Altronix T2428100220 220VAC to 24/28VAC 100VA Transformer
The Altronix T2428100220 is a single-output step-down transformer designed for security and access control systems operating on international 220VAC mains supply. Rated at 100VA capacity with selectable 24VAC or 28VAC output, this transformer provides straightforward voltage conversion for door readers, magnetic locks, alarm control panels, and distributed camera power in multi-building facilities across Europe, Asia-Pacific, and other regions where 220VAC service is standard. The fixed input/selectable output design eliminates field configuration complexity—choose your output voltage at installation and integrate with confidence.
Key Features
- 100VA Power Rating: Sufficient for single-access-point door stations, alarm panel standby backup, or distributed 24VAC camera feed across 2–4 midrange IP cameras. Typical access control draws 40–60VA per magnetic lock.
- Selectable Output (24VAC or 28VAC): Field-selectable output voltage accommodates both North American 24VAC and elevated 28VAC devices (common in European access control) without requiring separate SKUs or dual-output inventory.
- 220VAC Input: Direct 220VAC connection—no step-down pre-stage needed for international installations where 110VAC is unavailable or non-standard.
- Single Output Terminal: One-to-one wiring topology simplifies integration into control cabinets and reduces terminal block congestion versus multi-output models.
- UL Listed Safety Rating: UL approval confirms compliance with North American electrical safety standards; accepted by most code inspectors and insurance carriers on commercial security deployments.
- Lifetime Limited Warranty: Manufacturer backs the unit against defects in materials and workmanship for the product lifespan—standard coverage for Altronix passive components.
The T2428100220 fills a specific role in hybrid-voltage environments: facilities with 220VAC service in the main plant but which have purchased 24VAC access control equipment or IP cameras rated for North American voltage. A single transformer at the rack supplies the entire security subsystem without hunting for dual-voltage alternatives or custom quotes. The 100VA ceiling is the limiting dimension—if your access control console, multiple magnetic locks, and backup siren total more than 90–95VA steady-state draw, you'll need a larger transformer or dedicated power supply (Altronix manufactures several 150VA, 200VA, and 500VA single-output options for higher load cases).
Deployment context matters. If you're retrofitting a 220VAC facility with North American access control gear, or standardizing on 24VAC for a multi-site rollout across regions with mixed mains voltages, the fixed 220VAC input and selectable output eliminate on-site confusion. Terminal block integration is straightforward: feed 220VAC into the input terminals, select 24VAC or 28VAC via a jumper or tap selector (consult the datasheet for exact toggle location), and wire the output to your control panel's 24VAC input bus. No external wiring changes needed if you upgrade from 24VAC to 28VAC later—a five-minute selector adjustment and you're done.
The transformer is passive (no electronic regulation), so output voltage will sag slightly under full 100VA load and may creep upward if load drops below 20VA. This is normal transformer behavior—most commercial access control systems tolerate ±10% voltage swing. If your application requires tighter regulation (e.g., a sensitive camera power rail), pair the T2428100220 with a downstream regulated supply or select an Altronix regulated PSU instead. For bulk power distribution to multiple buildings fed from a central 220VAC source, stacking two or more T2428100220 units in parallel is not recommended without load balancing—use a larger single unit or a multi-output transformer if you need 200+ VA.
Marty AllisonPerspective based on aggregated IP Security Depot and affiliated engineering team experience.
We've deployed the Altronix T2428100220 in dozens of retrofits across European and Middle Eastern sites where legacy 220VAC distribution meets modern North American access control and IP camera systems. The core appeal is simplicity: a single fixed transformer that doesn't require custom engineering or dual-sourcing, which cuts procurement cycle time and reduces on-site integration confusion. In our experience, the biggest pain point in mixed-voltage environments isn't the transformer itself—it's cable run management and ensuring that the output of a single 100VA unit doesn't inadvertently supply an over-subscribed load (e.g., three magnetic locks plus a networked card reader all hung on one transformer). The T2428100220 forces discipline: you size the load first, then choose the transformer. That's actually a strength. We've seen integrators sidestep undersized units by defaulting to larger supplies, which costs more but guarantees headroom. The selectable 24/28VAC output is genuine convenience—you don't stock both a 24VAC and 28VAC variant, and if a customer standard shifts mid-project, you adjust the tap instead of scheduling an SKU swap.
Technical Highlights:
- 100VA Capacity at 220VAC Input: A single 100VA unit drops 220V down to 24/28V and can handle the simultaneous current draw of one large magnetic lock (60VA) plus a card reader (15VA) plus 25VA of ambient power draw. Real-world margin is thin at 100% load—spec at 85% capacity (85VA) for sustained thermal management in cabinet mounting without forced ventilation.
- Passive Transformer Design: No electronic components mean no failure modes from power surges or voltage spikes; however, there's no internal fusing or short-circuit protection. If your 24VAC output is shorted, the transformer will draw maximum current until an upstream breaker trips. Pair with appropriately rated upstream protection and a downstream circuit breaker or fused disconnect on the 24VAC side.
- UL Listed Single-Output Topology: Single secondary winding simplifies certification—this is not a multi-tap or multi-output unit. Certification applies to the entire transformer assembly, not individual terminals, so no field rewiring of the secondary without voiding the listing.
- Selectable Output Voltage: Switching between 24VAC and 28VAC is a field-accessible adjustment (typically a shorting block or terminal tap selector). Verify the selector position before energizing to avoid applying 28VAC to a 24VAC-only device downstream, which can degrade capacitors and shorten equipment life.
- No Built-in Filtering or Surge Suppression: The transformer passes through AC ripple and transients from the mains. If your downstream equipment is sensitive to noise (some networked access panels, wireless intercom stations), add a small LC filter or surge suppressor to the 24VAC output side.
Deployment Considerations:
- Load Planning is Critical: Verify that all devices on the 24VAC output (reader, lock, siren, backup battery charger if present) sum to no more than 85VA sustained draw. If you're margin-constrained, order the next size up (Altronix 150VA transformer) rather than discovering nuisance brownouts six months post-install.
- 220VAC Feeder Circuit Sizing: The transformer is 220VAC input, so confirm that your facility's main electrical panel has a dedicated 220VAC branch circuit available. If only 110VAC is available, you'll need a different transformer entirely. Do NOT wire two 110VAC branches in series or attempt a workaround—use the correct input voltage.
- Thermal Mounting: At full 100VA load, the transformer core will warm—ensure it's mounted vertically in a control cabinet with at least 2 inches of clearance above and below for natural convection. In sealed or undersized cabinets, consider mounting the transformer outside the main cabinet on a DIN rail in a ventilated enclosure.
- Output Voltage Selector Position: Take a photograph of the selector position at commissioning and file it with your as-built documentation. If the transformer is replaced in the field, the next technician may inadvertently flip it to 28VAC thinking it's a toggle switch, creating a silent over-voltage condition that gradually degrades downstream equipment.
- Grounding and Bonding: The transformer secondary (24/28VAC output) should be bonded to the building ground/equipment ground bus—do not float the secondary. This prevents ground-loop hum and ensures that any fault-to-ground condition is safely cleared through the upstream breaker.
The Altronix T2428100220 is the right choice for integrators standardizing on 24VAC access control and camera systems in 220VAC regions, or for hybrid deployments where you need one transformer to serve a small access control cabinet with modest load. It's not suitable for large multi-building campuses (order a larger single transformer or a multi-output panel supply instead) or for applications where output voltage regulation tighter than ±10% is required. For straightforward, mid-capacity 220-to-24/28V conversions with international compliance, explore the Altronix catalog for the full range of power transformers and regulated supplies.
