Vents Air duct heater NK 125 (Ø125MM/1.6KW/IP40)

An electric duct heater for round 125 mm ducting, 1.6 kW across two 0.8 kW elements. Minimum airflow 120 m³/h.

The NK 125 has the same power as the 100 mm version, in a larger duct. The question buyers ask is what 1.6 kW actually does to their air, and that can be worked out.

What 1.6 kW does to your air temperature

How much warmer your air gets depends on two things: the heater's power and the quantity of air you send through it. The same power spread across more air gives a smaller temperature rise.

A usable rule of thumb: the temperature rise in degrees is roughly 3000 times the power in kilowatts, divided by the airflow in cubic metres per hour.

For this heater at 1.6 kW that means approximately:

• at 120 m³/h, the minimum, about 40 degrees of rise
• at 200 m³/h about 24 degrees
• at 400 m³/h about 12 degrees

It is an approximation: duct losses are not in it, and the real rise comes out somewhat lower in practice. But the ratio holds, and the ratio is the point. Want a large temperature rise and it costs you airflow; want to move plenty of air and that air only warms a little.

So calculate from whichever side is fixed. If you know how much air your ventilation needs, the number of degrees follows from it. If that comes out lower than you hoped, more power is the answer rather than less air: reducing airflow below the minimum is not allowed.

Connection

7 amps on 230 volts, single phase, fixed wiring. Have a qualified electrician do it and follow the Vents manual. The heater goes in ducting of the same diameter, horizontally or vertically, and may only operate while your fan is running.

Technical Specifications:

• Duct: 125 mm
• Power: 1.6 kW, two 0.8 kW elements
• Minimum airflow: 120 m³/h
• Current: 7 A
• Supply: 230 V / 50 Hz, single phase
• Ingress protection: IP40
• Weight: 2.9 kg

Frequently asked questions

How much warmer will my air get?
Roughly 3000 times the power in kW divided by your airflow in m³/h. At 1.6 kW and 200 m³/h, around 24 degrees.

Can I send less air through to get more heat?
Not below 120 m³/h. That minimum is a safety condition.

Why is it lower in practice?
Because the rule of thumb does not count heat loss in the ducting.

Is this the same heater as the NK 100?
Same power and current, different collar: 125 rather than 100 mm.