Indeeco TFXU and TFZU Finned Tubular Duct Heaters
Indeeco TFXU slip-in and TFZU flanged finned tubular duct heaters are UL listed and built to your duct size, from 4.5 in up to 175 in wide. Specifying one for a new building, buying to a mechanical schedule, or building air handlers? We handle it. We match the kW, voltage, duct size, and control option to your job.
We size it, quote it, and return a selection ready for submittal. Our offices are in Houston and Dallas-Fort Worth, serving Texas and the Gulf Coast, and we ship nationwide.
Have questions? Need a quote?
Indeeco TFXU and TFZU Specifications
The TFXU and TFZU use the same elements and the same controls. The difference is how the heater mounts in the duct.
| Â | TFXU slip-in | TFZU flanged |
|---|---|---|
| Mounting | Slides through an opening cut in the side of the duct, fixed with sheet metal screws | Bolts or screws to matching flanges on both sides of the duct |
| UL listed duct width | 4.75 to 175 in | 4.5 to 175 in |
| UL listed duct height | 5.25 to 120 in | 4 to 120 in |
| Capacity | Built to the job, 0.1 kW to over 900 kW | |
| Voltage | Single-phase or three-phase, elements insulated for up to 600 V | |
| Elements | 80% nickel, 20% chromium coil in a 0.475 in stainless steel sheath, stainless steel spiral fin | |
| Control packages | Basic contactor, pneumatic, or SCR | |
Both models are UL listed (files E23192 and E53412) for zero clearance to combustible surfaces and for use with heat pumps and air conditioners. Indeeco tests every heater at a minimum of 1,200 V before it ships.
Common Questions
What is the maximum inlet air temperature for a TFXU or TFZU duct heater?
The maximum inlet air temperature for an Indeeco TFXU or TFZU finned tubular duct heater is 80°F. Open coil duct heaters such as the Indeeco QUA and QUZ allow 100°F. If the air entering the heater can run warmer than 80°F, we review the heater location before we quote.
How far from an air conditioner or heat pump must a TFXU or TFZU be installed?
A TFXU or TFZU duct heater used with an air conditioner or heat pump must sit at least 48 in from that unit. The NEC also requires 3.5 ft of clear working space on the terminal box side. When the side of the duct has no room, Indeeco can build the heater with a bottom terminal box.
How do you calculate the kW for a TFXU or TFZU duct heater?
Duct heater kW equals airflow in CFM times the temperature rise in °F, divided by 3,193. For example, 2,000 CFM heated from 55°F to 85°F needs 2,000 x 30 / 3,193 = 18.8 kW. We run this sizing and the minimum air velocity check as part of the quote.
Can a TFXU duct heater go in an insulated or lined duct?
A TFXU slip-in duct heater fits ducts with up to 1 in of interior lining with no change to the heater. The duct size to specify is the size inside the lining. For lining thicker than 1 in, or for a flanged TFZU in a lined duct, Indeeco builds a special insulated duct construction.
Slip-in TFXU or Flanged TFZU
Choose the TFXU when the heater goes into the duct from the side.
Choose the TFZU when the duct is built with flanges at the heater.
Slip-in is normally preferred because it is easier to install.
TFXU slip-in duct heater
- Goes in through a rectangular opening cut in the side of the duct
- Fixed to the duct with sheet metal screws
TFZU flanged duct heater
- Needs matching flanges on the duct, on the entering and leaving air sides
- Fixed with sheet metal screws or bolts through the flanges
- Slip-and-drive option: the solid mounting of a flanged heater with less installation labor than a slip-in, and a match for VAV boxes and other equipment with slip-and-drive connections
Built into both models
- Heavy gauge, corrosion resistant steel frame with wide flanges for stiffness
- Each element has its own mounting flange and comes out through the terminal box, one at a time
- Unheated section option, when the frame passes through a zone with little or no airflow or sits next to a cooling coil
Related Duct Heaters and Heating Equipment
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- Indeeco QUA and QUZ duct heaters – Open coil slip-in and flanged duct heaters for clean, dry air
- Open coil duct heaters – Lower cost and lower pressure drop for standard HVAC ducts
- Electric duct heaters – Every duct heater we supply, by type
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- Explosion-proof heaters – Heating for hazardous locations
- Indeeco UHIR unit heater – Electric unit heaters up to 50 kW for warehouses and plants
- Industrial heating system specification guide – Specifying heating across a multi-unit project