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HVAC Guide Specifications

Variable Speed Screw Chiller

Size Range:

300 to 550 Tons (1055 to 1934 kW) Nominal

Carrier Model Number:


Part 1 — General


A. Microprocessor-controlled liquid chiller shall use a semi-hermetic screw compressor using refrigerant HFC-134a only. Chiller refrigerant shall not have a planned phase out date.

B. If a manufacturer proposes a liquid chiller using HCFC-123 refrigerant, which has a planned phase out date, then the manufacturer shall include in the chiller price:

1. A vapor activated alarm system consisting of all alarms, sensors, safeties, and ventilation equipment as required by ANSI/ASHRAE Standard 15 Safety Code for Mechanical Refrigeration (latest edition) with the quotation. System shall be capable of responding to HCFC-123 levels of 10 ppm Allowable Exposure Limit (AEL).

2. A free-standing refrigerant storage tank and pumpout unit shall be provided. The storage vessels shall be designed per ASME Section VIII Division 1 code with 300 psig (2068 kPa) design pressure. Double relief valves per ANSI/ ASHRAE 15, latest edition, shall be provided. The tank shall include a liquid level gage and pressure gage. The pumpout unit shall use a semi-hermetic reciprocating compressor with water cooled condenser. Condenser water piping, 3-phase motor power, and 115-volt control power shall be installed at the jobsite by the installing contractor.

3. Zero emission purge unit capable of operating even when the chiller is not operating.

4. Back-up relief valve to rupture disk.

5. Factory-installed chiller pressurizing system to prevent leakage of noncondensables into the chiller during shutdown periods.

6. Plant room ventilation.

7. Removal and disposal of refrigerant at the end of the phase out period.

8. Chillers utilizing a purge unit shall include in the machine price the costs to perform the following regular maintenance procedures:

a. Weekly: Check refrigerant charge.

b. Quarterly: Charge purge unit dehydrator at least quarterly, more often if necessary. Clean foul gas strainer. Perform chemical analysis of oil.

c. Annually: Clean and inspect all valves. Drain and flush purge shell. Clean orifices.


A.Chiller performance shall be rated in accordance with ARI Standard 550/590-latest edition.

B. Equipment and installation shall be in compliance with ANSI/ASHRAE 15 (latest edition).

C. Cooler and condenser refrigerant side shall include ASME “U” stamp and nameplate certifying compliance with ASME Section VIII, Division 1 code for unfired pressure vessels.

D. A manufacturer’s data report is required to verify pressure vessel construction adherence to ASME vessel construction requirements. Form U-1 as required per ASME code rules is to be furnished to the owner. The U-1 Form must be signed by a qualified inspector, holding a National Board Commission, certifying that construction conforms to the latest ASME Code Section VIII, Div. 1 for pressure vessels. The ASME symbol “U” must also be stamped on the heat exchanger. Vessels specifically exempted from the scope of the code must come with material, test, and construction methods certification and detailed documents similar to ASME U-1; further, these must be signed by an officer of the company.

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