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Metal Air Distribution Box: Specs & Sizing

2026-10-30 · by GUANDE

This page sets out the technical specification of Metal Air Distribution Box, Galvanized Steel Pressure-Resistant Air Distributor Manifold 1 In 4/5/6 Way for Underfloor Fresh Air Ventilation HVAC System as supplied by GUANDE, together with the selection rules that determine which variant suits a given project. It is written for specifiers, estimators and contractors who need to confirm a size, a material build-up and a connection method without waiting on a quotation.

ItemSpecification
Available Sizes / Models4-way / 5-way / 6-way; custom configurations supported
DescriptionAvailable in 1 inlet to 4 outlets, 1 inlet to 5 outlets and 1 inlet to 6 outlets; round top inlet fits standard circular ventilation ducts; side flat outlets match underfloor flat air ducts; all-metal housing with ABS duct connectors; embedded concealed installation; port quantity and size can be customized
Material / ConstructionHousing: galvanized steel metal; Duct connection ports: high-grade ABS plastic

Specification in Detail

A galvanised steel air distribution box with a pressure-resistant metal housing. One round top inlet feeds four, five or six flat side outlets that match underfloor flat air ducts. Because the casing is metal it holds its shape under static pressure, and the duct connectors are moulded ABS for a clean push-fit interface.

Metal Air Distribution Box, Galvanized Steel Pressure-Resistant Air Distributor Manifold 1 In 4/5/6 Way for Underfloor Fresh Air Ventilation HVAC System — product view 2

Pressure Loss at the Box

A distribution box is a pressure-loss component and its contribution should be counted in the system calculation. Loss increases with the number of active ports and with any reduction in internal cross-section, and it is affected by how the incoming air is presented to the box. Units that accept a larger inlet spigot and split the flow internally perform noticeably better than units that simply have a common chamber. When a system is marginally short of air, the box is frequently the component that was left out of the calculation.

Mounting, Access and Serviceability

Distribution boxes are usually the largest single component in a residential ventilation system, which makes their mounting position a design decision rather than an installation detail. The box must be accessible enough to inspect and to re-connect a branch if required, but it should be located where its size does not compete with other services. Mounting it directly above a habitable room without acoustic consideration is a common cause of transmitted noise. A box located in a riser or corridor void is almost always the better choice.

Insulation and Condensation at the Box

Because the box is a high-surface-area component located in a cold void, it is a natural condensation risk in the same way a duct run is. Extract-side boxes handle warm moist air and are the higher risk of the two. An insulated box, or an insulated jacket applied on site, is the correct specification wherever the assembly sits outside the thermal envelope. Omitting this detail to save cost is a decision that typically reveals itself as staining on a ceiling within the first heating season.

Quality Control at Every Stage

Quality inspection at GUANDE is not a final gate — it runs through the whole process. Incoming raw material is checked against specification before it enters production. In-process checks monitor dimensions and surface finish at defined intervals during the run. Finished Metal Air Distribution Box, Galvanized Steel Pressure-Resistant Air Distributor Manifold 1 In 4/5/6 Way for Underfloor Fresh Air Ventilation HVAC System are inspected against the approved sample, and a batch record is kept against every shipment so that any issue can be traced back to its production parameters.

Capacity, Lead Time and Container Loading

Our plant runs scheduled production for Metal Air Distribution Box, Galvanized Steel Pressure-Resistant Air Distributor Manifold 1 In 4/5/6 Way for Underfloor Fresh Air Ventilation HVAC System with typical lead times of 15 to 25 days for standard items and 25 to 40 days for custom tooling projects. We load mixed containers directly at the factory, which lets us combine several product lines from your ventilation schedule into one shipment and reduce freight cost per unit. Confirmed lead times are stated on the order acknowledgement, not estimated at enquiry.

Construction and Materials

  • Galvanised steel housing — pressure resistant, holds shape under load
  • 1 in / 4, 5 or 6 out — flexible branch counts for larger floor layouts
  • Round top inlet — fits standard circular ventilation ducts
  • ABS duct connectors — a clean push-fit interface to flat duct
  • Concealed installation — embedded in the underfloor build-up

Selection Rules

Use the following rules when converting a project drawing into an order. They reflect how the product performs in ceiling voids, plant rooms and riser cupboards, where the practical limits are usually set by branch count, port configuration and pressure loss rather than by the headline dimension.

Sizing

Size the run from the design air flow and the acceptable pressure drop, not from the fan spigot. Undersizing a distribution boxes run is the most common specification error and it cannot be corrected later without re-opening the ceiling.

Material and Layer Build-up

Where the run passes through an unconditioned space, condensation risk — not mechanical strength — normally decides the specification. In those locations the insulated variant is the correct default and a bare equivalent is a false economy.

Connections and Transitions

Keep one connector family for the whole run. Every change of system introduces an adapter, and every adapter is an additional leak path and pressure loss point.

Applications

  • Underfloor fresh air distribution in larger apartments and villas
  • Layouts requiring more than four floor branches from one inlet
  • Systems where a pressure-resistant metal box is preferred

System Matching

Use with our ABS distributor box, insulated distribution box, rectangular flat duct and custom underfloor distribution box.

Supply, Packaging and Export

GUANDE manufactures Metal Air Distribution Box, Galvanized Steel Pressure-Resistant Air Distributor Manifold 1 In 4/5/6 Way for Underfloor Fresh Air Ventilation HVAC System at our factory in Dezhou, Shandong, China, and ships direct to HVAC contractors, distributors and project specifiers worldwide. Wholesale, OEM and ODM programmes are welcome. Items are supplied in export cartons with the size and quantity marked on the outer label. For OEM programmes we can apply your own artwork and labelling subject to a minimum order quantity.

Related Products in This Range

The products below are routinely specified alongside the item discussed in this guide. GUANDE manufactures the full range in our own plant for consolidated shipping:

Frequently Asked Questions

Q: Why choose metal over ABS?
A: The metal casing is more resistant to pressure and mechanical load in the floor zone.

Q: Which branch counts are available?
A: One inlet to four, five or six outlets, with custom configurations on request.

Q: What connects to the side outlets?
A: Underfloor flat air ducts connect to the flat side outlets.

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The southeast corner of the private entrepreneurship park in Huadian Town, Qihui County, Dezhou City, Shandong Province