Boilers Circulator Pumps

Learn about Circulator Pump in hydronic systems.

Circulation Pumps in Boiler Systems

Circulation pumps known as centrifugal pumps. Force the hot water from the heat source through the piping to the heat transfer unit and back to the boiler. These pumps rely on centrifugal force to circulate the water through the system. The impeller is the part of the pump spins and forces the water through the system. Circulating pumps do not add much pressure they are used just for circulation are a critical component in boiler systems, responsible for ensuring the smooth flow of water throughout the heating system.

Here, we delve into the 3 most popular circulation pump brands commonly encountered during boiler repairs: Bell and Gossett 100 Series, Taco 007, and Grundfos UPS26–99. We will also discuss their life expectancy, use cases, common problems, and key considerations for boilers installation.

At present, our focus is on slightly legacy systems, which remain available for replacement. These models are still in use due to their reliability and simplicity. However, newer models offer more advanced features, including ECMs, digital displays, variable flow capabilities, and flow rate monitoring, which will be explored in future articles.

It’s worth noting that in 2011, Xylem Inc. acquired Bell and Gossett, bringing these products under its umbrella.

Understanding Circulation Pumps

In the past, heating systems primarily relied on gravity, using the natural principle that hot water rises and cold water sinks. While this method worked for many years and is still in use today, it came with several limitations. Among the primary drawbacks were uneven heating throughout the rooms, restricted reach to higher areas, and a slower heating process. The introduction of circulation pumps revolutionized this system by rapidly moving hot water through pipes to heating terminals, such as radiators or baseboards, even to higher altitudes. This innovation not only solved these issues but also enhanced the efficiency and consistency of home heating. With a properly functioning circulation pump, you can expect evenly distributed heat and improved energy efficiency in your system.

Average Life Expectancy

On average, circulation pumps last between 10 to 30 years, depending on usage, water quality, and maintenance practices. Regular maintenance will significantly prevent boilers problems and extend their lifespan.

Popular Boiler Brands

Troubleshooting Pump Issues

Common Problems with Circulation Pumps

During boilers repair or preventive maintenance, we frequently encounter the following issues with circulation pumps:

Description: Air trapped in the system can prevent proper water circulation.
Diagnosis: Check for signs of air in the lines and ensure the system is properly purged.
Solution: Bleed or purge the system to remove trapped air.

Description: A blockage in the system, often caused by a closed valve before or after the pump, can restrict water flow. However, restrictions could be elsewhere in the system.
Diagnosis: Inspect valves and piping for blockages.
Solution: Open closed valves or clear the blockage.

Description: The motor may become stuck, preventing the pump from operating. Grundfos Circulators have an access port to check if the shaft is stuck.
Diagnosis: Measure the motor’s amp draw to determine if it is stuck.
Solution: Free the motor shaft or replace the motor if necessary.

Description: The impeller may be jammed by foreign objects, such as a rubber o-ring or gasketing material.
Diagnosis: Disassemble the pump and inspect the impeller for obstructions.
Solution: Remove the debris and reassemble the pump.

Description: Leaks may occur at the motor/body interface or flange interfaces due to poor gaskets, o-rings, or loose bolts.
Diagnosis: Identify the source of the leak and inspect the sealing components.
Solution: Replace gaskets, o-rings, or tighten bolts as needed.

Description: Even if the thermostat is calling for heat, the pump may not receive power.
Diagnosis: Check the Aquastat, Low Water Cutoff Switch, or zone control relay — the pump gets its power from one of these control components.
Solution: Repair or replace the faulty component.

Description: The motor’s windings may be open (O.L.), or shorted to ground.
Diagnosis: Measure the resistance of the windings using a multimeter and or measure short to ground.
Solution: Replace the motor if the windings are damaged.

Description: A faulty capacitor can prevent the motor from starting.
Diagnosis: Test the capacitor using a multimeter.
Solution: Replace the capacitor.

The Brands: Bell and Gossett, Taco, and Grundfos

Bell and Gossett 100 Series

  • Known for durability and robust performance.
  • Features traditional designs that are easy to maintain.
  • Ideal for larger systems requiring consistent operation.
  • Bell and Gossett 100 Series Boiler Circulation Pump.
Bell and Gossett Circulator Pump

TACO 007

Taco Circulator
  • Compact form factor, making it suitable for tight spaces.
  • Energy-efficient designs, including ECM (Electronically Commutated Motor) options.
  • Focused on user-friendly installation and maintenance.
  • The price of the capacitor at about $60 is about 1/2 of the price of a new motor. Keep in mind that replacing the capacitor could be easier than replacing the whole pump. The question is why the capacitor failed?

Grundfos UPS26–99

  • Advanced technology with quieter operation.
  • Offers both single-speed and variable-speed models.
  • Excellent for residential and small commercial applications.
  • The pump has an easy access port to check if the motor shaft is rotating freely.
Grundfos

Installation Considerations

When installing a circulation pump, one of the most valuable tips is to incorporate shut-off valves both upstream and downstream of the circulator. These valves are essential for simplifying future boiler repairs and routine maintenance tasks. By having these shut-off valves in place, you can easily isolate the circulator without draining the entire system, even if a part malfunctions or needs servicing. This proactive approach minimizes system downtime and potential disruptions, ensuring that maintenance can be completed efficiently without the hassle of emptying the entire system.

Supply Side vs. Return Side

The industry remains divided on whether to install the circulation pump on the supply side or the return side of the boiler. With boiler installation, our strategy is to always follow the manufacturer’s recommendations to ensure optimal performance.

Having said that, our experience installing the pump on the supply side provides the following advantages:

Zoning with Circulation Pumps

While some systems require only one circulation pump, additional pumps can be used for zoning purposes and target heating. Alternatively, a single pump can work alongside Zone Valves such as the Resideo for a cost-effective zoning solution.