🔧 Troubleshoot • Homeowner Edition

Backup Power Troubleshooting

When backup power fails, the cause is usually simple — if you check the right things in the right order. Pick what’s happening right now. This page will walk you through the most common failure points without guesswork.

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Safety First If there’s fuel smell, heat damage, sparks, water exposure, or an unknown wiring path — stop and shut down. Backfeeding and wet connections can be fatal.

Tap the symptom:

Check in this order:

Fuel + valve: correct fuel, fuel valve open, vent open (if equipped).
Oil level: many portables have low-oil shutdown and will not start if low.
Choke position: cold engine = choke ON; warm engine = choke OFF.
Electric start battery: if pull-start works but electric doesn’t, suspect battery/cables/solenoid.
Protection lockouts: CO sensor / overload logic may require a reset per manufacturer.

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Pattern recognition Starts then dies? Often fuel/vent/choke. Cranks but won’t fire? Often stale fuel/carb varnish.

If it still won’t start: suspect stale fuel, carburetor varnish, ignition fault, or internal failure.

This is one of the most common outage scenarios. Don’t guess — verify the chain.

Check in this order:

Generator breaker ON (many trip silently).
Connection seated (cord fully inserted, inlet twist-lock fully engaged).
Transfer switch / interlock position set to GEN properly.
Correct voltage: 120V-only generator on a 240V inlet can create “weird partial power” or no power.
No upstream GFCI tripped (garage/basement/exterior can kill multiple circuits).

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Fast win If the generator is running and your house is dark, the issue is often the transfer position or a tripped generator breaker.

Most likely cause: an upstream GFCI is tripped.

Reset every GFCI you have: bathrooms, kitchen, garage, basement, exterior.
If you have AFCI breakers, some may be sensitive to generator waveform and nuisance-trip.
Multi-wire branch circuits (shared neutral) can behave strangely if not fed properly.

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Rule of thumb One tripped GFCI can kill a whole chain of downstream outlets — often across multiple rooms.

If a breaker trips instantly every time, stop “retrying.” Repeated trips create heat damage.

Most common reasons:

Overload at startup: motor surge (fridge/furnace/pump) exceeds capacity.
Neutral bonded twice: generator bond + panel bond can trigger protection/GFCI behavior.
Undersized cords: voltage drop makes motors pull more current and trip.
AFCI/GFCI incompatibility: nuisance trip under generator power.
MWBC/shared neutral issues: imbalanced return current can trip protection.

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Hard stop If you see heat, melting, or burning smell — shut down and inspect connections before doing anything else.

This confuses homeowners because it looks like “bad outlets.” Often it’s not.

Why it happens (common scenario):

Some generators have a neutral-ground bond.
Your home service equipment bonds neutral-ground as well (normal for the main service).
Certain transfer configurations + protective devices interpret this as imbalance and trip.

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Important The “right” fix depends on your setup (portable vs standby, interlock vs transfer switch, neutral switching). Don’t defeat protection devices.

Practical move: Identify whether your generator is bonded, and whether your transfer method switches neutral. Then troubleshoot from there.

Start with reality: runtime claims are best-case lab numbers. Real homes pull harder.

Check first:

Actual load: watts you’re pulling vs inverter rating.
Surge cycling: compressors/air handlers starting repeatedly.
Temperature: cold reduces battery capacity fast.
Battery age/chemistry: older packs sag under load sooner.

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Translation If batteries drop fast, the system is usually undersized — not “broken.”

Most common causes:

Locked rotor surge exceeds generator/inverter capacity.
No soft-start (HVAC and some pumps are brutal at startup).
Shared circuits with other loads pushing you over the edge.
240V mismatch (trying to run a 240V load from a 120V source).

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Key insight “It runs sometimes” usually means you’re right on the edge. Reduce loads or address surge.

Call a licensed electrician or generator tech if you hit any of these:

Repeated breaker trips you can’t explain.
Burn marks / heat / melting at plugs, inlets, or panel areas.
Water intrusion anywhere in the power path.
Transfer switch behavior is inconsistent or unclear.
Code uncertainty (neutral bonding, grounding, inlet type, backfeed risk).

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Hard boundary If you can’t describe the wiring path confidently, you’re in “stop” territory.

Quick Triage Wizard

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Best practice Fix the chain: source → breaker → connection → transfer → loads. Most failures are one link in that chain.

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Next steps (link these to your tools) These buttons are placeholders — replace href values with your actual URLs.

Load Calculator → Runtime Estimator → Transfer Switch Guide → Wiring & Safety Guide →

Note: Your city/county inspector (AHJ) has final authority. This page is educational and safety-first.