Carrier 16JB Manuel d'utilisateur télécharger pdf (Page 24)

Guide speciﬁcations (cont)

B. Operating Characteristics:

1. Chiller operation shall be characteristic of a single

effectabsorption cycle. Theweak solutionpumped

from the absorber to the generator shall initially

pass through a solution heat exchanger to im-

prove operatingefﬁciency bypre-heating the weak

solution on the tube side with the strong solution

returning from the generator on the shell side.

2. Unit shall becapable of continuousoperation from

100% to 10% capacity, with entering condenser

water temperatures as low as 55 F (12.7 C), with-

outthe needfor acooling towerbypass valve.Ther-

mostat on/off control of the cooling tower fan is

recommended when cooling water temperature

falls below 55 F (12.7 C).

C. Heat Exchangers:

1. All heat exchangers shall be of shell and tube con-

structionwith shells,tubesheets,tube supportsheets

and waterboxesfabricated of carbonsteel. All heat

exchangers shall incorporate straight tubes, ex-

cept for the generator which shall use U-tubes. All

tubes shall be rolled into grooved tubesheets and

expanded into tube support sheets, and shall be

individually replaceable.

2. The evaporator, absorber, and condenser water-

boxes shall be designed for 150 psig (1034 kPa)

working pressureand shallbe supplied withnozzle-

in-head (NIH) type waterboxes. Removable water-

box covers shall permit access to all tubes from

either end. All waterboxes shall be provided with

vent and drain connections. Nozzle connections

shall be of the victaulic groove type, unless other-

wise noted.

3. The generator tube bundle shall consist of U-bend

tubes secured to the tube sheet on one end only

to allow for thermal expansion and contraction.

The tube side of the generator shall be designed

for 15 psig (103 kPa) working pressure for steam

applications;or 250 psig(1725 kPa)working pres-

sure for hot water applications. All hot water gen-

erators shallbe designed,constructed and stamped

in accordance with ASME Section VIII, Division 1

requirements on the tube side. For steam applica-

tions, a vacuum breaker shall be factory supplied

on the machine.

4. A solution heat exchanger shall be an integral part

ofthe machineto increaseefﬁciency bypre-heating

weak solution on the tube side with strong solu-

tion on the shell side. Tube material for this heat

exchanger shall be carbon steel.

5. Spray headsfor the evaporator, absorber and gen-

erator shall be of a non-clogging design, speciﬁ-

cally designed for the intended duty. Spray heads

shall be fabricated of a corrosion-proof material to

ensure continuous, high efﬁciency operation.

6. Heat exchanger tube material and minimum wall

thickness shall be contingent on the type of

corrosion inhibitor used in the machine. The

following tube speciﬁcations shall apply to ensure

long machine life and continuous operation:

Evaporator copper, externally ﬁnned

Absorber copper, prime surface

Condenser copper, prime surface

Generator 90/10 CuNi, prime surface

D. Pump/Motors:

Refrigerant and solution pump/motors shall be self-

contained, leakproof, hermetic type, without pump

seals, isolation valves or external seal water system

to minimize air leakage into the machine. Each pump

casing shallbe welded into suctionand discharge lines

and factory installed and shall include spring-loaded,

wear-compensating tapered carbon bearings. Lubri-

cation and cooling shall be accomplished by the ﬂuid

being pumped; auxiliary water piping for cooling and

lubrication shall not be acceptable. Pump/motor as-

sembliesshall bedesigned for50,000 to60,000 hours

of normal operation between inspections. If pump/

motor assemblies are furnished with less than a de-

sign of50,000 to 60,000hours between inspections,

they mustbe providedwith isolation valvesand a bear-

ing monitoring system to aid in diagnosing and per-

forming on-going maintenance.

E. Purge System:

An automatic motorless purge system shall be fur-

nished to provide a continuous purging action when-

ever the chiller is in operation to assure long machine

life andefﬁcient performance.Noncondensablesshall

be removed from the absorber by a liquid eductor,

which shall use ﬂow from the solution pump to cre-

ate a suction. Noncondensables shall be stored exter-

nal to the unit and shall be prevented from diffusing

back into the machine when the unit is not operat-

ing. Evacuation of the external storage chamber shall

be accomplished by manually positioning valves to

pressurize the chamber with lithium bromide solution

and exhausting it to atmosphere. If the purge system

design is such that it requires a vacuum pump, then

it shall beunit mounted and wired tothe control panel

by the chiller manufacturer.

F. Controls, Safeties and Diagnostics:

1. Controls:

a. The chiller shall be provided with a factory

installed and wired microprocessor control

system with individually replaceable modular

component construction.The systemshall in-

clude a control center, power supply, tem-

perature(thermistor) andpressure (transducer)

sensors, and all necessary auxiliary devices

required for proper operation.

The chiller control system shall have the abil-

ity to interface and communicate directly to

the building control system without the use

of additional ﬁeld-installed hardware or soft-

ware. Additional hardware will be necessary

if the building control system is not a Carrier

Comfort Network (CCN).

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Carrier 16JB Manuel d'utilisateur Page 24

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