The coldtail connection is the join between the coldtail and the heating wire where the live, neutral and earth wires from the coldtail are spliced together with the wires that make up the heating cable.
The coldtail connection is normally encased in a special epoxy or glue to ensure it is electrically protected to the required IPX7 rating that is necessary for electrical underfloor heating for use beneath tiles or levelling compound. The coldtail connections heat up rapidly once the system is turned on so it is vital that they are always encased in the tile adhesive, levelling compound or screed to enable them to conduct the heat away rapidly. The only exclusion to this rule is Heat Mat’s Underlaminate System.
The coldtail connections must never be bent or crushed and in many circumstances when the system is installed beneath tiles a small groove must be chiselled out beneath the connections to ensure it does not lay proud. Dual conductor heating mats and cables have one coldtail connection, and single conductor systems have two.