Connecticut Electric UBIZ0250 50 Amp Circuit Breaker for Level 2 EV Charging
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The Connecticut Electric UBIZ0250 is a 50 Amp, 2-pole, thin-series plug-in breaker designed as a modern replacement for outdated Zinsco RC3850 breakers still found in Zinsco circuit breaker panels – especially when installing a Level 2 EV charger.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.
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.
Compatible Level 2 EV Chargers for This Wiring Setup
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.
Compatible Level 2 EV Chargers for This Wiring Setup
The Enphase IQ 50 40 Amp Smart EV Charger delivers 9.6kW of power at 240V with a hardwired installation and a 25ft cable. Featuring Wi-Fi connectivity, a ruggedized J1772 connector, and safety certifications, it ensures reliable, efficient charging. Backed by a 5-year warranty, it's ideal for home use and future-proofing.
The Emporia Level 2 EV Charger with NACS delivers fast, reliable charging for Tesla and NACS vehicles. It offers up to 46 miles of range per hour, features easy installation, and is UL-listed for safety. Smart charging capabilities and durable construction make it a great value at a competitive price.
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.
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