A split system replacement scope should say whether the existing refrigerant line set is reused or replaced, how it is proven tight (nitrogen pressure test) and dried (deep evacuation), which refrigerant the new equipment uses, how condensate and safety switches are handled, and how ceilings and mechanical rooms are accessed and restored. The line set decision is the single biggest swing in effort and risk.
- The line set is the scope. Decide reuse or replacement on evidence, and write down the test that justifies it.
- Pressure test with dry nitrogen and evacuate to a recorded level; do not rely on a visual check or a short vacuum.
- Refrigerant transition can change line sizes, oil compatibility and equipment listing. Confirm what the new system requires before reusing anything.
- Condensate pumps, secondary pans and float switches are cheap and protect finished ceilings. Put them in the base scope.
- Access and restoration, meaning who opens the ceiling and who closes it, belongs in writing before the first tile moves.
What the job includes, end to end
A split replacement swaps an indoor unit (air handler, fan coil or furnace with coil) and an outdoor condensing unit that are connected by refrigerant piping. Commercial examples include a suite air handler above a dropped ceiling, a server closet fan coil, or a mechanical-room air handler fed by a roof or pad condenser. The scope should read like the work happens: shut down, recover, remove, set, pipe, prove, charge, start, document.
When the project moves from one or two splits to many indoor units on shared outdoor equipment, the design question changes. See VRF system installation scope of work and ductless mini-split installation scope of work for those.
Reuse or replace the line set
Line sets are hidden, so owners assume they are fine. Hidden is the reason to prove them. A line set that has carried acid, moisture or the wrong oil, or that has been kinked, crushed, or insulated with failed foam, will sabotage a new compressor.
| Condition | Points toward reuse | Points toward replacement |
|---|---|---|
| Pressure test | Holds at test pressure for the stated period | Loses pressure or cannot be isolated |
| Size | Matches new equipment's listed sizes and length | Undersized for the new capacity or run length |
| Refrigerant and oil | New equipment accepts the existing system's history | Prior compressor burnout, or oil and refrigerant not compatible |
| Physical state | Straight runs, sound brazes, intact insulation | Kinks, dents, corrosion, brittle or missing insulation |
| Access | Run is exposed or easily reached | Run is buried or in a wall that must be opened anyway |
The scope should state the base assumption, usually replacement or reuse after passing a test, and price the other path as an alternate. See bid alternates, allowances and unit pricing for HVAC for how to carry that cleanly.
Nitrogen pressure test and evacuation
These two steps are where good splits are made. Write them as results, not as vague words like leak check.
- Recover the existing charge into approved cylinders under EPA Section 608 practice and keep the recovery record.
- Cut in or braze with nitrogen flowing through the pipe to prevent oxide formation inside the line.
- Pressure test with dry nitrogen to the pressure stated by the equipment manufacturer and hold for a stated period; record the start and end readings.
- Evacuate with a micron gauge, not a compound gauge, to a stated level and hold test with the pump isolated.
- Break vacuum with refrigerant, weigh in the final charge, and verify by superheat and subcooling readings.
Contractor shall pressure test the refrigerant piping with dry nitrogen and record the test pressure, duration and result. Contractor shall evacuate the system using a micron gauge to the level required by the equipment manufacturer and record the final reading. Test and evacuation records shall be provided to Owner at closeout.
Refrigerant transition and equipment compatibility
New equipment may use a different refrigerant than the old system. Many replacement units are now designed for A2L refrigerants such as R-32 or R-454B, which are mildly flammable and bring requirements tied to ASHRAE 15, the California Mechanical Code and the manufacturer's listing, including charge limits, leak detection and room volume in some cases. The rules and the equipment list are changing, so confirm current CARB and EPA requirements and the manufacturer's installation instructions before pricing.
- State the refrigerant of the new system in the scope.
- State whether the existing line set is permitted by the manufacturer for that refrigerant. Some are not, and mixing oils is not a shortcut.
- State the metering device and filter drier changes, and whether the indoor coil is a matched replacement.
- State how old refrigerant is recovered, reclaimed or disposed of, with paperwork returned to the owner.
The regulatory background is in the refrigerant compliance guide for California.
Condensate, safeties and what protects the ceiling
Indoor splits live above ceilings, in closets and over tenant spaces, and they leak when condensate backs up. Include a primary drain with a trap that suits the unit's pressure, a secondary pan under any unit above finished space, and a float or sensor switch wired to shut down the system. If gravity drainage is not possible, specify a condensate pump with its own overflow switch and say where the discharge terminates.
Also name the other safeties: high and low pressure switches, freeze protection, smoke detector shutdown on air handlers where required, and any interlocks with a fire alarm or building system. Control wiring to a thermostat or building automation system should be part of the scope, as covered in building automation controls upgrade scope of work.
Ceiling and mechanical-room access
Many split replacements are limited by a hatch, a stair or a narrow corridor. A scope that does not mention access leaves each side assuming the other will deal with it.
- Who removes and replaces ceiling tile, and who repairs a hard-lid ceiling if it must be cut.
- Whether the indoor unit can pass through the hatch or door, and what happens if it cannot.
- Protection of floors, furnishings, and ceiling finish during work in occupied space.
- Working hours, noise limits and dust control for medical, dental, retail and office tenants.
- Clearances for service access in the new location, not just for the install.
What is commonly missed
- New filter drier and sight glass on reused line sets.
- Supports and insulation for line sets that run on a roof or in the sun, including UV-rated covering.
- Condensing unit pad, stand or wall bracket, and seismic restraint.
- Electrical disconnect and wire sizing for the new equipment; electrical work must be named to a licensed party, since Davinci's crew covers mechanical, refrigeration and controls.
- Duct transitions at a new air handler with different connection sizes.
- Existing coil or air handler removal where the old unit is in a tight room.
- Written startup, charge weight and readings.
Submittals and closeout
Request equipment data with matched model numbers (indoor and outdoor), the refrigerant and charge, line size and length limits, electrical data, and drain details before ordering. At closeout expect the nitrogen test and evacuation records, charge weight and final readings, warranty registration in the owner's name, permit final, and photos of concealed piping before it is covered. The new assets can be recorded in the DaVinci Portal so the next technician sees the same data you do. For related equipment guidance, see RTU and split system installs.