A thermostat swap in Novato, San Rafael, San Anselmo, Larkspur or Sausalito looks like a ten-minute job until the new model will not power up, the heat pump blows cold air in heating mode, or the old wall furnace does not respond at all. The thermostat has to match the system it controls. We check that match first, then install, program and connect the new thermostat and show you how to use it.
Signs it is time for a new thermostat
- It is outdated - a mercury dial or an early digital model with no schedule.
- Temperature control problems: the room is far from the setting, or the system short-cycles.
- You want smart home control from your phone or voice assistant.
- Energy savings goals that a schedule or occupancy sensing would help with.
- Zoning needs: an addition or an upstairs that needs its own control.
- An incompatible thermostat left by a previous owner or a do-it-yourself install.
If the thermostat simply stopped responding, read thermostat not working first; the cause may be batteries, a tripped safety switch or a wiring fault rather than the thermostat itself.
Compatibility comes first
Standard 24-volt furnace and AC. The easy case. The main question is power: Wi-Fi thermostats need a C-wire, and many older homes have only two or four wires at the wall.
Heat pumps. The thermostat must support heat pumps, use the correct reversing valve setting and control the backup heat. Set up wrong, a heat pump can heat in summer or run expensive backup heat all winter.
Multi-stage and variable-speed systems. Two-stage furnaces and compressors need a thermostat with matching stages. Some variable-speed systems use the manufacturer’s own communicating control; a generic thermostat may run them, but with fewer features.
Millivolt systems. Many wall furnaces and older floor or gravity furnaces with a standing pilot run on a tiny voltage made by the pilot flame. Most smart thermostats cannot power or switch these, and a millivolt-rated thermostat is needed.
Electric baseboard heaters. They run on line voltage, which a low-voltage thermostat cannot handle at all. They need line-voltage thermostats, some of which are programmable.
Smart, programmable or simple?
- Smart thermostats learn schedules, adjust from your phone and report run times and filter reminders. They suit most ducted systems with a C-wire.
- Programmable thermostats follow a weekly schedule without Wi-Fi. A good choice for rentals and for owners who want no app.
- Simple non-programmable thermostats make sense for a wall furnace or a rarely used guest room.
With a heat pump, deep night-time setbacks can backfire: the morning recovery may run the backup heat. A thermostat with heat pump recovery logic handles that.
Placement matters
An old thermostat on an exterior wall, in afternoon sun, near a kitchen or above a supply register reads the wrong temperature and runs the system on false information. If the current spot is poor, we discuss moving it to an interior wall in a room you use. In homes on hillside lots with rooms on several levels, a thermostat on one floor rarely represents the others; remote sensors or zoning help with uneven temperatures.
How the installation goes
- Assess compatibility - the equipment, the wiring and any zoning panel.
- Recommend options that fit the system, with an itemized price.
- Install - remove the old unit, add or reuse a C-wire, mount and wire the new thermostat. Old mercury thermostats are set aside for proper recycling.
- Configure the system type, stages, heat pump settings and fan, then build a schedule with you.
- Connect to Wi-Fi and your smart home app or voice assistant.
- Walk-through of the controls, the schedule and the filter reminder.
We test the heating and cooling from the new thermostat before we leave. A new thermostat on a system that needs work will not fix it, so if we see a problem with the equipment, we tell you. Pair the install with an HVAC maintenance visit or, for heat pumps, see heat pump services. Town pages: thermostat installation in Larkspur and in San Anselmo.