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Connecticut Electric UBIZ0250 50 Amp Circuit Breaker for Level 2 EV Charging

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9.3
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The Connecticut Electric UBIZ0250 is a 50A, 2-pole, 120/240V thin Zinsco replacement breaker, perfect for 40A Level 2 EV charger installations in older Zinsco electrical panels.

The Connecticut Electric UBIZ0250 is a 50 Amp, 2-pole, thin-series plug-in breaker designed as a modern replacement for outdated Zinsco RC3850 breakers still found in Zinsco circuit breaker panels – especially when installing a Level 2 EV charger. It’s a newly manufactured, ETL-listed unit (never refurbished or salvaged) that offers a safe, reliable solution for wiring 240V Level 2 EV chargers requiring a 40A load on a 50A branch circuit, particularly in homes where the original Zinsco load center is still in use.

As an EV charger installer, I’ve encountered many homes with aging Zinsco panels where panel replacement isn’t immediately viable due to budget constraints, structural limitations, or renovation delays. Considering the combined costs of purchasing an EV charger and paying for installation, upgrading a Zinsco panel can significantly increase the overall expense. In these cases – if the Zinsco panel can safely support the 40A Level 2 EV charger load – I recommend the UBIZ0250 from Connecticut Electric as a replacement Zinsco circuit breaker for Level 2 EV charger installations. It’s ETL-listed to UL 489 standards for the U.S. and Canada, making it a critical component for achieving a code-compliant EV charging installation while preserving legacy infrastructure.

The Connecticut Electric UBIZ0250 breaker is classified as a direct replacement for the Zinsco RC3850 two-pole breaker, offering precise fitment and full compatibility with Zinsco panels. It snaps firmly into place, creating a solid and reliable connection – eliminating the loose or brittle fit often found in original Zinsco breakers and many off-brand alternatives. With a 10,000 AIC interrupt rating, the Connecticut Electric UBIZ0250 is a dependable replacement that can safely handle the continuous high-current demands of fast Level 2 EV charging, even in older Zinsco panel-powered electrical circuit components and panels.

We tested the Connecticut Electric UBIZ0250 as a replacement Zinsco circuit breaker on a 50A dedicated EV charger branch circuit installed in an original Zinsco panel. Our 50A EV charging circuit used a NEMA 14-50R outlet paired with a NEMA 14-50 Grizzl-E Smart EV Charger delivering a 9.60 kW charging load at 240V.

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Our NEMA 14-50 Grizzl-E Smart EV charger installation used 6 AWG solid copper THHN conductors housed in ¾-inch non-metallic conduit with grounding bonded to the load center’s busbar. The 50A EV charging branch circuit terminated into a NEMA 14-50 outlet mounted in an outdoor-rated enclosure using a heavy-duty outlet weatherproof cover to ensure full protection of the EV charger circuit outlet.

The Connecticut Electric UBIZ0250 breaker (Zinsco RC3850 Replacement) was installed smoothly into the Zinsco panel with a secure plug-in mount that provided immediate confidence in the connection quality. We used the EV charger as our daily EV charger for a month, including high ambient summer conditions that we experience here in California and extended overnight charging sessions – the Connecticut Electric UBIZ0250 breaker and the 50A EV charger branch circuit components showed zero signs of heat stress, dedicated circuit breaker tripping, or EV charging voltage fluctuation. This level of stable performance is essential in Zinsco panels, which are historically prone to contact degradation and thermal wear under sustained high loads.

Wiring the UBIZ0250 Breaker for a 240V Level 2 EV Charger

When installing a 240V Level 2 EV charger using the Connecticut Electric UBIZ0250 breaker as a replacement for a Zinsco RC3850 in an original Zinsco panel, this approach can be a practical alternative to a full panel upgrade – especially given the difficulty in finding reliable Zinsco replacements for EV branch circuit protection. If your existing Zinsco panel can accommodate a 50A EV charging circuit, this replacement breaker is a solid option that we recommend. However, proper installation practices are essential – always when installing EV chargers on old panels we recommend starting with a thorough panel inspection, including a close look at the bus bars – if you notice signs of corrosion or arcing, an upgrade or professional remediation may be necessary.

In our case, we used the UBIZ0250 with a NEMA 14-50 circuit to install a NEMA 14-50R outlet, paired with a Grizzl-E Smart EV Charger drawing 40A at 240V. However, wiring configurations may vary based on your EV charger configurations and Zinsco panel setup. This breaker supports both 3-wire and 4-wire configurations for either plug-in or hardwired 40A EV charger installations. Below are the most common EV charger wiring setups using the UBIZ0250 as a 120/240-volt Zinsco 50 amp, double pole, thin series replacement circuit breaker, with diagrams for complete 40A Level 2 EV charger installations.

EV Charger Wiring – 240V (4-Wire: L1, L2, Neutral, Ground) – UBIZ0250 Breaker

Installing a plug-in EV charger in a Zinsco panel using a 4-wire circuit (L1, L2, Neutral, Ground) is one of the most common and reliable methods for Level 2 EV charger installations. The NEMA 14-50 EV charger is the most widely used plug-in configuration on the market today, supported by numerous EV charger brands – including our top-rated NEMA 14-50 option, the NEMA Grizzl-E Smart EV Charger, and many OEM Level 2 EV chargers.

This circuit uses 6 AWG copper conductors: two hot wires from the 240V double pole 50A UBIZ0250 breaker (Zinsco RC3850 Replacement), one neutral wire connected to the neutral bus, and one ground wire bonded to the panel’s ground bus, as shown in the wiring diagram below. This wiring method ensures compatibility with both plug-in and hardwired EV chargers that require a neutral, making it ideal for safe, code-compliant installations in older Zinsco panels.This diagram, titled "EV Charger Wiring - 240V (4-Wire: L1, L2, Neutral, Ground) - UBIZO250 Breaker," illustrates the electrical setup for an EV charger. It shows power from the utility, consisting of L1 (Hot 1), L2 (Hot 2), and Neutral (N), entering a Zinsco circuit breaker panel. A warning highlights that active lugs on the main breaker are always live. Inside the panel, the utility lines connect to the main panel breaker. A dedicated 50A 2P Connecticut Electric UBIZO250 breaker is installed for the EV charger. The neutral wire from the utility connects to a neutral busbar, and a ground busbar is connected to an earth conductor, ground rod, and finally to the ground. Electrical bonding between the neutral and ground busbars is indicated. From the dedicated EV charger breaker, a 240V branch circuit, using 6 AWG copper wire, carries L1 (red), L2 (black), Neutral (white from neutral busbar), and Ground (green from ground busbar) through a 3/4" conduit towards the EV charger. A note advises keeping this wiring clear of gutter posts and avoiding crossing wires over breakers, and to upsize wires on long runs to manage voltage drop. The diagram shows two connection options for the EV charger: a NEMA 14-50 outlet for a plug-in charger, and a hardwired connection with terminal wiring specified as L1 (Black), L2 (Red), N (White), and G (Green). It depicts a 40A Level 2 EV Charger (9.6kW). A crucial safety note states that a 40A charger requires a 50A breaker according to the NEC 80% rule. The "ELECTRIC VEHICLE GEEK" logo is visible.

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EV Charger Wiring – 240V (3-Wire: L1, L2, Ground) – UBIZ0250-New Breaker

This 3-wire configuration is ideal for hardwired EV chargers like the Wallbox Pulsar Plus 40-Amp EV Charger or NEMA 6-50 plug-in EV chargers using a NEMA 6-50 outlet, such as the Grizzl-E Classic. Since these chargers don’t require a neutral, the 6 AWG solid copper, 50A branch circuit consists of two hot conductors from the dedicated UBIZ0250 breaker (Zinsco RC3850 Replacement) and one ground conductor connected to the panel’s ground bus as shown in the diagram below. This wiring configuration simplifies the installation of both plug-in and hardwired EV chargers in Zinsco panels while remaining compliant with NEC standards.This diagram, titled "EV Charger Wiring - 240V (3-Wire: L1, L2, Ground) - UBIZO250 Breaker," illustrates the electrical setup for a 3-wire EV charger system. Power from the utility, consisting of L1 (Hot 1), L2 (Hot 2), and Neutral (N), enters a 120/240V Zinsco circuit breaker panel. A warning indicates that active lugs on the main breaker are continuously live, regardless of the main breaker's status. Inside the panel, the utility lines connect to the main panel breaker. A Zinsco RC3850 Replacement, specifically a 50A 2P Connecticut Electric (UBIZO250) dedicated circuit breaker, is installed for the EV charger. The incoming utility neutral connects to a neutral busbar, and a ground busbar is connected to an earth conductor, a ground rod, and ultimately to the ground/earth. Electrical bonding between the neutral and ground busbars is shown. From the dedicated EV charger breaker, a 240V branch circuit (L1, L2, & G) is run using 6 AWG 90C copper wire. This circuit includes L1 (red wire) and L2 (black wire) from the breaker, and a ground wire (green wire) from the ground busbar. These wires pass through a 3/4" conduit towards the EV charger. Notes advise keeping branch circuit wiring outside gutter posts, avoiding crossing wires over breakers, and upsizing wires on long runs to keep voltage drop under 3% per NEC. The diagram shows two connection options for the EV charger: a NEMA 6-50 Outlet for a plug-in EV charger, or a hardwired connection. The hardwired EV charger terminal wiring is specified as L1 - LINE 1 (Black), L2 - LINE 2 (Red), and G - GROUND (Green), notably omitting a neutral connection for this 3-wire setup. It depicts a 40A Level 2 EV Charger (9.6kW). A crucial safety note states that a 40A charger needs a 50A breaker per the NEC 80% rule. The "ELECTRIC VEHICLE GEEK" logo is visible in the bottom left.

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EV Charger Wiring – 240V (3-Wire: L1, L2, Neutral, No Ground) – UBIZ0250-New Breaker

Some older outlet or junction box installations still use a bonded neutral-ground configuration without a dedicated ground wire – commonly found in legacy NEMA 10-50 outlet setups. While wiring an EV charger this way does not meet current code standards, it may still be allowed for certain plug-in EV chargers that explicitly support it, as shown in the wiring diagram below – provided it’s permitted by local code and the EV charger configuration supports this kind of set-up such as NEMA 10-50 EV chargers. This setup should only be used with caution and always under the guidance of a licensed electrician or your local electrical inspector.This diagram, titled "EV Charger Wiring - 240V (3-Wire: L1, L2, Neutral, No Ground) - UBIZO250 Breaker," illustrates an outdated electrical setup for an EV charger. Power from the utility (L1, L2, Neutral) enters a Zinsco circuit breaker panel. A warning notes that active lugs on the main breaker are always live. Inside the panel, utility lines connect to the main panel breaker. A dedicated 50A 2P Connecticut Electric UBIZO250 breaker (Zinsco RC3850 Replacement) is for the EV charger. The neutral from the utility connects to a neutral busbar. A ground busbar is present, connected to an earth conductor and ground rod, with electrical bonding to the neutral busbar, but it is not used for the EV charger branch circuit in this configuration. A 240V branch circuit (L1, L2, & N) runs from the dedicated breaker using 6 AWG 90C copper wire. L1 (red) and L2 (black) come from the breaker, and Neutral (white) comes from the neutral busbar, passing through a 3/4" conduit. Advice is given to keep wiring clear of gutter posts, avoid crossing wires over breakers, and upsize wires for long runs to manage voltage drop. Two connection options are shown: a NEMA 10-50 Outlet (with Y, X, and W prongs) for a plug-in charger, or a hardwired connection. The hardwired EV charger terminal wiring is L1 (Black), L2 (Red), and N (Neutral - White), with no ground connection. It shows a 40A Level 2 EV Charger, and a note states a 40A charger needs a 50A breaker per NEC 80% rule. A prominent warning states: "The configuration (L1, L2, N - no ground) is outdated and not permitted under modern NEC requirements for EV chargers. According to NEC 250.4(A)(1) and NEC 625.54, grounding is essential for all electrical installations, including EV chargers. Avoid using this setup in new installations." The "ELECTRIC VEHICLE GEEK" logo is present.

9.3Expert Score
For legacy Zinsco electrical panels still in use that can support a 50A EV charging circuit, the UBIZ0250 by Connecticut Electric is the most dependable and code-compliant 50A Zinsco breaker replacement for 40A Level 2 EV charger installations. Finding reliable Zinsco replacements isn’t easy, but this breaker performs exceptionally well in EV charger setups — including most plug-in chargers and many hardwired units adjusted to 40A. With consistent thermal performance, UL-standard compliance, and safe handling of high-current EV loads, it’s a must-have for upgrading older homes with reliable EVSE branch circuits.
Features
9
Real World Usage
9.5
Materials
9.5
Durability
9.5
Craftsmanship
9
Design
9.5
Monetary Value
9.5
Product Value
9.5
Brand Reputation
8.5
Expert Valuation
9.5
PROS
  • ETL listed to UL 489 standards
  • Direct fit for Zinsco panels
  • Supports 240V Level 2 EV chargers
  • Handles continuous 40A EVSE loads
CONS
  • Only compatible with Zinsco panels
  • Doesn’t address underlying panel safety concerns

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