A sealed cable entry is only as reliable as its fitting selection and completed installation.

"Is this gland waterproof?" is probably the most common question asked when quoting wiring accessories. The difficulty is that waterproofing is not a yes-or-no property. Among glands that all carry a protection rating, some are IP68 as supplied, some only qualify once a washer is added, and in some series only two part numbers meet the rating. Writing "IP68" in a specification is easy, but if one component is left out on site, or the cable diameter falls outside the permitted range, the stated rating no longer holds. This article explains how to read IP ratings and, using the KSS catalog, sets out the actual rating of each gland series and the conditions required to achieve it.

1. The two digits after IP describe two different things

An IP rating consists of two digits. The first covers protection against solid objects and dust; the second covers protection against water. The two are independent, so a conclusion cannot be drawn from one digit alone.

Take the two ratings compared here. In IP55, the first digit 5 means dust protected: dust is not completely excluded, but the quantity that enters does not affect operation. The second digit 5 means protection against water jets from any direction. In IP68, the first digit 6 means dust tight, so no dust enters at all, and the second digit 8 means the product can remain submerged under conditions specified by the manufacturer.

IP55 and IP68 differ in both dust and water protection.

In other words, the gap between IP55 and IP68 is not simply "a bit more waterproof". It is a step from "a small amount of dust is allowed and water jets are resisted" to "completely dust tight and able to stay submerged". That gap is reflected directly in unit price and installation requirements, so the right approach is to select by the actual location rather than to default to the highest rating everywhere.

2. The actual rating of each KSS series: not everything is IP68 as supplied

This is where selection most often goes wrong. Among the gland series in the KSS catalog, the conditions for reaching IP68 are not the same:

Series	Thread size	Cable diameter range	Protection rating	Conditions and notes	Catalog page
AG series (0604, metric thread)	M12x1.25 to M75x2.0	3 to 66 mm	IP68 (tested and approved for dust and water)	Supplied with a PVC washer; a compact AG-D version is also available; UL file E186042	P.124
CAG series (0604, metric thread)	M12x1.25 to M63x1.5	3 to 44 mm	IP68 (tested and approved for dust and water)	Supplied with a PVC washer; UL file E186042	P.125
EG series (0606, PG thread)	PG7 to PG48	3 to 44 mm	Reaches IP68 only with a washer fitted	The washer is a separate item (EGW series); without it the gland is not IP68	P.126
AGJ series (0604, PF / JIS thread)	PF1/4 to PF2	3 to 44 mm	AGJ-17 and AGJ-34 meet IP68	Not every part number in the series qualifies, so confirm by part number	P.128
NPT series (0608, NPT thread)	NPT1/4-18 to NPT1-1/4-11.5	3 to 32 mm	Reaches IP68 only with a washer fitted	Both the lock nut and the washer are separate items	P.129
NPTA right-angle (0609)	NPT3/8-18 to NPT1-1/4-11.5	5 to 29 mm	Reaches IP68 only with a washer fitted	Right-angle body for locations with limited space at a bend	P.129
BG conduit fittings (0615)	M12x1.25 to M40x1.5	According to conduit size	IP55 (tested and approved for dust and water)	Used together with the BG-xxP conduit	P.150
BM watertight conduit fittings (0615)	By part number	According to conduit size	IP68	UL recognised NYLON 66 body in black with a TPE clamping ring	P.153

 

Protection ratings are compiled from the IP rating index in the KSS master catalog (P.257) and from the specification page of each series. Please confirm individual part numbers against the latest catalog with our sales team.

Three practical points follow directly from this table. First, the metric-thread AG and CAG series are supplied with a washer and are therefore the simplest choice. Second, for the PG-thread EG series and the NPT-thread NPT and NPTA series the washer is a separate item and must be included in the purchase order. Third, for the PF / JIS thread AGJ series the catalog lists AGJ-17 and AGJ-34 as meeting IP68, so the rating cannot be applied to the whole series.

The IP rating depends on the series, washer condition and exact part number.

3. Three conditions that must be met on site to actually reach IP68

A stated rating is measured under laboratory conditions. For it to hold on site, three things must all be done.

First, fit the washer. The washer, from the AGW, EGW, AGJW and NPTW series in black PVC (P.145), creates a watertight, non-slip seal between the gland and the panel surface. If the washer is omitted on the EG, NPT or NPTA series, only the mechanical thread fixing remains and the protection rating no longer applies.

Second, keep the cable diameter within the permitted range. Every part number has its own cable diameter range: the AG series covers 3 to 66 mm, CAG covers 3 to 44 mm and NPT covers 3 to 32 mm. The TPE clamping ring seals by compressing the cable jacket, so a cable that is too thin will not be gripped and one that is too thick will not fit. Either case defeats the seal. Select against the actual measured diameter rather than the conductor size.

Third, seal the holes that are not in use. Where a gland position is prepared on the panel but not yet wired, fit a BPA sealing plug or a BPB sealing rod first (P.144-145). The catalog states plainly that these should be installed before wiring so that dust and water cannot get in. For unused holes in a multi-hole gland, use the MH multi-hole seals (P.146-147). This step is almost always overlooked on site, and it is the most common path for water ingress.

The stated rating holds only when the washer, cable diameter and unused openings are handled correctly.

4. Selecting by location: when IP68 is needed and when IP55 is enough

• Outdoor enclosures, solar system wiring and outdoor instruments: directly exposed to wind and rain, so the IP68 AG or CAG series is recommended. The catalog also lists these as typical applications for the AG series.

• Nacelle and tower cable entries at wind sites: humidity, salt spray and temperature swings occur together, so this is an IP68 case, and the washers and sealing plugs should be checked at the same time.

• Conduit runs between zones inside a plant: the priority is mechanical protection and dust exclusion, so the IP55 rating of the BG conduit fittings is usually sufficient. If the conduit passes through a wash-down area or runs outdoors, switch to the IP68 BM series.

• Inside a control panel: the enclosure already provides the external protection, and fixing points inside the panel are about mechanical support and insulation, so IP68 is not needed at every point.

5. Three common misunderstandings

First, that IP68 is always better than IP65 or IP55, so choosing the highest rating is always safe. The two digits are independent ratings, and a higher figure means a more demanding test, but it also means a higher unit price and more installation requirements in terms of washers, torque and cable diameter matching. Specifying IP68 everywhere, including places that only need dust and jet protection, spends money on a risk that will not occur.

Second, that buying IP68 glands makes the whole enclosure IP68. A protection rating applies to the component. The rating of the complete enclosure depends on the box, the door seal, any viewing window and the treatment of every opening, and a single unsealed hole invalidates the overall rating.

Third, that every part number in a series shares the same IP rating. In the AGJ series, for example, the catalog lists AGJ-17 and AGJ-34 as meeting IP68 rather than the whole range. As with certification, the protection rating should always be verified down to the specific part number.

Write these three items, washer, cable diameter and hole sealing, into the specification at the drawing stage. That is how you avoid the situation where the right material was purchased but the rating was never achieved on site.

Contact

For full specifications and quotations on KSS cable glands in the AG, CAG, EG, AGJ and NPT series, BG and BM conduit fittings, or the matching washers and sealing plugs, please contact us:

Jwo Yiih Enterprise CO., LTD.

Contact us at sales@jwoyiih.com or call +886-4-8760280 for the full solution package and part number list.

Note: all part numbers, specifications and protection ratings cited in this article are taken from the KSS factory master catalog with verified page references (page numbers are the printed catalog pages); IP ratings are compiled from the IP rating index on catalog P.257 and from the specification page of each series. Protection ratings and certification coverage vary by specific model and SKU; for a formal quotation, please confirm the current part numbers and the latest valid certificates with our sales team.