How To Change a Zone Valve

Figure 1: Boiler room with a heating system

Replacing a zone valve is necessary when it fails, leading to heating inefficiencies or disruptions in specific zones. Zone valves ensure efficient temperature control in different areas by regulating the flow of hot water to them. Each zone or piping loop has its thermostat connected to a boiler zone valve. When the temperature drops below the thermostat setting, the valve opens to allow more hot water to flow. Conversely, it reduces or stops the flow when the temperature is above the setting. This article is a step-by-step guide to identifying and replacing a faulty zone valve.

Locate the zone valve

Zone valves are usually found near the boiler, connected to the main supply lines that distribute hot water throughout the building. Ideally, each valve should be labeled to indicate which area it controls (e.g., "Living Room," "Upstairs Bedrooms"). If not labeled, you can identify them manually:

1. Turn up thermostats: Set all thermostats in the building to their maximum setting. This should open all zone valves, allowing hot water to flow.
2. Observe the valves:Return to the boiler room and check the valves. In a functioning system, all valves should be open.
   1. A ball valve with continuous position feedback provides real-time information about the valve's position to a control system.
   2. To identify an open electric ball valve without a visual indicator, listen for the sound of water flowing through the pipes, which suggests the valve is open. Additionally, feel the pipe downstream of the valve; if it's warm, hot water is likely passing through, indicating the valve is open.
3. Identify the faulty valve: If a valve remains closed while others are open, it is likely defective, preventing hot water from reaching its zone.

Figure 2: Belimo zone valve

Signs of a faulty zone valve

Boiler zone valves endure high temperatures, leading to wear and tear. If not addressed, faulty valves can reduce the boiler's efficiency and lifespan and cause discomfort due to improper heating. Here are some signs that the boiler zone valves may be malfunctioning:

• No heat: A zone that stays cold may have a stuck valve. Check for mechanical or electrical issues and manually override if necessary.
• Uneven heating: Some zones may become too hot or cold when valves are stuck open or closed, causing unintended heating in certain areas. For example, activating the thermostat in one room might accidentally heat another.
  • Some valves include a manual switch for overriding the thermostat. This feature might be used to keep a faulty valve open, which can disrupt the zoning system. Manual switches set to "on" in a new building could indicate a defective valve.
• Leaking valves: Leaks at pipe connections can be repaired, but valve leaks usually require replacement.
• Banging or hammering: Changes in pressure can cause valves to produce loud noises when the thermostat is adjusted. Switching to slow-close valves can help mitigate this issue by reducing sudden pressure changes.

Note: Ensure thermostat settings are correct, which can cause uneven heating or noise.

How to replace a zone valve

Tools and materials needed

• New zone valve
• Wrenches
• Bucket
• Cleaning cloth
• Heat source (e.g., a heat gun or torch)
• Screwdriver

How to change a zone valve

1. Diagnose the problem:
   1. First, determine whether the issue is with the actuator or the valve.
   2. Test the actuator by manually operating it or using a multimeter to check for electrical issues. If the actuator is faulty, replacing it might resolve the problem. Recheck the system to ensure functionality.
   3. If the valve is stuck or leaking, it needs replacement.
2. Safety precautions:
   1. Turn off the power to the heating system to avoid electrical hazards.
   2. Shut off the water supply to the specific line where the valve is located, ideally before the valve, to prevent leaks.
   3. Drain the system or at least the section of the line where the valve is being replaced to minimize water spillage.
3. Remove the zone valve:
   1. If only the valve needs replacement, disconnect the wiring and unscrew the entire valve assembly.
   2. If replacing both the valve and actuator, remove the actuator first to make handling more manageable, but this is not strictly necessary.
   3. Place a bucket under the valve to catch any residual water that may spill out.
   4. Use a wrench to loosen the threaded connections and turn the valve counterclockwise to unscrew it. Be cautious, as the valve may remain hot after the boiler is off.
4. Clean the fittings:
   1. Once the valve is removed, clean the threads of the fittings with a cloth. This ensures a proper seal when installing the new valve and prevents leaks.
5. Install the new valve:
   1. Install the new zone valve according to the user manual. Ensure the connection size matches the system it will connect to.
   2. Install the valve and actuator as a single unit if they are designed to be assembled before installation.
6. Reattach the electrical components:
   1. If the actuator was removed separately, reattach it securely to the valve.
   2. Connect the wires correctly, matching the colors to their respective terminals.
7. Test the system:
   1. Turn the water supply and power back on.
   2. Check for any leaks around the new valve. If everything is secure, the system should operate without issues.
8. Bleed the system:
   1. After replacing the valve, bleed the system to remove any introduced air. If the system has an automatic bleeder, this may not be necessary. Otherwise, manually bleed the system for optimal performance.
9. Final check:
   1. Increase the heat setting in the area and ensure that the zone valve opens appropriately.

Read our electric ball valve installation and wiring articles for more information on the installation process and detailed wiring diagrams.

FAQs

How to install a zone valve?

To install a threaded zone valve, shut off the system, drain the water, apply a sealant to the threads, connect the valve to the pipes, and secure it with a wrench.

How do you know if a zone valve is bad?

A bad zone valve may cause no heat in a zone, uneven heating, leaks, or loud noises.