Fixing HVAC pipes: clamps and suspensions for air-conditioning and refrigeration systems

7 min read

Heat pumps, air-conditioning and refrigeration systems are installed more and more often. Pipes that are fixed wrongly cause vibration, noise and sagging, and in the long run leaks. Below you read which clamp to choose for each pipe, how to absorb expansion, how to limit noise and what to fix the suspension to.

Which clamp for which pipe?

Pipe clamps with a sound-insulating insert

For most pipes in buildings, you choose a pipe clamp with an insert. The insert prevents metal-to-metal contact and damps vibration. The Fischer FRS clamps have a chlorine-free and silicone-free sound-insulating insert. The FRS-L Universal is also tested for fire resistance R120. For heavier pipes, the FRSM with a sound-damping layer meets the requirements of DIN 4109. If you do not need sound insulation, the FRSN without an insert is an economical choice.

Cold insulation clamps for refrigeration and air-conditioning pipes

On refrigeration pipes, you prevent the clamp from forming a cold bridge. The KFT refrigeration pipe clamp has a core of rigid PUR foam and fits around pipes from 12 to 219 mm with an insulation thickness up to 40 mm. For a fixed point in an insulated refrigeration pipe, there is the FFRC cold fixed point clamp. The FRSK insulated pipe clamp combines a clamp and 19 mm insulation for pipes from 10 to 219 mm.

Heavy pipes

For heavy or large pipes, you choose a clamp with two bolts and a double connecting nut, such as the FRSMN for outside diameters from 15 to 521 mm.

Several pipes: mounting rails

If several pipes run side by side, build a support structure from mounting rails such as FUS or FLS, with brackets such as the FCA. You fix the clamps to the rail with a T-head bolt such as the FHS Clix. This way you drill fewer holes in the ceiling, and you can easily add a pipe later.

Spacing between clamps

Follow the pipe manufacturer's specification. It applies to the material and wall thickness of that pipe, and these differ per manufacturer. If the documentation says nothing, ask for it before you start.

Always calculate with the weight that actually hangs from the clamps: the pipe, its contents and the insulation. A thickly insulated refrigeration pipe weighs a lot more per metre than the same pipe without insulation, so it needs shorter spacing than the standard specification.

Absorbing expansion with fixed points and sliding points

Hot and cold pipes expand and shrink. If every clamp is fixed, stress builds up on couplings and connections. So work with a combination:

• Fixed points hold the pipe in one place and guide the expansion in the right direction. For example the FSFP with a sound-insulating insert, or the light fixed points FFP.
• Sliding points let the pipe move along its length. The FASM slider is intended for pipes up to DN150 and carries a maximum of 3.0 kN. The FASH roller slider is intended for pipes up to DN350 and carries a maximum of 10.0 kN. Both have a fire test report up to R120.
• Pendulum hangers such as the PDH move with the pipe in all directions, for pipes that expand sideways. On moving pipes, fit them in pairs.

Air ducts and spiral duct

You hang spiral duct with a ventilation clamp such as the LGS or the LRBN. Both have a sound-insulating element that stops vibration and flow noise. From 450 mm diameter, the LGS has holes in both halves of the clamp. With two threaded rods, you then double the recommended load.

You fix rectangular ducts with an air duct hanger: type L on the flat side of the duct, type Z on the corner of the duct. If ducts hang on mounting rails, use the EMS rubber inlay to decouple rail and duct acoustically.

What do you fix the suspension to?

• Concrete ceiling: a bolt anchor such as the FAZ II Plus, or a hammerset anchor such as the EA II for multiple fixings in non-cracked concrete.
• Steel structure: a beam clamp such as the TKL, without drilling or welding.
• Trapezoidal roof sheet: the KDS spring toggle. It is also intended for mounting rails and ventilation ducts. Stay within the permitted load.
• Hollow-core slab floor: do not just drill. Fix in the solid parts between the cores, or use an anchor that is explicitly approved for hollow-core slab floors.

Air-conditioning units and heat pumps on the wall

For outdoor units on the facade, there are complete bracket sets. The KSU set has cantilever arms from 450 to 600 mm and is intended for air-conditioning systems, pumps and fans. The KSU-S has four extra vibration dampers. The Klima Klik (MCE) is a powder-coated set with vibration dampers for units with a fixing distance up to 760 mm, suitable for outdoor use.

Choose the anchor based on the wall: concrete needs a different anchor than masonry. If in doubt, ask the Product finder or contact us.

This article is general information, not design advice. The text was checked on 21 October 2026 against the sources below. The design of your installation and the certifying body decide what applies in your project.

Sources

• fischer product page hammerset anchor EA II (in German)
• fischer product page bolt anchor FAZ II Plus (in German)
• Product data and approvals per product: the Certification property in our webshop