Atherton homes sit on large lots, and many of the houses are large too, from mid-20th-century ranch houses that spread across the lot to big newer houses on two or more floors. For heating and cooling that usually means two or more systems or zones, long duct runs to the far rooms, and equipment split between the attic, a basement and a side yard. Most HVAC work in Atherton, CA starts with mapping that layout, because a comfort problem in one wing can come from equipment at the other end of the house. We are a heating and cooling contractor based in neighboring Menlo Park, and we repair, maintain and replace systems across the 94027 zip code.
First: which system serves which rooms
A house with several systems can hide a failure. When one system stops cooling, another may run longer and keep part of the house comfortable, so the fault shows up only as one wing that drifts a few degrees, or a unit that never seems to shut off. Remodels add to the confusion: thermostats get moved, replaced or wired to different equipment.
Before testing anything, we confirm:
- which thermostat controls which indoor unit and which outdoor unit;
- which rooms each system or zone supplies, and where its return grilles are;
- the age, model and filter size of each system.
It is worth keeping that list in writing near each piece of equipment. It shortens every later visit and makes it clear which system a repair record belongs to.
Zoned systems
Some houses use one larger system with motorized dampers that divide the ducts into zones, each with its own thermostat, all wired to a zone control panel. The usual faults:
- a damper motor that sticks open or closed, so one zone gets all the air or none of it;
- a zone panel or transformer fault that stops calls from reaching the equipment;
- too much air pushed into one small zone when it is the only one calling: whistling vents, an iced indoor coil in cooling, or a furnace that shuts off on its high-limit switch in heating.
The last one is a design issue more than a broken part. The fix may be adjusting zone and blower settings, or, at the next replacement, variable-speed equipment that can slow down when a single zone calls.
Long duct runs
In a single-story ranch house the bedrooms at the end of a wing can be a long way from the air handler; in a bigger house the far rooms sit at the end of long trunk lines. Every extra length of duct is more surface to lose heat through and more joints to leak. What the far rooms usually suffer from:
- leaks at joints and register boots in the attic or crawlspace;
- flexible duct that has sagged, kinked or been crushed during other work;
- thin or missing insulation on ducts in a hot attic;
- a run that was undersized for the room from the start.
We measure airflow and supply temperature at the far register and compare it with the air leaving the equipment. A big loss on the way points to the duct, not the unit, and duct repair is often the fix. A bigger system is rarely the right answer to a duct problem.
Where the equipment sits
| Location | What tends to go wrong | What we check |
|---|---|---|
| Attic | Equipment works in summer attic heat; a clogged condensate drain can overflow into the ceiling below | Main drain, secondary pan and float switch, safe access, duct connections at the unit |
| Basement | Damp air, condensate pumps that fail quietly, stored items blocking returns or combustion air | Pump operation, clearances, venting, filter access |
| Side yard | Plantings crowding the outdoor unit, sprinklers wetting the coil, leaves packed in the fins | Clearance around the unit, coil condition, level pad, disconnect and wiring |
With equipment in several places, upkeep takes more planning than in a one-system house. Each system should be checked before its season: cooling in spring, heating in fall. An HVAC maintenance plan keeps that schedule for every system in the house; otherwise book an AC tune-up and a furnace tune-up for each one.
Replacing one system out of several
When one of several systems fails, you do not have to replace them all. We look at each system’s age, condition and repair history and put the options in writing: replace only the failed system, replace it and plan for the next, or change how the house is divided between systems. Separate systems can move to heat pumps one at a time. If the house needs new ducts or a complete ducted system, see central air installation; ductless mini-splits suit an addition or a room the ducts never served well. Estimates for new and replacement systems are free.
Lindenwood, West Atherton and all of 94027
We work throughout Atherton, including Lindenwood and West Atherton, from our base in Menlo Park. Urgent no-heat, no-cooling, gas-odor and breaker-trip calls are taken 24/7, and same-day service is available for other repairs when the schedule allows. When you call, say which system is acting up and where its equipment is, attic, basement or yard, so the technician arrives with the right access and parts. We also serve Portola Valley; every service we offer is listed on our services page.