TacoSR501 Single Zone Hot Water Circulator Switching Relay

Even though this item was a new version of the one I replaced, the wiring was exact. Took 20 minutes to exchange.

works on my boiler

Works like a champ.

Designed an in floor and under floor radiant heat system for my cabin, in floor inside slab of addition, styrofoam under and around perimeter of slab, and PEX under floor with aluminum heat spreaders in the 100 year old main building portion. C-wire is a little vague on both instructions in this product and the Sensi thermostat I used, did not prepare and have sensor wire in slab, and did not wish to take a chance on another hole into slab. Thermostat is working, calling for heat, this relay then turns on the circulator pump which initializes the Takagi instant on LP heater and the heating process begins.There is a white plastic divider under cover that looks like it will get in way with routing wires, but it must bend when cover is put on, used just the holes on top for the 3 sets of wires coming into unit, 1 from thermostat, 1 from pump, 1 for power to system.Was thinking of using some of the unused contacts to run a LED light on wall so knew when system was running, everything is so quiet that even with just 1 door between me and system and system less than 15 feet away I can barely hear it, and would like to know if it were cycling too often. Cabin has single pane windows, new windows delayed 4 times so far with Covid, hopefully they come soon, we already had snow...Device came with a pack of resistors for the C wire, of which I do not know if the resistors negate the need for the C wire or what they actually do, again, the instructions were pretty vague on this wire in a Heat only scenario, the system worked without, but added one and did not hook up an additional C wire and thermostat appears to be functioning normally. I sent Sensi support an email about the wire, gave them model of both thermostat and relay, and no replies to date..If they reply will update review in case others have questions about the C wire.As of now, system operating as expected, and place is warm.

For my baseboard heater circulator pump thermostat.

With the same SR501 model number, I figured it would be the same, but there is one less knockout on the box for electrical connections. I was using all 3 on the old one, so I had an hour's worth of rewiring to do in order to make this work. The unit itself is working just fine, and my issue with it is not a factor for a new installation.

This is a versatile, high quality single zone control. It simplifies my application, replacing the 2 controls i needed previously. It has both NC and NO relay contacts. Highly recommended.

Used it to replace my original 1969(!) Hydrotherm single zone relay RTS-20B. Not that there was anything wrong with the original, it just looked pretty 'baked' after sitting on the side of my furnace for 49 years. This new unit was a simple swap and works flawlessly in my single zone application. Nice to have power and operate LEDs now too.