Chiller Plant Replacement and Efficiency Retrofit in Occupied Buildings 

When a retrofit makes sense

Owners usually start thinking about chiller replacement when machines reach the end of their service life, spare parts become hard to find, refrigerant availability tightens, or electricity bills climb while comfort complaints rise. In older UAE towers and hotels, plants were often oversized at design and now run at low part load, which wastes energy.

Before specifying new chillers, measure what the building actually needs. Trend data from the BMS, chiller logs and electricity bills over a full summer reveal true peak load, part-load profile and delta-T. Many retrofits end up with smaller or fewer machines than the original plant, plus improvements in pumps and controls.

• Chiller age, overhaul history and spare-part availability
• Refrigerant type and its supply outlook
• Measured peak load and part-load hours
• Delta-T, pump energy and control performance
• Structural, crane and access constraints for replacement

Phasing in an occupied building

Tenants, hotel guests or patients cannot lose cooling in a UAE summer, so the plant must keep delivering while machines are swapped. Typical phasing replaces one chiller at a time while the others carry the load, with the heaviest work planned for cooler months when demand is lower. Each phase needs its own method statement, isolation plan and fallback.

Header modifications, valve replacements and new pump connections are the riskiest moments, because they may require draining parts of the chilled-water system. Line stopping or freezing techniques, temporary bypasses and pre-fabricated spools reduce shutdown windows. Night work and weekend shutdowns are usual for offices; hotels and hospitals need even tighter planning with operations teams.

Temporary cooling

When capacity margin is too small to remove a chiller, rental air-cooled chillers are connected through temporary hoses or pipe spools to a dedicated tie-in point. That tie-in, with isolation valves, should be installed early during a planned short shutdown so later phases can switch over quickly.

Temporary chillers need a location with free airflow, a power supply sized for their full load at high ambient, noise control near residents, and protection from vehicle traffic. Generators may be needed if the building's electrical capacity is limited. All of this must be coordinated with the building management and, where relevant, the civil defence and utility authority.

Variable speed drives and pumping

Many older UAE plants use constant-speed primary pumps, three-way valves and fixed-flow systems. Converting to variable primary flow, or adding VFDs to secondary pumps, with two-way valves at coils, cuts pump energy significantly and improves delta-T. Chillers with VFD compressors perform much better at the part loads where most operating hours are spent.

The conversion must respect chiller minimum flow limits, include a properly controlled minimum-flow bypass where needed, and use differential pressure sensors located where they represent the real system index circuit. Poorly located sensors are a common reason VFD retrofits fail to deliver savings.

Controls and plant optimisation

A new plant controller or upgraded BMS sequence typically decides how many chillers run, when to stage them, how to reset chilled-water temperature and how pumps respond. Good sequences keep chillers at efficient load points and avoid running two half-loaded machines when one can carry the load.

Metering is part of the retrofit: electrical meters on chillers and pumps, flow and temperature sensors on headers, and trend logs let the owner verify savings and spot drift. Without measurement, a new plant can slowly degrade back to old performance as setpoints are changed manually.

Refrigerant and equipment selection

Refrigerant choice affects future service, compliance and efficiency. Older plants often run refrigerants that are being phased down or out under international agreements, which the UAE follows, so supply becomes limited and costly over time. New equipment is moving toward lower-GWP refrigerants, some with different safety classifications that affect plant room ventilation, leak detection and machinery room requirements.

Selection should also confirm capacity at the project's high design ambient for air-cooled machines, physical dimensions for the available replacement route, weight on existing slabs, electrical supply capacity, and coastal corrosion protection. Water-cooled options must include cooling tower condition and water treatment.

Testing, commissioning and handover

Each new chiller is tested and commissioned before the next old machine is removed. That includes factory start-up, control integration, interlock checks, flow verification and performance under real load. After the final phase, the whole plant is re-balanced and sequences are tuned across summer and winter loads.

Handover should include updated schematics, O&M manuals, refrigerant records, training for operators and a measurement baseline to compare against pre-retrofit data.

How Manolia approaches occupied retrofits

Manolia Group has completed HVAC renovation work in occupied buildings, including an A/C renovation of a G+11 twin tower in Sharjah and HVAC and BMS design-build on American University of Sharjah main and language buildings. We plan phasing with the facility team, build tie-ins and temporary cooling into the method statement, and commission each machine before the next comes out. Call +971 54 569 3856 or email info@manolia.co.

Frequently asked questions