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SR504-4 has been discontinued
Discontinued February 10, 2026
This product was discontinued by the manufacturer.
MANUALS (3)
This item replaces: SR504, SR504-2
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Direct Replacement:
Product Highlights
–
120 VAC Input
4
10-1/4" Width
6.75" Height
2-3/4" Depth
20 Amps
Description
–
The Taco SR504-4 Switching Relay is the best choice for all your zoning needs, with advanced PowerPort Cards, external diagnostic lights, and contractor friendly PC board layouts. Combined with the time proven reliability of the 00 family of circulators and thermostats, total system integrating is achieved. External indicator lights provide instant diagnostic feedback, making a snap of service calls or new installation start-ups.
- 24-Volt power input or output terminal
- Fuse protected
- Simplified wiring
- Compact design
Specs
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| Application: | Zoning |
|---|---|
| Number of Zones: | 4 |
| Width (Inches): | 10-1/4" |
| Height (Inches): | 6.75" |
| Depth (Inches): | 2-3/4" |
| Amperage: | 20 |
| Power Method: | 120 VAC Input |
| Voltage: | 120v |
Questions?
Speak with a real person who will go out of the way to help!
Call or text 888-757-4774
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Friday
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Saturday – Sunday
9am–5:45pm
Compare Similar Products
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Number of Zones
You May Also Need
3 Replacement Parts
Replacement Fuse - 5 Amp (10 Pack)
SKU: SR5A-005RP
TacoReplacement Fuse - 1 Amp (10 Pack)
SKU: SR1A-001RP
TacoReplacement Fuse - 6 Amp (10 Pack)
SKU: SR6A-001RP
Taco
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Product Reviews
4.78 out of 166 reviews
98% would recommend this product
5 star
85%
4 star
11%
3 star
2%
2 star
1%
1 star
1%
Customer Images
Most Liked Positive Review
Zones!
Bumping my system from three zones to ten, this controller was the perfect choice for the master position. Wiring is basic & easy, Controls the furnace & four Taco 007-f5 circulator pumps, and (in my system anyway) two Taco 503 relays.
VS
Most Liked Negative Review
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Fairly good. Could be better.
Needs better construction. The legs that hold the circuit board to chassis are plastic and weak. These were damaged during shipping, causing indicator led lights to be misaligned. Functional but a fail on robust build! Please improve Taco.
Showing 1-10 of 166 reviews
Broke down in the first season
Installed in August, indicator lights failed by December, then began sending heat to zones with no signal, called taco they sent me here for a warranty replacement, and Supply House sent me back to Taco on a run around, purchased name brand to avoid this type of trouble, last time I purchase from either company
Angry in VT
Vermont
27 days ago
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I would not buy again
installed unit , lest than a week later all lights for power and zones do not work, relays still work. moved control board alittle bit and lights started working again. most likely there is a break in the Netural ( return) in the board.
bri
NY
6 months ago
Verified Buyer
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This zone controller is what i needed
It was delivered quickly and was packed well
D Emme
New Jersey
6 months ago
Verified Buyer
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Good product
Bought this to replace 20 yr old unit since mechanical relays are present.
Cip
WI
6 months ago
Verified Buyer
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Solid product.
Bought this to replace old 20+ year pumps that are still running strong but some make weird noises. I do not want them to break in the middle of the winter
Cip
WI
6 months ago
Verified Buyer
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Works great
Did exactly what I wanted to run multiple pumps with multiple thermostats
Slim
Wisconsin
9 months ago
Verified Buyer
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Best product
Reliable. Easy to install. Customer service very helpful.
Joe
New York
9 months ago
Verified Buyer
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6 Zone Relay for Circulator Pumps
This is the newest generation 6 zone relay for circulator pumps. It offers R/W/C connections so it will work for Smart thermostats. It also offers Bluetooth connectivity from within the home to check which zone is active or allowing you to force a zone on. It was an easy DIY replacement of an older Taco switching relay.
RFW5
Boston, MA
1 years ago
Verified Buyer
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I would buy this again
Great service and the part came ahead of estimated delivery.
Peter
Bayside, NY
1 years ago
Verified Buyer
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Great price and fast shipping.
Just what I needed and at a great price. I am definitely going to use this site from now on.
Dan
Pa
1 years ago
Verified Buyer
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Product Q&A
53 Questions53 Questions
Q: What does it mean when the zone 1 red button is on? It seems to go on every time the heat is on. Is that supposed to do that?
Asked by Cher 15 years ago
Add your answer
Verified Reply- PexSupply StaffYes, that is normal. As long as the power is connected, the green light should always be on, When the thermostat calls for heat, both the appropriate circulator and red indicating light are energized.
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- John
On mine thats attached to the coal stove it goes on when the thermostat calls for heat so its turning on my coal feeder to push coal into the fire.
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Q: How do I connect to my on demand Prestige boiler from my SR502 to make sure there is hot water when thermostats call for heat
Asked by 15 years ago
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Verified Reply- PexSupply StaffYou need to connect the end switch in the switching relay to the "tt" thermostat connection in the boiler control.
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Q: I have a White-Rogers Type 829A-845 controling one zone. Can the Taco SR501 repleace this Switching Relay?
Asked by Joe 15 years ago
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Verified Reply- PexSupply StaffAccording to the manufacturer, the SR501-2 replaces White-Rodgers models 889-189 and 829-845.
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Q: I have 2 existing zones on my boiler and adding a third zone. Can I add this 1 zone SR or do I need change to a 3 zone SR?
Asked by 15 years ago
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Verified Reply- PexSupply StaffIf your boiler is not set up to run off priority, you can just add the SR501.
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Q: what does the low voltage end switch do on the 3 zone switching relay?
Asked by joe 15 years ago
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Verified Reply- PexSupply StaffIf you are referring to X1 and X2 end switches, they are connected to the aquastat and are involved in firing the boiler. You can take a look at this install guide http://s3.pexsupply.com/manuals/1249544859835/SR503102-083.pdf .
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- Jian the Swimmer
the connections on the top of the board are for thermostats for the heating zones, up to three, and X1 X2 go to the boiler's ignition control(called TT mostly), so whichever of the three thermostat circuits is closed, the normally open switch between X1 and X2 will close, and the normally open condition between TTs will becomes close, and cause the boiler to ignite and fire up.
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Q: I have a 5 zone Taco relay running my current system, I'm expanding by 3 more zones. Will this relay run as a slave to my 5 zone relay?
Asked by 16 years ago
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Verified Reply- PexSupply StaffNo, it will not.
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Q: Does this switching relay have the capability to open my Zone valves, if so how is it wired. My valves are 2 wire.
Asked by Steve 16 years ago
Add your answer
Verified Reply- PexSupply StaffThis switching relay is for pumps, not zone valves. For zone valves, you need a zone valve controller. You can view zone valve controllers here: http://www.pexsupply.com/Taco-Zone-Valve-Controls-326000
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Q: Will this power my circulator pump from my zone valve controller (ZVC406-3)or is there a better option?
Asked by xander 16 years ago
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Verified Reply- PexSupply StaffYes, it will. You can also wire your pump through the ZVC controller. Take a look at this wiring diagram: http://www.taco-hvac.com/uploads/FileLibrary/102-092.pdf
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- bt
yes
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Q: Is there a programable digital timer available that I could use with this relay? My system has 3 zones...heat, hot water & radiant floor. I am tring to put the radiant floor loop on a timer system where I could put on several cycles in a 24 hour period.
Asked by Johnny Radiant 16 years ago
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Verified Reply- PexSupply StaffNo, but you can use a low voltage, programmable thermostat.
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Q: since this will control up to 3 pumps I assume then it would handle things if all 3 thermostats call for heat at the same time, depending on the hp/amps of each pump? If I'm understanding the literature, it can handle a max size pump of 1/3 hp at 7.2 amps, with all 3 pumps not exceeding 15 amps total draw at once? Thank you!
Asked by rafer johnson 16 years ago
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Verified Reply- PexSupply StaffYes, the SR503 can handle your application.
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