A genset cable entry has to hold the cable, keep water out and keep a fire rating intact, and one plate does all three. Compare the plate, the glands and the seal against the cable schedule before you accept an offer. Tesla Power cuts the plate to the schedule; send it to the technical desk and we confirm the entries.
- Ask for the plate thickness and the gasket, not just the number of holes.
- Check the gland rating against the cable rather than against the breaker.
- Look at the bending radius below the plate, because a tight bend cooks a lug.
- Ask how the entry is resealed when a cable is added later.
What does a genset cable entry have to do?
It has to pass the power and control cables through a steel wall without letting water in and without cutting the wall strength. It also has to hold each cable so the weight of the run does not hang on the terminals. Three duties on one plate, and a plate designed for one of them usually fails the other two, and the failure shows up as water in the plinth rather than as a loose cable.
The entry is also the place where a canopy leaks, because a hole in a wall is a hole whatever is put through it. A plate with a gasket and a gland per cable seals; a plate with a single slot and a foam filler does not. Tesla Power presses the plate to the cable schedule rather than drilling it after the canopy is painted.
How many cables should one plate take?
One gland per cable is the rule, because a gland grips one cable and seals around one sheath. A plate with a slot that takes four cables seals none of them. A plate with four glands costs more and it is the only arrangement that keeps water out of a plinth, and the extra cost is a gland rather than a plate.
The number of entries is set by the cable schedule rather than by the set rating, so a set with a remote control panel needs more entries than the same set without one. Leave a spare entry on every plate, because a cable added later is a plate cut on site. Ask for the spare to be fitted with a blind gland rather than a plastic plug. Tesla Power lists the spare as a separate line so it is not dropped to save cost.
| Item | Typical figure | Note |
|---|---|---|
| Gland plate | 3 mm steel | Removable, with a gasket |
| Gland | One per cable | Rated above the cable |
| Bending radius | 12 x the cable diameter | Below the plate, not above |
| Fire stop | Intumescent, 2 h | On a rated wall |
What keeps water out of the entry?
A gasket between the plate and the wall, a gland around each cable and a drip loop in the cable outside the plate keep water out. The drip loop is the one that gets forgotten, and a cable that runs straight down into a gland carries water into the canopy along its sheath, so a loop of at least 300 mm below the gland is worth more than a better gasket.
The plate itself is usually 3 mm steel so it does not dish when the glands are tightened. A thinner plate bows between the bolts and the gasket loses contact in the middle. Ask for the plate thickness and the number of bolts. A plate held by 8 bolts on a long opening stays flat, and a plate held by four leaks at the centre, where the bow is worst, and the leak appears on the inside of the plate where nobody looks.
How is the entry earthed?
The plate is bonded to the canopy with a braided strap, because a painted plate on a painted wall is not an earth path. A gland that is earthed through its locknut is a gland that loses the path when the paint cures. Ask for the strap and the stud on the drawing. A strap that is bolted to a painted surface is a strap that carries nothing until the paint is removed.
A 400 V feeder at 630 A needs a gland rated above the cable rather than above the breaker: 630 A x 1.25 = 787 A, so the gland is an 800 A part and the strap carries the fault current. A strap sized for the load rather than for the fault is a strap that burns off in a short circuit. Tesla Power Equipment sizes the strap from the fault level on the site sheet, because the fault level at the terminals is a different figure from the load.
What does the entry do to the fire rating?
A cable entry is a hole in a rated wall, so it needs a fire stop that closes when the cable burns. An intumescent block around the cable and a sealant around the plate keep a 2 h wall at its rating. A plate with no fire stop turns a rated wall into an unrated one at the entry, and a cable rated to 90 C is the minimum that survives inside it.
The fire stop also has to survive the cable tray, because a tray that runs through the wall carries heat with it. A tray that stops at the wall and a cable that continues through a sealed plate is the arrangement that holds. Ask for the detail on the fire drawing. Tesla Power Equipment fits the fire stop before the plate is bolted, so the block cannot be left out.
How is the entry sealed after a change?
A spare entry with a blind gland is the cheap answer, because a blind gland is removed and a cable is passed through it without cutting the plate. A site that drills a new hole in a painted plate has a bare edge and a rust line within a season, and the rust starts on the inside face where the paint did not reach. Ask for two spare entries rather than one.
A cable added to a sealed plate also needs the fire stop renewed, and that is the step that gets skipped on a Friday afternoon. Write the renewal into the method statement rather than into the drawing notes. Tesla Power ships spare intumescent blocks with the canopy so the next cable does not wait for a part.
What does the offer need to state?
The offer should give the plate size and thickness, the gland list, the spare entries, the earth strap and the fire stop. Five items on one line let a buyer check the entry against the cable schedule without opening a drawing, and the gland list is the line that most offers leave out. Ask for the gland rating against the cable size as well, because a gland one size small is a gland that will not seal, and a gland one size large leaks on the sheath.
The wording on the offer matters too. Chinese genset cable suppliers often quote an entry as a hole with a plate over it, and a genset cable entry manufacturers page can show a gland list the factory buys in. Ask for genset cable entry for a riser, genset cable for the alternator and genset in a bunded yard as three separate cases. Tesla Power prints the five items on the entry drawing.
What does the handover file record?
The file carries the plate size, the gland list, the spare entries, the earth strap size and the fire stop type. One page covers the entry when those five items sit under the canopy serial number. Add the genset cable entry documentation for the site when the installation is part of a permit package and the cable schedule is signed off by a designer, and the spare entries are counted on that schedule rather than on the drawing.
Hand the page to the electrician who will pull the cable rather than to the buyer who placed the order. the Yangzhou factory describes the bay where the plate is cut and painted, the commissioning notes lists the canopies that ship with two spare entries, the build range explains how the bending radius is checked, the 500kVA silent set with ATS changeover shows the export build for this rating, the ISO 8528-1 duty definitions sets the cable standard the gland is chosen to, and the NFPA 110 maintenance routine covers the installation rules behind the seal.
Frequently asked questions about genset cable entries
It can on a canopy that is not painted, and it cannot on a finished canopy without a bare edge and a repaint. Order the entries from the cable schedule and leave spares. A site cut is the most common reason a canopy shows rust in the first year.
The gasket has lost contact because the plate bowed, or the cable has no drip loop and water runs along the sheath. Check both before adding sealant. Sealant over a bowed plate hides the leak for a season and then fails.
It does for a sealed entry, because a gland seals on one sheath diameter. A multi-cable transit block is the exception and it costs more than glands. Ask which arrangement the drawing shows before the plate is cut.
A braided strap from the plate to the canopy, with a stud on each side, and the strap sized for the fault current. A gland alone is not an earth path on a painted wall. Ask for the strap size and the stud position.
It depends on the fire stop, and a plate without one leaves the wall unrated at that point. An intumescent block and a sealant restore the figure. Ask for the fire stop type on the same drawing as the plate.
Two on a set with a remote panel and one on a set with a local panel, because a control cable is usually added in the first year. Tesla Power fits the spares with blind glands so the spare costs a gland rather than a plate.