Want to MakeYour Building Green? Pump less water in your HVAC System!
Pumping less water in a hydronic system is the easiest way to save money on electric bills every month. While this may not earn you LEED points for a GREEN building design it does go a long way toward reducing the overall energy consumption of a commercial building.
Unfortunately though, it takes more than just a design calculation to make this happen. When the system is being designed, the designer can make adjustments to the flow rate by changing the heat transfer selection criteria for coils and radiators. Out in the field though, the pump and the pipe find a “natural” flow rate regardless of the design calculation. The illustration shows how a typical pump and system curve react. Between design safety factors, and installation modifications, it’s very easy for a system to operate with 15%-20% more water than expected.
The actual flow rate is determined by the way the pipe and fittings are actually installed, and the pump’s ability to deliver water. When too much water is flowing you spend more money - money to move the water, and money to heat or cool it. You can see that the example pump operates with an extra 1.5 HP. That difference in electricity adds up over time, and is never noticed.
If the system gets the opposite though, too little water, occupant comfort is affected, and they’ll find a way to become comfortable, which usually means opening valves for more water flow and as a result, more money to operate the system. Adjusting the water flow rate is called “balancing”. Often, the pumps are larger than they need to be, and head and flow rates are over estimated. The end result is that system flow will be greater than design. Options to reduce this flow include limiting the pump discharge flow, or limiting the heat transfer devices’ flow rates.
To limit flow at the pump, a Bell & Gossett Triple Duty Valve
is used to throttle the pump flow.
The extra advantage to the system is that the built-in check valve prevents reverse system flow, and depending on the type of Triple Duty Valve, it may also reduce the number of fittings required to install the pump. Plus, limiting the system flow saves pump energy.
The other way to adjust the system flow is to balance the flow rates at the heat transfer terminals. Bell & Gossett Circuit Setter® Plus
and Circuit Sentry
™ balancing valves allow the water to be reduced to the optimal flow rate.
|Circuit Setter Plus® Calibrated Balance Valves
||Circuit Sentry™ Flow Limiting Valves
You’ll find the best source of knowledge you’ll need to achieve energy savings in hydronic systems at Bell & Gossett. Bell & Gossett focuses on the whole system in a practical way to help make your project perform the way you want.
We’ve been sharing this knowledge with the industry for more than 90 years through our HVAC Representatives, and for more than 50 years through our famous Little Red Schoolhouse
, and through involvement with industry groups. We are happy to share our knowledge with you.
TIPS: Green Design Techniques To Save HVAC System Energy Costs:
There are lots of ways to save energy in hydronic systems! When you attend Bell & Gossett Little Red Schoolhouse classes in Hydronic Systems design, you learn about energy savings techniques like these that help add to a greener environment, and a more comfortable and economical system to operate…
- Design Systems Around High Differential Temperatures
Try 14° Delta T to 20° Delta T On Chilled Water Systems and 30° Delta T to 60° Delta T On Hot Water Systems
- Limit Hydronic System Head Losses In Distribution Systems To One Half the Head Losses of Branch Piping
A 2:1 Branch To Riser Pressure Difference Ratio Allows the System to Flow 90% of Design Flow and Limits Impacts On Other Branches. It Can Also Lower Pump Head.
- Use Two Way Modulating Valves Instead of Three Way – Two Position Valves
In Typical HVAC Systems, the Last 10% or 20% of the Valve Stroke Is Needed for a Limited Number of Hours Per Year, But the Flow Is Greatly Reduced, Saving Much Pump Horsepower
- Use Variable Speed Pumping Techniques To Limit Pump Horsepower Input to the System
When Properly Combined With Two Way Valves, Pumps Can Operate Nearly the Whole Year At Less Than 20% of Design Horsepower
- Consider Using Advanced Pumping Strategies Such As Primary-Secondary-Tertiary with Variable Speed Drives To Hydraulically Organize Systems Into More Manageable Sub-Systems
- Use Dual Function Balancing Valves Like B&G Circuit Setter’s or Circuit Sentry to Help Adjust Sub-System Pressure Losses and Replace Extra and Unnecessary Shutoff Valves
Balancing Valves Don’t Add Any Unnecessary Pressure Losses To Hydronic Systems, and Help Assure Design Flow to All Circuits.