3 FM quick reads on HVAC
1. Low-Temperature Air Distribution Can Reduce Costs
Typical HVAC systems distribute air cooled to 55 degrees. If lower temperature air is used – for example, 48 degrees – both construction and operating costs can be reduced. The reason is that less air has to be moved if the temperature of that air is lower. That allows smaller ductwork and fans to be installed during construction. And operating costs are lower because less fan power is required to move the air and because the economizer mode can be used for more hours.
With low temperature air distribution, it’s important to ensure that the colder air does not reach occupants directly. It’s also essential to prevent condensation by using continuous external insulation with a vapor barrier even at spots where insulation isn’t typically used, such as the return bends of hot water reheat coils.
The use of a thermal storage system is one way to produce the colder chilled water required for low temperature air distribution
Thermal Storage Can Minimize Demand Charges
I’m Ed Sullivan, editor of Building Operating Management magazine. Today’s topic is using thermal storage to minimize demand charges.
Facility electric bills have two basic components. One is consumption – the amount of energy used. The other is a demand charge, which is based on a facility’s peak demand. The demand charge may reflect the highest peak demand in an entire year.
Thermal storage systems can help minimize demand charges. Thermal storage systems create ice or cool water at night, when rates are low, then use that ice or cool water to provide cooling during the day. That reduces consumption of power during the hours of peak demand, reducing the demand charge.
In addition to its impact on operating costs, a thermal storage system can also reduce the construction cost of the mechanical system. That’s because the HVAC system can be downsized based on how much of the peak load the thermal storage system can handle.
Life-cycle cost optimization can be used to help determine how much of the load the thermal storage system should be designed for.
When Selecting HVAC Products, Look at Part Load Performance
Iï¿½m Ed Sullivan, editor of Building Operating Management magazine. Todayï¿½s topic is the importance of the part-load performance of HVAC systems.
HVAC systems are designed to handle extreme conditions. Components of the system are sized for the hottest and coldest days of the year. On those days, the chiller or boiler is running at full load ï¿½ and at maximum efficiency.
But for the rest of the year, the system is running at part load. And in the past that has meant a sharp drop off in energy efficiency.
Today, that neednï¿½t be the case. Variable frequency drives, for example, can bring significant improvements in the part load performance of chillers. On the heating side, consider modulating boilers to achieve the same goal.
When youï¿½re evaluating HVAC equipment, determine how often your system will be running under part-load conditions. And if that will be a frequent occurrence, look for a system that will be efficient at the part-load conditions that it will actually be facing.