Argo 6 Zone Relay With Priority For Circulators ARM6P Robust Enough To Handle Up To 15 Zones / Separate XX (Isolated Switch) & ZC/ZR Relays Protect Boiler Aquastat / Relay Diagnostic Light- Easily Seen Through Window On Cover / High Relay Load Rating- 7.2 Amp , 1/3 HP / Switchable Priority / Plug In, Add-On Zone Modules (AD1 Or AD4) / 24 Vac Transformer Terminals / Premium Plug-In Replaceable Relays / 5-Second Time Delay For Boiler Shut-Off / Prioity Saftey Timer- Ensures Other Zones Get Heat Every 30 Minutes & Prevents Freeze-Ups