Taco SR501 switching relay

Sweto · September 7

I need help! I am trying to add the taco sr501 one zone switching relay to my system to control my in floor radiant heat. The problem I am having is my in floor has a zone valve and the wiring diagram from SR501 does not show how to wire in the zone valve. The In floor system has its own T-stat, zone valve, and circ pump, using a common boiler. I am using the ZVC404-4 for the other 4 zones in the house with hot water being my primary.

hot_rod · September 7

You want a ZVR, zone valve relay, not a ZSR zone switching relay ,pump relay. The zone valve relay has a easily accessible 24V supply, and a larger transformer, for the zone valve.

Generally a zone valve relay box will be at least 2 or 3 valve connection. So you have a spare or two.

A 6 valve ZVR as example.

Screenshot 2025-09-07 at 11.54.26 AM.png

Sweto · September 7

I read an old discussion stating what I’m trying to do can be done, however the discussion has been closed so I can not see any images that where posted showing how to wire in the zone valve.

Big Ed_4 · September 7

Once you wired the relay to the radiant circulator . Wire the end switch of the zone valve to the thermostat TT terminals of the 501 . From a fused 24V transformer wire through the thermostat the zone valve . With a call of heat from the thermostat , it will power up the zone valve . When the zone valve fully opens it will close the end switch and the 501 will pull in to turn on the circulator …

That is the basic

109A_5 · September 7

" I am using the ZVC404-4 for the other 4 zones " So now you actually have 5 zones ???

Big Ed_4 · September 7

What size is the radiant zone ?

109A_5 · September 7

One method to do it.

Sweto · September 7

I have solved the problem and system is working. Thanks to those who actually tried to help.

109A_5 · September 7

OK, good you have it working. I missed that you stated you have a circulator too. Updated drawing if anyone needs it.

Joe Mattiello · September 8

couple of techs already mentioned it.

Protocol, thermostat to ZV, end switch from ZV to RW on SR50, and end switch on SR501 to TT on boiler.

BDR529 · September 8

Interesting.. No one says anything about outside re-set and/or room sensor, Not a T-stat and relay

Clearly says in floor radient heat. Hope you have a 3-way mixing valve.

109A_5 · September 8

https://forum.heatinghelp.com/discussion/comment/1864284#Comment_1864284

A few questions were asked, with no response. The OP did not seen to want to discuss the rest of the system. Have no idea what they have, a 4 wire zone valve would have been easier, so I used a three wire zone valve. No power needing thermostat was mentioned. Hopefully they don't have the zone valve after the SR-501.

hot_rod · September 8

Or what type of thermostat. How large is the transformer in those switching relays? Some of the heat motor ZV take a bit of Va.

GroundUp · September 8

If it's piped correctly, there is no reason to have a zone valve at all.

EdTheHeaterMan · September 8

https://forum.heatinghelp.com/discussion/comment/1864293#Comment_1864293

I found that out when the zone valve for my air handler coil failed. I robbed the motor from my radiant heat zone to get heat and just left the zone valve open manually. I was using a ZVC-404 and placed a jumper across the end switch terminals. I just figures that radiant zone would overheat for a few days until I got a replacement zone valve motor. As it turns out, leaving the zone valve open manually did not cause any overheating of the radiant zone. That is because the thermostat for the radiant needs to call for heat to operate the low temperature. circulator from the mixing valve. I never replaced the zone valve motor and it is still operating perfectly with no zone valve.

I have redesigned subsequent radiant floor systems since that discovery. Sometimes you need to see it (experience it) to believe it.

GroundUp · 1:15AM

@EdTheHeaterMan bingo. There are certainly some applications where the piping is less than ideal that some sort of positive shutoff would be necessary, but when properly piped there is absolutely no need for a zone valve in addition to the circulator.

EdTheHeaterMan · 2:37AM

When I originally did the boiler room piping, I was not sure on how I was going the heat the garage once I converted it to living space some time in the future. I mounted 4 zone valves on a manifold. One for the existing indirect DHW, two for the first and second floor air handler hydronic heat coils, one for the future garage converted to living space. So the valve was already there to use once i decided to use low temperature radiant tubing under a false floor I added to allow for insulation on the concrete and room for the tubing.

Eventually my father gave his grandson (my son) a pool table for his 16th birthday, so I needed a room to put it in. That's when the room was converted from storage to "The Game Room". Today my son owns the home and that is now "The Music Room" with its own wet bar. The pool table got moved to the living room (that is now called the game room). Darts, pool and/or cards depending on the crowd visiting. Radiant heat still working with an addition to the master bedroom just above the former garage/game room, that also has radiant heat. Nice to wake up to warm hardwood floors and warm floor tile master bath.

I may have spoiled him.

Taco SR501 switching relay

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