Industrial process cooling generates significant heat as a by-product. In most facilities that heat is expelled to atmosphere and lost entirely. Installing a heat recovery system captures this excess heat and redirects it for practical uses: reducing reliance on gas boilers, cutting energy costs and lowering carbon emissions. Whether that investment makes sense depends on your site, your chiller type and what your heating infrastructure can actually accept.

This guide will lead you through the selection process: how to assess your site, what to check before specifying equipment and the practical factors that will determine whether a heat recovery project delivers a return, drawing on our engineers’ first-hand experience across industrial and process cooling projects, including retrofits to existing chiller systems and new-build installations.

Key Takeaways: The right heat recovery system depends on whether you have an air-cooled or water-cooled chiller. Older heating pipework may require isolation and filtration before connection. Heat recovery and free cooling are mutually exclusive in water-cooled systems, which is a design decision you’ll need to make upfront. A site survey is the most reliable way to confirm viability and likely payback.

Start with your chiller type

The single most important factor in selecting a heat recovery approach is whether your chiller is air-cooled or water-cooled. The two configurations require fundamentally different solutions.

Air-cooled chiller heat recovery

An air-cooled chiller rejects condenser heat by blowing ambient air across refrigerant coils. That warm discharge air is normally vented to atmosphere. With heat recovery, the warm air is ducted into the building instead (typically a factory floor, warehouse or production area) where it contributes to space heating.

The control mechanism is a damper system. On simpler installations this is manually operated, whereas more practical setups use a temperature-controlled automatic damper that opens when the internal space requires heating and closes when the set temperature is reached, or when outside conditions make heat input unnecessary.

This approach works best for smaller industrial units and single-building sites that do not have a centralised heating circuit. It’s straightforward to retrofit and relatively low-cost compared to water-cooled alternatives.

Water-cooled chiller heat recovery

A water-cooled chiller uses a secondary water circuit to carry condenser heat away – typically to a dry cooler or cooling tower where it’s rejected. Heat recovery works by diverting some or all of that secondary circuit flow into a low temperature hot water (LTHW) ring main, which then distributes recovered heat around the site.

The recovered heat from a water-cooled chiller is low-grade, typically in the 35-45 degrees Celsius range. That is sufficient for radiators, fan heaters, unit heaters and air handling unit coils, but not for domestic hot water or wash-down applications, which require higher temperatures for Legionella control compliance.

Water-cooled heat recovery suits larger industrial sites with an existing centralised heating infrastructure. If your site has a ring main serving multiple buildings or production areas, the water-cooled route offers greater flexibility and a wider range of end-uses for the recovered energy.

Check your site heating infrastructure

The heat recovered from a chiller condenser needs somewhere to go. Without the right infrastructure to distribute and use it, the economics of a heat recovery project fall apart. Before specifying anything, assess what your site actually has in place.

 

Assess whether heating and cooling demands overlap

Heat recovery delivers value when your cooling system is running at the same time as your site has a heating demand. That overlap typically occurs in winter and the surrounding months.

A process cooling system that runs year-round, common in pharmaceutical, food and beverage, chemical and manufacturing environments, will generate recoverable heat throughout the winter, exactly when the heating demand is highest. In that scenario heat recovery can reduce or offset the running costs of your gas boilers or electric heaters directly and consistently.

A site that only runs cooling in summer with no concurrent heating need will see little practical benefit. The heat is available, but there is no demand for it, so it contributes nothing to energy cost reduction.

From our experience: the best candidates for heat recovery are sites with continuous or near-continuous process cooling requirements running alongside significant space heating loads: manufacturing plants, multi-building industrial campuses and pharmaceutical or chemical processing facilities are typical examples.

Check the condition of your existing heating pipework

If you have an existing LTHW heating circuit, its condition matters before anything else is connected to it. This is a step that is easily overlooked and can cause serious problems if ignored.

Heating circuits installed over 15-20 years ago are commonly built from mild steel pipework. Over time, corrosion produces rust particles and other contaminants that accumulate in the system. When heat recovery equipment (particularly a heat exchanger or chiller condenser) is connected to a contaminated circuit, those particles migrate into the new equipment and cause fouling, reduced performance and potentially early failure.

The correct approach is to install an intermediate heat exchanger that isolates the new heat recovery circuit from the old heating system, so the two water circuits never mix directly. A magnetic filter or strainer on the return side of the old circuit adds a second layer of protection, capturing particulate before it can reach the new equipment.

We encountered this issue on a project at a chemical manufacturing site where the existing LTHW circuit was well over a decade old. The contamination risk was identified during the site survey and isolation plus filtration was designed in from the start. Without that assessment, the result would have been a blocked condenser and a costly early failure.

The lesson: a site survey covers more than sizing the equipment. Understanding what the equipment will be connected to is equally important.

Decide between heat recovery and free cooling

If you are also evaluating free cooling systems as an energy efficiency measure, you need to resolve one key constraint: heat recovery and free cooling are mutually exclusive in water-cooled installations.

Free cooling uses low ambient temperatures to pre-cool the secondary water circuit before it reaches the chiller, reducing compressor load and energy consumption. Heat recovery uses the same secondary circuit to carry condenser heat to the site heating distribution system. The two approaches pull that circuit in opposite directions.

Trying to optimise for both simultaneously undermines the performance of each, making this a design-stage decision that must be made before installation begins. Which option delivers greater financial value for your site depends on your energy profile, heating and cooling loads and operating hours.

If you’re weighing up both options a site assessment will help establish the relative value of each and clarify which path to take.

Sizing and specification: what you need to know

Sizing a heat recovery system starts with understanding your cooling load. A useful planning approximation is that for every 100 kW of cooling a chiller delivers, approximately 133 kW of heat is produced at the condenser (reflecting the physics of the refrigeration cycle: the chiller’s compressor adds energy to the system, so the heat rejected at the condenser is always greater than the cooling delivered at the evaporator). The actual figure varies depending on the chiller’s design, coefficient of performance and operating conditions, but the 100:133 relationship gives a reliable starting point for estimations.

Beyond the cooling load, the specification process needs to account for:

  • Available heating demand on site: how much heat can actually be used and when
  • The type of heat distribution infrastructure: ring main temperatures, AHU coil ratings, heater specifications
  • Pipework materials and condition: particularly relevant for water-cooled retrofits on older sites
  • Seasonal operating patterns: the proportion of the year where heating and cooling overlap
  • Control strateg: whether automatic dampers or a BMS-integrated circuit bypass is required

Sizing that ignores any of these factors risks either undersizing the heat recovery capacity (leaving recoverable energy on the table) or oversizing it (investing in equipment the site cannot use). A site survey resolves this by gathering the actual figures before any equipment is specified.

Can heat recovery be retrofitted?

Yes, heat recovery can be retrofitted to both air-cooled and water-cooled chillers. The main variables are the age and condition of the chiller, the available space for ducting or pipework modifications and the state of the existing heating infrastructure.

Air-cooled retrofits are generally more straightforward. The main requirement is adding a duct connection to the condenser discharge, a damper system and appropriate controls. On many sites, this can be done with minimal disruption to the cooling system.

Water-cooled retrofits involve more detailed assessment. In addition to the pipework contamination considerations covered above, the existing secondary circuit configuration needs to be reviewed to confirm that heat recovery can be integrated without compromising chiller performance or free cooling capability.

In both cases, the retrofit process should start with a site survey rather than a specification. The survey identifies what is possible, what constraints apply and what the likely return on investment looks like given the site’s actual operating profile.

Assess Your Site for Heat Recovery

Selecting the right heat recovery system means working from your site’s actual data – chiller type, heating infrastructure, operating hours, pipework condition – rather than assumptions. Getting those inputs wrong at the design stage leads to undersized systems, equipment failures, or projects that simply do not deliver a return.

Our engineers carry out site surveys specifically to assess heat recovery potential. We review your existing cooling and heating configuration, identify any constraints and provide practical recommendations – including whether heat recovery for industrial process cooling is suitable or an alternative energy reduction strategy is the better fit for your site.

We also offer a free energy assessment for sites looking to reduce the energy consumption of their existing cooling systems. Contact our team to discuss your requirements.

FAQ's

How do I know if my site is suitable for heat recovery?

The key tests are: does your cooling system run during the months when your site needs heating? Do you have an air-cooled or water-cooled chiller? Is there existing heating infrastructure (a ring main, radiators, fan heaters or AHUs) that can accept low-grade hot water or ducted warm air? If the answers are yes, a site survey will establish the specifics. If your cooling only runs in summer with no concurrent heating demand, heat recovery is unlikely to be cost-effective.

What is the difference between air-cooled and water-cooled heat recovery?

Air-cooled heat recovery ducts warm condenser discharge air into a building for space heating. Water-cooled heat recovery diverts condenser heat via the secondary water circuit into an LTHW ring main, supplying radiators, fan heaters and AHUs. Air-cooled suits simpler sites without a centralised circuit. Water-cooled suits larger sites with existing heating distribution infrastructure.

Can heat recovery work alongside free cooling?

Not simultaneously in a water-cooled installation. Both systems use the secondary circuit – heat recovery to distribute warmth around the site, free cooling to exploit low ambient temperatures. This is a design-stage choice. If you are evaluating both, a site assessment will identify which delivers greater value for your specific energy profile.

How much heat can I recover from my chiller?

As a planning figure, for every 100 kW of cooling your chiller provides, approximately 133 kW of heat is generated at the condenser. The actual amount available for recovery depends on how much of that heat your site can use, when and via what distribution route. A site survey will assess your real demand against the available supply.

Does the age of my heating pipework matter?

Yes. Older mild steel pipework commonly contains rust particles and contaminants that can block or damage new heat recovery equipment. If your LTHW circuit is more than 15-20 years old, isolating it from the new heat recovery equipment using an intermediate heat exchanger (alongside appropriate filtration) is the standard approach to protect your investment.