Boiler Circulator PumpBoiler Circulator Pump: The boiler circulator pump induces the flow of hot water through the boiler and the boiler loop. Usually, the boiler circulator pump is controlled by the aquastat. However, there are various levels of control that can be found that control pumps.

One way is by the aquastat as mentioned above. Another way is an end switch in a zone valve. A thermostat in a particular zone will call for heat and the thermostat calls for the zone valve to open.

When the zone valve is fully open, an end switch closes the circuit to energize the circulator pump. Typically, the circuit is a control circuit so when the end switch closes it closes the circuit for a relay to energize the circulator pump

Boiler Circulator Pump - Proper Pump Sizing

It is important when the circulator pump is installed that the proper size of the pump is selected for the amount of flow needed for the loop. Oversized pumps can cause issues with the flow and cause efficiency issues with the system. Too much velocity causes laminar flow issues, which cause the loop not heat properly and the boiler to fire unnecessarily. It can be a big difference in fuel consumption. The circulator pump should be sized by an HVAC professional familiar with sizing circulator pumps. Furthermore, by having a professional do it, you will eliminate any performance issues which may cost you in efficiency.

It is essential when the circulator pump is installed that the proper size of the pump is selected for the amount of flow needed for the loop. Oversized pumps can cause issues with the flow and cause efficiency issues with the system. Too much velocity causes laminar flow issues, which cause the loop not heat properly and the boiler to fire unnecessarily. It can be a big difference in fuel consumption.

The circulator pump should be sized by an HVAC professional familiar with sizing circulator pumps. Furthermore, by having a professional do it, you will eliminate any performance issues which may cost you in efficiency.

Boiler Circulator Pump - Proper System Sizing and Installation

A properly sized pump in a properly sized loop will be efficient. However, if the pump is not sized properly, you can waste money unnecessarily on wasted energy in both electricity for the pump use and energy for the boiler running.

So, in that case, it is necessary to hire a qualified contractor whether that contractor is a plumber or an HVAC company to install the components and the piping system. Otherwise, you can waste a lot of money on unnecessary energy costs for an improperly installed system. That includes the circulator pump.

Bell & Gossett Pumps | Boiler Circulator Pump Service and Maintenance

Bell & Gossett is a popular brand of circulator pump used in many light commercial and residential hydronic systems. The pump in the photo on the right has many moving parts that often need to be replaced. (click on the image to see current pricing for that pump). From service calls, the most common part in need of a replacement for this pump is the coupling device that connects the motor to the impeller.

Sometimes, this coupling device breaks and needs to be replaced. This can be a result of poor maintenance on the pump which also relates to poor boiler maintenance. The pump has a bearing assembly, seals, a motor, and motor mounts that need to be inspected and lubricated periodically.

Other popular brands include Grundfos and Taco. All boiler circulator pump manufacturers offer direct drive pumps that require little to no maintenance with fewer moving parts. If changing the type or brand of pump, it is important to use a pump of similar pumping capacity. The pump curves need to match to get the same performance. Changing this could result in poor performance, which means your gas or oil bill will be higher. It could also cause issues with proper heating.

Boiler Circulator Pump - Hydronic Components - Conclusion

In conclusion, it is important to understand the basic principles of Hydronics to get the correct circulator pump to meet the velocity requirements and the capacity requirements for your system. System sizing is also important to good performance. When in doubt, consult a plumbing or HVAC specialist to make sure it is correct.

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Boiler Circulator Pump

Question from readers about Circulator Pumps
What can I do if my circulator Pump is making noise?

First, you need to inspect the pump and find the particular part that is making the noise. Assuming you have a bearing assembly the noise is likely coming from the coupling device. This is the most common part of a circulator pump that can make noise. You find a new coupling device for that pump here. This goes on the Bell and Gosset circulator pump.

Most of these pumps are red but there are some that are gold. This pump has a bearing assembly and it requires periodic lubrication. Make sure you put lubrication oil in the port on the bearing assembly to reduce or eliminate this problem in the future.

My Circulator pump is not working?

This could be another problem other than the circulator pump. Many different problems can prevent the circulation of water through the loop. Check this page for boiler loop circulation problems. It has detailed troubleshooting tips to help you with this problem.

How can I tell if my circulator pump is working?

To test a circulator pump to see if it is working you can:

  • Check the loop including all the radiators and convectors when the boiler is in heating mode. If everything is hot then the circulator pump is working. If some are hot but some are not hot or just warm check the radiator or convector for air. See the page: How to Bleed Radiators or Baseboards for more help on this problem.
  • For this check you need a clamp-on amp meter. Find one of the wires going to the circulator pump. This is likely easily done at either the pump by removing the wiring cap or where the relay is for engaging the pump. On a call for heat, when the pump should be running, place the clamp-on amp meter over the wire. You should get an amperage reading that is clode to the rating data on the pump.
How do I change a failed circulator pump?
Replacing a circulator pump is an easy task for a trained boiler technician or plumber. Hopefully, the installation was done correctly, and isolation valves were placed on either side of the pump. If not, then the hardest part of changing the pump will be getting the air out of the loop when the job is complete. The best advice is to replace the pump with an exact replacement. Never change anything when replacing parts. The new pump should have the same parameters as the old pump. The flanges should be the same and with flanges the gaskets. Rubber or heavy cork gaskets are the best.

See this page for a comprehensive list of circulator pumps.

First, turn off the power to the boiler. If you have isolation valves on either side of the pump, close the valves. Replace the circulator pump. Make sure the wiring connections are tight. Pay close attention to how you take it apart and put everything back together the same way you took it apart. That includes any wiring. When you are finished, open the isolation valves and inspect for leaks. If no leaks, restore power and turn the boiler on. Check the radiators or convectors to make sure they are receiving hot water from the boiler.

 

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