Ice rink refrigeration systems sized from the real heat load

The refrigeration plant is the engine of a real-ice rink, but nominal cooling capacity alone does not determine whether the system will perform well. Two rinks with the same surface area can require very different plants because climate, building conditions, solar radiation, humidity, ice temperature, resurfacing, operating hours and hydraulic design change the actual heat load.

SPORTWAVE therefore selects refrigeration as part of the complete rink system: chiller or refrigeration plant, heat rejection, pumps, secondary circuits, manifolds, controls, ice-floor technology and energy management are engineered together.

Do not size an ice rink from square metres alone

ASHRAE provides useful preliminary capacity ranges for checking a calculated design. For a sports arena it gives approximately 2.9–4.2 m² of ice per kW for operation up to seven months and approximately 2.6–3.7 m²/kW for eight-month to year-round operation.

These values are deliberately broad. ASHRAE states that the table should be used only to check the calculated refrigeration requirement, not replace the heat-load calculation.

The actual design capacity must satisfy the larger of two conditions: the capacity needed to build the ice within the required time, or the capacity needed to maintain the required ice temperature during the most severe coincident operating conditions.

Engineering note
A full-size rink cannot be specified reliably by saying “X kW per square metre”. The same ice area in a controlled indoor arena and on an exposed outdoor site can have fundamentally different loads.

Source: ASHRAE Handbook — Refrigeration, Chapter 44: Ice Rinks.

Where does the refrigeration load actually come from?

Indoor-rink research published by ASHRAE shows why refrigeration is a system problem rather than a simple floor-area calculation. In the example conditions, major components of the daily refrigeration load are approximately:

The exact percentages vary with climate and operation, but the design lesson is consistent: improving only the compressor does not address most of the variables that create the load.

Indoor and outdoor rinks are different refrigeration problems

An indoor arena can control air temperature, humidity, air velocity and roof radiation. An outdoor rink must accept weather as part of the design condition.

For exposed outdoor ice, ASHRAE identifies solar radiation, wind, rain, air temperature and humidity as direct refrigeration-load factors. Solar load alone can become a major component. Shade, site orientation and operating strategy can therefore change the plant requirement without changing the rink area.

This is especially important for long seasonal operation or professional outdoor events where the refrigeration system must maintain ice through unfavourable daytime conditions rather than only during cold nights.

Three practical refrigeration architectures

AST refrigeration solutions can be configured around several plant concepts. The correct choice depends on capacity, site constraints, heat-rejection method, sound limits, installation speed, service access and whether heat recovery is required.

Air-cooled compact chillers

Factory-built outdoor units combine the main refrigeration components in one package. They are practical for many mobile and seasonal projects because installation and connection can be relatively fast.

Selection should consider maximum and minimum ambient temperatures, sound limits, electrical supply, hydraulic distance to the rink, transport and service access. A compact unit is not automatically the best choice for a large permanent arena simply because installation is easier.

Air-cooled split systems

Split concepts separate parts of the refrigeration and heat-rejection system. This gives more freedom where plant location, architecture, noise or service constraints prevent the complete package from being installed in one position.

The trade-off is greater project coordination: refrigerant piping, controls, commissioning boundaries and service responsibility have to be defined carefully.

Liquid-cooled and central plant systems

For larger permanent facilities, the refrigeration plant may reject heat through a separate liquid circuit and dry cooler, cooling tower or building energy system. This arrangement can be especially useful where indoor plant rooms, lower outdoor noise, centralised equipment or substantial heat recovery are priorities.

Indirect versus direct ice cooling

Many rink systems are indirect: the primary refrigerant remains in the refrigeration plant and cools a secondary fluid, such as a glycol-water mixture, which is pumped through the ice floor or EPDM mats. This limits refrigerant distribution across the rink and gives flexible hydraulic integration.

Direct systems circulate the primary refrigerant through the rink circuit itself. They can remove an intermediate heat exchanger and pumping stage, but refrigerant charge, pressure, safety and installation requirements become more significant.

The IIHF Arena Guide shows both approaches and emphasises that system selection must account for refrigerant characteristics, pumping energy, heat recovery, safety and lifecycle efficiency rather than one efficiency number alone.

Hydraulics can consume a meaningful part of the cooling capacity

The secondary circuit is not a passive connection between chiller and ice. Pump electricity ultimately becomes heat in the coolant and therefore adds to the refrigeration load.

ASHRAE notes that coolant pump heat can represent up to approximately 11% of refrigeration load. Correct pipe sizing, low pressure loss, balanced manifolds, high-efficiency pumps and variable or staged flow control can therefore produce material savings.

Uniform flow is also essential for ice quality. Poor hydraulic balance can create temperature differences across the rink even when the chiller itself has sufficient capacity.

Engineering note
A larger pump is not a substitute for good hydraulic design. Excessive flow increases pumping energy, while insufficient or unbalanced flow creates poor heat transfer and uneven ice.

Source: ASHRAE Handbook — Refrigeration, Chapter 44.

Ice temperature is an energy setpoint, not just an ice-quality setting

Every reduction in required ice temperature makes the refrigeration system work against a larger temperature difference. The plant should therefore maintain the warmest ice that still provides the required quality for the activity.

Hockey generally requires harder and colder ice, figure skating somewhat warmer ice and recreational skating warmer conditions again. Controls should support different operating modes instead of forcing every session to run at the coldest possible setpoint.

Secondary-fluid temperature should also not be driven lower than necessary. A lower suction or evaporation temperature reduces refrigeration efficiency and can increase compressor energy considerably.

Refrigerant strategy must match the project

Refrigerant selection is not only an environmental decision. It also affects operating pressure, plant-room safety, heat-recovery temperature, refrigerant charge, service competence, efficiency and regulatory obligations.

Permanent ice facilities may use natural refrigerants such as CO₂ (R744) or ammonia (R717), while other systems may use lower-GWP HFO or HFC/HFO solutions where appropriate. The final design must comply with applicable European refrigerant, pressure-equipment and machinery requirements as well as EN 378 where relevant.

SPORTWAVE evaluates refrigerant together with plant architecture and local serviceability rather than presenting one refrigerant as universally correct.

Heat recovery changes the economics of a permanent plant

Refrigeration moves heat from the ice to the condenser. That rejected heat can be treated as a waste product or as a useful energy source.

For permanent arenas, recovered heat may support domestic hot water, showers, ventilation heating, dressing-room heating, resurfacing water, snow melting or underfloor frost protection. ASHRAE reports that suitable heat-recovery systems can provide approximately 75–100% of facility space- and water-heating requirements, depending on plant type and building loads.

Heat recovery must nevertheless be designed around useful temperature levels and simultaneous demand. Raising condensing pressure only to obtain hotter water can increase compressor energy, so the complete energy balance matters.

Controls determine how much of the installed efficiency is actually used

Refrigeration load changes continuously with weather, occupancy, resurfacing and operating schedule. The plant should therefore modulate rather than behave as a fixed-capacity machine.

Useful control functions include ice-temperature sensing, secondary-fluid supply and return temperatures, compressor staging, variable pump control, condensing-pressure optimisation, alarms, energy metering and remote diagnostics.

AST EasyCHILL can be integrated with suitable systems for monitoring, functional supervision, automatic fault messages and operating optimisation. AST currently communicates savings of up to 60% in chiller operating time / energy consumption in suitable applications; actual results depend on climate, rink design, schedule and control strategy and should not be treated as a guaranteed project saving.

Redundancy should match the consequence of failure

A seasonal public rink and a year-round competition venue have different risk profiles. Permanent facilities may justify multiple compressors, pumps or other redundant components so that normal ice can be maintained if one component is unavailable.

ASHRAE recommends multiple compressors for rink systems and notes that a remaining compressor should be capable of maintaining the ice under normal operating load when a two-compressor arrangement is used. The redundancy philosophy should be defined from the operational and commercial consequence of downtime.

Noise, location and service access are design parameters

Plant location influences more than pipe length. Air-cooled equipment may be limited by nearby housing, hotels or event spaces. Enclosures and acoustic screens can affect airflow and condenser performance if added without engineering.

Permanent plants require safe service clearances, ventilation, lifting or replacement routes and access to pumps, strainers, controls and heat exchangers. These requirements should be shown in the building layout before equipment is ordered.

Integration with rink technologies

SPORTWAVE refrigeration systems can be engineered for:

• AST EPDM mobile and semi-mobile ice mats;
• AST IceBox and SkateWay® configurations;
• AST IcePhalt® permanent and multifunctional surfaces;
• traditional concrete ice slabs;
• temporary professional and event ice;
• existing-rink refrigeration modernisation.

The objective is one coordinated thermal and hydraulic system from plant room to ice surface.

Information required for a refrigeration concept

• rink dimensions and geometry;
• project location and design climate;
• indoor, covered or outdoor installation;
• operating season and daily operating hours;
• intended use and required ice quality;
• ice-floor construction and insulation;
• planned resurfacing method and frequency;
• available electrical supply;
• preferred plant and heat-rejection location;
• noise restrictions;
• building HVAC and humidity conditions for indoor arenas;
• potential heat-recovery loads;
• required redundancy and service strategy.

From these inputs, SPORTWAVE can calculate the design heat load, define the refrigeration and hydraulic architecture, establish the required control strategy and prepare the technical basis for equipment selection and quotation.