Thermal and Power Management in Outdoor Telecom Cabinets

A street cabinet is a small data centre with a much harder life. It has active equipment that must stay within its temperature range, batteries that age faster when they are hot, a power supply that has to keep working through a fault, and no air conditioning technician within a hundred kilometres. Thermal and power design is what decides whether the cabinet survives the summer and the winter, and how often someone has to visit it.

Know the Heat Load and the Ambient Range

• Get the equipment losses from the datasheets, at the worst operating point, not the average.
• Add the battery losses during charge and discharge, which are often overlooked.
• Use the local design ambient, including the record high and the solar gain on the cabinet.
• Decide the internal temperature limit for the equipment and, separately, for the battery.
• Keep the margin honest; a design that only works at night in spring is not a design.

Passive Cooling: Cheapest and Most Limited

• Use the cabinet's surface area to reject heat where the load is modest.
• Provide solar shades or double skins where the sun is the dominant load.
• Choose a light, low-absorbance finish on exposed faces.
• Keep the cabinet clear of walls, vegetation and other cabinets that block airflow.
• Accept the limit: passive cooling cannot move heat that the ambient will not accept.

Heat Exchangers, Cooling Units and Filtered Fans

• Provide the opening sizes and mounting details each device requires, and keep them off the door if the device is heavy.
• Provide space for the air path on both sides of a heat exchanger or fan.
• Document the maintenance interval, and make the parts that need maintenance accessible without opening the live compartment.

Keeping the Battery Bay Cool

• Treat the battery compartment as its own thermal zone where the design allows.
• Insulate the battery bay from the hot side of the cabinet.
• Provide ventilation or cooling provisions sized for the battery, not inherited from the electronics.
• Keep the battery clear of the direct sun face where the layout allows.
• Provide a temperature sensor position so the battery temperature can actually be measured.
• Remember that a battery bay that is cool in the lab can be the hottest part of a cabinet in service.

DC Distribution, Rectifiers and Protection

• Provide bays and mounting for the rectifier or power shelf, sized to the equipment and to a reasonable replacement.
• Provide separation between the DC distribution and the equipment section where the design requires it.
• Give protective devices a short, direct earth path, and keep the earth bar accessible.
• Provide a metering or monitoring position with access to the front of the device.
• Keep unprotected and protected sides of the surge protection device separated.
• Provide labels and a single-line diagram position inside the cabinet, because service happens years later.

Cable, Jumper and Fibre Routing

• Provide separate routes for power, signal and fibre, and maintain separation through every entry.
• Give fibre its own bend-radius discipline and its own protection.
• Provide strain relief at the cabinet entry, where the cable weight is real.
• Keep jumpers or feeders clear of doors and of service space.
• Provide spare capacity in every route, because the next upgrade will add something.

Sealing, Drainage and Service in Bad Weather

• Keep the openings that must stay open, such as a vent or a heat exchanger, protected from rain.
• Provide drainage so that water cannot collect in the base or on a horizontal surface.
• Design doors so that a technician can work in rain without flooding the cabinet.
• Provide hoods over locks and handles where the site is exposed.
• Keep the door bottom seal protected, since it is the seal that fails first.

Checks on the Build

How We Approach Telecom Cabinet Internals

• We fabricate cabinet bodies, doors, bases, equipment bays, battery compartments, internal frames, mounting plates, cable management parts and earth bars in steel, stainless and aluminium.
• We work to the thermal device, power equipment and battery drawings you supply, and we hold their mounting and openings to the sizes those devices require.
• We will tell you when a protection class, a cooling method and a battery temperature requirement cannot all be met in the geometry you have drawn.
• We do not supply the radio equipment, antennas, power systems, batteries, thermal devices or the surge protection, and we do not certify radio performance or the electrical design.
• Our sheet metal scope is the cabinet and its internals; antenna, mast and RF structures are outside it.
• Every quotation states which operations are completed in our plant.

Send the heat load, the ambient range, the battery requirement and the power layout, and the cabinet can be built to hold its own temperature and its own supply.

Frequently Asked Questions