additional storage volume to allow the
machine to adjust slowly to changes in load.
Normal

air-conditioning

applications

are

not

subject to such requirements.

Systems having large storage volumes of chilled

water transmit load changes to the machine slowly,
allowing accurate chilled water temperature con­
trol. Small storage systems transmit load changes
rapidly, making temperature control more diffi­

cult. For fine temperature control, the chilled

water system volume should be at least ten times
the gpm flow through the cooler. If a tank is added
to the system for extra storage volume, it should
be located in the line from the load to the cooler.»

Two-Pipe

Cooling-Heating

Systems

— When

machines are used in conjunction with a two-pipe

cooling-heating system, certain precautionary steps

should be taken during changeover from heating to
cooling.

Maximum water temperature permitted thru

the evaporator is 130 F because of the possibility
of tube stress. If system water temperature is above
80 F but less than 130F at changeover time,
evaporator flow should be throttled to prevent
machine overload.

It is recommended that hot water temperatures

be reset, based on outside air temperature. If a
reset-type control is used, the entering hot water
temperature at changeover will normally be lower
than 130 F.

STEAM MACHINES

Boilers

— Generally, any boiler capable of modu­

lating its input to maintain design operating steam
pressure within 1 psi under varying loads, is suit­
able for application with the absorption machine.
This generally includes all gas- and oil-fired boilers.

Some oil-fired boilers are conversions from

coal-fired to oil-fired and may have control systems

which are too sluggish to give proper response to
machine load changes. Direct control of oil feed
rate normally ensures proper response.

Coal-fired boilers, due to slow buildup and

shutdown characteristics, should be used only

when the absorption machine represents less than

15% of boiler operating load. This generally limits

coal-fired boiler applications to large industrial jobs

where process steam is generated in large quantities
year-round.
BOILER CAPACITY — Minimum boiler capacity
for use with the absorption machine is equal to full
load steam consumption, plus sufficient capacity

to offset piping radiation losses. In the absence of a
detailed study of radiation and vent losses, a
minimum 10% safety factor should be used.

Pressure Reducing Valves

— Maximum unit ratings

are based on 14 psig steam pressure at the
generator inlet. Operation at higher inlet pressures
or with more than 100 F superheat is not per­
missible. Higher inlet pressures may lead to over­

concentration.

Where steam supply pressures are above 15 psig

(14 psig + 1 psig for control) and below 20 psig,
the steam control valve can be used to reduce the

pressure. If steam supply is above 20 psig, a
pressure reducing valve must be provided between
the steam supply and the control valve inlet. A
safety relief valve should be provided between the
steam control valve and the generator inlet. This

valve must be set in accordance with paragraph
UG-133 (f) of the ASME code to relieve at a

pressure not exceeding 17 to 18 psig or the setting
determined by apphcable local codes.

Further specific details relative to pressure

reducing stations should follow accepted standards,

such as the ASHRAE Guide and manufacturer’s
recommendation. For applications on high-pressure
district heating, the steam utility should be con­
sulted for local codes or standards.

Steam Piping

should be sized to avoid excessive

pressure drop or excessive velocities. Recommenda­

tions and pipe sizing tables are given in the Carrier
System Design Manual. It is recommended that
lines be sized on the basis of design system flow for
the machine plus a 10 to 20% safety factor to
allow for normal radiation losses.

© Carrier Corporation 1971

Form 16JB-2XA

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