What Is the Maximum Installation Length of a Single Heating Film Strip?

Hello, this is Jay Lee from Hi Heat.

In this article, we will discuss a question that installers frequently ask:
“How long can one strip of heating film be installed continuously?”

This question usually comes up when installing heating film in large rooms
or long corridors.
For example, is it possible to install one continuous strip over a length of
10 meters in a large room, or 15 meters in a long hallway?

The short answer is:
sometimes yes, sometimes no.
The correct answer depends on the internal structure of the heating film
and its electrical limitations.

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1. Internal Structure of Heating Film and the Copper Busbar

Inside the heating film, electricity flows through a component called the
copper busbar.

Based on Hi Heat products,
the copper busbar has a width of 15 mm
and a thickness of 0.05 mm.

This results in a cross-sectional area of 0.75 mm²,
which is equivalent to approximately AWG 18–19 wire.

A conductor of this size typically allows
about 5.5–7 A of current.

However, because heating systems operate for long periods,
it is safer to calculate based on a conservative limit of
5.5 A.

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2. Calculating the Maximum Allowable Length

In many countries, including Korea,
the most common heating film rating is 220 W/m².

At a voltage of 220 V, the current per square meter is:

220 W ÷ 220 V = 1 A

This means that each square meter of heating film draws approximately 1 ampere.

If the allowable current of the copper busbar is 5.5 A,
the maximum allowable heating area is therefore 5.5 m².

When using a heating film with a width of 50 cm,
this corresponds to a length of approximately 11 meters.

For safety reasons, we recommend reducing this value by about 10%,
resulting in a practical maximum length of around 9.9 meters.

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3. Why Safety Margins Are Necessary

Even though we already reduced the allowable current
from 7 A to 5.5 A, why should we reduce the length again?

The main reasons are power tolerance and
voltage fluctuation.

Heating film typically has a power tolerance of ±10%.

For example, a film labeled as 220 W/m²
may actually operate at up to 240 W/m².

In addition, supply voltage is not always constant.
Depending on the building or country,
the voltage may rise or drop during operation.

If these factors are not considered,
the copper busbar may be subjected to excessive load.

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4. Effect of Voltage Changes

Let us assume the voltage drops from 220 V to 200 V.

With the same power rating of 220 W/m²,
the current increases from 1 A to approximately 1.1 A.

As a result, even with the same 50 cm wide film,
the maximum allowable length is reduced by
approximately 90 cm.

This is why a safety margin of around 10% is practical and necessary.

In 110 V systems, the current doubles compared to 220 V,
which further reduces the allowable installation length.

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5. Differences Between Low- and High-Power Films

In some European markets, very low-power heating films,
such as 60 W/m², are commonly used.

In this case, the allowable heating area increases to
approximately 21 m²,
which corresponds to a length of about 37–38 meters
for a 50 cm wide film.

On the other hand, when using a high-power film rated at
400 W/m²,
the allowable length drops significantly to around 5.45 meters.

This clearly shows that the maximum installation length
varies greatly depending on both voltage and power rating.

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6. Important Notes for Long Installations

If the calculated maximum length is 9 meters,
the film should be installed in separate 9-meter sections.

Some installers cut the film into sections
but reconnect them in series, which defeats the purpose.
This should never be done.

Each section must be connected to power independently.

For very long installations,
connecting power at both the starting point and the end point
can help reduce temperature differences along the film.

This method helps maintain more uniform heating
and reduces localized overheating.

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Conclusion

Installing heating film in excessively long continuous runs
can reduce heating performance
and place dangerous stress on the copper busbar.

If long installations are required,
divide the area into smaller sections
or connect the film in appropriately sized lengths.

For a detailed explanation with real products and examples,
please refer to the video below.

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