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Heat shrink or cold shrink: two different recovery mechanisms

One wants 125 °C at the wall. The other wants a core pulled out of it. Every difference below, the 1.1 kV ceiling included, comes off that one split.

The cold shrink range and its ceiling

This is the one page on this comparison across the reference sites published here; the others link in rather than write their own. Hold the axis to the polymer. Not the asset, not the kit, not the permit.

Take the ceiling first, because it settles most enquiries. Cold shrink stops at 1.1 kV, with conductor sizes to 1000 sq mm in copper or aluminium. It appears on four of the manufacturer's 175 datasheets: an EPDM tube, a silicone tube, a close-ended cap, a crutch sleeve. All four are sealing parts. None is a joint, a splice or a termination, and no voltage changes that. Above 1.1 kV the insulating duty is heat shrink — GMW medium wall to 3.3 kV, GHW heavy wall to 36 kV, with IEC 60684-3-247 covering both.

Heat shrink is crosslinked polyolefin, and the crosslinks are the memory. The manufacturer's technology note puts the crosslinking as chemical or electron-beam, and describes ties that pin each molecule against the ones around it. Nothing moves below the crystalline melting point, which is why an expanded tube keeps its supplied bore in a warm store. The medium and heavy wall sheet prints the trigger as a shrink temperature of 125 °C. The chemistry is set out at how heat shrink tubing works.

Cold shrink names no temperature anywhere. Read all four sheets and there is no shrink temperature, no recovery temperature and no shrink ratio on any of them. The only trigger printed is the core: each sheet says the part was factory expanded and assembled onto it, and each drawing labels it a PP coil. Nothing goes in at the working position; something already loaded is let out.

The two mechanisms, axis by axis

Every row is a property of the material. No row here describes a job.

Axis	Heat shrink — crosslinked polyolefin	Cold shrink — EPDM or silicone
What stores the recovery	The crosslinked network. Chemical or electron-beam ties hold every chain against its neighbours, and the moulded bore is what they hold.	Nothing in the polymer. A removable core, drawn as a PP coil on all four sheets, has held the rubber open since the factory.
What triggers it	Heat past the crystalline melting point. Shrink temperature 125 °C to IEC 216, on the GMW and GHW sheet.	Withdrawal of the core. No temperature of any kind appears on the four cold shrink sheets.
Any published way back	None. No sheet in the set describes reheating a recovered tube to its supplied bore.	None. No sheet in the set describes reloading a recovered sleeve onto a core.
Shelf state	Unstressed, at the supplied bore. The GSC chart ships 25 to 400 m spools and 1.2 m cut lengths.	Stressed. Every sleeve in stock is stretched rubber working against its coil, and no storage period is printed.
Recovered stress state	Relaxed. Recovery stops where the substrate stops it, and the wall sets there.	Still stretched, by design. GCTE 20/7 free-recovers to 7 mm but is applied over 8 to 15 mm, so it never reaches rest.
What the chart lets you check afterwards	Recovered ID and recovered wall, code by code. GLC 25.0/12.5 closes to 12.5 mm at a 0.78 mm wall.	The application band only. Confirm the finished diameter sits inside 8–15 mm for GCTE 20/7, and that Lf reached its 500 mm minimum.

Three consequences that fall straight out of the polymer

Envelope

Temperature belongs to the compound

Both cold shrink tube sheets give −40 °C to 105 °C, EPDM and silicone alike. Hardness, elongation and dielectric strength separate those two compounds; the thermal window does not. Polyolefin runs wider — −55 °C to +125 °C on GLC, GSC and GDW, and a +110 °C continuous limit on the medium and heavy wall grades. Read that last figure against 125 °C. It sits 15 °C under the temperature that makes the same tube move.

Chemical against elastic

Sealing: a bond or a fit

GDW co-extrudes hot-melt adhesive under the polyolefin, charted at 0.35 to 0.9 mm after recovery on the 3:1 range, with IP 68 claimed for it. Hot-melt means what the name says: the layer bonds by flowing at temperature and setting as it cools. A cold shrink seal is elastic instead — no mastic, no tape, stretched rubber bearing on the substrate, with the water seal requirement of ANSI C119.1 behind it. They fail differently. The bond fails where the adhesive never reached flow temperature, which no GDW sheet prints; the fit fails where the diameter drifts outside the band.

A shared limit

Neither one turns a corner

Both recover radially about a single axis. So neither follows a branch, an elbow or a Y, whatever ratio or compound you specify. At a crutch the part has to change shape rather than grade, which is why cold shrink carries the GCEB crutch sleeve and heat shrink carries moulded breakouts. The argument itself belongs to tube or moulded shape.

Four arguments this page deliberately does not make

Each is a different reference's subject, named here so you know it was not overlooked.

Whether the asset can be reached at all — threading a sleeve onto a run already in place is a wrapped-sleeve question. Nothing about the polymer decides it.
The kit bill of materials and the jointer's step order — a joint is specified as a packet of parts, never as a length of tube.
How either technology grades the field at a screen cutback — stress control is its own subject, and the tube side of it is at semi-conductive and screening tube.
Where a flame is prohibited outright — worked through at anodecap.com, a reference on the same manufacturer's range from the publisher of this site.

Not published: a shrink temperature for the thin wall and dual wall grades

53 of the manufacturer's 175 datasheets print a shrink temperature. GLC, GSC, GDW and the vented GLC-SV are not among them. Each of those four gives an operating temperature and stops there — −55 °C to +125 °C on the first three, −40 °C to +125 °C on the vented grade — with no recovery figure at all. The medium and heavy wall sheet prints 125 °C, and nothing states that it carries across to a 0.56 mm thin wall. So the number a gun would be set by is missing for exactly the grades most often recovered by hand. Ask for it in writing before it reaches a work instruction.

Asked when both would physically fit

How does cold shrink work?

The sleeve is stretched cold at the factory and assembled onto a removable core. Nothing in the polymer holds it open; the coil does that on its own. Pull the coil and stored elasticity closes the sleeve onto whatever is underneath, at once and over the full length. Lf is 500 mm minimum on all seven tube codes, so the covered length is settled before you start.

How does cold shrink tubing work differently from a heat shrink tube of the same diameter?

Same finished diameter, opposite direction of energy. A heat shrink tube is inert until 125 °C reaches the wall, and inert again once cool. A cold shrink tube has been loaded since it left the factory and starts the instant the coil clears. One is quiet in the store and demanding at the work. The other is the reverse.

Is there such a thing as cold heat shrink?

No. Two technologies, two polymer families, and the phrase almost always means one or the other. Where no torch or hot-air gun is permitted at the position, cold shrink is the mechanism — capped at 1.1 kV and limited to sealing parts. Above that a heat shrink part is the only published option, and the permit becomes the thing to solve rather than the product.

Is a cold shrink fitting the same as a cold shrink tube?

There is no fitting here in the plumbing sense. Every published cold shrink part is a sealing part, sized on the band it will grip rather than on a nominal bore. On the tube that band runs 8 mm to 94 mm across seven codes.

Which mechanism for a buried joint?

Above 1.1 kV there is nothing to choose between them: GHW heavy wall is the published part over an underground straight-through joint to 36 kV, carrying the mechanical protection and the outer seal. At or below it, both are offered. Note where the buried claim comes from, though — the manufacturer's web page for the EPDM tube says the formulation withstands backfilling, and the datasheet itself carries no such line.

Where each mechanism is set out in full

Three answers usually settle the mechanism

Send the largest diameter the part must close onto, the system voltage, and whether a hot work permit will be granted at that position. With those three the mechanism picks itself, and a GCTE, GMW or GHW code can be named against it.

What to put in the enquiry Cold shrink size chart