In short. A compressor selection is decided by six inputs, not one: the duty point, the operating envelope around it, the refrigerant, the electrical supply, the control interface and the mechanical envelope. Capacity alone is not a selection input, because the same figure describes different machines at different conditions.
Start with the duty point
The most common way a compressor enquiry stalls is that it arrives as a single capacity figure. Capacity on its own is not a selection input. It only becomes one once the conditions it applies at are stated: evaporating and condensing conditions, and the superheat and subcooling assumptions behind them.
This matters because two projects quoting the same capacity can need different machines. The published families are separated less by size than by the conditions they are built around — the H series is published for high-lift and low-temperature operation, while the T series is published for application-specific chiller and thermal-system integration. Lift, not capacity, is what tends to move a project from one family to another.
Then the operating envelope
The duty point is one moment in a machine's life. The envelope is the rest of it: ambient or water conditions across the year, the part-load profile, transients, and the expected annual hours.
The S, T and H families publish capacity regulation from 10 to 100 per cent. That range is a capability statement, not a recommendation — where a particular plant actually operates inside it is a project fact, and it shapes both the selection and the control strategy that has to sit around it. A machine chosen only for its design point can be a poor match for the hours it will really run.
Refrigerant and region
The published catalog fields for the S, T and H families state R134a. That is a documented property of the current catalog, and it has two consequences worth being explicit about.
First, a project requiring a different refrigerant is a product-development conversation rather than a substitution. Second, regional phase-down timelines usually decide when that conversation has to happen, which makes the target market and the programme schedule part of the selection input rather than commercial detail to settle later.
Electrical supply and drive
The compressor and the drive are selected together. The published high-power VFD table states an input of 380 VAC ±10 per cent at 50/60 Hz, so supply voltage, frequency and the power architecture behind them are selection inputs and not installation details.
Two further items belong in the brief because they are difficult to retrofit: harmonic limits that the site or the local code imposes, and the restart behaviour the plant expects after a supply interruption. Both shape what has to sit between the supply and the machine.
Controls and communications
The published VFD communication fields are RS485 Modbus and CAN. Whether those match the chiller controller already chosen for the platform is a question worth asking early, because a protocol mismatch is usually resolved with a gateway, and a gateway is a component that has to be specified, powered, mounted and maintained.
Beyond the protocol, the brief should state how faults are expected to surface and what the supervisory system expects to read. A control interface that satisfies a commissioning engineer and one that satisfies a building management system are not always the same interface.
Mechanical interfaces
The last group is the one most often left until the packaging drawings are already in progress: envelope and mounting, pipe connections and their orientation, sound requirements, and the service access the maintenance plan assumes.
These are worth stating early because they constrain the others. A machine that satisfies the duty point and the electrical architecture can still be the wrong choice if it cannot be serviced where the plant intends to put it.
What an incomplete brief can still do
Few enquiries arrive with all six settled, and that is not a reason to wait. An incomplete brief is enough to open a useful conversation: which family is plausible, which inputs are load-bearing for this particular project, and which open questions have to close before anything can be confirmed.
What an incomplete brief cannot do is support a confirmed selection. The distinction is worth holding onto, because most late-stage surprises in an OEM programme trace back to a selection that was treated as settled while one of the six inputs was still an assumption.
Source basis
Published ChillerRotor catalog fields for the S, T and H series (CAT-202607-P06/P07/P08) and the application-review sequence published at /oem-integration/. No performance value is introduced that the catalog does not state.
Independent standards and regulation
These are external to this catalog and were checked against the issuing body before being cited. They define the method or the rule; they do not validate any value published on this site.
- ANSI/AHRI Standard 550/590 (I-P) 2023 — Standardises how a water-chilling package's capacity and efficiency are rated, including the part-load values (IPLV, NPLV) a selection is usually compared on. It fixes the rating method, not the duty point a project needs.
- IEC 61800-2:2021 — Rating specifications for adjustable speed AC power drive systems, covering the drive, its control and the AC motor as one system — which is why the electrical supply input cannot be settled from the motor alone.
Catalog values describe the documents this website works from. They are not a performance guarantee for a delivered unit, and project values are confirmed in writing. Read the source policy