Taco SR Series Troubleshooting: Complete Guide

Taco SR Series Troubleshooting: Complete Guide

The Taco SR series is a reliable and efficient switching relay for your HVAC system zoning solution. However, like any electrical component, the switching relay can cause problems over time that require troubleshooting and repair.

So, what are the common Taco SR Series troubleshooting?

Common problems of the Taco SR series are the switch relay not turning on, getting no power, and getting overheated or underrated. To resolve these issues, you have to make sure the wiring is properly connected and not damaged, and that the thermostat, transformer, and circulating pump are properly working. Also, make sure the valves are in good working condition. 

To know these troubleshooting procedures in detail, keep reading. 

Taco SR Series Troubleshooting: Reasons & Solutions 

Depending on the model and zone, different switch relays in the Taco SR series can show different problems. Let’s discuss that problem with proper reasons and solutions. 

Problem 1: Taco SR501 Not Turning On

A common problem you can face with the SR501 is the switch relay doesn’t turn on and no light comes up. Let’s see the reason behind this problem and the possible solution.

Reasons:

There can be several reasons behind this problem. A faulty thermostat, incorrect relay wiring, and a blown fuse are the main reasons behind this. Due to these reasons, the switch relay is not getting the power it needs and as a result, it’s not working. Also, the Taco SR501 may not work due to a bad transformer. 

Solutions:

Check the thermostat first. Here’s how to test the thermostat with a multimeter. 

Step 1: Turn off the HVAC system by switching off the circuit breaker.

Step 2: Remove the cover of the thermostat to access the wiring terminals.

Step 3: Set the “AC voltage” mode in the multimeter.

Step 4: Attach the red probe of the multimeter to the red wire of your thermostat. Attach the black probe to the other wire available.

Step 5: You will get a voltage reading in the multimeter as per your thermostat’s voltage. For example, if the multimeter is 24V, you will get a reading of around 24 volts in the multimeter. 

Step 6: Repair or replace the thermostat if you don’t get the desired reading in the multimeter.

If the thermostat is fine and the switch relay is still not turning on, check the wiring of the relay switch.

Taco SR501 Not Turning On

Figure: Taco SR501 Wiring Diagram

Make sure all the wiring is connected properly and there is no visible damage in the wire including wear or tear. If any of the wires are found damaged, replace them. 

Check the fuse of the switch relay. Here’s what you have to do. 

Step 1: Remove power sources from the SR501 relay.

Step 2: Locate the fuses on the circuit board of the SR501 relay. It has a 1 amp fuse on the left side of the relay box and a 5 amp fuse in the middle of the box. 

Step 3: Remove the fuses with a fuse puller one by one and visibly check the fuses. If the fuse is blown, you will be able to see a break in the metal wire or a darkened area inside the plastic body.

blown fuse

Source: New Equipment

Step 4: Replace the fuse if the existing fuse is blown. Make sure the new fuse has the same amperage rating.

Step 5: Turn the power back on to the SR501 and test to see if it is working properly.

If the fuse is okay, check if the output source of the Taco SR501 is getting 120V or not. Here’s how to do it. 

Step 1: Locate the 120V input L (live) and N (neutral) terminals in the switch relay board. You can also recognize them from color coding. The live one will be a red-colored terminal and the neutral one would be a grey-colored terminal. 

Step 2: Set your multimeter to the voltage setting.

Step 3: Touch the multimeter’s black probe of the multimeter to the N or neutral terminal of the switch relay. And touch the red probe with the  L or live terminal of the relay. 

Step 4: Check the multimeter reading. If it shows 120v, then the power supply is working fine and the switch relay is in good condition. 

In this case, the transformer is bad and you have to repair or replace that. If you don’t get a 120v reading from the switch relay, it’s possible the switch relay itself is faulty and you have to replace it.

Taco SR502 No Power:

Taco SR502 No Power

In SR502, you can sometimes get no power and as a result, the red light won’t come on at all. It will also cause the thermostat and other HVAC components to not get power.

Reasons:

The reason behind this problem is, the switch relay is not getting 120v. It can happen due to many reasons including the switched circuit breaker, or damaged wiring.  

Solutions:

Make sure the circuit breaker is turned on. 

Next, you have to jump-test the thermostat terminal on the different zones of the switch relay with a jumper wire. Here’s how to do it.

Step 1: Locate the terminals for the problem zone on the SR502. There should be two terminals labeled R and W.

Step 2: Remove the wires from these terminals and then use a jumper wire or paperclip to connect the R and W terminals together.

Step 3: If the Red LED on the SR502 lights up after jumping the terminals, it means that the issue is with the thermostat or the wiring between the thermostat and the SR502.

Step 4: Replace the thermostat wire between the thermostat and the relay.

Step 6: If the red light on the SR502 still does not light up, the issue may be with the relay itself or with the power supply to the relay. In this case, repair or replace the switch relay.

Problem 2: Taco SR503 Lack of Continuous Volt

A common problem with the SR503 is not getting persisting voltage, especially while connecting with alternative wiring. As a result, the HVAC component with the switch relay such as the circulating pump doesn’t run properly. 

Reasons:

The power source of your SR503 is not enough to provide continuous voltage to it. 

Solutions:

You can use a separate R832 relay for getting continuous power. You have to connect both relays in the following way. 

Step 1: Identify the X-X terminals on the SR503 switch relay and T-T terminals on the R832 switch relay.

Step 2: Connect a wire from the X terminal on the SR503 to the T terminal on the R832.

Step 3: Connect a wire from the X terminal on the SR503 to the other T terminal on the R832. The connection should be according to the cold start or basic wiring method of the switch relay.

You can also use a 24V transformer to power the SR503 switch relay which will provide continuous voltage.

Problem 3: Taco SR503 One Zone Cold

Another problem some homeowners face with an SR503 is that one of the zones remains cold. Let’s find out the reason and solution for this problem.

Reasons:

If the thermostat has dead batteries or the thermostat is not working, you can face this problem. Also, sometimes, having a frozen pipe can cause one zone not to heat properly. 

Solutions:

Replace the battery of your thermostat. If it does not work, test the thermostat and repair or replace it as required. 

Check if you have a frozen pipe in the problematic zone. Freezing can cause the pipe to burst leading to a huge accident. So, if you have a frozen pipe, here’s what you need to do. Follow the steps below:

  • Turn off the main water supply to your home to prevent any water from flowing through the frozen pipe and causing it to burst.
  • Open the faucet on the frozen pipe to relieve any pressure that may be building up in the pipe as a result of the frozen water.
  • To thaw a frozen pipe is to apply heat to the affected area. You can use a space heater,  a hairdryer, or a heating pad to slowly warm up the pipe. Never use an open flame or propane torch to thaw a frozen pipe, as this can be dangerous and can cause a fire.
  • Once the pipe has thawed, check for any leaks or damage that may have occurred as a result of the frozen water.

Problem 4: Taco SR503 One Zone Overheating

In this case. One of the zones in the SR503 will overheat. It needs to be addressed immediately before it starts a fire. 

Reasons:

Stuck open zone valves can be a reason behind this problem. In circulating pumps, the stuck check valve can also cause this issue. Also, a faulty switch relay itself can cause this problem. 

Solutions:

Check the zone valves or check valves. If they don’t work, check the replay and repair them as required. The Taco zone valve can indicate different lights for notifying the problem. Keep an eye on them.  

If the zone valve is stuck open, you have to fix it as shown in the following video. 

And the following video will help you with fixing the stuck check valve. 

Problem 5: Taco SR503 One Zone Fuse Keeps Blowing

In this situation, suddenly the 1 amp fuse of your SR503 will keep blowing. No matter how many times you replace it, the fuse will blow again. 

Reasons:

It happens due to a faulty circulating pump. A damaged circulating pump draws too much current to the switch relay, as a result, the fuse keeps blowing. Another reason could be damaged wirings in the circuit.

Solutions:

If you have multiple circulating pumps, check which one is blown. You will need several fuses for this test. 

Keep removing the circulating pumps one by one and run the switch relay. And check if the fuse still blows. When the fuse will not blow after removing a particular pump, that pump is faulty and you need to replace it. 

Also, inspect the wires whether they are damaged or frayed. Replace the damaged or frayed wires accordingly and see if the problem is fixed now.

Problem 6: Taco SR506 6 Zone Relay Heating Issue

In this case, one of the zones in SR506 is always hotter than the other zones. No matter how much you adjust the thermostat.

Reasons:

A faulty valve zone or check zone or a faulty switch relay itself can be the reason behind this problem. 

Solutions:

You have to solve the problem in the same way mentioned in the SR503 solution

Problem 7: Taco SR506  No Heat Is Being Sent To Any Zone

In this SR506 problem, the switch relay will be turned on and there will be power in other heating systems, but the heat won’t be circulating. 

However, this problem won’t occur all the time. Your SR506 will start acting up like this when you turn on the priority switch. 

Reasons:

The faulty relay cubes can be the reason behind this problem. A faulty circulator pump can also cause this issue. 

Solutions:

The relay cubes will be mentioned by zone names, such as Zone 1, zone 2, and so on. These are easily removable and replaceable. Remove the zonal relay cube of your priority switch zone and replace it. This should solve the issue. 

A circulator pump lasts around 2 to 6 years depending on its quality. If replacing the relay cube doesn’t solve the issue, replace the circulating pump. 

Frequently Asked Questions (FAQs):

What Does The Red Light Mean On Taco SR503?

The red light in the Taco SR503 means the switch relay is activated and receives the signal of the thermostat. It also means the zone valve is opened and the switch relay is working. 

What Is The Warranty On Taco SR501?

The warranty on Taco SR501 is 3 years from the day you installed and activated it. In the case of the shelf life, the manufacturer gives 3.5 years of warranty from the day of the shipment. 

What Does The Green Light Mean On Taco SR Series?

The green light on a Taco SR series indicates that the device is receiving power and is functioning properly. Also, the switch relay is ready for receiving instruction. 

Conclusion 

Here goes all the Taco SR Series troubleshooting. I hope after reading this article you can easily understand and resolve the switch relay problem. If you are not experienced with fixing electrical things, consult a professional. 

That’s all from me. All the best and have a great day!


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