Heat Pump Repair in Los Altos Hills, CA

Why heat pump repair in Los Altos Hills is its own job

I will start with the thing a heat pump page for this town has to admit. There is no heat pump in my Los Altos Hills records. The work I have been called out for here is cooling equipment and controls, and I am not going to invent a local heat pump history to make this page look better than it is. I do this work, I will come and do it here, and that is a different sentence from claiming I already have.

What my file does carry is dates, and the dates are the useful part. Every install date on file for this town falls in 2020 or 2021. On most of my route that is not remotely true. Los Gatos runs back to 1990, Santa Clara to 1997, Campbell to 1989. Here the whole file is five or six years old, and on a heat pump that matters more than it would on a furnace, because it tells you what kind of control is on the wall.

A control platform from 2020 or 2021 is not a mercury bulb and a mechanical stage. The outdoor temperature at which backup heat is allowed to run, how far from setpoint the control waits before it gives up on the compressor, how the system recovers from an overnight setback: on equipment that age all of those are settings rather than wiring. Settings get left wherever the installer had them, and a control set up as though it were driving a gas furnace will call the backup stage in every time somebody turns the temperature up.

That is why my first suspicion on a heat pump here is configuration rather than failure. Recent equipment fails less and gets misconfigured more.

What actually fails on a Los Altos Hills heat

Three faults account for most heat pump calls, and only one of them is expensive.

Backup heat running when it should not is the most common and the most costly to ignore. Every heat pump has a second stage for the coldest mornings and for recovery from a setback. On some systems that is electric resistance heat and on others it is a gas furnace, and which one you have changes the cost of running it enormously, so it is worth knowing before the night you need it. Either way, a wrong staging setting, a schedule asking for a large jump at six in the morning, or a relay that sticks will leave that stage running when the compressor should be carrying the house alone.

Nothing feels broken, because the house is warm. The only symptom is the bill. In a zoned house the backup can end up heating one wing all winter while everybody assumes the heat pump is doing it.

A reversing valve that will not shift is the fault that produces cool air on a heating call. That valve is what makes a heat pump a heat pump: it turns the refrigerant circuit around so the outdoor coil absorbs heat and the indoor coil releases it. When the valve sticks or the solenoid coil fails you get air conditioning in January, or a system stuck in a mode it will not leave. I test the coil for voltage and resistance, then read line temperatures across the valve body, because a valve leaking internally looks perfect from the outside.

Defrost is the third, and around here it is the one nobody catches. In heating the outdoor coil runs colder than the outdoor air, so it frosts, and the control is supposed to run a cycle that melts the frost off and then stop. On an acre plus lot, with the unit wherever it ended up going, nobody is standing next to it at two in the morning to see whether that happens.

A failed sensor or board leaves the coil packed solid, which strangles capacity and calls the backup stage in, or it defrosts every few minutes and throws away run time. Frost on the outdoor unit is not by itself a fault. Frost that never goes away is.

Replacing Propane With A Heat Pump

On properties that run on propane, a heat pump is often the upgrade that pays for itself fastest. It moves heat instead of burning fuel, and the mild winters here keep it in its efficient range. Many owners keep the propane furnace as backup in a dual fuel setup for the coldest mornings.

Heat pump repair in Los Altos Hills on a dual fuel system often comes down to the balance point and the outdoor sensor. A setting that hands off to propane too early burns fuel the heat pump could have saved.

Defrost On Open Hillsides

Open lots get frost on clear winter nights, and heat pumps run defrost cycles to clear the outdoor coil. A few minutes of steam and a paused fan is normal. Ice that stays on the coil, or a defrost that never ends, points at a defrost sensor, the defrost board, low charge, or a unit sitting where melt water cannot drain away.

Generators And Matched Equipment

On generator power, heat pumps with backup heat strips can pull more than the generator can supply. Knowing which stages run on backup power, and sizing the generator for them, prevents a cold night during an outage. When equipment is replaced, check that the outdoor unit and indoor coil are a matched rating in the AHRI directory, because a mismatched pair can fall well short of its advertised performance.

A yearly check in the fall covers the outdoor coil, the defrost controls, the charge in heating mode, and the backup heat, with readings saved so the next visit has a baseline. Keep leaves and dry grass cleared from around the outdoor unit through the winter.

Note any error codes on the thermostat before you call.

When you book, mention whether the heat pump has a propane or gas furnace as backup, and whether it serves the main house, a guest house, or an outbuilding. If the outdoor unit has been icing up, a quick photo of the coil sent with your message helps us figure out whether it is a defrost issue, a charge issue, or a drainage problem before we arrive.

How I diagnose it

On a heat pump I read in both modes, because a machine that is right in cooling can be wrong in heating.

Supply air temperature in heating, with the backup stage locked out and then with it allowed in, is the fastest honest answer available and it is where I start. I lock the backup out, let the compressor do the work on its own, and read the supply air. Then I let the backup come on and read it again. If those two numbers sit close together, the compressor is not contributing much and your backup stage has been heating the house.

Superheat and subcooling in both heating and cooling, against the charging chart for your model, comes next. A charge that looks acceptable in cooling can leave the machine short in heating, and that is exactly the condition that brings the backup on early and keeps it there.

Then I watch a defrost cycle run start to finish and confirm it terminates on the sensor rather than timing out. That means standing at the unit for it, in the cold, and it is the reading most people skip. If your complaint is a cold wing rather than a cold house, I take static pressure across the air handler as well, because with supply air as mild as a heat pump makes it, airflow decides everything.

Repair or replace

Repair, almost always, and before anything gets replaced I want one measurement standing in front of both of us.

The pitch to be careful with on a heat pump is the one that says the technology does not really work when it is cold, so you should go back to gas or add capacity. Before you believe that, lock the backup stage out, let the compressor work alone, and read the supply air temperature. Most of what gets called a heat pump that cannot keep up is a heat pump that has never been allowed to try: backup heat coming on too early, a charge that was never verified in heating, or zone dampers starving the indoor coil.

All three of those are setup and service, not a new machine, and none of them can be diagnosed from a driveway.

Sensors, boards, contactors, fan motors, solenoid coils and thermostats are all repairs, and on equipment with life left they are the right call. A reversing valve replacement is a bigger job, because it means recovering the charge and brazing a new valve body into the circuit. On a machine that has already lost a compressor, or that is leaking somewhere in a line set buried under a driveway, that is where replacing starts to make honest sense.

If you do replace, size it to the duct you already have. Heating capacity you cannot push through the duct only brings the backup stage on sooner, and you pay for that every month.