Category: Air Conditioning

Trying to cool a five-storey office building with split units is like putting a separate generator in every room: it works, but it can neither be managed nor run efficiently. Dozens of outdoor units on the façade, fault tracking floor by floor, a total on the bill that nobody can account for. VRF exists precisely to end that mess.

What does VRF do?

VRF (Variable Refrigerant Flow) is a central system in which dozens of indoor units connect to a single outdoor unit. The critical difference is this: the outdoor unit runs only as hard as the current total demand of the indoor units. If 12 of 40 offices are occupied, the system spends energy for 12 rooms. Each space picks its own temperature independently, and on heat recovery models one room can be cooled while another is heated at the same moment — a single system answers the different demands of a sunlit south façade and a shaded north façade on the same day.

Where do split and multi-split end and VRF begin?

Roughly past five or six spaces, multi-split starts to strain both in pipework and in management; at building scale VRF has no alternative left.

What does it give the operator?

• Part-load efficiency: a system almost never runs at full load; VRF holds its efficiency at part load, and that is where the bill gains.
• Management from one point: every indoor unit is monitored from a central panel, working-hours scenarios are defined and empty floors are turned down automatically.
• A clean façade: a few units on the roof instead of dozens on the walls.
• Scalability: floors can be commissioned and expanded one at a time.

When you combine the central management side with our approach to corporate energy efficiency, VRF stops being merely air conditioning and becomes the building’s energy management tool.

Two conditions for success with VRF: design and maintenance

VRF is not a forgiving system: if the load calculation, the pipe runs and the indoor unit selection are not designed correctly from the start, comfort complaints get blamed on the system. The second is maintenance: if the filters of dozens of indoor units and the coil of the outdoor unit are not cleaned to a schedule, efficiency quietly melts away. That is why we hand VRF over to our corporate customers together with a periodic maintenance agreement.

Projenza Engineering and Energy Solutions — an Ankara-based mechanical installation and energy company. About Us • Services • Projects • References

Last winter we took a call from the management of an office tower: “We have three floors of offices, the fan coils are practically new, but nobody is happy with the temperature. One floor is sweating, another is freezing.” We went, we looked; there was nothing wrong with the units. The problem was in the thermostats fitted ten years earlier — single-speed, neither programmable nor centrally monitored. In fan coil systems the real key to both comfort and the bill is usually not the unit itself but the small box that governs it.

Changing a thermostat sounds simple, but pick the wrong model and it will either fail to drive the valve, fail to manage the fan, or not suit the existing wiring. Below is the selection logic we have been applying on site for years, set out as plainly as we can.

First, know your system: two-pipe or four-pipe?

This is the most critical question in the selection, and the answer is hidden in your pipework. In two-pipe systems a single flow-and-return line reaches the fan coil; hot water in winter and chilled water in summer pass through the same pipe. It is enough for the thermostat to manage one valve. In four-pipe systems the heating and cooling lines are separate — one room can be heated while another is cooled on the same day. Here the thermostat has to drive two valves independently. Fitting a four-pipe thermostat on a two-pipe system is a waste of money; the reverse is a system that plainly does not work.

Fan control: the on-off era is over

Older thermostats either run the fan flat out or switch it off. Until the room reaches the target the fan runs at full noise, then falls completely silent, then starts again half an hour later. That cycle is both loud and inefficient. Even three-speed control (low-medium-high) makes a large difference; on units with EC fans, proportional (modulating) control adjusts fan speed continuously with the temperature difference. The result: a quieter office, less electricity, a steadier temperature.

Wireless or networked?

For a single shop or home a wireless thermostat is the practical answer; it goes in without breaking walls or renovating. Once you reach a building with dozens of spaces — a hotel or a multi-storey office — the picture changes: walking room to room to change settings is not manageable. Thermostats that communicate over Modbus or IP gather every space onto one panel. Reception puts the air conditioning of empty rooms into eco mode with one click; at the end of the working day every floor is turned down automatically. In hotels you can even tie this to the reservation system — a room that is not sold is a room that is not heated.

Our recommendation: Cosa for app-based control, Siemens at building scale

The solution we install most often in homes and small businesses is the Cosa smart room thermostat family, developed in Türkiye: programming from an app, remote control, location-based automation (turn down when you leave, warm up as you approach) and a 230 V model for fan coils. There is also an air conditioner control version for making an existing split unit smart.

On the commercial side we also supply Siemens. The RDF300.2 is a flush-mounted fan coil thermostat that supports both two-pipe and four-pipe systems and whose user settings can be locked — which is exactly what shared buildings need. Where comfort expectations are higher, the RDG160T with its touch surface and modulating 0-10 V output removes the temperature swing of on-off control altogether. We carry out the installation and commissioning ourselves and recommend the model that fits whatever wiring you already have.

Answer these five questions before you decide

• Is my system two-pipe or four-pipe? (How many valves will be driven?)
• How many fan speeds are there, is it an EC fan? (On-off or proportional?)
• How many spaces are there? (A single room, or central management?)
• What wiring do I have? (Is wireless needed, or 230 V?)
• Do I want remote access and programming?

If the answers to these are clear, the right thermostat appears on its own. If you are unsure, we come out for a survey; we look at the existing installation and recommend a specific model. If you are curious how much difference a thermostat makes on the energy side, have a look at our article on saving energy with a smart thermostat.

Projenza Engineering and Energy Solutions — an Ankara-based mechanical installation and energy company. About Us • Services • Projects • References

The first question anyone buying an air conditioner asks is predictable: “How many BTU do I need?” Yet most wrong answers come not from the question itself but from looking at nothing except floor area. The same 25 m² room wants one capacity if it faces south, another if it is a top-floor flat under the roof, and something else entirely if five people work in it.

Capacity: floor area alone is not enough

BTU figures worked out roughly from room area are a starting point, not a decision. Insulation, glazed area, which way the façade faces, ceiling height, the number of people and machines in the room all enter the calculation. An undersized unit cannot keep up and runs non-stop; an oversized one switches on and off in short cycles, fails to remove humidity and leaves an uncomfortable chill behind. Both mean excess electricity. If you are in doubt, ask for a survey; ten minutes of looking beats years of the wrong capacity.

Inverter: not even a debate any more

A fixed-speed compressor either runs at full power or stops. An inverter compressor adjusts its speed to demand: when the room reaches the target it glides along at low speed instead of stopping. Less electricity, less wear from starting and stopping, quieter operation. For any space with long running hours, inverter is the clear choice.

How do you read the energy label?

The SEER (cooling) and SCOP (heating) figures on the label show the real seasonal efficiency. An A+++ unit produces the same coolness with noticeably less electricity than a class A one. The difference in purchase price comes back within a few seasons under heavy use. If you are going to use the air conditioner for heating in winter as well, pay particular attention to SCOP — in an Ankara winter that difference shows up on the bill.

Installation: bad installation ruins a good air conditioner

The airflow from the indoor unit must not be blocked by furniture, the outdoor unit must hang somewhere out of the sun with air circulation around it, the copper pipe run must stay within the manufacturer’s limits, and the vacuum procedure must not be skipped. In most installations boasted about as “we fitted it in half an hour”, the vacuum was skipped — and that comes back as lost efficiency and early failure. We do the installation with our own team, with a workmanship guarantee.

After the purchase: a maintenance calendar

An air conditioner is the appliance you bought while its filter is clean and its refrigerant charge is full; both deteriorate with time. Servicing once a year (twice under heavy use) preserves efficiency and prevents bad odours and breakdowns. We provide one-off servicing for households and contracted periodic maintenance for businesses — the details are on our Ankara air conditioner maintenance and service page.

On the product side we handle selection, installation and maintenance from one place, from domestic air conditioners to commercial solutions and VRF central systems for multi-storey buildings.

Projenza Engineering and Energy Solutions — an Ankara-based mechanical installation and energy company. About Us • Services • Projects • References