Mike Dolt Enterprises
Mike Dolt Enterprises
User: Dsg319, Location: West Virginia
Asked on: Wednesday, June 25, 2025 at 10:15 pm EDT
Answered on: Wednesday, June 25, 2025 at 10:15 pm EDT
Question: Panel is a LC4040B1200 (40space Murray load center)Installing a 50 amp rv outlet so needing a gfci.I can get a Siemens 50 amp double pole gfci (QP) for like 60 dollars cheaper online than the Murray breaker. And more readily available.Only issue is I don’t see QP listed in the branch breaker chart on the load center. Am I missing something. All the listings on the panel start with the MP or MD.Is there info somewhere stating that the Siemens QP is a listed replacement for this panel?
You're right to be cautious and check compatibility. Using the wrong breaker can be dangerous.Here's the breakdown of why you're not seeing the QP listed and what your options are: Load Center Compatibility is Key
Load centers (breaker panels) are designed and tested to work with specific breaker types. Using an unlisted breaker can void the panel's UL listing, create a fire hazard, and potentially nullify your insurance.
Siemens QP vs. Murray/Siemens MP/MD
While Siemens did purchase Murray, their QP breakers are designed to fit Siemens panels, not necessarily Murray panels. The Murray MP/MD series are designed for that panel, while the QP is not.
Why the Difference Matters
The bus bar design within the panel is crucial. The way the breaker clips onto the bus bar and makes electrical contact must be precise. Different manufacturers (and even different series within the same manufacturer) use different clip and contact designs.
The Danger of Using a Non-Listed Breaker
A non-listed breaker may not make a reliable electrical connection, which can lead to arcing, overheating, and fire. It might also not trip correctly in an overload or short circuit, defeating its safety function.
What to Do Instead
Stick with Listed Breakers
Use only breakers that are specifically listed for your Murray LC4040B1200 panel. This means looking for Murray MP or MD breakers.2.
Locate the Correct Breaker
A Murray MP250GFA or MD250GFA 50 amp double pole GFCI breaker is the correct breaker for your panel.3.
Check Online Retailers
While local supply houses may have limited stock, check online retailers like Amazon, Home Depot, or electrical supply websites. Search specifically for "Murray 50 amp GFCI breaker" and verify the MP or MD designation.
Important Safety Note
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If you are not comfortable working with electrical panels, hire a qualified and licensed electrician. Electricity is dangerous, and mistakes can be fatal. The cost of an electrician is far less than the potential cost of a fire or electrocution.In conclusion, while the Siemens QP GFCI breaker may be cheaper and more readily available, it's not a safe or approved replacement for a Murray MP or MD breaker in your LC4040B1200 panel. Prioritize safety and use the correct, listed breaker. Flag for review