Chiller Maintenance Dubai

Approach is the difference between the refrigerant temperature in a heat exchanger and the water temperature leaving it. In a clean machine that gap is small, because heat moves easily across clean metal. As the tubes foul — scale, biofilm, silt — heat moves less easily, and the gap widens.

That widening starts long before anyone in the building feels anything. The chiller compensates by working harder, so supply temperature stays where it should and the only outward sign is a rising electricity bill that gets blamed on the weather.

Two approach figures are logged, one at the condenser and one at the evaporator, and they mean different things. Condenser approach rising points at the water side — tube fouling, or a cooling tower not doing its job. Evaporator approach rising more often points at refrigerant charge, oil carryover or flow. Reading them together tells you where to look; reading neither, which is common, means the first indication of trouble is a trip.

A chilled water system is designed around a temperature difference between flow and return — commonly around five or six degrees. Deliver cold water, absorb heat at the coils, return it warmer. The design flow rate follows directly from that figure.

When the return water comes back only two or three degrees warmer, the system is moving far more water than it needs to for the cooling actually being delivered. Pumps run harder, more of them may stage on, and the chiller sits at part load where it is least efficient. The building is comfortable and the energy bill is substantially higher than it should be, which is exactly why nobody investigates.

The causes are usually at the far end rather than at the plant: fan coil valves passing when they should be shut, three-way valves bypassing, coils fouled so they cannot absorb heat, or a balance that was never set properly. It is a distribution problem that presents as a plant problem, and it is the most common thing we find on buildings whose chillers are described as underperforming.

It is worth knowing that a chiller cannot fix this. Lowering the setpoint makes it worse. It is corrected at the valves and coils, and finding it requires somebody to look at flow and return together rather than at the machine alone.

Chilled water circuits are closed loops, which leads people to assume the water inside them is inert. It is not. Dissolved oxygen drives corrosion, minerals deposit as scale on exactly the surfaces that need to transfer heat, and bacteria form biofilms that insulate tubes far more effectively than their thickness suggests.

Every litre of make-up water introduces fresh oxygen and minerals, so a system losing water is being continuously re-contaminated. This is why rising make-up consumption is a maintenance finding rather than a plumbing footnote.

A treated system has a dosing regime, and it is tested rather than trusted. Where the building has an open circuit or a cooling tower, treatment also carries a public health dimension, because warm aerosolised water is the environment Legionella needs. That regime belongs to the building and its specialist, and we verify it is being followed and that results are recorded rather than assumed.

The damage from neglect is not recoverable by mechanical means. Brushing removes fouling; it does not restore a tube wall thinned by years of corrosion.

Compressor oil in a chiller is both a lubricant and a diagnostic sample. Level and pressure differential are checked every visit, but the analysis is what earns its cost.

Acid in the oil indicates the refrigerant and oil are breaking down, usually from moisture in the circuit or from heat. Metal particles indicate wear in bearings or on rotating surfaces. Moisture content indicates a drier that has done its job and is now saturated. Each of those is a warning weeks or months before the machine gives any outward sign.

On a large machine this is the difference between a scheduled oil and filter change and a compressor overhaul. Sampling is inexpensive relative to what it prevents, and it is the item most often dropped from a maintenance quote to make the price look competitive.

Much of the packaged chiller plant in this city is air-cooled, sitting on a roof and rejecting heat directly into ambient air. In July that air is already extremely hot, so the machine spends the summer operating near the top of its design envelope with very little margin.

Fine sand packs the condenser coils and reduces heat rejection further, which raises head pressure, which raises consumption and pushes the machine toward its high pressure cut-out. A dirty coil in a mild climate is inefficiency; in a Dubai August it is the reason the plant trips at three in the afternoon.

Cleaning those coils properly means through their depth, not a hose across the face, and combing flattened fins rather than ignoring them. Fan condition matters as much: one fan out of six not running changes the airflow pattern across the whole coil bank, and it is easy to miss on a roof nobody visits.

A large share of "the chiller is not coping" reports turn out to be distribution. A blocked strainer restricts flow, which shows at the plant as poor performance and in the building as warm upper floors. Air trapped at a high point does the same thing and is fixed with a vent rather than a machine.

Pump seals, bearings and impellers wear, and a pump delivering less than its duty starves the far end of the system while the chiller sits at part load wondering why there is no demand. Valves that have not been operated in years seize open or closed, so the balance the system was commissioned with no longer exists.

This is why the visit covers the loop rather than the box. On several buildings the most useful thing done in a year has been cleaning a strainer and re-commissioning two valves — no parts, no plant work, and the complaints stopped.

Many Dubai developments buy chilled water from Empower, Emicool or a similar provider rather than running their own plant. In those buildings the chillers belong to the provider and sit off site, and there is nothing of that kind in your building to maintain.

What does belong to the building is everything downstream of the energy transfer station: pumps, valves, strainers, risers and the fan coil units in each apartment. Those need exactly the maintenance described on this page minus the machine, and neglect there produces the same symptoms people blame on the provider.

Individual apartments in those towers need AC maintenance Dubai for the fan coil unit — filters, coil, drain pan and valve. If cooling is poor across a whole tower rather than one apartment, that is a building-side or provider-side question, and knowing which is the first useful step.