Steve Slater, UK Product Manager for Electrical Installation at HellermannTyton, looks at the differences between gel and cast resin jointing kits.
As a wholesaler, you will have noticed the vast number of products that are available for connecting cables. Although this remains a basic skill for installers, the right connection method often depends on the type of job.
Whilst wholesalers are increasingly stocking a number of different gel and cast resin jointing kits, they need to be in a position to recommend the right product for the right application.
Gel and resin joints have the same purpose, but they look very different, are installed in different ways and can be used for different applications. For example, gel joints are intended for use with low voltages. Resin joints are also most often used with low voltages, but different formulations of resin are available and some can be used with medium voltages.
This is important because, as far as an installer is concerned, one of the most important determinants of joint selection is the voltage level; the joint must be able to cope with the voltage involved, and joints designed for low voltages may fail if subjected to too high a current. So how do you identify the right product for each application?
Gel and resin joints look very different. Gel joints have a rigid shell, made of polypropylene that resists UV light, extremes of temperature and impact – obviously, this is to protect the electrical connection within the joint when it is installed, in day-to-day use. The shell comes pre-filled with a specialist gel, which is non-toxic and highly insulating (>20kV/mm).
Fitting a gel joint is very simple and does not require any special training, so it’s a good choice for installers early on in their careers. Perhaps, most importantly, gel joints can easily be re-opened after installation, for testing and/or inspection purposes. Consequently, they are ideal for general domestic and light industrial uses.
CAST RESIN JOINTS
In contrast, cast resin joints require a little more skill to install and time for the resin to cure (usually about 50 minutes) before the cable can be buried or concealed. However, they are probably a little more versatile than gel joints. Resin joints can be used with both armoured and non-armoured cables, with a wider range of voltages, and provide a very robust join once the resin has cured. They are more appropriate for cables with larger cross sections, and better able to cope with heavy-duty conditions and harsh environments, than gel joints.
WHICH ONE TO CHOOSE
It is important to stock both gel and cast resin jointing kits as they both are user-friendly, ‘out of the box’ solutions.
A further similarity is that both solutions can be used inside and outdoors, and underground. However, where conditions are likely to be hostile, for example under water or in installation ducts, the more robust and durable cast resin may be the best choice. Indeed, it could be argued that cast resin is generally a little more versatile, in that it can be used in a wider range of settings, but this has to be weighed against the sheer speed and convenience of gel joint installation, and the gel kits’ indefinite shelf life. Wherever it is known that access to the joint will be needed in the future, for example for testing purposes, in settings such as homes and offices, the gel option is the best to recommend.