Heat shrink and cold shrink are the two dominant technologies for medium voltage cable joints. Both restore insulation, screening, and outer protection to the cable. The difference is how they install — and that difference determines where each one belongs. This guide compares the two across seven factors so you can pick the right one for your project.
The Fundamental Difference
Heat shrink joints (like our JRSY series) use crosslinked polyolefin tubes that contract when heated with a propane torch or hot-air gun. The installer prepares the cable, positions the joint components, and applies heat from the center outward until each tube fully recovers and the adhesive seals flow.
Cold shrink joints (like our JLS series) use pre-stretched silicone rubber tubes held in the expanded state by a removable plastic core. The installer positions the joint over the prepared cable, pulls the core out by hand, and the silicone contracts onto the cable. No torch, no heat gun, no hot work permit.
Both systems are type tested to GB/T 12706.4 with partial discharge results of ≤2 pC — well below the 20 pC limit. Electrically, they perform identically. The choice is operational, not technical.
Side-by-Side Comparison
| Factor | Heat Shrink (JRSY) | Cold Shrink (JLS) |
|---|---|---|
| Heat source | Torch or heat gun required | None |
| Installation time | 45-60 min | ~30 min |
| Weather | Dry conditions only | Rain OK |
| Hazardous areas | Hot work permit needed | No permit needed |
| Shelf life | 5+ years | 12-24 months |
| Material cost | Lower | Higher |
| Total project cost | Lower (if dry, safe area) | Lower (if permits/delays avoided) |
When to Choose Heat Shrink
Choose heat shrink joints when you have:
A controlled environment. If the joint is being installed in a substation, workshop, or indoor switchroom where you have access to a torch and dry conditions, heat shrink is the economical choice. Material costs 20-30% less than cold shrink for the same voltage class.
Long storage requirements. Crosslinked polyolefin is thermally stable and doesn't degrade under normal storage. A heat shrink kit stored in its original packaging at room temperature has a shelf life of 5+ years. This makes it ideal for utility stockrooms and contractor inventory.
Budget-sensitive projects. If the project specification allows either technology and site conditions are favorable, heat shrink delivers the same electrical performance at a lower unit cost.
When to Choose Cold Shrink
Choose cold shrink joints when you face:
Hazardous area restrictions. Offshore platforms, refineries, and fuel farms classify many areas as Zone 1 or Zone 2, where open flames are prohibited. Cold shrink requires no hot work permit, no fire watch, and no permit wait time.
Wet or windy weather. Cold shrink relies on mechanical contraction, not adhesive activation. Light rain, high humidity, or wind does not affect installation quality. Heat shrink, by contrast, requires a dry cable surface for proper adhesion.
Confined spaces. Underground vaults, handholes, and cable ducts often have limited ventilation where torch operation poses safety risks. Cold shrink installs safely in these environments.
Emergency repairs. During storm response or unplanned outages, speed matters. Cold shrink joints install in roughly half the time of heat shrink (30 minutes vs 45-60 minutes for a two-person crew), and weather is not a limiting factor.
The Cost Question
Cold shrink material costs more. But total project cost can be lower when you factor in:
- No hot work permit application (saves 2-8 hours of waiting)
- No fire watch personnel (saves one person's time for the duration of hot work)
- No weather delays (saves rescheduling costs)
- Faster installation (saves crew time)
For a single joint, heat shrink is cheaper. For a project requiring 20 joints in a Zone 1 area during rainy season, cold shrink is likely cheaper overall.
FAQ
Can cold shrink be installed in the rain?
Yes. Cold shrink relies on mechanical contraction of the silicone body, not heat-activated adhesion. Light rain does not compromise the seal. The mastic sealant is applied under the silicone body and is compressed during contraction regardless of ambient moisture.
Why does cold shrink cost more than heat shrink?
The pre-stretched silicone rubber body is more expensive to manufacture than crosslinked polyolefin, and the removable support core adds material cost. The price difference narrows when you factor in the labor savings from faster installation and the elimination of hot work permits.
How long can cold shrink joints be stored?
Typically 12-24 months at room temperature in original sealed packaging. The pre-stretched silicone gradually relaxes over time. Check the manufacturing date before installation and rotate stock on a first-in-first-out basis. Heat shrink, by comparison, stores for 5+ years.
Written by Long, Sales Engineer at ZZ Heat Shrink. ZZ manufactures both JRSY heat shrink joints and JLS cold shrink joints at facilities in Hubei and Guangdong, China. Both are type tested by the Power Industry Electrical Equipment Quality Inspection and Testing Center. For a quotation, contact our engineers.