What is the maximum temperature permitted for plastic underground ducts?

What is the maximum temperature permitted for plastic underground ducts?

Plastic duct and fittings shall be utilized in underground installations only. The maximum design temperature for systems utilizing plastic duct and fittings shall be 150°F (66°C). 603.9 Joints, seams and connections.

What is the disadvantage of flex duct?

The downside of flex ducting is that it is considered temporary with an acknowledged lifespan of only about 15 years. Another major disadvantage is that they are a little too flexible, so they are often incorrectly installed. And with greater friction than metal ducts, proper sizing is critical.

Is flex duct fire rated?

Flexible air ducts shall not penetrate a fire-resistance-rated assembly or construction. Flexible air connector lengths shall be not more than 5 feet (1524 mm) and shall not penetrate a wall, floor, or ceiling.

How long are flex ducts?

5 feet
It says, “Length limitation: Factory-made flexible air ducts and connectors should not be more than 5 feet (1,524 mm) in length and shall not be used in lieu of rigid elbows or fittings.”

Is flex duct waterproof?

FlexClad, designed specifically for HVAC ductwork and piping, is a water and weather-resistant, pre-fabricated, self-adhering, sheet-type protective membrane. The top surface is UV-resistant embossed aluminum that can be left exposed indefinitely, reflects heat and can aid in reducing energy costs.

What is the R value of flex duct?

For example, a six-inch diameter, nominal R-8 flex duct has an actual R-value of only 5.62 not counting surface films. With the film resistances the total R-value of 6.45 is 19% less than the nominal value. For R-11 ducts (six-inch diameter) the R-value with films is only 7.81, 29% less than the nominal value.

Is flexible duct fire resistant?

This is a 100mm / 4 inch diameter 6m flexible ducting ideal for high, medium, and low pressure ventilation and air conditioning systems. Suitable for high, medium and low pressure applications. Fire resistant: Complies with the requirements of BS476. Suitable for air conditioning and fume extraction systems.

How often should flex ductwork be replaced?

“If your ductwork is over 15 years old, you probably should replace it. Ductwork has a maximum lifespan of 20-25 years. By 15 years, however, it begins to deteriorate, significantly reducing your HVAC system’s efficiency, so replacement is the prudent option.”

Does Flex duct reduce airflow?

Friction is the enemy of airflow. Unlike rigid ducts, which are cut to length within a tolerance of 1 inch or less, it’s easy to cut a length of flexible duct that’s several feet longer than is needed to get from point A to point B [2A]. That creates slack in the duct, which reduces airflow for two reasons.

What does UL mean in HVAC?

Underwriters Laboratories
When it comes to making a purchase, finding a reliable product is sometimes difficult to recognize. Luckily, UL (Underwriters Laboratories) approved products make that decision simpler, ensuring required standards are met such as safety, sustainability, performance, and quality.

How much flexible duct will you be allowed to use?

Events unfolding over the next few months could ultimately determine how much flexible duct you will be allowed to use when installing duct systems. A recent proposal from the International Association of Plumbing and Mechanical Officials (IAPMO) limits the use of flexible duct to only 5 feet in length.

Why are flex ducts bad for air flow?

Flex duct intentionally left too long. Some installers do this to reduce noise from the air handler. The two ways that air flow gets reduced in duct systems is through friction and turbulence. Flex ducts do worse at both of those than hard pipe. Because of the helical wire running the length of the duct, there’s more resistance to air flow.

What is the pressure drop on a flexible duct?

Duct fittings and any bends and turns in flexible duct all produce a resistance to airflow. This resistance creates a pressure drop measured in inches water column (IWC) which is physically equivalent to the pressure drop produced by a straight section of duct. So the total pressure drop for any duct run equals the

Are you guilty of sloppy flexible duct installation?

If you’re guilty of sloppy, poorly performing flexible duct installations, stop doing it. Have the courage to install your duct systems the way the manufacturers intend and your customers deserve. If we don’t improve, other legislative groups and associations will continue to look at reducing the use of flexible ducts.