Review on 🔌 6 Zone SR506 Switching Relay by Sean Davis

C. Eclair is right in his assessment. I had to replace our Taco SR-504 EXP unit because it burned out on the 120VAC input terminals. The replacement EXP unit (the one shown) is part number SR506-4. The SR506-4 differs in appearance and is completely solid and the relays are not interchangeable. The device is the same size and all internal connections are the same. Our original unit was only 5 years old and was defective from the start as we had trouble using it. We fixed it on 120VAC input terminals. We cannot say if the replaced device is of better quality as it was only installed on 10/18/15. A photo of the failed unit is attached. We were in a bind and paid 318.00 to replace an SR506-4 unit at a local heating/plumbing shop.