What Is Refrigerant Conduit Casing? (PVC Trunking)
Refrigerant conduit casing, often called PVC trunking or line-set cover, is a removable exterior housing for insulated air-conditioning refrigerant pipes and related services. It protects and tidies the route, but it is not refrigerant pipe, electrical conduit, insulation, or ductwork. Choose and install it around the complete insulated bundle, following product instructions and local code.
Warning: A neat, tightly closed cover can hide crushed insulation, a blocked condensate drain, or a refrigerant joint that needs service. Do not close the route until you have checked what is inside and how it must be accessed. The casing protects the installation; it does not make an incorrect one safe or code-compliant.
What refrigerant conduit casing is
Refrigerant conduit casing is a protective cover fitted over an air-conditioning or heat-pump line set, usually on an exterior wall. The line set carries refrigerant between indoor and outdoor equipment. PVC trunking is a common casing type, with a base and removable cover, but product designs vary.
The insulated copper tubes inside carry refrigerant. The insulation limits heat transfer and helps prevent condensation on cooler tubing. Some cover systems can also house approved control wiring or other related services, but check the product instructions and local rules before combining services.
The casing is not a pressure-containing part of the refrigerant circuit. It has no refrigerant pressure rating. The tubes, fittings, and joints must be suitable for the refrigerant and system design pressure specified by the equipment maker and applicable code.
It is also not electrical conduit or an air duct. Do not use it to carry unrelated electrical wiring unless the product and applicable electrical rules allow that use. It has no airflow or CFM requirement, and it must not cover ventilation or combustion-air openings.
Planning the refrigerant-line route and trunking size
Start by measuring the full insulated bundle and mapping its route, not by selecting a cover from the bare copper tube sizes. Include bends, fittings, approved wiring, and any changes in route. There is no universal trunking size: the correct size depends on the actual bundle and the casing manufacturer’s instructions.
Before buying materials, survey the route from the equipment to the wall penetration. Note the refrigerant tube sizes, insulation, condensate drain, wiring, supports, exposure to sun and weather, and access needed for equipment service. Confirm the locally adopted mechanical, energy, and building codes, along with equipment and trunking instructions.
A useful planning sequence is:
- Measure the widest part of the insulated bundle, including bends and fittings.
- Check the casing’s internal dimensions and how its cover attaches.
- Confirm the tubing can follow its required bend limits without kinks or undue strain.
- Plan the condensate drain so it can keep its required slope and discharge.
- Locate serviceable joints and other points that must remain accessible.
- Check the wall penetration, weather protection, and equipment service clearances.
Do not compress insulation to force a bundle into a smaller casing. If the cover will not close without pressure, select a suitable larger product or revise the route. Also check that the casing does not interfere with equipment panels, required working space, or access to a service valve.
Access, insulation, and clearance requirements
Insulation must remain continuous, uncrushed, and sealed at joints and terminations. The required insulation type and thickness depend on the adopted energy code, pipe size, equipment instructions, and installation conditions. Trunking does not replace insulation, and it should not be used to hide a damaged or incomplete insulation layer.
There is no one clearance value that fits every casing or installation. Follow the trunking maker’s directions for clearances, supports, access panels, and joint locations. Keep enough room to remove the cover and inspect or service the line set. Where code or equipment instructions require access to a refrigerant joint, do not bury it behind a permanently closed section.
| Item | What to check | Why it matters |
|---|---|---|
| Insulated tubes | Bundle fits without pressure; insulation stays continuous | Prevents damage and preserves insulation performance |
| Refrigerant joints | Access is available where required | Supports inspection and service |
| Condensate drain | Route and outlet remain unobstructed | Helps prevent backup and water damage |
| Wiring | Use only as allowed by product instructions and applicable rules | Keeps services properly separated and protected |
| Cover and fittings | Match product parts and installation instructions | Helps the system fit and remain serviceable |
Do not assume that a sealed-looking cover is watertight or that it should trap water. Follow the product’s weathering and drainage details. Keep the casing separate from required ventilation and combustion-air openings.
Installing PVC trunking and managing expansion
PVC is a rigid plastic that changes length as its temperature changes. A commonly used expansion value for rigid PVC is about 3 × 10⁻⁵ inches per inch per °F. Use the casing manufacturer’s support, joint, and sliding details to allow movement; do not lock long runs in place unless the product instructions call for it.
For a simple estimate, multiply the coefficient by the run length in inches and the expected temperature change in °F. A 10-foot run is 120 inches. Across an 80°F change, the estimated movement is 0.00003 × 120 × 80, or about 0.29 inch. This is an estimate, not a substitute for the product’s expansion-joint instructions.
Install in a controlled sequence:
- Mark the route and check it against the surveyed bundle and service needs.
- Fit the base and supports as directed by the casing manufacturer. Do not invent a support spacing; use the product’s stated spacing for the conditions.
- Place the insulated line set without pulling, twisting, or crushing the tubing or insulation.
- Fit bends, joints, and expansion details made for that casing system.
- Protect the wall penetration and weather-seal it using suitable materials, without blocking drainage or trapping water.
- Fit the removable cover and confirm it can be taken off for inspection.
Take care where the route crosses corners or changes direction. A tight casing bend can force a sharp bend in copper tubing or squeeze insulation. If the line set does not sit naturally in the route, change the casing layout rather than forcing it.
Real-world installation scenarios
These examples are illustrative situations, not reports of specific jobs. They show how a survey can reveal problems that are easy to miss when choosing a cover by appearance alone.
Exterior wall with a long, sun-exposed run: The route may look straight, but temperature changes can move the PVC. I would check the casing maker’s expansion and support details before fixing the run. I would also confirm that the cover can be removed along its length for service.
Wall penetration near a condensate drain: A cover may have room for the insulated tubes but still pinch the drain where the bundle turns into the wall. I would check the whole route, including the penetration, and verify that the drain remains clear and functions as intended.
Existing line set with a concealed joint: If the casing would place a joint out of reach, first check whether the adopted code or equipment instructions require access there. If access is required, the route or cover arrangement must preserve it. A removable lid does not help if another building finish blocks its removal.
In each case, the practical test is the same: the complete bundle fits without pressure, the services remain functional, and inspection or service is still possible.
Final inspection and performance verification
Before considering the work complete, inspect the route with the cover both open and closed. Check that insulation is intact, the tubing is not pinched, and the drain and wiring have not been displaced. Then confirm that joints, penetrations, and service points remain accessible as required.
Use this checklist:
- The cover closes without pressing on the insulated bundle.
- Insulation remains continuous, sealed, and uncrushed.
- Tubing bends and supports follow equipment and product instructions.
- Expansion joints and supports are installed as specified.
- The condensate drain is not blocked or forced out of its intended route.
- Penetrations are protected from weather without trapping water.
- Required service access and equipment clearances remain open.
- Ventilation and combustion-air openings are not covered.
If the equipment can be operated safely, check that the condensate drain works during operation and look for signs of water at the route and penetration. Refrigerant testing, repair, or opening of the refrigerant circuit should be handled by a qualified technician. The casing itself cannot confirm that the refrigerant system is sound.
Conclusion
PVC refrigerant trunking is a removable protective cover for an insulated line set, not a substitute for correct piping, insulation, or service access. Measure the complete bundle, follow the casing and equipment instructions, allow for PVC movement, and check the route before closing the cover. When in doubt, resolve fit or access problems before installation.
FAQs
These answers address common questions about PVC refrigerant-line covers. Product designs and local requirements differ, so use the casing instructions and locally adopted codes for the final details.
Is refrigerant conduit casing the same as refrigerant pipe?
No. The casing is an outer cover. Refrigerant flows through the rated tubing and fittings inside it, not through the PVC trunking.
Can I run a line set without insulation inside PVC trunking?
No. The casing does not replace insulation. Keep the insulation type and thickness required by the adopted energy code and equipment instructions.
How do I choose the right trunking size?
Measure the complete insulated bundle, including fittings and bends, then check the casing’s internal dimensions. Do not size it from bare copper tube diameters.
Can PVC trunking contain refrigerant pressure?
No. It has no refrigerant pressure rating. The refrigerant tubing, fittings, and joints must be rated for the system and refrigerant.
Can refrigerant joints be hidden inside the cover?
Only if allowed by applicable code and equipment instructions. Preserve access wherever it is required for inspection or service.
Does line-set trunking need a CFM rating?
No. It is not an air duct and has no CFM requirement. Keep it separate from ventilation and combustion-air openings.
Can I put electrical wiring in the casing?
Only when the casing is intended for that use and the product instructions and applicable electrical rules permit it. Do not assume every line-set cover is electrical conduit.
Does PVC trunking expand in hot weather?
Yes. Rigid PVC changes length with temperature. Follow the manufacturer’s support, sliding, and joint details for the product and route.
Can the cover block or share space with a condensate drain?
The drain must remain unobstructed and function as designed. Check the full route before closing the cover, especially at bends and wall penetrations.
Is one support spacing or clearance correct for every installation?
No. Spacing and clearance depend on the specific product, route, and installation conditions. Use the casing instructions and applicable local requirements.
(This article was written by one of our staff writers, Garrett Vance. Visit our Meet the Team page.)
