Preventive HVAC and Chiller Maintenance — Efficiency, Comfort, and Real Savings

The HVAC system is the beating heart of an office building, and also the most expensive system to maintain and operate. The chiller alone accounts for the largest share of energy in the building, and when it fails on a hot day — the entire building grinds work to a halt within a few hours. The problem: HVAC tends to look fine as long as the load is low. It passes a relaxed inspection in spring, and then collapses at the peak of August — exactly when the tenants need it most. From my experience as a building manager, this pattern repeats itself with maddening consistency. Proper preventive maintenance is built to catch this silent failure before it erupts.

Why HVAC That Passes an Inspection in Spring Fails in August

This is the classic mistake of owners and property managers: they order an HVAC inspection in a comfortable month, the technician measures pleasant air temperatures on every floor, signs off that "everything is fine" — and in August the calls begin. I have seen it happen more than once: an HVAC contractor who shows up in the weeks between Passover and Shavuot, stands in a pleasantly air-conditioned room, and reports that everything is excellent.

The explanation is physical and simple. In spring, the thermal load on the building is low — less solar radiation, fewer employees actually present, and sometimes a bit of night cold that helps the system recover. The chiller works lazily and provides cooling even when it is far from full output. Hidden faults — a refrigerant shortage, a compressor beginning to wear, a dirty condenser, poor water flow — simply do not manifest when there is no real demand.

The moment the outside reaches 35 degrees, the building fills with people, computers, and servers, and the load jumps to its peak. Now the chiller must deliver full output — and this is where the hidden defect becomes a visible failure: the cooling is insufficient, consumption spikes, and in the worst case the compressor shuts down on pressure or heat protection. That is why the first rule in HVAC maintenance: test under load, not in a comfortable inspection.

The Pre-Summer Load Test — The Inspection That Catches the Silent Failure

This is the most important inspection of the HVAC year, and it is deliberately scheduled for late spring — usually May: close enough to summer that there is real demand, and early enough that there is still time to repair before the peak. Instead of measuring "is the room comfortable," it checks whether the chiller is actually capable of delivering its rated output:

• Running at high output and measuring the chilled-water temperature differential — at the chiller inlet and outlet, against design values. Too small a gap indicates the chiller is not removing enough heat.
• Checking refrigerant gas pressures — on the high and low sides. Measuring sub-cooling and superheat to detect a gas shortage, excess gas, or an expansion valve fault.
• Comparing compressor current to the rated value — high current hints at excessive strain, a blocked condenser, or an electrical load problem.
• Cleaning the condenser and evaporator, checking the circulation pumps and water flow, and inspecting the cooling tower if present — including cleaning the sprayers and fins.
• Checking the control array: the capacity stages, the pressure and heat guards, the temperature sensors, and the operating logic.

If something does not meet design values — you repair it now, in spring, while the building can still function without the system for a few hours. Not in the middle of a heat wave when every HVAC contractor is swamped with urgent calls and callout prices soar. This is exactly the practical difference between preventive maintenance and breakdown maintenance: catching the defect at a time when it is convenient to handle it.

A chiller doesn't fail in August. It fails much earlier — August is just the month you find out about it.

The Chiller — The Most Expensive Mechanical Asset in the Building

In every large office building the chiller is the most expensive mechanical asset and also the largest energy consumer — and therefore the top priority in any maintenance plan. Two practical principles keep it healthy for years.

Cleanliness = Direct Efficiency

A dirty condenser or evaporator forces the chiller to work harder for the same amount of cooling — every layer of dirt translates directly into higher electricity consumption and accelerated compressor wear. Periodic cleaning of the heat-exchange surfaces is the highest-return action in chiller maintenance: the cost of cleaning is negligible compared to the electricity savings over a whole season.

In buildings where I've worked, a noticeable difference in efficiency — expressed in the electricity bill — was seen after a thorough cleaning of a chiller that had not been properly serviced the previous season. The figure is not stated as a claim about a precise percentage, but as an impression from reality: after cleaning, the chiller simply does the same work with less electricity.

Water Quality — Not a Marginal Detail

In water-cooled systems, proper treatment of the circulation water — preventing scale, corrosion, and biological sludge — significantly extends the chiller's life and preserves the coefficient of performance (COP). Neglecting the water is one of the common causes of gradual performance decline that no one notices, until consumption spikes and an inspection reveals significant deposits in the pipes.

Any system involving a cooling tower or a water reservoir also has an important health interface — a topic we expand on separately in the context of water systems, backflow prevention, and legionella.

Air Balancing by Floor — Why One Floor Freezes and Another Suffocates

A complaint that recurs in every office building I know: on one floor it's too cold, on another it's stuffy, and the conference room at the far end is never comfortable. The tenants blame the chiller; the chiller is perfectly fine. The real problem is air balancing.

The amount of air supplied to each zone does not match its thermal need: the air dampers are too open on the floors near the main fan, too choked at the ends of the duct, and the terminal units are not calibrated. The result — parts over-cooled and parts that barely receive air, with the whole building "balancing" itself by opening windows, and that is exactly the problem.

Air balancing is a systematic process of measurement and adjustment: you measure the actual air flow rates at each outlet and tune them to design values. This is one of the most cost-effective actions in HVAC maintenance — it requires no new equipment, solves most comfort complaints, and lowers consumption, because you stop freezing an entire floor to satisfy one problem zone.

Important: in a building that has undergone a change to its internal layout — a demolished wall, added rooms, an opened open space — the original balance is no longer valid. It is worth repeating the balancing process after every material change to the internal layout.

Filter Regime and Indoor Air Quality — The Simplest Component That Is Most Neglected

Filters are the simplest component to maintain, and therefore also the most neglected. A clogged filter causes double damage: it chokes the airflow and forces the fan and chiller to work harder (wasted energy), and at the same time loses its ability to filter the air the tenants breathe. In humid conditions — and Israel is humid — a clogged filter can turn from a barrier against moisture and biological growth into a genuine source of it.

What a Proper Filter Regime Includes

• A frequency adapted to the building, not to a generic calendar — a building next to a main road or a construction site needs more frequent filtration than an office on a quiet street.
• An appropriate filtration grade — too fine a filter chokes the flow and strains the fan motor; too coarse does not protect air quality. The right balance is set according to the system and the character of the building.
• Checking the tightness of the filter frame — air that leaks around the filter bypasses it entirely, as if it weren't there. This is a case caught far less often than a dirty filter.
• Sufficient fresh-air supply — in a sealed building with poor fresh-air intake, carbon dioxide accumulates; this is one of the common causes of the fatigue and reduced concentration employees feel in the afternoon hours.

Indoor air quality directly affects employee productivity and health, and it is one of the first things tenants feel — even when they cannot articulate it precisely.

Regulatory Obligations — Energy Efficiency Inspection and Fitness Certificate

Beyond the technical maintenance, HVAC in an office building in Israel has two separate regulatory obligations that the building owner and the management company are responsible for fulfilling.

Energy Efficiency Inspection for Large Chillers

A chiller with an output above 100 tons of refrigeration is required to undergo an energy efficiency inspection performed by a certified examiner on behalf of the Ministry of Energy. The inspection examines how much cooling the chiller actually provides relative to the energy it consumes — that is, what the COP (coefficient of performance) is in practice versus design values. This is not merely a formal stamp: a chiller whose efficiency has dropped consumes unnecessary electricity every working hour, and therefore the inspection is also a management tool that points directly to savings potential.

Fitness Certificate for the Air-Conditioning System

A fitness certificate for the air-conditioning system is issued by a registered engineer and confirms that the system is sound and safe to operate. As with other fitness certificates in the building, the responsibility to carry out the inspection on time and keep the certificate valid rests with the building owner and the management company — an expired certificate is one of the first defects that come up in any safety audit.

These two obligations are part of a broader web of annual certificates a building must keep valid; we gathered all of them in the complete preventive maintenance guide for an office building.

Annual Checklist — HVAC and Chiller Maintenance

Three Common Mistakes Seen Again and Again in the Field

From direct experience in building management, these are the recurring failures that were preventable:

1. An "annual" maintenance contract with no load test — many maintenance companies offer contracts that include a visit twice a year with an "inspection," but with no real load run. The inspection looks organized on paper and catches nothing in practice.
2. Neglecting the cooling tower — when the tower is outside the management's field of view (roof, technical storeroom), it is forgotten. A neglected tower directly harms chiller performance and can also create a health risk.
3. A layout change with no repeat air balancing — an internal renovation, an opened open space, added server rooms — and the building manager forgets to update the HVAC. The result: comfort complaints that persist for years.

How a BMS Makes All of This Measurable and Manageable

The big problem with HVAC is that performance deteriorates gradually and quietly — no one calls to complain that "the chiller is consuming a bit more than last year." This is where the building management system comes in: a BMS continuously collects water temperatures, compressor current, filter status, flow rates, and consumption, and lets you see a trend before it becomes a failure. Gradual efficiency decline, a filter beginning to choke, a floor consuming abnormally — all of these are visible in the data long before they are visible in complaints.

Connecting the chiller and HVAC to the building management system (BMS) is what separates maintenance that responds to calls from maintenance that manages performance. It is also the tool that connects the HVAC load to the rest of the building picture — for example, to the electrical system and generator, since the chiller is the consumer that dictates a large part of the electrical load and the emergency backup requirements.

At Domera we supervise the HVAC contractors, schedule the inspections and the pre-summer load test, and keep the efficiency and fitness certificates valid and in one place — so that nothing falls through the cracks.