Question 1

When do you need a chiller and when is a cooling tower enough?

Accepted Answer

You need a chiller when the water has to be colder than the site's design wet-bulb temperature plus 4 K. A cooling tower cools by evaporation and cannot take water below that limit. For central Russia our catalogue puts it simply: if you need water colder than 23 °C, you need a chiller. If the process is fine with 25–30 °C, a compressor is usually unnecessary. Often the right answer is both: in summer the tower cools the chiller condenser, in winter it supplies cold water on its own. More in the article "What is a chiller"

Question 2

Which is better: an air-cooled or a water-cooled chiller?

Accepted Answer

Water-cooled is more efficient, air-cooled is simpler. An air-cooled condenser runs 10–15 K above outdoor air temperature, while a water-cooled one on cooling tower water condenses at about 35 °C. Per NCT catalogues, for 1,000 kW of cooling an air-cooled packaged unit (12/7 °C, +35 °C ambient) draws about 370–420 kW, a centrifugal machine on 30 °C tower water about 145–165 kW. The water-cooled option needs a cooling tower or dry cooler, water treatment and a plant room. A packaged air-cooled unit is never put indoors without powerful ventilation. If both options fit the site, compare their operating costs over 15–20 years. More in the article "How to choose an industrial chiller"

Question 3

How do you calculate the required chiller capacity?

Accepted Answer

For water, capacity follows from flow and temperature difference: Q = 1.163 × G × Δt, where G is flow in m³/h and Δt is the inlet-outlet difference in K. Example: 20 m³/h cooled from 17 to 12 °C gives 116 kW. Take the peak and minimum load of each consumer, not the sum of nameplates: without a diversity factor (typically 60–80%) the machine comes out twice as big as needed. Catalogue capacity is quoted at 12/7 °C and +35 °C ambient; hotter air, colder water or glycol instead of water means less cooling, so the model is selected at your own duty point. More in our design guides for engineers

Question 4

How much capacity margin should you add, and why is an oversized chiller a problem?

Accepted Answer

A sensible margin is 10–15%, added once and in one place, to cover heat exchanger fouling, hot weather and pipe losses. If the process engineer adds 15%, the designer another 10% and the model is rounded up, the machine ends up a third larger than needed. It then short-cycles: many machines are limited to two starts per hour, and more frequent starts trip the unit. For future load growth, leave space and valves for one more machine instead. More in the article "How to choose an industrial chiller"

Question 5

How long does an industrial chiller last?

Accepted Answer

There is no single figure: service life depends on operating hours, water quality in the loop and maintenance. The biggest repair item is the compressors: an overhaul around year 10 costs roughly half the price of the machine. A centrifugal compressor on oil needs an oil change every 3 years and new oil filters every year; one on gas-dynamic bearings does not. A brand leaving the market is no reason to replace a working machine, but its compressors and heat exchangers should have an official representative with a spare parts warehouse in the country. More in the article "Chiller total cost of ownership"

Question 6

What glycol and concentration should go into a chiller, and how often is it replaced?

Accepted Answer

Only inhibited ethylene or propylene glycol rated for heat exchangers; automotive antifreeze will not do. Choose the concentration by the lowest temperature the loop will see: 40% ethylene glycol freezes at −23 °C, 40% propylene glycol at −22 °C. Extra percent costs money: 40% propylene glycol cuts machine capacity to 0.90 of the water rating and raises pressure drop 1.53 times. In food plants only propylene glycol solution may go directly through the evaporator. Glycol is replaced every 3–5 years and the concentration is monitored, because a diluted solution sharply speeds up corrosion. More in our design guides for engineers

Question 7

What is in a chiller winter kit, and can it run in winter without one?

Accepted Answer

Without a winter kit, an NCT air-cooled chiller operates at +10 to +35 °C outdoors. A panel heater and fan speed controller extend the range down to −5 °C. The full kit — fan speed controllers, condensing pressure and receiver pressure regulators, a receiver and a panel heater — allows operation down to −30 °C. Without it, refrigerant collects in the cold condenser in frosty weather, condensing pressure drops and the machine trips. The winter start kit is needed for starts below +5 °C, so spring and autumn count as winter too. Freeze protection of the water loop is a separate decision. More in the article "How to choose an industrial chiller"

Question 8

How do you prepare a chiller for winter and keep it from freezing?

Accepted Answer

For every section where water can end up in sub-zero air, pick one of three solutions. Glycol, if the machine or outdoor piping runs in winter. Draining, if no cooling is needed in winter: a slope of at least 2 mm/m, drains at low points, air vents at high points and blow-down, otherwise water freezes in pockets of bends. Electric heat tracing, for a short outdoor section on water, with a backed-up power supply and a fault alarm. Below +6 °C leaving temperature, NCT machines run on glycol only. An evaporator heater is available as an option, but glycol is more reliable. More in our design guides for engineers

Question 9

What is chiller free cooling and how much does it save?

Accepted Answer

Free cooling means chilling water with outdoor air and no compressor whenever it is colder outside than the water the consumer needs. It is not a separate machine but a heat exchanger, a glycol loop and motorised valves. In central Russia it runs about 4,500 hours a year. On a year-round 1,000 kW load in Moscow (12/18 °C, cooling tower and plate heat exchanger) free cooling saves about 1.78 million kWh a year — 61% of compressor electricity. Without winter load, as in office air conditioning, it does not pay back, and it does not cut peak demand, which falls in summer. More in the article "Chiller free cooling"

Question 10

At what outdoor temperature does free cooling start?

Accepted Answer

The threshold is set by the water temperature. Partial free cooling starts when outdoor air is colder than return water minus Δ, full free cooling when it is colder than supply water minus Δ, where Δ is the sum of approaches of the dry cooler or tower and the intermediate heat exchanger. With Δ = 7 K and 7/12 °C water, partial free cooling runs below +5 °C and full below 0 °C. At 12/18 °C both thresholds move up by 6 K. So check a request for "7 °C with no compressor at +5 °C outdoors" against this first: each degree of warmer supply adds free cooling hours. More in the article "Chiller free cooling"

Question 11

Built-in free cooling or a chiller plus a separate dry cooler — which to choose?

Accepted Answer

Both work; choose by water availability and the machine already installed. A packaged unit with built-in free cooling suits sites with no water that need quick commissioning and modular expansion: the free cooling coil and three-way valve are already in the machine, and the loop runs on glycol. With a water-cooled chiller, a dry cooler does two jobs: in summer it rejects condenser heat, in winter two three-way valves switch it to the chilled water heat exchanger. A cooling tower with a plate heat exchanger works off wet-bulb and gives more hours, but needs water treatment and a winter mode. Compare annual kWh and cost. More in the article "Chiller free cooling"

Question 12

Why doesn't a chiller deliver its rated capacity or hold temperature in summer?

Accepted Answer

Usually the water and heat exchangers are to blame, not the machine. Nine times out of ten it is water quality: 1 mm of scale on a heat exchanger takes away about 30% of capacity. Glycol instead of water also reduces capacity, so the machine should have been selected on the solution. Air-cooled units add summer problems: dirt on condenser fins (about 1 mm costs 21% efficiency, per EPA data), hot air recirculating near a wall or behind a high fence, and selection on a table temperature instead of real peak heat. Before adding capacity, check water, condenser and the selection duty point. More in our summer cooling readiness checklist

Question 13

Will a chiller run in +45 to +50 °C heat?

Accepted Answer

Up to +45 °C, yes, if the machine is selected for that temperature rather than a table value. The base range of NCT NASA packaged units goes up to +35 °C ambient, NARV modular screw units run from +5 to +45 °C; for hotter sites the model and options are selected for the design temperature. Adiabatic pre-cooling lowers air temperature at the condenser inlet by 5–15 K and keeps capacity in the hottest hours. If a unit trips in direct sun, first check roof heat, recirculation and condenser cleanliness: on a dirty condenser, condensing pressure can rise from 10 to 15 bar. More in the article "How to choose an industrial chiller"

Question 14

Can you order a chiller with a built-in pump module?

Accepted Answer

Yes. A pump module with isolation valves, a standby pump and a strainer on the chilled water line are options in all our NCT chiller proposals. The pump head to the network is specified in the questionnaire from the calculation of the most demanding circuit; otherwise the pump is selected blind. For a typical 1,000 kW secondary loop it is about 16 m; in a closed loop, the height of the piping run does not add to the head. Each option goes on its own line in the specification, or it risks being left out of procurement. More in our design guides for engineers

Question 15

Does a chiller need a buffer tank, and how big?

Accepted Answer

Yes, if the water that actually returns to the machine at low load is less than the manufacturer's minimum. Size it from the smallest capacity step: for a 125 kW step with a 2 K hysteresis and a cycle of at least 10 minutes you need 2.24 m³. If the primary loop holds 1 m³, the tank is about 1.2 m³, checked against the machine data sheet. Network water beyond the bypass does not count: at night two-way valves close and the machine sees only the primary loop. Put the tank on the primary return, with flow through it. A machine with stepless control down to low load may not need one. More in our design guides for engineers

Question 16

Is refrigerant included in the chiller supply?

Accepted Answer

It depends on the configuration. NCT chillers leave the factory under nitrogen; factory refrigerant charging is available on request. Units with a remote condenser are charged only on site, after the refrigerant piping is installed: the charge is calculated from line length, height difference and the locations of the unit and condenser. The additional charge for the piping is a separate line in the specification. When comparing proposals, check whether refrigerant is included in the price and in what quantity. More in our design guides for engineers

Question 17

What capacities do NCT chillers come in — do you make small and very large ones?

Accepted Answer

The NCT range in the 2026 catalogue covers 69 kW to 7,033 kW of cooling per machine. Scroll units NASA, NCSA and NWSA give 69–621 kW depending on conditions, water-cooled screw NWRA 436–1,412 kW, oil-free centrifugal NWCV 229–7,033 kW. Compare models only at your duty point: water 2 K colder and you need the next size up. For large chiller plants, machines are combined into a group with common control, which also gives N+1 redundancy. More in the article "What is a chiller"

Question 18

How Russian are NCT chillers?

Accepted Answer

They are built in Russia, while import dependence remains in certain components. Since 2014 the NCT plant in Sertolovo near St Petersburg has made chillers, cooling towers, dry coolers, pump stations and control panels, and we assemble screw machines ourselves. Nobody in Russia makes centrifugal compressors in series yet, so centrifugal machines use imported compressors. For any machine, check that compressor and heat exchanger makers have an official representative with a local parts warehouse. The best check of a supplier is a factory visit and a call to the chief engineer of a running site of the same capacity. More in the article "Cooling equipment made in Russia"

Question 19

What data is needed to select a chiller or a replacement for an old one?

Accepted Answer

At minimum: capacity or flow, the fluid (water, or glycol with type and concentration), inlet and outlet temperatures as fixed numbers rather than a range, and the design outdoor temperature with its source document. Add the machine type and installation location; for a water-cooled unit, the condenser loop temperatures; for a remote condenser, line length and height difference. Limits on noise, electrical capacity and dimensions are stated too: an empty field reads as "no limit". For a replacement, check the door opening and delivery route in advance. NCT runs the selection from the questionnaire free of charge. More in our design guides for engineers

Question 20

How do you provide redundancy: two circuits in one machine, a standby compressor or a second machine?

Accepted Answer

It depends on how long the site can live without cooling. Two independent refrigerant circuits in one machine give partial redundancy. Full redundancy is N+1: if any machine fails, the rest cover the load the customer has declared critical. For example, with 600 kW of process load and 400 kW of air conditioning, three 350 kW machines are enough if only the process needs backup. Machine redundancy is useless without power redundancy. Pumps are duplicated 1+1 with automatic changeover, and a buffer for 30–120 seconds of operation covers the switchover time. More in our design guides for engineers

Question 21

Can chiller capacity be controlled steplessly?

Accepted Answer

Yes, but it depends on the compressor type. Scroll and screw machines change capacity in steps by switching compressors on and off; screw units also have capacity control on the compressor itself. The number of steps is stated in the proposal for the specific model. NWCV centrifugal chillers are controlled steplessly by an inverter. If the site has deep part load, compare the smallest step with the minimum load and consider a stepless machine: it stops less often and needs a smaller buffer tank. More in the article "What is a chiller"

Question 22

What are a chiller's starting currents and how can they be reduced?

Accepted Answer

Starting current depends on the starting method. Per NCT catalogues, the NARV 95 screw unit with star-delta starting has a running current of 181 A and a starting current of up to 358 A. The NWCV 65-1 centrifugal unit with a variable frequency drive starts at 15 A against a maximum running current of 90 A. On a weak supply this argues for a soft starter or a compressor VFD; reactive power compensation also removes starting surges. Enter the power or current limit in the questionnaire, or the selection will ignore it. More in our design guides for engineers

Question 23

How can a chiller be made quieter?

Accepted Answer

Calculate noise before choosing the location, not after start-up. Sound levels add up: two identical machines give +3 dB, four give +6 dB; each doubling of distance in open space takes off 6 dB. Noise is reduced with a low-noise condenser, fan silencers, lower fan speed at night, acoustic screens, or a remote condenser with a larger coil and slower fans. A requirement like "no more than 40 dBA" cannot be met with factory options alone — it needs screens on site. Above residential and office spaces, use spring isolators: they pass less than 2% of pump vibration versus 16% for rubber pads. More in our design guides for engineers

Question 24

How much refrigerant to add per metre of piping, and why doesn't the factory give the pipe sizes?

Accepted Answer

The machine and condenser are charged per their data sheets; the piping is calculated separately. For R410A that is about 0.50 kg per metre of 28×1 liquid line and 0.12 kg per metre of 42×1.2 discharge line; a 25 m run needs 15.5 kg per circuit. Pipe sizes depend on length, elevations and the smallest capacity step — that is project data. Up to 15 m, pipe sizes equal the machine connections per the NCT manual; longer runs are calculated together with the factory and confirmed in writing. In practice refrigerant lines rarely exceed 30–50 m. More in our design guides for engineers

Question 25

How much space does a chiller plant room need?

Accepted Answer

As a first estimate: length three machine lengths, width two machine widths plus 4 m, height the machine plus 1.5 m for piping. For two 3.5 m long machines that is about 10.5 × 6.8 m. Final dimensions come from the tube pull and panel service zones on the factory drawing of the ordered model; no water piping above the panels, and the delivery route is checked in advance. An outdoor NASA packaged unit needs 1.5 m clearance on the control panel side and 1 m on the other sides. More in our design guides for engineers

Chillers: questions and answers