The 20Amp Contact Relay is designed to increase the number of high-powered heaters that can be wired into a single MD2 thermostat.
Our MD2 mains-powered WiFi thermostat is capable of handling up to 3.6kW or 16Amps, for most domestic scenarios this is more than enough capacity to have several small heaters being controlled by a single MD2. In larger commercial spaces or hot yoga / Bikram where higher output heaters are required it can be easy to exceed this maximum load meaning you would therefore require contactors to manage this. The contactors act as a switch that can control up to 20Amps worth of heaters, the MD2 can then control multiple contactors at once allowing you to reach much higher load limits with a single thermostat.
When using two or more 20Amp relays with the same thermostat, you will likely also need to use our 6kW Soft Starts to manage any potential inrush current. This is particularly important for hot yoga / Bikram. Please contact Herschel for advice on this.