Installing central air conditioning in Daly City, or replacing a system that has reached its end, is mostly a question of fit. The design day here is not a heat wave. It is a mild afternoon with damp air coming off the ocean, and the equipment will spend most of its hours at part-load. So we start with a room-by-room load calculation and a ductwork assessment, and only then talk about equipment. The same steps apply to new construction, additions and replacements.
Size for the ordinary days
A Manual J load calculation accounts for your walls, windows, orientation, insulation, air leakage and the people in the house. It does not copy the old unit’s size or use a rule of thumb per square foot.
Getting this right matters more on the coast than inland. An oversized air conditioner reaches the setpoint in minutes and shuts off before the cold coil has pulled much moisture from the air, and if the blower keeps running, some of that water evaporates back into the house. You get rooms that are cool but clammy, and equipment that wears from short cycles. Two-stage or variable-speed (inverter) equipment runs long, slow cycles at low output, which removes more moisture and runs quieter.
The SEER2 rating measures seasonal cooling efficiency. With so few cooling hours, the premium for the top rating pays back slowly here, and low-speed operation usually does more for comfort than the last few efficiency points. We show you the trade-off; you choose.
Air conditioner, heat pump or mini-split
- Adding AC to a home without cooling. Plenty of homes here were built with a furnace only. A cooling coil can be added to the furnace, with an outdoor unit, refrigerant lines and a new circuit, if the ducts can move enough air.
- A heat pump instead. Heating is needed in most months in the fog belt. A heat pump does the air conditioner’s job and heats too, and the existing furnace can stay as backup.
- Rooms the ducts never reached. For a converted garage room or an addition, a ductless mini-split is often simpler than extending ducts.
- Multi-zone systems. A house where the front room over the garage door runs warmer than the back can be split into zones with dampers and separate thermostats; see zone control.
Replacing an older system
Replacement usually comes up when a compressor or coil fails on an older unit, when repairs keep returning, or when the system uses R-22, as most systems installed before about 2010 do. R-22 is no longer produced in the US. Obsolete cooling systems are often oversized too, so replacement is a chance to correct the size.
- Match the pair. The outdoor unit and the indoor coil are rated as a set, and new equipment uses newer refrigerants, so the old coil comes out with the old condenser.
- Refrigerant lines. We check the existing lines for size and condition and replace them when they do not suit the new equipment. In mid-century houses they sometimes run inside walls or floors, which affects the cost.
- Ducts. Ducts sized only for a furnace often carry too little air for cooling. A duct modification may come before the new unit.
- High-efficiency upgrades. Worth it when the house will use the cooling, less so when it runs a few days a year.
Where the outdoor unit goes
- Hillside lots. The unit needs a level, solid base: a pad set into the grade, a raised platform or a wall bracket. Every manufacturer limits the line length and how far the outdoor unit may sit above or below the indoor coil, and longer runs need a charge adjustment.
- Access. A unit three terraces down a back slope rarely gets rinsed or serviced. We look for a spot that a technician, and you, can reach.
- Salt air. Out of the direct ocean wind where possible. Corrosion-protected coils are available for coastal sites, and an occasional fresh-water rinse helps (see coil cleaning).
- Neighbors. Houses sit close together on many streets, so bedroom windows on both sides of the property line count.
Garage and over-garage homes
Many Daly City homes have the living floor above a ground-floor garage, with the furnace and water heater below. The cooling coil sits on the furnace, the condensate line runs to a proper drain rather than onto the garage floor, and the supply ducts rise through the floor to the rooms above. Rooms at the far end of the house may need balancing or a duct change to get their share of air.
What the job includes
Most installations take one to three days: removing the old system and recovering its refrigerant; setting the base, outdoor unit, coil, lines and drain; a dedicated circuit and disconnect; thermostat wiring; a nitrogen pressure test and deep evacuation; then commissioning, where we measure airflow, charge and temperature drop and test the drain.
What moves the price
Most systems run $4,500 to $15,000 installed. Single-stage versus variable-speed equipment, capacity, duct work, new lines, electrical upgrades, the outdoor base and zoning make the difference. The written estimate lists each item, with no hidden fees. Our work carries a warranty on parts and labor, and the equipment carries the manufacturer’s warranty.