A chiller replacement scope should define the rigging path, how the loop is isolated, drained, flushed and refilled, how new controls tie into the building system, which outage windows the owner can accept, how refrigerant is handled, and how the new machine is commissioned against written sequences. Most delays come from the path in and the water side, not the machine.
- Begin the scope with the route: how the old chiller gets out and the new one gets in, and what must be removed or protected along the way.
- Hydronic work is half the job. Isolation valves, draining, flushing and water treatment decide whether the new machine is clean on day one.
- Controls integration needs a point list and a written sequence. Do not leave it to startup day.
- Phase the outage around cooling load, not around the installer's convenience; plan temporary cooling if the building cannot ride through.
- Commissioning is a deliverable with data, tested sequences and training, not a single startup visit.
Air-cooled or water-cooled: how the type changes the scope
A chiller swap is never one scope. The two main types pull the work in different directions.
| Item | Air-cooled chiller | Water-cooled chiller |
|---|---|---|
| Location | Roof, pad or yard; needs clear airflow | Central plant or mechanical room |
| Heat rejection | Fans on the machine | Cooling tower, condenser water pumps, piping and treatment |
| Rigging | Crane lifts common | Often rolled or skated through a building, sometimes disassembled |
| Water side | Chilled water loop only | Chilled and condenser water loops |
| Added scope | Sound, coil protection, wind and seismic anchoring | Tower condition, condenser tubes, water chemistry |
State the type in the scope, and say plainly whether the tower, pumps and primary piping are included, repaired or left as-is. Owners often assume a chiller replacement fixes the plant; it fixes the chiller. See chillers and central plant service for the broader context.
The rigging path comes first
A chiller is heavy, wide and awkward, and the building was not designed around its replacement. Write the path as a sequence: staging area, any door, wall, floor or louver that must be opened, protection for finishes, floor load or slab capacity, and the point where the old unit leaves. When the machine is split into sections to fit, note who warrants the reassembly and the refrigerant circuit after it is reopened.
- Structural capacity of the floor, roof or stand under rigging loads. The scope must name the party who verifies this; that is an engineer's job, not a mechanical crew's.
- Wall, louver or door removal and restoration, with the trade named.
- Crane or rigging company coordination, street or lot closure and notice to neighbors.
- Housekeeping pads, vibration isolators and seismic anchors for the new footprint.
The mechanics of lifts and hauling are covered in equipment removal, crane and rigging scope of work.
Isolating, draining and flushing the loop
The chiller connects to a loop that may hold thousands of gallons and years of scale, sludge and glycol or inhibitor. Opening it without a plan creates floods and dirty water, and closing it without flushing puts that debris into a new heat exchanger.
- Confirm isolation valves hold. If they do not, the scope must include draining a larger section or replacing the valves.
- State where drained water goes, how it is tested, and who handles disposal of treated or glycol-bearing water.
- Flush and clean the piping or install temporary strainers that stay in place until the loop runs clear.
- Sample the water before fill and set the target chemistry with the water treatment provider.
- Fill, vent, pressurize and verify flow with the pump before the chiller starts.
Contractor shall isolate, drain and flush the chilled water piping connected to the chiller, install temporary strainers at the new unit, and refill the system with Owner's water treatment provider present. Contractor shall record water quality readings before startup. Disposal of treated water shall follow applicable local requirements.
Controls integration and sequences of operation
Modern chillers arrive with their own controller. It still has to talk to the building. The scope should list the integration protocol, the points to be shared (status, alarms, leaving water temperature, setpoint reset, demand limit, run hours), and who programs the graphics and alarms on the building automation side.
- Written sequence for staging, lead-lag, reset and failure behavior, approved before startup.
- Interlocks with chilled and condenser water pumps, tower fans and isolation valves.
- Freeze protection and low-flow cutouts.
- Alarm routing and who is notified.
Davinci's crew handles mechanical, refrigeration and controls work directly. Third-party firms, if the owner has an incumbent controls vendor with protected software, should be named in the scope. More on that is in building automation controls upgrade scope of work.
Outage windows and temporary cooling
The build-out of the schedule is part of the scope because the cooling load does not stop. Ask for the owner's tolerance in writing: which months, which days, which hours, and which spaces cannot lose cooling at all.
In much of Southern California the cooling season runs long, so the true low-load window can be short. Some plants carry multiple chillers and can swap one at a time. Others cannot. If the building needs temporary cooling, the scope states who supplies it, the connection points, power, and how long it stays. Phasing by building zone is discussed in how to write a commercial HVAC scope of work.
Refrigerant handling and removal
The old chiller holds a significant refrigerant charge, and the new one may use a different refrigerant. Recovery follows EPA Section 608 practice, and the recovered refrigerant is reclaimed, reused or disposed of with paperwork. The new machine's refrigerant classification can trigger machinery room requirements under ASHRAE 15 and the California Mechanical Code, such as ventilation, leak detection and alarms. Confirm current CARB and EPA requirements for refrigerant type and equipment, and state the new refrigerant in the scope.
What is commonly missed
- Electrical feeders, starters or variable drives for the new unit. Name the licensed electrical contractor; mechanical scope stops at the unit connections.
- Flexible connections, strainers, flow switches and balancing valves at the new nozzles.
- Relief valve piping and refrigerant vent routing.
- Insulation restoration on chilled water lines.
- Condenser tube cleaning or replacement on water-cooled machines.
- Tower and pump condition checks before they inherit a new chiller's demands.
- Rental, utility and overtime charges for off-hours work.
- Training for the operators who will run the machine.
Submittals, commissioning and closeout
Submittals should include the selection data at design and part-load conditions, nozzle locations, drawings with clearances, electrical data, controls points list, and a rigging plan. Commissioning should include verified flow and temperature differentials, tested sequences, alarm testing and a documented run at load.
At closeout the owner should receive startup reports, as-built piping and controls information, operating and maintenance manuals, warranty registrations, refrigerant records and operator training notes. For public or school projects, add the testing and commissioning requirements from the contract documents; see testing, balancing and commissioning scope of work. The commercial chillers and hydronic systems guide covers the equipment background.