Breakout or boot?
A breakout has one mouth and two to seven legs. A boot has one entry and one to three outlets. Where both say three, the count is not what decides it.
The split is inside the cable, or it is not
One observation separates the two families, and it is geometric rather than electrical. Does the outer sheath stop inside the part, with the cores of a single cable carrying on past it? That is a crutch, and a crutch takes a breakout. Does the cable arrive intact, with the part covering something that is not cable at all — a connector shell, a bushing, a bar? That is a transition, and a transition takes a boot.
Core count and outlet count then borrow the same digits without meaning the same thing. A three-core cable takes a three-core breakout, and LV3GBB-1330 goes on over 80 mm and closes down to 30 mm on the body. A harness branching three ways takes GHS3-N-407, which goes on over 14 mm and closes to 6.6 mm on its entry bore. Both parts are described as three. One digit counts conductors under a sheath; the other counts branches leaving a connector, and neither can be read off the other.
The trade fuses the words anyway. Breakout boot is asked as one term, and so is two-way outlet breakout boot, and no chart in these sources catalogues a part under either name. The fusion costs nothing in conversation. It costs a re-order when it reaches a drawing, because the two families share no part code, no selection column and no sealing claim.
What follows from the answer is material as much as shape. A breakout is lined — hot melt adhesive on the low-voltage family, water-resistant mastic on the non-tracking one, red mastic on the semi-conductive one. That lining flows into the fork and is why the installed assembly can carry an ingress class. A harness boot is semi-rigid flame-retarded polyolefin, published with or without adhesive lining. Its job is insulation, mechanical protection and strain relief at a point that was never holding water on its own.
Eight rows, read straight down
Each row answers a different part of the same decision. The last one lands on a family and a chart.
| What is being decided | Breakout | Boot |
|---|---|---|
| Where the part sits | At the crutch of one cable, where the sheath ends and the cores part. | At a transition: a connector on a harness, a bushing in a termination box, a bar in a panel. |
| Openings catalogued | One mouth with two, three, four, five, six or seven legs on Insulcore-LV. GAB and GCB are three-core only; the cold shrink GCEB is two-core and four-core. | One, two or three outlets. GHSB and GHRB are single outlet, GHS2-N and GHYB two, GHS3-N three. |
| What settles the size | Cable outside diameter at the crutch, one core's outside diameter just past it, and the core count. | Connector or bushing diameter at one end, cable diameter at the other, and the exit angle. |
| What settles the family | Voltage class and cable construction. PVC, XLPE, rubber and PILC to 3.3 kV on Insulcore-LV; three-core to 36 kV on the non-tracking GAB; belted PILC on the semi-conductive GCB. | Fluid, temperature and geometry. Petrol, diesel, acid and alkali exposure, flexibility at −55 °C, and whether the cable leaves straight, at ninety degrees or as a Y. |
| Material | Cross-linked polyolefin, non-tracking or semi-conductive in the families above 3.3 kV, EPDM rubber where no flame is permitted. | Semi-rigid flame-retarded polyolefin at a connector, cross-linked non-tracking polyolefin at a busbar or bus-duct termination. |
| Lining | Always lined. Hot melt adhesive on Insulcore-LV, water-resistant mastic on GAB, red mastic on GCB. | An order option. GHS2-N and GHS3-N are published with or without adhesive lining, so an unlined one closes the shape and seals nothing. |
| Sealing claim printed | IP68 once installed on Insulcore-LV and on the semi-conductive family. A water-resistant seal to ANSI C119.1 on the cold shrink. | Mechanical protection, strain relief and environmental sealing on a harness assembly. No ingress class appears on any boot sheet here. |
| Where it ends | A code between LV2GBB-0308 S and LV7GBB-1845, or a GAB, GCB or GCEB code above it. Rows at breakout size chart. | One of eighteen catalogued sizes across GHSB, GHRB, GHYB, GHS2-N, GHS3-N, GRB and GSB. Rows at boot size chart. |
Five moves from a part in the hand to a chart row
Written as observations rather than instructions, because at this stage nothing is being installed.
Where the sheath ends
The outer sheath either stops inside the part or runs straight through it. That single observation fixes the family before any dimension is read, and everything after it is narrowing rather than choosing.
The count narrows, it does not decide
Two and three appear in both catalogues. Breakouts run two to seven legs; boots run one to three outlets. A count of two or three says which rows to read once the family is settled, and nothing at all before that.
Two diameters, taken separately
Both families print every diameter twice. The a or Ds figure is the as-supplied minimum, the largest thing the part will pass over. The b or Df figure is the fully recovered maximum, the smallest thing it will still grip. Where only one of the pair is checked, the shortfall shows up after installation rather than during it.
The exposure each side publishes
Breakouts are qualified against voltage and cable construction, and the charts carry a core column and a voltage ceiling. Harness boots are qualified against fluids and low temperature: petrol, diesel, acid and alkali figures sit on the boot sheets and on no breakout sheet in these sources.
One family, one chart
The breakout answer is an LV2GBB to LV7GBB code, or a GAB, GCB or GCEB code above it, set out at cable breakouts. The boot answer is a GHSB, GHRB, GHYB, GHS2-N or GHS3-N code at a connector, or a GRB or GSB code at a bushing, set out at heat shrink boots.
Four cases where both parts would physically go on
- A three-core LV cable ending at a multipin connector
- Both a three-leg breakout and a three-way boot will pass over the assembly. What decides is which end carries the exposure. If the sheath has been cut back and the three cores run on to the pins, the crutch is real and wants a breakout. If the cable is intact to the shell and only the shell is exposed, it wants a boot, and the geometry is covered at 2-way, 3-way, Y and T boots.
- A two-way split standing in fuel or oil
- Geometry does not settle this one; the published record does. After 24 hours at 23 °C the two-way and three-way boots hold at least 11 MPa in petrol, 10 MPa in diesel oil and 12 MPa in acid or alkali. No breakout sheet in these sources publishes a fluid figure at all, so on that side the answer would have to be sought rather than read.
- A crutch on a run already made off at both ends
- Neither family fits, because a moulded part of either kind has to travel over a cable end to reach the fork. The branch off clip is what goes there instead, working with an outer sleeve rather than on its own. Three sizes, GBOC 1 to GBOC 3, are set out at cable breakouts.
- A termination that has to be opened again
- Recovery is one-way in both families, so a heat-shrink part comes off by being cut off. Where the same bushing is tested and re-covered repeatedly, the moulded rubber shroud is the only part in these sources published for it. Bushing diameters run 46 to 70 mm. It is covered at reusable insulating boots.
What neither chart carries
The breakout selection charts carry a core column, a cable type and a voltage ceiling, and no fluid data. The boot selection charts carry dimensions and letters and nothing else: no core column, no cable type, and no system voltage class on any heat-shrink boot sheet in these sources. What those sheets publish is dielectric strength in kV/mm, which is a property of the moulded material and not a rating for the installed assembly. No chart here cross-references a breakout code to a boot code either, so a swap between the two families cannot be looked up. Where the decision turns on a figure that sits on neither sheet, it has to go to the manufacturer with both diameters and the exposure named.
The same question, asked five ways
Is a breakout boot one part?
What is a two-way outlet breakout boot, then?
Could a boot do a breakout's job if the shape fits?
Does a three-core cable need a three-way boot?
The part in my hand has three openings and no marking left. Which chart?
Which chart, once the family is settled
Both charts are on this site in full, with the as-supplied and recovered figures side by side. Where the size falls between two rows, the manufacturer needs the largest diameter the part must pass over, the smallest it must close onto, the count, and the exposure named.