How to Diagnose Boilers Common Issues 2025

As mid-November settles in the Northeast, heating becomes a necessity rather than a choice. For those relying on boilers, understanding common issues is crucial for maintaining warmth and efficiency. While our operations are based in Clifton, NJ, these insights apply to most boiler systems. Below, we explore five boiler problems, sorted by order of frequency, and the key components involved, offering practical tips for diagnosis and maintenance. We will be editing and adding more professional advice to this article upon your comments and interactions.

1. Zone Valve

The zone valve is critical for regulating heat delivery to specific areas (zones) within your home. Its primary functions are:

• Opening and Closing: The valve opens when the thermostat calls for heat, allowing hot water to flow through the respective zone and deliver hot water to cold room for warmth.
• Signaling the Boiler: The zone valve sends a signal to the boiler's aquastat relay to initiate the ignition process. This signal is delivered via the End Switch, which completes the circuit, firing the boiler and starting the circulation pump.

Common Issues with Zone Valves:

• Failure to Open: If a zone valve fails, hot water will not reach to target area, as such the affected zone will not receive heat. On a multi-zone installation one or multiple zones many not function properly.

• Stuck End Switch: When the End Switch is stuck in the closed position, the boiler may run continuously without a call for heat, wasting energy and overworking the system.

Maintenance Tips:

• Cascading Failures: Before replacing a zone valve, inspect other system components to rule out related issues. Such as manually closing a ball valve.

• Replacement Strategy: Replace all zone valves simultaneously if they were installed at the same time. Honeywell zone valves typically last between 12 and 20 years, with 14 years being the average lifespan.

Furnace Zoning vs. Boiler Zoning:

While zoning for furnaces involves dampers, boiler zoning relies on zone valves. This distinction means that furnace repair requires different tools and techniques compared to boiler systems.

Popular Zone Valves:

• Honeywell V8043 (4-wire): Easy to wire and operate, making it a top choice for homeowners and professionals.

• Taco 571-2: Another widely used option for reliable boiler zoning.

Efficient zoning ensures your home's heating system is tailored to meet specific comfort needs while maintaining overall energy efficiency.

2. Aquastat Relay

The Aquastat relay, commonly it is the Honeywell 8148, serves as the boiler's central control unit, managing communication between various components, including:

• Thermostats

• Zone valves

• Circulator pump

• Low-water cutoff switch

• Boiler ignition system

Role in System Operation:

• Ignition Control: Signals the boiler's ignitor to start the burner.

• Circulator Management: Activates or deactivates the circulator pump based on the heating demand.

Troubleshooting:

If the pump is not running or the burner is not firing:

1. Check the aquastat relay for faults.

2. Note that newer systems may use a PCB (Printed Circuit Board) in place of a traditional aquastat relay.

Before performing any boiler repair in Clifton or anywhere else in the Northeast, we recommend a guided diagnostic approach to identify the root cause of the issue accurately.

3. Boiler Circulator Pump

The circulator pump is responsible for moving hot water through the home's heating system. It ensures that heated water reaches all zones effectively.

Common Symptoms of a Faulty Pump:

• The boiler fires up normally, but no heat is distributed due to a lack of water circulation.

• Diagnosis Tip: A non-operational pump is easy to identify but replacing it can be time-consuming, as it often requires purging the system unless isolation valves are in place.

Other Causes of Circulation Issues:

• A closed ball valve that was mistakenly shut off can also stop water flow.

Among the most common Circulator Pumps are the Bell & Gossett, or Taco.

4. Air Eliminator or Bleeder Vent

These components remove trapped air from the heating system, ensuring proper circulation and preventing noise.

Air Eliminator Types:

• Some, like Honeywell air eliminators with threaded connections, have serviceable float valves that can be replaced.

• If a bleeder vent fails, air accumulates in the system, leading to:

Gurgling noises during operation.

Decreased heating efficiency.

General Maintenance Recommendations

• Routine Checks: Inspect all components periodically for wear and tear.

• Proactive Replacements: Consider replacing aged components like zone valves and air eliminators as a preventative measure.

• System Purging: Ensure proper air removal after maintenance or component replacement to avoid circulation issues.

By understanding these key components and their roles, you can diagnose and address heating issues more effectively, ensuring a warm and comfortable home throughout the winter.