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SunStat Sub Control Relay II for extending your system beyond 15 amps

SKU# 500810

Sorry, this item has been discontinued



The SunStat Relay II ONLY works with the SunStat Pro II and View Thermostats.

The NEW Relay II is not compatible with legacy SunStat models 500670 and 500675.
If you require a relay for those thermostats look for the 500680

When your SunTouch Floor Heating System is larger than 300 Sq Feet in one area (240v) it will require more than 15 amps. The easiest solution for control of larger zones is to install SunStat Relay II’s in conjunction with your PRO II or VIEW thermostat. Connect SunStat relays to SunStat thermostats for safe, simple, elegant control of larger systems. Each SunStat Control (120 or 240 VAC) can accommodate up to 10 SunStat Relays. 

Each Sunstat Relay II model 500810  is controlled by the SunTouch Thermostat via a low voltage wire connection. You may drive up to 10 SunStat Relays with one SunStat thermostat acting as the Master control of all attached relays. This allows 1 thermostat to control up to 10 additional circuits of floor warming for a total of 11 floor warming circuits.

This Relay controls the Voltage to either a 120v or 240v system. Power from the panel (dedicated circuit recommended) and floor heating is connected to each relay (just like a thermostat) and then low voltage wire connects each relay to the Thermostat. A SunStat thermostat is required for the Relay to function.


  • Built-in Class A GFCU test Light and button - 5milliAmp trip for safety.
  • 3 year Warranty
  • Dual Voltage for either 120v or 240v systems
  • Durable 15 Amp Relay controls 300 SF (240v) at 12 Watts per Sq Ft (150 SF/120v)
  • Daisy Chain up to 10 Relays to 1 SunStat for large zones
  • LED indicator Lights for Power, Heating, GFCI test/trip modes, Troubleshooting
  • Door is paintable for a custom installation




UPC 840213158149
What's In The Box Relay, Wire Nuts,Mounting screws,Screwdriver
Voltage 120 VAC /240 VAC
Visible Depth 13/16" (20.6 mm)
Inside Box Width 1 11/16" (42.9 mm)
Inside Box Height 2 3/4" (69.8 mm)
Inside Box Depth 15/16" (23.8 mm)
Display Height 2.75
Display Width 1.75
Manufacturer Watts Radiant
Instructions + Video

Instructions + Video

Instruction Manual
Install Steps

Read Instructions for Thermostat and Relay completely and make all connections with Circuit breaker OFF. Install in a single-gang extra deep box (1 or 2 power leads) or a 4” square box with single gang mud ring for 3 power leads.

Signal Wire (Low Voltage) Connection

  • Use 18 – 24 AWG 2-conductor shielded wire to connect SunStat to Relay or Relay-Relay.
  • This signal wire length can be up to 100 Feet for 18 AWG wire
  • Connect installer provided signal wire to thermostat (models 500750 or 500775 only) and Relay

Included with Each SunStat Relay:

  • Small Screwdriver for making connection
  • Wire nuts for wiring connections
  • Mounting Screws
  • Not Included : Low voltage signal wire 
Unit and wires protrude into box 0.81
Floor Sensor Included Sensor with T-stat
Floor Sensor Length Ft 15' Sensor
Floor Sensor Length Meters 4.57
Floor Sensor Type Sensor with T-stat
Floor Sensor Resistance Range (@ 20,000) 8-14k
Floor Temperature Sensing Primary Controlled only by T-stat
Ambient Air Temperature sensing Mode Controlled only by T-stat
Ambient Air w/ Floor Temp option Controlled only by T-stat
Location / Use : Indoor Only Indoor Dry Location Only
Outside temp and humidity sensor option (purchased separately) n/a
GFEP / GFCI Protection (Ground Fault Circuit Interrupter) 5 mA Class A Built In - With Test Button Feature & indicator light
More Details

More Details

Warranty from Manufacturer 3 yr
Control Multiple areas Yes
Remote control Mode yes
Home Automation Integration Yes
Smart Technology/Early Start yes
Manual Temperature Override Possible yes
Regulator Mode option no
Heating Cycle length n/a
Safety Listing Safety Listed in USA & Canada : UL 873, UL 943 & CSA C22.2 No. 24, CSA/CAN C22.2 No.144, ETL Control No. 3037530
Programming Method Controlled only by T-stat
Pre-Loaded program options Controlled only by T-stat
User Settable program Controlled only by T-stat
7 Day Prog (Su - Sa) Controlled only by T-stat
5-2 Program (M-F + S-S) Controlled only by T-stat
5 - 1 - 1 Prog (M-F - Sa - Su) Controlled only by T-stat
Programming Saved Indefinitely (or number of hours) Controlled only by T-stat
No Battery Required No Battery Required
Minimum Display Temp Controlled only by T-stat
Maximum Display Temp Controlled only by T-stat
Accuracy Degrees F Controlled only by T-stat
Minimum Setting Temp Controlled only by T-stat
Maximum Setting Temp Controlled only by T-stat
Repairable Heating Wire No serviceable parts
Packaging Easy Open Cardboard - no frustration

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