Commercial Heat Pumps: Types, Where They Fit, What to Check

What the federal rules count as a commercial heat pump

DOE's rule in the Code of Federal Regulations (CFR), 10 CFR 431.92, defines commercial package air-conditioning and heating equipment as electrically operated unitary central air conditioners and central air-conditioning heat pumps for commercial application. It covers air-cooled, water-cooled, evaporatively-cooled and water-source equipment. Ground water source equipment is excluded from that definition.

The same rule sorts the equipment by rated cooling capacity: small is below 135,000 Btu/h, large is at or above 135,000 and below 240,000 Btu/h, and very large is at or above 240,000 and below 760,000 Btu/h.

The rule then names the configurations. A single package unit has all its major assemblies in one cabinet. A split system has one or more major assemblies separate from the others. Separate definitions cover variable refrigerant flow (VRF) multi-split heat pumps, water-source heat pumps and packaged terminal heat pumps (PTHPs).

A PTHP is a packaged terminal air conditioner that uses reverse cycle refrigeration as its prime heat source. A PTHP also has a supplementary heat source of hot water, steam or electric resistance, and the rule says it is industrial equipment. Through-the-wall units are covered on through-the-wall AC and PTAC.

The rule also defines these ratings. It calls the integrated energy efficiency ratio (IEER) a weighted average calculation of mechanical cooling EERs determined for four load levels and corresponding rating conditions, in Btu/watt-hour. It defines the coefficient of performance (COP) as cooling or heating effect over net work input, in identical units. For water-source heat pumps it adds the applied coefficient of performance (ACOP), the ratio of heating capacity to power input, including system pump power.

Heat pump rooftop units: all-electric, dual fuel, cold climate

DOE's Better Buildings guide on heat pump rooftop units says they are technologically similar to air-conditioning RTUs. The difference is that they add reverse-cycle heating. The guide names three kinds: all-electric, dual fuel and cold climate. A dual fuel unit combines heat pump heating with gas or propane backup heating.

The guide says heat pump heating efficiency falls as outdoor temperatures drop, trending toward parity with electric resistance heat. It says these units are best suited to mild-to-moderate winters. For most of the U.S. South and West, it calls today's heat pump RTUs an appropriate solution. It says they can cover most or all winter heating demand there.

The guide also warns that southern climates can still see sharp winter heating demand, citing the Texas cold snap of February 2021. It notes that most all-electric units bring on electric resistance heat during the defrost cycle. That keeps the space warm while the refrigeration cycle reverses to heat the outdoor coil. Defrost itself is explained on heat pump defrost mode.

For procurement, the guide lists capacity, seasonal efficiency, heating performance and switchover temperature as key points to compare across manufacturers. Our reading of its footnote: the switchover temperature is the outdoor temperature at which the unit hands heating to its backup. Ask for that figure, and for the backup heat's capacity, in writing.

VRF heat pumps and heat recovery

DOE's rule defines a VRF multi-split heat pump as a unit of commercial package air-conditioning and heating equipment that is configured as a split system heat pump that uses reverse cycle refrigeration as its primary heating source. It may add supplemental heat from electrical resistance, steam, hot water or gas. The rule says the equipment incorporates a single refrigerant circuit, one or more outdoor units, at least one variable-speed compressor or an alternate compressor combination that varies capacity by three or more steps, and multiple indoor fan coil units. Each fan coil unit is individually metered and individually controlled by a control device and common communications network, and can operate independently in response to multiple indoor thermostats. The rule says variable refrigerant flow implies three or more steps of capacity control on common, inter-connecting piping. In the rule, heat recovery means the heat pump is also capable of providing simultaneous heating and cooling operation, where recovered energy from the indoor units operating in one mode can be transferred to one or more other indoor units operating in the other mode.

The 2012 PNNL report, prepared for the General Services Administration (GSA), gives the scale. Compressor units run from 6 to 30 tons without heat recovery, and 6 to 24 tons with it. Fan coil units typically range from 0.5 to 8.0 tons. A single compressor unit can serve 60 or more indoor units.

The report describes two piping layouts. A two-pipe system sends heating or cooling to each space through one pipe and returns refrigerant through the second. A three-pipe system has separate cooling and heating lines to each indoor unit, plus a return line.

PNNL notes that energy codes require economizers but may exempt VRF systems in some cases. It says components are not compatible across manufacturers, and manufacturers are often involved in system design. PNNL says ASHRAE Standard 15 is the Safety Standard for Refrigeration Systems. Long refrigerant lines through small rooms could exceed its refrigerant-to-space limit, triggering its requirements for refrigerant mechanical rooms. The choice between VRF and a chilled-water plant is on chiller vs VRF.

Water-source heat pumps and shared water loops

DOE's rule defines a water-source heat pump as commercial package air-conditioning and heating equipment that is a single-phase or three-phase reverse-cycle heat pump that uses a circulating water loop. The loop is its heat source for heating and its heat sink for cooling. The listed components are a compressor, refrigerant-to-water and refrigerant-to-air heat exchangers, expansion devices, a reversing valve and an indoor fan. Coil-only units have no indoor fan.

PNNL describes this kind of water loop when it covers water-source VRF compressor units, which it says are less frequently linked by a common water loop similar to water-source heat pump systems. The cooling source is typically a cooling tower and the heating source is typically a boiler. Ground-source well fields, ground or surface water, or waste heat can also serve. In the report's words, "If a boiler is used, this becomes the primary heat source and does not reduce heating energy usage."

When multiple VRF compressor units are connected through the water loop, PNNL says heat recovery between them can occur when some operate primarily in cooling and others primarily in heating. Within a single VRF system, PNNL says heat recovery occurs inside the refrigerant loop of a compressor unit and its fan coil units, not between multiple compressor units as with a water-source heat pump system. It adds that VRF uses smaller refrigerant piping and needs no cooling tower or boiler.

The condo case, where the loop is shared building equipment, is on condo water-source heat pumps.

Where each type fits, and what to check before you replace

The Better Buildings guide calls RTUs suitable for many buildings, especially low- to mid-rise buildings with flat roofs and ductwork.

For outdoor air, PNNL says VRF systems typically recirculate room air, so outdoor air has to be provided separately. It says a dedicated outside air system (DOAS) is typically used. PNNL notes that in humid climates, much of the cooling energy goes to removing moisture. It also says coordinating DOAS control with the VRF fan coil units can be problematic.

PNNL notes lab testing by the Florida Solar Energy Center and the Electric Power Research Institute (EPRI). That testing was raising questions about possible differences between actual VRF performance and AHRI-certified performance. Our reading: ask how a quoted system's ratings were tested.

Before replacing a gas or electric-heat RTU with a heat pump unit, the guide raises these checks.

1. Plan ahead. The guide says switching during an emergency replacement is typically not ideal, and the most efficient units are built to order with longer lead times.
2. Electrical capacity. All-electric units may need upgrades to the electrical infrastructure, and depending on the local electrical code, the utility may need to upgrade the building's electrical service.
3. Curb and roof. The new unit may differ in size and weight, so a larger curb may be needed.
4. Ductwork. Supply air temperatures differ between heat pump and fuel-fired heat, so the ducts may need redesign if design airflow differs.
5. Gas lines. An all-electric retrofit may leave gas piping to decommission and remove.
6. Contractor experience. The guide says contractors who have already worked on heat pump RTUs should be preferred.

The guide says it is essential to do a more holistic evaluation of costs via a lifecycle cost analysis. Curbs, cranes and phasing are covered on rooftop unit replacement planning.

Refrigerant dates, Florida license class and certification

EPA's technology transitions tables list residential and light commercial air conditioning and heat pump systems, with mini-splits and unitary systems as examples, at a global warming potential (GWP) limit of 700. The installation compliance date for those systems is January 1, 2025, and EPA lists no installation compliance date for systems where all specified components were manufactured or imported before January 1, 2025. The sources here do not say whether a given commercial packaged unit falls in that residential and light commercial row. EPA lists VRF systems at the same GWP limit of 700, with an installation compliance date of January 1, 2027, subject to exceptions in its footnote.

EPA says components used to repair existing systems are not subject to these restrictions. It calls the tables informational and says they should not be relied on for compliance. The commercial page on the refrigerant transition covers the new refrigerants.

Under the 2026 Florida Statutes, a Class B air-conditioning contractor is limited to 25 tons of cooling and 500,000 Btu of heating in any one system. Our reading: one VRF system can pass the 25-ton Class B limit, so ask which class the contractor holds.

EPA's Section 608 rules treat attaching gauges or adding and removing refrigerant as technician work. Type II certification is for servicing or disposing of high- or very high-pressure appliances, except small appliances and motor vehicle air conditioners (MVACs). Our reading: ask which certification type covers the equipment you are buying.