Duct Heater and its calcualtions

 

Duct Heaters

Duct heaters provide enhanced comfort and increased system efficiency by maintaining or accelerating warm air flowing throughout duct work within a building, especially in areas furthest away from the main HVAC unit. Duct heaters are traditionally used in forced air systems to provide standalone space heat or to supplement existing heating systems.

Finned tube and open coil styles are available and can be custom designed up to 1000 KW, in slip-in or flanged configurations, with galvanized steel frame and terminal box constructions.

All duct heaters are custom engineered to match a specific application. Optional construction features include recessed, dust-tight, or insulated terminal box, and/or insulated flanges and protective screens. They are designed for comfort ventilation applications. They are used in forced air applications to provide standalone space heat or to supplement existing heating systems.

Typical installations are:

• Space heating
• Primary heating
• Booster air heater
• Emergency/backup heat
• Multi-zone or VAV
• Reheat
• Fan coils
• Secondary/auxiliary heating
• Make-up/outdoor air preheat
• Return air heating

Duct heaters are designed to meet most residential and light commercial requirements for use in forced air duct systems. They may be used as the primary source of heat or as supplementary or stand-by heat to heat pump, gas, or oil-fired systems. Several units may be used in a large duct or systems with branch ducts for zoning or separate thermostat for zoning or separate thermostat control. All units are CSA and UL listed to exceed the requirements of the National Electric Code (NEC) by using components to include primary and secondary limit protection, magnetic disconnecting contactors (24-volt control), a fan relay, and circuit fusing where required.

Duct heaters are designed for vertical or horizontal airflow in either direction, but most manufacturers offer units that are available for flange mount, round duct, bottom mount, and rain-tight installations.

Open Coil vs. Finned Tubular

There are two types of duct heater designs being used today:

1. Open Coil
2. Finned Tubular

Open Coil Duct Heaters

For most simple space heating comfort heating applications, open coil models are the most cost-effective solution as they tend to have lower kW and are smaller in size than a finned tubular unit. The most important differentiator is that the open coil element releases its heat directly into the airstream, which allows the duct to heat up quicker.

Finned Tubular Duct Heaters

Finned tubular models are typically used for applications that require a high kW output as finned tubular elements help to reduce watt density, which allows for more consistent air flow streams. Duct heaters that have finned tubular elements are typically made for outdoor use or in harsher environments. Elements that use stainless steel fins can withstand the external elements of outdoor usage and are widely used in commercial and industrial applications.

Sizes and Types of Duct Heaters

There are many different sizes and types of duct heaters, but every application is different, so there is no easy way to determine what your application may need without discussing the specifics. The way to start is by understanding the basics and then contacting an expert. Start with the items below, and we can help you fill in the rest of the blanks:

1. What line voltage, phase, and hertz?
2. What duct size? (Dimension in inches) Width and height.
3. What type of duct? (Sheet metal, internally lines, external insulation)
4. Preferred mounting method?
5. Ceiling height (See chart below for how this affects the needed kW)

Download calculation sheet from below link

https://docs.google.com/spreadsheets/d/180okC5jV9gOy2HhWf5bwg3H9g-o4UTZF/edit?usp=sharing&ouid=104463453804281489603&rtpof=true&sd=true