**Your symptoms strongly suggest a loose or broken main neutral connection. Treat this as an urgent electrical hazard.** An electrician needs to confirm the fault and locate it.

In a typical Texas home’s 120/240-volt supply, the neutral keeps each side’s outlets near 120 volts. When that connection fails, switching on a load can pull one side’s voltage down and push the other side’s voltage up. That explains lights dimming in some places, becoming unusually bright elsewhere, and heaters changing output. The excessive voltage can damage equipment and create fire and shock hazards. [Explanation from a licensed electrician](https://www.askthejourneyman.com/guides/open-neutral-warning-signs).

**Do this now:**

1. **Stop plugging things in to test the problem.** If you can safely operate the main disconnect using its normal external handle, turn the house’s power off. Leave it off until inspected. If the equipment is hot, sparking, or making crackling sounds, keep away.
2. **Call your utility’s emergency/outage number and a licensed electrician now.** Tell them: “Lights across the house get unusually bright or dim when loads turn on. I suspect a failing service or feeder neutral.” Explain that you installed the 300-foot underground feed.
3. **Tell the electrician about every 50-amp breaker you installed.** This is a separate, serious hazard that must be corrected before restoring power.

Ordinary lighting and receptacle circuits generally need 15- or 20-amp protection matched to their wiring. **A 50-amp breaker can allow those wires to overheat before it trips.** Increasing breaker size cannot stabilize voltage; breakers protect against excessive current. Your history of never tripping one does not establish safety. The [CPSC’s home-wiring guide](https://www.cpsc.gov/s3fs-public/518.pdf) specifically warns that oversized breakers on lighting and outlet circuits can cause fires.

Given the widespread symptoms, the electrician should prioritize the neutral path from the utility supply through the meter, underground cable, and house panel. A deteriorated termination or damaged buried conductor could explain why the problem appeared after six months; inspection is needed to establish the cause.

Also have them evaluate the **300-foot cable’s sizing, burial suitability, and grounding arrangement**. If “4-4-2” describes three conductors, they need to establish whether your installation requires a separate equipment-grounding conductor. Keep the walls open until the wiring and breaker corrections have been inspected.

If you see smoke or fire, leave and call 911.