Boiler 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 by 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 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 causes 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 in unnecessary energy cost 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 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 requires 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 done correctly.
Additional resource information can be found here.
Boiler Circulator Pump
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