One of the most misunderstood—and most critical—questions homeowners ask when installing or troubleshooting an electric furnace is deceptively simple: What is the correct breaker size for an electric furnace? When the furnace in question is the Goodman MBVK electric furnace, the answer becomes even more nuanced, because breaker sizing is not a one-size-fits-all number. It depends on heat strip configuration, staging, electrical service, and the way the furnace is designed to protect itself and your home.
As Savvy Mavi, I’ll tell you this up front: breaker size is not just about power—it’s about safety, reliability, and long-term system performance. Choosing or verifying the correct circuit breaker size for an electric furnace is not optional housekeeping; it’s foundational to whether the system heats properly, avoids nuisance trips, and complies with electrical code.
In this deep-dive guide, we’ll walk through:
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Why breaker sizing matters specifically for electric furnaces
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How the Goodman MBVK draws power differently than gas furnaces
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How to determine the correct breaker size for an electric furnace
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Why many MBVK systems use multiple breakers
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Common breaker sizing mistakes that cause no-heat or partial-heat problems
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How breaker sizing interacts with heat strip staging and airflow
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When breaker issues signal a deeper electrical or furnace problem
Let’s start with the fundamentals.
1. Why Breaker Size Is So Critical for Electric Furnaces
Unlike gas furnaces—which primarily use electricity to run controls and blowers—electric furnaces generate heat entirely through electrical resistance. That means they draw significantly more amperage, particularly when heat strips are energized. In fact, electric furnaces are often among the highest-load appliances in a residential electrical system.
This is why questions about breaker size for electric furnace installations are so common—and so important.
A breaker that is:
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Too small will trip repeatedly, leaving you without heat
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Too large can fail to protect wiring and components, increasing fire risk
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Incorrectly paired with wire size violates electrical code
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Improperly staged can cause heat strips to fail silently
The Goodman MBVK electric furnace is designed with safety and modularity in mind, but it relies on the installer (or technician) to provide properly sized circuit protection.
2. How the Goodman MBVK Electric Furnace Uses Electrical Power
To understand breaker sizing, you first need to understand how the MBVK consumes power.
The Goodman MBVK is an electric furnace/air handler platform that supports multiple electric heat kits. These heat kits are essentially banks of resistance heating elements that energize in stages. The furnace does not energize all heating elements simultaneously unless the thermostat calls for full heat capacity.
This staged design improves efficiency and comfort—but it also means electrical demand changes dynamically.
In a typical MBVK setup:
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One circuit may power the blower and control board
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One or more additional circuits power the heat strips
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Each heat strip bank has its own amperage draw
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Each bank may require its own breaker or shared breaker depending on configuration
This is why asking for “the breaker size for an electric furnace” without specifying heat kit size is incomplete.
3. The Concept of MCA and MOCP (And Why They Matter)
When determining the correct circuit breaker size for an electric furnace, two specifications are critical:
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MCA (Minimum Circuit Ampacity)
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MOCP (Maximum Overcurrent Protection)
These values are listed on the furnace nameplate and in Goodman documentation.
Minimum Circuit Ampacity (MCA)
MCA tells you the minimum amperage the circuit must safely carry under continuous load. This value determines wire size, not breaker size.
Maximum Overcurrent Protection (MOCP)
MOCP tells you the largest breaker size allowed to protect the furnace safely. This value determines the maximum breaker size you may use.
A properly designed circuit always satisfies:
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Breaker amperage ≤ MOCP
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Wire ampacity ≥ MCA
Anything outside this range is either unsafe or non-compliant.
4. Typical Breaker Sizes for Goodman MBVK Configurations
Now let’s talk real numbers. While exact values depend on the installed heat kit, here are common breaker size scenarios you’ll see with Goodman MBVK electric furnaces:
Blower and Controls
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Often powered by a 15-amp or 20-amp breaker
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This circuit handles only the blower motor and low-voltage transformer
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It does not power heat strips
Heat Strip Circuits
Depending on the heat kit installed, you may see:
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30-amp breaker (small heat kits, partial heat)
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40-amp breaker (moderate heating capacity)
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50-amp or 60-amp breakers (larger heat kits or multiple stages)
Many MBVK installations use two or more breakers, not one. Homeowners are often surprised by this, but it’s completely normal for electric furnaces.
This modular approach allows the furnace to stage heat safely without overloading a single circuit.
5. Why One Breaker Is Often Not Enough
A common misconception is that an electric furnace should be powered by a single large breaker. In practice, this is rarely the best—or safest—design.
The Goodman MBVK is engineered to:
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Separate high-current heating loads from lower-current control loads
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Reduce voltage drop during startup
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Prevent nuisance tripping during staged heat operation
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Improve serviceability and diagnostics
When a homeowner says, “My furnace turns on but doesn’t heat,” one of the first things I check is whether one of the heat strip breakers is tripped while the blower breaker remains on. In that situation, the furnace appears operational—but produces no heat.
This scenario is so common that it accounts for a significant percentage of “no heat” service calls in electric furnaces.
6. Breaker Size vs. Wire Size: A Critical Distinction
One of the most dangerous misunderstandings around breaker size for electric furnace installations is confusing breaker size with wire size.
Here’s the rule Savvy Mavi lives by:
The breaker protects the wire—not the appliance.
If the breaker is too large for the wire feeding the furnace, the wire can overheat without tripping the breaker. That’s a serious fire hazard.
For example:
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A 60-amp breaker requires appropriately sized copper or aluminum conductors
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You cannot simply “upgrade” a breaker without upgrading wiring
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The furnace nameplate tells you the maximum breaker size allowed—not the minimum
The Goodman MBVK documentation clearly outlines acceptable breaker and wire combinations, and those guidelines must be followed precisely. (acdirect.com)
7. How Heat Strip Size Affects Circuit Breaker Size
Heat strips are the single biggest driver of breaker size in an electric furnace.
Each heat strip bank has:
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A fixed wattage rating
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A predictable amperage draw based on voltage
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A defined MCA and MOCP
For example (simplified for illustration):
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A 10 kW heat strip at 240V draws ~41.7 amps
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A 15 kW heat strip draws ~62.5 amps
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A 20 kW heat strip draws ~83.3 amps
These loads are often split across multiple circuits so that no single breaker exceeds safe limits. That’s why a Goodman MBVK with a larger heat kit might use two 60-amp breakers instead of one massive breaker.
This staged, multi-breaker approach is intentional—and safer.
8. Code Compliance and Manufactured Homes
In manufactured or mobile homes, breaker sizing becomes even more critical.
Electrical panels in manufactured homes often have:
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Limited total service amperage
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Tighter space constraints
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Stricter code enforcement
When installing a Goodman MBVK in this environment, the circuit breaker size for an electric furnace must be coordinated carefully with the home’s service capacity. Oversizing breakers—or heat kits—can overload the main panel even if the furnace itself is wired correctly.
This is another reason Goodman designs MBVK systems with flexible, modular breaker requirements rather than a single rigid configuration.
9. Symptoms of Incorrect Breaker Sizing
If the breaker size for an electric furnace is wrong, the symptoms often appear gradually. Watch for:
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Breakers tripping only during cold weather
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Furnace heating partially but not fully
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Blower running without heat
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Heat strips cycling erratically
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Burnt wire insulation or warm breaker handles
These are warning signs—not annoyances. Persistent breaker trips should never be ignored, especially in high-load systems like electric furnaces.
10. Troubleshooting Breaker-Related Furnace Issues
If you suspect a breaker issue with your Goodman MBVK, follow a structured approach:
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Identify all furnace breakers, not just one
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Reset breakers fully (off, then on)
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Observe which breaker trips and when
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Check furnace nameplate MCA and MOCP
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Verify wire gauge matches breaker size
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Call a professional if trips persist
Never upsize a breaker “just to stop it from tripping.” That approach bypasses the protection system and creates risk. (Vernon Air Conditioning, Plumbing & Electrical Services)
11. Why Professionals Start With Breaker Analysis
When a technician arrives at a no-heat call for an electric furnace, breaker sizing is often the first thing they verify. That’s because:
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Breakers reveal how the system was designed
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Tripped breakers often indicate underlying electrical stress
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Incorrect breaker sizes point to improper installation
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Heat strip failures frequently trace back to electrical supply problems
In many cases, correcting breaker sizing and wiring resolves heating issues without replacing furnace components.
12. Long-Term Reliability Starts With Correct Breaker Sizing
The Goodman MBVK electric furnace is engineered for durability—but only when supported by correct electrical infrastructure. Proper circuit breaker size for an electric furnace ensures:
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Stable voltage under load
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Accurate heat staging
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Reduced wear on heat elements
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Lower risk of electrical faults
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Compliance with electrical codes
Think of breakers as the foundation under your furnace. If that foundation is weak or mismatched, performance suffers.
13. Final Thoughts from Savvy Mavi
If there’s one takeaway from this guide, it’s this:
Breaker size is not a detail—it’s a design decision.
The correct breaker size for an electric furnace like the Goodman MBVK is determined by heat kit configuration, electrical service, code requirements, and manufacturer specifications. It’s not something to guess, generalize, or copy from another installation.
When installed correctly, the MBVK delivers reliable, consistent heat with minimal electrical stress. When installed incorrectly, breaker issues become the silent saboteur behind no-heat calls, nuisance trips, and premature component failure.
Take the time to verify your breaker configuration. Read the nameplate. Respect MCA and MOCP. And when in doubt, consult a licensed professional who understands electric furnace design.
Because in the world of electric heating, power without protection is just risk wearing a disguise.
