Images of sky scrapers in city

Reduce HVAC energy consumption with Siemens Pressure Independent Control Valves

By: Jack Kang, Product Portfolio Manager, Byran Blackham, Valves Senior Product Manager, Siemens Smart Infrastructure USA

Buildings contribute to nearly 70% of our nation’s energy usage and we know most organizations have a commitment to achieving sustainability goals. Taking one step at a time helps make improvements that will have a positive impact on the environment and to your bottom line.

 

Buildings that use hydronic heating and cooling can minimize HVAC energy consumption by over 30% by optimizing hydronic flow. Improving hydronic flow increases overall building efficiency, operational performance, and overall comfort. Hydronic flow optimization helps system performance by improving  delta-T through precise control using the right mix of valves, variable frequency drives and differential pressure sensors for optimal hydronic balancing.

 

Let’s review Pressure Independent Control Valves (PICVs) and the many benefits PICVs offer as part of implementing hydronic flow optimization in a building. PICVs boast an easier installation process, a smaller footprint, fewer leak points, faster response time, and higher reliability than standard control valves and electronic dynamic balancing valves. In addition, choosing PICVs in a hydronic system up front can lead to greater energy efficiency and significant savings in first costs, maintenance costs and performance costs. The Peachtree Center commercial office building in Georgia achieved significant cost savings while improving tenant comfort deploying PICVs.

 

Commercial office buildings consume a large amount of energy and water to heat and cool the indoor environment. The Peachtree Center was no exception, and the hot, humid Atlanta summers made the challenge even more daunting.

 

The main concern at Peachtree was that the tenants in the building couldn’t get the temperature where it needed to be in the summer. Part of the problem was the older equipment in place. The hydronic HVAC system relied upon pneumatic butterfly valves to control the flow of water through the air handlers. To get more chilled water to the furthest zones of the building, the valves were opened wider, but that had the negative effect of pushing the water through the air handling coils too fast to transfer cooling energy properly. On top of that, chilled water was required, which made the problem worse.

 

This cycle resulted in a costly waste of energy for Peachtree Center. The chiller and pumping systems were both overworked. They were using 75% more water than was needed for zones that had the right temperature when they still needed it for other zones that were too hot. Even though they could make the water temperature what they needed, they just couldn’t deliver it properly. The pneumatic valves themselves were also at risk – continuous temperature adjustments, or “hunting,” increased the chance of them breaking.

 

To solve this issue Siemens developed an innovative and cost-effective solution: replace existing pneumatic butterfly valves with 2-way PICVs. This option made sense because PICVs automatically respond to pressure changes in the hydronic system. The integrated differential pressure regulator keeps pressure across the internal control valve constant while also keeping volumetric flow constant. So, even with a rise or drop in pressure, the PICV keeps flow constant which ensures that water maintains the desired flow for optimal comfort. With PICVs, the valves no longer need to “hunt” for the right flow. This allows the whole HVAC system – valves, pumps, and chillers to work easier, reducing the amount of energy used as well as wear and tear on equipment.

 

The Siemens PICV is a three-in-one device that combines a control valve, adjustable flow limiter, and automatic pressure regulator. PICVs provide greater control of water through the air handling coils, improving the accuracy and reliability of chilled water throughout the HVAC system. One major difference with Siemens is that the field adjustable flow limiter is independent of the valve stroke. With other PICVs, the way a reduced maximum flow through the valve is set is by limiting the control valve stroke. By reducing the flow, the valve stroke is reduced. Since the Siemens PICV maximum gallons per minute (GPM) setting is independent of the valve stroke, you can maintain full valve stroke and full controllability, regardless of the maximum flow setting of the PICV.

 

After switching to PICVs, Peachtree Center can set the exact GPM flow for each zone, providing greater control over the discharge air temperature. Peachtree Center installed two, 3” Siemens PICVs within each of its four air handling units. By using PICVs, they saved money and eliminated the need for two valves – a flow control balancing valve and a globe valve. All functions were integrated into a single unit, simplifying installation and improvement in system performance was immediately noticeable. Barry Jacobs, Chief Engineer at Peachtree noted, “My chillers and pumps are running at really low rates. The first day that it reached 80°F, we were only pulling 75% of full load.” More importantly, tenants have been receiving the level of air conditioning they need to maintain an optimal working environment.

 

Siemens PICVs reduced Peachtree Center’s energy usage by 13.8% and greatly improved control over chilled water, which allowed operators to engage only one chiller and its associated pumps and cooling towers. Prior to installation, two chillers were needed under similar conditions. Eliminating the need for the extra pump and cooling tower resulted in significant savings for Peachtree Center.

In summary, Siemens PICVs help achieve your design intent with energy savings while maximizing comfort through hydronic flow optimization. Read the full Peachtree Center Case Study for further details on how installing PICVs to optimize hydronic flow is one step you can take to reduce HVAC energy costs and bring balance to your bottom line.

 

Additional Resources:

Discover Hydronic Flow Optimization

Learn about Pressure Independent Control Valves