Welcome to FloorLife!
Some floor heating jobs are just too large for a single radiant heating thermostat to handle alone. The nJoin power module is here to help you heat those larger projects. The refined and modern-looking nJoin links up to any WarmlyYours thermostat in the nSpiration series (nSpire Touch WiFi, nSpire Touch, nHance, or nTrust) to increase the electrical output in 15 amp increments to allow for heating additional areas or large rooms, like basements, with a single thermostat.
Waramly Yours nSpiration Series of Controls Comparison Chart