An outdoor UPS for a traffic intersection cannot be sized from the traffic controller nameplate alone. The real load may also include signal heads, CCTV cameras, a network switch, a modem, road sensors, cabinet fans or heaters, and service lighting. If those loads are mixed together without separating continuous demand, short peaks and backup priority, a UPS can look adequate in kVA while the battery runtime or output waveform is wrong for the site.
A practical sizing process has four parts: establish the critical load in watts, check peak and transfer requirements, convert the required outage duration into usable battery energy, and then match the electrical result to an outdoor enclosure, mounting method and monitoring plan. The calculations below are engineering screening tools; final values should be confirmed against the actual load schedule, local grid data and project specification.
Define What Must Stay Online During an Outage
Start with the operating objective, not the UPS catalogue. A traffic-safety cabinet often contains equipment with different consequences if power is lost, so not every connected device has to receive the same backup priority.
Separate safety-critical and non-critical loads
The traffic controller, required signal heads, communication link and essential cameras are normally the first candidates for uninterrupted power. Cabinet lighting, convenience outlets, auxiliary heaters or non-essential analytics equipment may be shed during a long outage if the project permits it. A priority list prevents a secondary load from consuming battery energy intended for the safety function.
Record operating watts, VA and operating mode
For each device, record measured running watts where possible, apparent power or power factor, startup or switching behavior, and whether the load runs continuously. LED signal drivers, power supplies, heaters and motors can behave differently even when their average wattage is similar. Use the highest credible simultaneous operating condition rather than an average collected during a quiet period.
- Traffic controller and signal heads
- CCTV cameras, infrared illuminators and pan-tilt-zoom drives
- Network switch, router, fiber converter or cellular modem
- Road sensors, radar units and communication equipment
- Cabinet cooling, heating and service accessories
Calculate Running Load and Peak Demand Separately
Add the continuous watts first. Then evaluate whether any equipment produces a short peak that the inverter must support. The UPS power rating must satisfy both conditions; battery energy is normally based on the sustained load profile, not on a brief peak that lasts only seconds.
Use watts for output capacity and retain design margin
A simple screening relationship is: required UPS output watts >= maximum simultaneous running watts x design margin. The margin is not a substitute for measuring the load. It covers documented load growth, measurement uncertainty and normal operating variation. For a stable, well-characterized roadside cabinet, project engineers may begin with a modest reserve and increase it when future devices, high temperature or uncertain peak behavior are expected.
Illustrative load example
Assume an intersection has a 70 W controller, 120 W of signal heads, 40 W of cameras, 25 W of networking equipment and 25 W of essential auxiliaries. The continuous load is 280 W. Applying a 25% screening margin gives 350 W. A 360 W UPS would therefore leave almost no room for measurement error or expansion, while a 600 W or 800 W output class gives a more workable engineering range, subject to the real peak and waveform requirements. These figures illustrate the method and are not ratings for a specific project.
Convert Backup Time Into Usable Battery Energy
UPS capacity and battery autonomy answer different questions. The inverter may be large enough to carry the load but still stop after a short outage if the battery energy is undersized.
Use an energy calculation, not battery Ah alone
A useful first-pass formula is: required nominal battery Wh = load W x backup hours / (UPS efficiency x usable battery fraction). The usable fraction accounts for discharge limits; the final design must also allow for battery aging, temperature, cable loss and the manufacturer’s discharge-rate data.
Using the 280 W example, four hours of backup, 88% conversion efficiency and an illustrative 80% usable battery fraction gives about 1,590 Wh before aging and temperature allowances. Adding a 25% energy reserve raises the screening value to roughly 2.0 kWh. The next step is to confirm the selected battery at the actual DC voltage, discharge current and lowest expected site temperature.
Check recharge time and repeated outages
A battery that supports one long outage may not recover before the next event. Record the available charging current, expected outage frequency and the time allowed to restore the design state of charge. This is especially important for weak grids and locations where technicians cannot visit after every event.
Choose Topology From the Load’s Transfer and Power-Quality Needs
Traffic and CCTV equipment does not automatically require the same UPS topology. The decision depends on how the controller and power supplies respond to transfer time, voltage variation, frequency change and waveform quality.
When line-interactive may be sufficient
CONSNANT’s CNW110-1K pole/wall-mounted outdoor UPS is listed in 600 VA/360 W and 1000 VA/600 W configurations. Its published technical data specifies a typical 2-6 ms transfer time, simulated sine-wave output, IP55 construction and pole mounting. It can be evaluated for compact roadside loads only after the controller and camera power supplies are confirmed to tolerate those characteristics.
When online double conversion is the safer direction
The CNW110L-1K 1 kVA/0.8 kW outdoor UPS uses online double-conversion topology with pure sine-wave output and 0 ms transfer from line mode to battery mode. Its published input range is 100-300 VAC. That direction is more appropriate when the site has sensitive mixed electronics, severe voltage fluctuation, or a specification that does not allow an interruption during grid failure.
Treat the Outdoor Cabinet as Part of the Power System
Electrical sizing is incomplete if the enclosure cannot maintain the required internal environment. Direct sun, dust, wind-driven rain, condensation, insects, salt exposure and vandalism can all affect the UPS, battery and connected communication equipment.
Match mounting to access and site risk
Pole or wall mounting can reduce ground footprint and help keep equipment above localized flooding or casual interference, but it makes lifting, cable routing and service access more demanding. Floor-mounted cabinets offer more space for batteries and thermal equipment, but they need a suitable plinth, drainage, anchoring and protected cable entries.
Do not use IP rating as a thermal specification
CONSNANT’s CNW110 1-3 kVA pole-mounted outdoor UPS is published with an IP55 enclosure and is listed for CCTV, traffic-light and telecom applications. IP55 addresses dust and water ingress; it does not by itself prove that the battery and electronics will remain within temperature limits. The project specification should separately state ambient range, solar load, ventilation or active cooling, condensation control and any corrosion requirement.
Coordinate surge and grounding protection
Roadside cabinets are connected to long outdoor cables and exposed metal structures. Define the upstream protective device, surge-protection arrangement, earthing method, neutral configuration and cable routing as one system. A cabinet label that says ‘lightning protection’ is not a substitute for a coordinated site design.
Plan Monitoring and Maintenance Before Deployment
A remote intersection is expensive to diagnose after failure. Monitoring requirements should be written before procurement so the UPS can report the states the maintenance team actually uses.
Specify actionable alarms
At minimum, decide how the site will report mains failure, battery operation, low battery, UPS fault, bypass state and abnormal cabinet temperature. Also confirm the protocol, network path, alarm destination and whether dry contacts, SNMP or serial communication are required. The CNW110L-1K technical table lists RS232/USB with optional SNMP and dry-contact interfaces, so the ordered communication configuration should be confirmed rather than assumed.
Design for front access and replaceable assemblies
Technicians should be able to isolate the load, inspect the battery, replace filters or fans, and remove the UPS control assembly without dismantling the complete roadside cabinet. The CNW110L product information describes front access, a separated internal layout and a drawer-type control unit intended to simplify installation and maintenance.
Match the Result to a CONSNANT Product Direction
The calculation should narrow the product family; it should not be reverse-engineered to fit a preferred model. The following matrix is a starting point for commercial discussion, not a final project specification.
| Site requirement | Primary decision | Relevant CONSNANT direction |
| Compact low-power cabinet; brief transfer is acceptable | Verify 360/600 W output, simulated sine wave and 2-6 ms transfer against the load | CNW110-1K line-interactive pole-mounted UPS |
| Sensitive controller or cameras; poor grid; no line-to-battery interruption | Pure sine wave, online topology and 0 ms transfer | CNW110L-1K, 1 kVA/0.8 kW |
| Load exceeds 0.8 kW or significant expansion is planned | Increase inverter and battery range after measuring peak demand | CNW110 pole-mounted outdoor UPS, 1-3 kVA |
| Long autonomy, high heat or a larger integrated cabinet | Separate battery, charger and thermal calculations from UPS kVA | Project-specific configuration within the outdoor UPS range |
CONSNANT has also published a Kuwait transportation security project using 2 kVA outdoor UPS equipment across 230 sites. That project is useful evidence that traffic-security applications involve more than one standard cabinet, but a new project should still be sized from its own load, autonomy and environmental data.
For a broader comparison of available capacities and enclosure formats, review the CONSNANT outdoor UPS product range.
Send Suppliers a Complete Procurement Specification
A useful request for quotation should allow the supplier to check the complete duty rather than guess from ‘traffic-light UPS’ as a label. Include:
- Equipment list with running watts, VA or power factor and peak behavior
- Critical and non-critical load priorities
- Required backup time and expected outage pattern
- Grid voltage/frequency range, generator use and surge environment
- Required transfer time and output waveform
- Lowest and highest ambient temperature, solar exposure and humidity
- Pole, wall or floor mounting constraints and service clearance
- Battery technology, service-life target and recharge requirement
- Monitoring protocol, alarm points and remote-management platform
- Applicable enclosure, safety and local project standards
Providing this information lets CONSNANT evaluate the inverter, battery, cabinet and communication configuration as one roadside power system. It also makes supplier quotations easier to compare because each bidder is working from the same duty profile.
Conclusion
Sizing an outdoor UPS for traffic lights and roadside CCTV is a load-and-energy problem before it is a model-selection problem. Calculate continuous watts and peak demand separately, convert the required outage duration into usable battery energy, confirm transfer and waveform requirements, and then specify the enclosure, surge coordination, monitoring and service access. This sequence prevents a project from buying enough kVA but not enough runtime, or enough battery but the wrong topology for the controller and cameras.
FAQs
How much UPS capacity does a traffic-light site need?
Add the maximum simultaneous running watts, verify any short peak or inrush demand, and apply a documented design margin. Select the UPS by output watts as well as VA; do not assume a 1 kVA unit can always support a 1 kW load.
How is battery runtime calculated for roadside CCTV?
Start with load watts multiplied by backup hours, then divide by UPS efficiency and the allowed usable battery fraction. Apply temperature, aging, discharge-rate and cable-loss allowances using the selected battery data.
Is online UPS always required for traffic signals?
No. It depends on the controller and connected electronics. A line-interactive UPS may be acceptable when the load tolerates its transfer time and waveform. Online double conversion is the safer direction when zero line-to-battery interruption, pure sine-wave output or stronger power conditioning is required.
Can an indoor UPS be installed inside an outdoor cabinet?
Only if the complete cabinet design maintains the UPS and battery within their permitted temperature, humidity and contamination limits and provides suitable protection, ventilation, cable entry, grounding and service access. An enclosure alone does not automatically make indoor equipment suitable for outdoor duty.
What information should be sent to an outdoor UPS supplier?
Send the load schedule, peak demand, backup time, grid data, ambient conditions, mounting limits, monitoring protocol, battery preference, required standards and maintenance constraints. Photos and a cabinet single-line diagram help the supplier check physical integration and interfaces.
