You'll know right away when your hydronic system is out of balance – you might hear a loud noise or notice spikes in energy usage and occupants' complaints. Age and temperature tweaks will slowly throw off the system, nudging your energy bills up and thermal comfort down.
If your building's hydronic system isn't performing as well as it used to, it may be time to balance it.
When Your Building
The hydronic system should have been balanced during installation when your building was new, says Bruce Kafenbaum, senior vice president of business development for US Energy Group, a developer and supplier of building energy management systems.
But as years pass, the system can fall away from the set point. When occupants have individual temperature controls, one person's attempt to change his or her local temperature can have ramifications for others.
"You balance a building by setting it and leaving it alone," says Kafenbaum. "It's set and balanced, but typically, that's not what happens. People adjusted balancing valves because they were too hot or cold and didn't realize they affected the people upstream."
That change can set off a domino effect with your energy costs. If the unbalanced system starts making some occupants too hot, they'll respond by opening their windows, leading to an unnecessary waste of energy.
Balancing must go hand-in-hand with energy monitoring, says David Unger, COO of US Energy Group. A building energy management system will keep an eye on temperature data and other indicators that your system might need to be balanced again.
"The main thing you want to look for is the temperature spread of what you're delivering throughout the building," Unger says. "Look for an energy management system that shows your highest and lowest temperatures."
The highest temperature spread you should tolerate in distribution is 6 degrees F., Unger says, while Tour & Andersson's TA Hydronic College endorses a stricter standard of 4 degrees.
In some severe cases, the temperature spread in distribution can be up to 15-20 degrees F.
Get Back on Track
Ensuring that your system is balanced first requires a diagnostic to ensure each coil is receiving water flow, says Bhumika Lathia, technical engineer and marketing manager for TA Hydronic College. TA identifies three key hydronic conditions to look for when assessing your system:
- Design flow availability: Pipes and other pieces of the hydronic system are often oversized because they're designed to cover the maximum need and created from commercial sizes, which may not exactly fit the flow calculations made for the building. Balancing for design flows will compensate for oversizing and enable the coils to obtain the correct water flow.
- Differential pressure variations: Variable control systems are increasingly popular, TA says, due to reduced pumping costs and other factors. However, the differential pressures in the plant vary during operation, which results in higher energy costs and less stable control. Maintain the valve authority sufficiently by using a differential pressure control valve, which will restrict how widely the pressure varies.
- Compatibility between flows: If the system's flows are not compatible at all interfaces, the design supply temperature may be too low for heating or too high for cooling. Make sure the system's production capacity is always greater or equal to the distribution requirements. This will ensure the system operates as efficiently as it can at the lowest operating cost.
Janelle Penny ([email protected]) is associate editor of BUILDINGS.