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SR501-4 has been discontinued
Discontinued May 4, 2026
This product was discontinued by the manufacturer.
MANUALS (3)
This item replaces: SR501, SR501-2, SR501-5, SR100
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Direct Replacement:
1 Zone Next Generation Switching Relay, Expandable
Product Highlights
–
120 VAC Input
1
5-1/4"
2-3/4" Depth
7.2 Amps
120v
Description
–
Taco SR501 Single zone switching relay is a standard equipment for every installer. It can easily replace any brand made by any manufacturer, and will even fit into the existing metal enclosure without rewiring incoming connections. The SR501 single zone switching relay is UL and CSA listed, uses a standard "ice cube" replaceable relay and is compatible with conventional and programmable thermostats. External indicator lights provide instant diagnostic feedback, making a snap of service calls or new installation start-ups.
Features:
Features:
- External Indicator Lights
- Switchable Priority
- Simplified Wiring
- Fully Enclosed Snap-Out Relays
- Compact Design
- Fuse Protected
- 100% Factory Tested
- Isolated End Switch
- Contractor Friendly PC Board Layout
- Universal Thermostat Compatibility
- UL and CSA Approved
- 24 Volt Power Input or Output Terminal
- Extended 3 Year Warranty
- Made in the USA
Specs
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| Application: | Zoning |
|---|---|
| Number of Zones: | 1 |
| Width: | 4-1/4" |
| Height: | 5-1/4" |
| Depth (Inches): | 2-3/4" |
| Amperage: | 7.2 |
| 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
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SKU: SR1A-001RP
TacoReplacement Fuse - 6 Amp (10 Pack)
SKU: SR6A-001RP
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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
1 months 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: can i operate a circulator pump like a zone valve using a control box ? or do i need relays for each to power the cir. pumps when the therm calls for heat?
Asked by 15 years ago
Add your answer
Verified Reply- PexSupply StaffA switching relay works with circulator pumps as a zone valve control module works with zone valves. The SR506 can control up to 6 pumps if you are zoning by circulator.
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Q: i have a taco 3 zone im try to hook up the 4th zone . do i need to buy a 4 zone taco or is ther a cheeper way
Asked by 15 years ago
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Verified Reply- PexSupply StaffYou would most likely be best off using a 4-zone switching relay. Multiple -EXP units can also be combined.
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- Anonymous
If you have a 4th zone you should stick with a 4- way.
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Q: Sr503 power light green, but all 3zone lights red. What does this mean?
Asked by 15 years ago
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Verified Reply- PexSupply StaffThe red light would indicate that zone is calling for heat.
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- Joe
All three zones are getting the signal from their thermostats. Their pumps should be running/the heat should be on.
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Q: Hi. I have a zvc 406 with priority installed in my boiler. It powers 4 zones, being the inderect water heater the priority zone. Priority switch is turned off. There are two extra zones. Id like to hook up the infloor zone to one of the zvc 406 extra zones and have the sr501 power the circulator on for the infloor. Do i just tie in the extra end switch from the zvc 406 to the switching relay? if so, where is it? i dont see an end switch on it, only on the sr501 exp. Thanks
Asked by leo 15 years ago
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Verified Reply- PexSupply StaffYou will tie the extra end switch in the ZVC control to the TT connection in the SR control.
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Q: i have a munchkin contender boiler and dhw.4 zones of heat with a main circulating pump which needs to come on when each tt calls for heat .does the line voltage for this pump come from the taco or boiler .
Asked by 15 years ago
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Verified Reply- PexSupply StaffNormally the power for the zone circulators will come from the switching relay.
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- Paul the tech
The main power should come from the taco control
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Q: I have this relay installed. It is the non-exp model. I want to take the one of the zones and split it into three other zones running off the same circulator. I will control the three new zones using zone control valves. I have a tankless coil for DHW. How do I go about wiring this up? Do I need to buy extra controllers? Thanks, Craig
Asked by Craigabooey 15 years ago
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Verified Reply- PexSupply StaffYou will need a Taco Zone Valve Controller. You will wire the end switch of the zone valve controller to the thermostat connect on your switching relay.
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Q: I am installing radiant floor heating for one room. The heat source will be a tankless heater, this is one zone. So how and what to I use to send 24 volt to the thermostat and power only the taco pump? Thanks for you answers in advance.
Asked by Tom 15 years ago
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Verified Reply- PexSupply StaffThe Taco switching relay will power/control your 24 volt thermostat and power your 120 volt pump. The relay has a built in transformer.
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Q: Have a sr502 switching relay. Can I replace the transformer?
Asked by Rich 15 years ago
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Verified Reply- PexSupply StaffTaco does not offer a replacement part for the transformer.
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Q: The red and green lights do not come on at all and the Taco is not functioning. Is there a basic troubleshooting sheet available somewhere? Ken
Asked by Kenny the owner 15 years ago
Add your answer
Verified Reply- PexSupply StaffWe would recommend that you check all the terminals with a volt meter to make sure they are functioning properly and that you also check the cube relays to see whether or not they need to be replaced.
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Q: I am setting up a radiant heat system with 2 zones, heat exchanger and 50 gal water heater. Each zone will be on a separate thermostat. I understand how to connect 2 pumps to run 2 separate zones. However I am not sure how to connect the 3rd pump to circulate hot water between water heater and heat exchanger so it turns on whenever one or both termostats call for heat.
Asked by Pawel 15 years ago
Add your answer
Verified Reply- PexSupply StaffYou will also need a single-zone switching relay that the end switch from the two-zone switching relay will tie into.
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- Jim
You essentially have three zones not two. Set up the DHW loop as the third zone and assign priority. This zone needs an Aquastat to set the desired water temp (usually ~160) I suggest using a pre wired zone controller with priority and follow the wiring plans supplied. You can set your boiler controler for "cold start" since there is no need to maintain 160 degree water in the boiler when no zone calls for heat. The DHW water is kept at the pemperature set by its aquastat. Good luck!
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