Delayed trip = overload.
Thermal trips happen when sustained load exceeds circuit capacity. The breaker isn't broken — it's protecting against overheating wires.
By Steven Lockhart · Reviewed by Alex Towery, C-10 #989290
Updated 2026-06-16
Breakers that trip after sustained operation (minutes to hours of running) are thermal trips — overload protection. Cause: total load on circuit exceeds breaker rating sustainably. Solutions: reduce simultaneous loads on the circuit, redistribute loads to other circuits, or install dedicated circuit for high-load appliance. If overload is moderate and intermittent: load management can suffice. If chronic or severe: dedicated circuit work needed.
01Why thermal trips happen.
Wiring is sized for specific current capacity (14 AWG for 15A circuits, 12 AWG for 20A circuits in typical residential). The breaker is sized to match — 15A breaker on 14 AWG wire, 20A on 12 AWG. When sustained current approaches the breaker rating, the breaker's bimetallic strip heats up and eventually trips. This protects the wire from overheating, which can damage insulation and start fires inside walls.
Modern Marin homes have growing load demands. Original wiring from 1980s and earlier was sized for then-typical loads (incandescent lighting, modest appliance counts). Today's home loads include LED lighting (lower per-fixture but more fixtures), more electronics (computers, network equipment, charging stations), more appliances (microwaves, coffee makers, induction cookers), and sometimes EV charging. Loads that fit yesterday's wiring exceed today's needs in many older homes. Result: circuits that work most of the time trip when heavy simultaneous loads occur.
02Diagnosis and solutions.
Identify the trip pattern
When does it trip? Specific time of day (suggests scheduled load), after certain appliances on (load combination), during cooking (heavy kitchen load), in summer afternoons (AC + other loads). Pattern helps identify cause.
Load redistribution
Sometimes the fix is moving one appliance to a different circuit. Microwave on a different outlet (different circuit), coffee maker plugged into another outlet, space heater on a low-load circuit instead of the kitchen circuit. Free fix if circuits allow.
Dedicated circuit
For high-load appliances that run frequently (microwave, electric water heater, induction cooktop, EV charger, space heater used daily): dedicated circuit eliminates overload risk. Cost $400-$1,200 for typical residential dedicated circuit install depending on length and access.
03Cost and decision framework.
For light or occasional overload: load management is enough — no electrician needed, just behavioral change (don't run microwave + toaster + coffee maker simultaneously). For moderate overload happening regularly: diagnostic to identify which loads are problematic, then either load redistribution or dedicated circuit work. For severe overload (trips multiple times daily, can't run normal appliances): dedicated circuit work needed; cost $400-$1,500 typical.
Larger context: if your home has multiple circuits experiencing overload, it may signal that the panel or service is undersized for current usage. A 100A service home that's added significant load (EV charger, AC, modern electric appliances) may need 200A service upgrade — cost $3,500-$6,500 typical Marin. Solves multiple overload issues at once and provides headroom for future load growth. Discuss with electrician during diagnosis.
Common questions.
Is upgrading the breaker (larger amp rating) a solution?
No — and it's dangerous. Breakers protect the wire. Putting a 20A breaker on 14 AWG wire (rated for 15A) removes the protection — wires can overheat without tripping, creating fire risk. Breaker size must match wire size. Solutions involve adding circuits or upgrading wire+breaker together, never just upsizing the breaker.
Why didn't this trip before?
Either total load on the circuit has grown (added more devices, started using existing devices more), the breaker has degraded (older breakers can become more sensitive to thermal as their bimetallic strip ages), or environmental conditions changed (warmer ambient temperature in panel area, which affects breaker thermal sensitivity). Or the original load was always near limit and you're just noticing more now.
Should I upgrade my electrical panel?
Maybe — depends on the breadth of the issue. If a single circuit is overloaded: dedicated circuit work, not panel upgrade. If multiple circuits show overload, or your panel is older and you're adding significant load (EV, induction range, heat pump): panel upgrade makes sense. Discuss during diagnostic; we recommend based on the full picture, not just immediate issue.
How long is too long to wait between trips and repair?
Not urgent if trips are infrequent and you can manage by reducing simultaneous load. Same-week if trips affect daily life. Same-day if you can't run essential appliances (refrigerator on tripping circuit, for instance). Thermal trips don't typically present fire risk in moments — the breaker is doing its job protecting the wire. Inconvenience is the main driver of urgency.
How do you handle pricing — flat fee or hourly?
Both, depending on scope. Routine service calls and predictable scope (panel replacement, EV charger install, transfer switch install, fixture replacement) are flat-fee quoted up front. Diagnostic visits and emergency scope are hourly because we don't know what we'll find. Either way, you get a written quote before work starts on anything significant, and we don't proceed beyond the quote without your sign-off.
How quickly can you schedule?
Depends on scope and season. Emergency dispatch: same-day across Marin County (1-3 hours business hours, 1-4 hours after-hours). Same-day standard service: 3-6 hours from call when capacity allows; otherwise next business day. Scheduled service work: 1-3 weeks typical. Larger projects requiring permits and PG&E coordination: 4-12 weeks depending on scope. We're upfront about timeline at the quote stage.
What warranty do you offer on work?
Our standard residential warranty: 2 years on labor, manufacturer warranty on parts (varies by product — typically 1-10 years). Major installs (panels, generators, EV chargers) often have longer manufacturer warranties (5-10 years). If there's an issue with our work in the warranty period, we come back and fix it at no cost. We also stand behind work past warranty — repeat customers and referrals matter more than a transactional fix.
Are you licensed and insured?
Yes. California State License Board C-10 Electrical Contractor #989290, in good standing. Carry general liability insurance and workers' compensation insurance as required by California law. Bondable on projects requiring it. Happy to provide proof of insurance to clients or property managers on request. License lookup: cslb.ca.gov.
Same-day diagnostic visit in Marin.
We bring the right test gear and most common parts. Single-visit repair on roughly 80% of diagnostics.