AC Tripping the Breaker in Portola Valley

AC Tripping the Breaker in Portola Valley

An AC that trips the breaker is the system protecting itself from a part pulling too many amps. The compressor or fan motor draws a hard inrush at startup, and if a capacitor is weak, a bearing is seizing, or wiring has shorted, the current spikes past what the breaker will hold and it cuts power. That is the breaker doing its job. The fix is finding which part is drawing too much, not installing a bigger breaker.

Cooling load stays moderate in Portola Valley's oak and redwood hills. The elevation and shade keep summers mild enough that these systems rarely run flat-out the way an inland unit does. That works in your favor. The failures we see are usually one aging component on one of several condensers on a larger property, not a compressor cooked from constant heavy use. Because these homes often run more than one system, the unit that trips is the one to test, and the rest of the house usually stays comfortable while we work.

It is usually one fixable part. A failed run capacitor will trip a breaker. So will a pitted contactor or a condenser fan motor dragging on a worn bearing. All of these are repairs using parts we usually stock, and we measure the actual amp draw to tell them apart before quoting anything.

Common causes

Failed run capacitor. When a capacitor weakens, the compressor or fan motor struggles to start, pushing amp draw up until the breaker gives out. We meter the capacitance and compare it to the rating printed on the can. When a capacitor tests well below spec, we replace it after you approve the written estimate, and that's the most common cause we run into.

Shorted or grounded compressor windings. If compressor windings break down and short to the case, the unit pulls a dead-short level of current the moment it tries to start. We isolate the compressor and ohm the windings to ground. A grounded compressor is a real failure, and on a property with more than one system we tell you honestly whether replacing that one compressor or the condenser makes more sense.

Pitted or welded contactor. The contactor is the relay that powers the outdoor unit. Once the contacts pit and stick, arcing current can spike past what the breaker allows. We inspect the contacts and measure the draw across them. A burnt contactor is an inexpensive part and a quick swap.

Locked or dragging condenser fan motor. Should the outdoor fan bearing seize, the motor stalls and draws locked-rotor amps until the breaker trips open. The fan gets checked for free spin, and running amps are read against the nameplate. We replace a dragging motor before it drives head pressure high enough to damage the compressor too.

Dirty condenser coil raising head pressure. On Portola Valley's wooded lots, leaf litter and pollen pack the outdoor coil. A clogged coil holds in heat, head pressure climbs, and the compressor strains and draws more amps until it trips mid-cycle. Pressures and amps get checked, the coil cleaned, and the draw confirmed to drop back into range.

Shorted or chafed wiring. Wiring that has rubbed through its insulation against a cabinet edge, or been chewed by wildlife on a wooded lot, will short and trip instantly. We check the disconnect, whip, and low-voltage wiring runs for any damage. Repairing the short is the fix, not a part replacement.

How we diagnose it

• Confirm which of the property's systems is tripping and reset once under a clamp meter to read the actual amp draw at the moment it cuts out.
• We test the run capacitor's rating and inspect the contactor for pitting.
• We ohm the compressor windings to ground to confirm or rule out a shorted compressor before condemning anything.
• Hand-spinning the condenser fan and checking its running amps catches a motor on the verge of seizing.
• The disconnect, whip, and low-voltage wiring get checked for shorts, and we confirm the breaker size matches the unit's nameplate.

$99 diagnostic, credited toward the repair. You get a written quote before any work begins.

AC Tripping the Breaker in Portola Valley: common questions

Nearby and related

AC Tripping the Breaker near Portola Valley: Woodside · Menlo Park · Los Altos Hills .

This is usually a ac repair in Portola Valley job. See our ac repair overview or the Portola Valley service area.