CTC heat pumps: EcoHeat, EcoAir and EcoZenith

CTC is a Swedish heating manufacturer whose UK-relevant range spans air-to-water heat pumps, ground source heat pumps and hot water storage, sold under the EcoAir, EcoHeat, EcoPart, EcoZenith and CombiAir names¹. Its air-to-water heat pumps are described by the maker as cost-effective and modulating, and every heat pump bought from CTC is supplied with its EnergyFlex concept, which prepares the system to be supplemented with other heat sources from the start¹. The company's paper trail in Europe is long: declarations of conformity for EcoAir, EcoHeat and EcoPart models were issued by Enertech AB in Ljungby, Sweden, between 2005 and 2013, and the GSi 16 ground source model holds a Keymark certificate dated June 2019.

For a household weighing energy independence, a CTC heat pump removes the gas pipe and the gas supplier from the equation, but it does not remove every dependence. The system runs on electricity, so the home remains tied to the grid and an electricity tariff, and the smart-control layer ties remote operation to broadband and the manufacturer's app. What CTC's design philosophy does offer is flexibility: a system built to accept solar heating, pools and additional heat sources is harder to lock into a single supplier's ecosystem than a closed one.

A Swedish maker with a long European paper trail

CTC's product pages present a manufacturer with a broad domestic range rather than a single flagship: air-to-water heat pumps, ground source heat pumps, hot water tanks and controls, all under one brand¹. The historical record backs the impression of an established European maker. Enertech AB, signing in Ljungby, issued the manufacturer declaration for CTC EcoLogic in February 2005, a declaration for CTC EcoAir in May 2005, a declaration of conformity for EcoAir products in November 2009, conformity declarations for the EcoHeat 306, 308, 310 and 312 in August 2011 and for EcoPart models in May 2012, and the EcoHeat 300 manual in April 2013. The GSi 16 ground source heat pump's Keymark certificate reached its second issue in June 2019.

That European manufacturing base is not the global norm. Only 15% of all heat pumps sold globally are manufactured in Europe⁴, so a buyer choosing a European-built unit is choosing a shorter supply chain for parts and service than most of the world's heat pump stock enjoys. The trade-off is that CTC is a smaller presence in the UK market than the big British and German brands, which shows up in the practicalities: fewer UK-trained installers, and product documentation that leans on the maker's own pages rather than a deep field of independent UK testing. The maker's claims about its own products are the main source of model-level detail, and they should be read as such.

The range at a glance

CTC's current families divide by heat source and by role in the system. The EcoAir line is air-to-water: the C100 is described as a cost-effective, modulating air-to-water heat pump providing on-demand heating and cooling all year round, the 600M is a series of ultra-efficient, speed-controlled air-to-water heat pumps, and the 700M is a modulating air-to-water heat pump¹. CombiAir is an efficient and speed-controlled heat pump in the same stable¹. The EcoHeat and EcoPart families are ground source, and the EcoZenith i360 sits alongside as the hot water and control unit².

The structure mirrors the wider heat pump market: an air source line for the majority of homes, a ground source line for those with land or borehole access, and a storage and control layer that ties the two together. More on the two main types is at air source heat pumps and ground source heat pumps.

EcoAir: air-to-water heat pumps that warm and cool your home

An air-to-water system distributes heat via the home's wet central heating system, so radiators or underfloor heating carry the warmth rather than blown air⁷. That is the key difference from air-to-air units, and it is why an EcoAir fits a house that already has, or can accommodate, a wet system. Air-to-water heat pumps tend to heat water to lower flow temperatures than boilers⁸, which shapes both the emitter choice and the running efficiency.

The C100's headline feature is that it provides on-demand heating and cooling all year round¹. Cooling through a wet system needs the right emitters: heat pump convectors and underfloor heating are the options that make the most of cooling via an air-to-water heat pump system⁹. A standard radiator circuit will heat well but cools poorly, so a household buying an EcoAir partly for summer cooling should check what the emitters can actually deliver.

On hot water, an air-to-water heat pump normally feeds a cylinder, and many heat pumps can provide hot water over 60°C consistently, the minimum temperature a hot water cylinder needs to guard against legionella¹⁰. Where a household instead considers an air-to-air unit, hot water is a separate question: some air-to-air systems can be connected to a domestic hot water tank, although not all do this, and otherwise a separate hot water heat pump cylinder, heat battery, electric immersion heater or point-of-use water heater would be needed⁹. On cold performance, heat pumps can work to an outdoor temperature of -20°C¹², which covers the coldest conditions a British winter produces. The full comparison of the two approaches is at air-to-air vs air-to-water heat pumps.

EcoHeat and GSi: heat pumps drawing warmth from the ground

CTC's ground source line, EcoHeat and EcoPart, works on the same principle as any ground source heat pump: it transfers energy from the natural heat stored in the earth to heat the home and domestic hot water⁶. Ground source heat pumps transfer heat from the ground into a building to provide space heating and, in some cases, pre-heating domestic hot water⁵. The ground loop or borehole is the expensive, permanent part of the installation, and it is what makes ground source the most independent of weather of the main heat pump types.

The GSi 16 holds a Keymark certificate, second issue dated June 2019, which is the European product certification scheme for heat pumps. UK recognition matters too: ground source heat pumps, including water source heat pumps and shared ground loops, are eligible technologies under the Boiler Upgrade Scheme¹³, the grant scheme that pays toward the installation cost. Ground source heat pumps are also within the scope of the VAT relief for energy-saving materials⁶. Detailed technical guidance on ground source heat pump systems, their design considerations and application, is published by CIBSE¹⁴, and the practical UK picture is at ground loops and boreholes and shared ground loop networks. A closer look at one model is at CTC EcoHeat 300.

EcoZenith i360 and accumulator tanks: holding heat for when you want it

CTC recommends the EcoZenith i360 for control and hot water alongside the EcoAir 600M². In a CTC system the tank is not an optional extra but the hub: it stores the hot water the heat pump produces, and in the i360's case it carries the control function too. Storage is what lets a heat pump run when conditions suit it and deliver heat when the household wants it, and it is the natural landing point for any second heat source, since solar input and heat pump input both end up as hot water in the same vessel.

That role is common to solar thermal as well. For domestic hot water from a solar thermal system you will need a heat transfer system and a hot water cylinder¹⁵, which is exactly the arrangement a tank like the EcoZenith is built to host. The sizing of the cylinder matters as much as the heat pump: a heat pump heating a cylinder takes longer than a boiler would, so undersized storage shows up as cold showers rather than cold rooms. The general principles are at hot water cylinders for heat pumps and buffer tanks and volumisers.

EnergyFlex: combining heat and electricity sources

EnergyFlex is CTC's name for the idea that a CTC heat pump is prepared from the start to easily supplement with virtually everything there is for heating¹. In the maker's own words:

CTC product page¹

In practice the concept shows up in the connections the systems accept. CTC states that pools and other heat sources such as solar heating can easily be added to its air-to-water heat pumps¹, and solar water heating can be used in the home or for larger applications such as swimming pools¹⁶. The EcoLogic control supports up to four different heating systems², which is the framework that lets a household combine, say, an EcoAir, a solar thermal loop and an immersion backup under one controller.

This is the most independence-oriented part of the CTC design. A system that can absorb solar heat, a pool loop and additional heating is a system the household can extend without discarding the original unit, and one that can keep some heating capability even if the heat pump itself is down. The limits are real, though: the control layer that orchestrates the combinations is CTC's own, so the flexibility runs through the manufacturer's ecosystem rather than around it. The wider picture of pairing panels with a heat pump is at solar panels and a battery with a heat pump.

What a CTC setup requires: water-based heating and the right size

A CTC air-to-water system is a hydronic system, and hydronic heating systems designed for heat pumps operate at low flow temperatures: published design guidance for efficient hydronic heating systems works at 55°C and below¹⁷. That single number drives most of the installation. Lower flow temperatures mean larger emitters, better insulation or both, and it is why the survey stage matters more with a heat pump than with a boiler replacement.

Sizing is the other half. The building regulations guidance is that heat pumps should be selected to meet the full space heating requirement at the design condition chosen for heat loss calculations¹⁸, and the practical method behind that is correctly sized heat pumps based on peak heat demand in watts¹⁹. An undersized unit may struggle to meet demand, while an oversized unit may cycle on and off often and lessen efficiency²⁰. Compact heat pumps are specifically designed to heat small, well-insulated modern flats and homes²¹, which is where a smaller EcoAir output fits.

Two house-specific checks are worth naming. Existing microbore pipes, typically 6 to 12mm, can be a problem: the household may need a high-temperature heat pump, which will be less cost-effective to run, or to replace all the pipework²². And the heat loss calculation itself is not optional paperwork; it is the difference between a system that holds the house at temperature on the coldest day and one that does not. The process is set out at heat pump sizing and heat loss calculations.

Efficiency: 2.5 to 4.5 units of heat per unit of electricity

A heat pump moves heat rather than burning fuel to make it, so its efficiency is expressed as a ratio. For every one unit of energy it uses, a typical heat pump produces between 2.5 and 4.5 units of heat, making heat pumps 250 to 450% efficient³. UK official guidance puts it more plainly: they can produce around 3 units of heat for every unit of electricity they use²³. A well-designed and installed heat pump typically provides 3 to 4 units of heat for every unit of electricity used²⁴, and the range across independent assessments runs wide, from 2 to 7 kilowatt-hours of thermal energy for every kilowatt-hour of electrical energy consumed²⁵.

The official measure is the seasonal performance factor. An SPF of 4.0 means that for every 1 kWh of electricity consumed, the heat pump delivers 4 kWh of heat²⁶. What moves a real installation along that range is mostly flow temperature: most heat pumps are capable of supplying 45 to 55°C heat with moderate efficiency, some exceeding 60°C²⁷, and every degree lower the system can run at buys efficiency back. That is the connection back to the hydronic design section: the emitters and the insulation determine the flow temperature, and the flow temperature determines the running cost. The measures are explained at COP, SCOP and SPF, and what UK homes actually achieve is at heat pump performance in UK homes.

Controls, charge pumps and other components alongside the unit

CTC's control system is EcoLogic, described by the maker as a unique control system that monitors and controls CTC's heat pumps, additional heating, buffer tanks, pools, cooling and more, for up to four different heating systems². On which units it pairs with, CTC's own pages give two designs: one for EcoAir 400-700M air-to-water heat pumps and one for EcoPart 400-600M geothermal heat pumps. The two statements differ, and neither is corrected by the other, so the pairing is a question to settle with the installer against the exact model being fitted.

On the smart side, the general pattern is well established: most smart heating controls link to your phone, and heating can be controlled via smartphone, tablet or laptop, or by telling your smart speaker what you want²⁸, with temperature settings accessible using a mobile app²⁹. What that adds to a CTC system is convenience and monitoring; what it costs is a standing dependence on broadband, the app and the manufacturer's servers for anything done remotely.

The circulation side has its own parts list. CTC publishes charge pumps matched to output: the Charge pump 25/75-130 is suitable for 10-12 kW heat pumps, specified at 7.5 m A-class PWM, and the Charge pump 25/85-130 is suitable for 14-22 kW heat pumps². For smaller outputs, CTC's published material does not name a matched charge pump, so that choice sits with the installer. Controls in general are covered at heat pump controls.

The limits of a CTC system

The first limit is the grid. A CTC heat pump is an electric appliance: no electricity, no heat, unlike a gas boiler that runs without mains power for its fuel. The household's exposure is to electricity prices and to the supply itself, which is why time-of-use tariffs and storage matter more with a heat pump than with a boiler. The second limit is the maker's ecosystem. EnergyFlex, EcoLogic and the app are CTC's own layer, and the flexibility they give is flexibility inside that layer; a household buying into it depends on CTC continuing to support the products.

The third limit is the house itself. Microbore pipework can force a high-temperature model or a full repipe²², and cooling through a wet system needs emitters built for it⁹. Where an air-to-air route tempts instead, hot water is not automatic: not all air-to-air systems connect to a hot water tank⁹. The maker's marketing also carries a claim of up to 85% savings on heating and hot water, which appears in CTC's own guidance and product pages; it is a maker's claim, not an independent finding, and the independent efficiency figures above are the sounder basis for expectation. Set against all this, the balance a CTC system offers is genuine: off the gas grid, into a European-built product line designed to take solar and other inputs, with the honest dependencies being electricity, the installer and the manufacturer's control layer.