Function
A hot-water heater for duct installation, or hot-water duct heater, is used in an air transport system to heat air. The heat transfer takes place by means of hot water.

Material quality and thicknesses
For normal comfort ventilation, hot-water heaters for duct installation are manufactured from the following materials:

• Casing: Sendzimir galvanised steel or Alu-zinc sheet material;
• Heating element:
  • Pipes: copper
  • Slats: aluminium;
• Other choice of material, depending on the application, in consultationwith the supplier.

Connections
The hot-water duct heater is available with circular and rectangular connections.

Dimensions
The nominal sizes available for the intermediate hot-water heaters are standardised to NEN-EN 1505 (rectangular connections)
distributor collector and NEN-EN 1506 (circular connections) and can be selected as indicated in the tables for standard dimensions given in this guide in section 2.1.1.6 (rectangular connections) and 2.1.3.6 (circular connections). They refer to the internal dimensions with a tolerance of +0 to -5 mm. The dimensions depend on the manufacture.

Inspection possibilities
It must always be possible to inspect intermediate hot-water heaters for leaks and contamination. To this end, the heater must be equipped with a removable inspection cover. This cover is attached to the housing in an airtight manner.

Assembly instructions
Hot-water duct heaters should be fitted in accordance with the manufacturer's instructions. If present and at least meet the requirements according to section 3.1.4.

Sustainability aspects
Built-in heaters with circular connections are more efficient to connect to the air ducts than heaters with rectangular connections and contribute to the airtightness of the air duct system, if these fittings have sufficient airtightness according to NEN-EN 15727.