HVAC Systems
The second step to achieve energy and HVAC system optimization is knowing your system. Your HVAC system is critical to your interior environment, but it also represents a large component of your utility expenses. While it is beyond the scope of this article to discuss every system, a few recommendations can be addressed. Every HVAC system component has increased in efficiency over the years. If your system is more than 13 years old, it's time to begin planning for an upgrade to new equipment. Well maintained residential systems have a life expectancy of about 15 years or so but seem to fail at the worse times. Have a replacement plan ready for the day your equipment fails.
Commercial systems vary, but if your building is using packaged equipment or split systems, the same lifetime can be expected. For larger commercial systems and industrial applications, the HVAC system may be more complex and require an individual analysis by a mechanical engineer. As I said, HVAC systems vary and no one-size-fits-all analysis works for larger systems. What all these systems have in common is they are normally fueled by electricity. Electricity cost money, so any efforts in the direction of increased efficiency is a plus.
HVAC System Tips:
Find a qualified consultant you trust. If you are a home owner or small commercial building owner, find a good HVAC company or mechanic to evaluate and maintain your system. If you are a large commercial building owner, find a commercial HVAC company for normal maintenance and a good mechanical engineer for specific guidance. I do not recommend using a mechanical engineer employed by the HVAC Company; find a third party engineer for unbiased information.
Verify your HVAC system load. Home owners should use ACCA's Manual J calculation method and all others should have a load conducted by a mechanical engineer. Commercial buildings have more requirements related to code conformance, minimum ventilation rates, etc and are individual to each building.
Load reduction-Read the information above.
Select equipment sized for your load. NEVER OVERSIZE! More-is-better does not apply for HVAC systems. It will cost more to purchase the equipment as well as operate it. Get the load and the equipment selection right the first time.
Purchase high efficiency or Energy Star equipment. Many of the new systems include variable speed drives for fans and compressors. Over the years of ownership this will be paid back many times over. Compare standard efficiency equipment to high efficiency equipment in terms of initial cost and life cycle costs. Any good HVAC company or mechanical engineer can obtain this information.
Consider some form of energy recovery for any air exhausted from the building and use it to condition the incoming fresh air. This is air you have paid to condition, so extracting some of the energy before exhausting it should be a priority.
For large commercial buildings, consider conditioning the outside air with a dedicated outside air unit. This will eliminate any problems related to humidity control in most instances. It will also increase occupant comfort and allow for further downsizing of equipment.
Commercial buildings should consider economizers on their equipment. Most current codes require economizers on equipment over 15 tons in size. Often available at a low incremental cost, these units draw in fresh air from the outside when the temperature (sometimes humidity) outside is lower than the temperature inside.
Home owners and small commercial building owners should install programmable thermostats. Commercial building owners should install a Direct Digital Control (DDC) system. The investment in either of these will pay back more than the cost in a small amount of time. Read more below.
Control Systems
The third step to achieve energy and HVAC system optimization is controlling your system.
Programmable Thermostats-The age of digital controls has made saving energy easy. One of the best investments for the homeowner or small commercial building owner is a programmable thermostat. These are simple to use and incorporate strategies based on time scheduling. Most manufacturers offer 7 day programs and setback/setup programs which will turn the HVAC system on and off to compliment your schedule and desired indoor temperature. This is a great way to ensure HVAC systems are used only when necessary.
DDC Systems-For the large commercial building, I consider this as a must have system. Installation costs have steadily decreased and the performance reliability has steadily increased. They can be integrated into any system and expanded as required. Some of the more popular features of these systems are optimized start/stop of the HVAC system, multiple zone control, multiple temperature sensor locations and ventilation control. The best part of these systems is their ability to be scaled up to the largest of commercial applications. This means you can install a simple system and add more controls later to incorporate your whole HVAC system. Again, the payback is short and well worth the investment.
The second step to achieve energy and HVAC system optimization is knowing your system. Your HVAC system is critical to your interior environment, but it also represents a large component of your utility expenses. While it is beyond the scope of this article to discuss every system, a few recommendations can be addressed. Every HVAC system component has increased in efficiency over the years. If your system is more than 13 years old, it's time to begin planning for an upgrade to new equipment. Well maintained residential systems have a life expectancy of about 15 years or so but seem to fail at the worse times. Have a replacement plan ready for the day your equipment fails.
Commercial systems vary, but if your building is using packaged equipment or split systems, the same lifetime can be expected. For larger commercial systems and industrial applications, the HVAC system may be more complex and require an individual analysis by a mechanical engineer. As I said, HVAC systems vary and no one-size-fits-all analysis works for larger systems. What all these systems have in common is they are normally fueled by electricity. Electricity cost money, so any efforts in the direction of increased efficiency is a plus.
HVAC System Tips:
Find a qualified consultant you trust. If you are a home owner or small commercial building owner, find a good HVAC company or mechanic to evaluate and maintain your system. If you are a large commercial building owner, find a commercial HVAC company for normal maintenance and a good mechanical engineer for specific guidance. I do not recommend using a mechanical engineer employed by the HVAC Company; find a third party engineer for unbiased information.
Verify your HVAC system load. Home owners should use ACCA's Manual J calculation method and all others should have a load conducted by a mechanical engineer. Commercial buildings have more requirements related to code conformance, minimum ventilation rates, etc and are individual to each building.
Load reduction-Read the information above.
Select equipment sized for your load. NEVER OVERSIZE! More-is-better does not apply for HVAC systems. It will cost more to purchase the equipment as well as operate it. Get the load and the equipment selection right the first time.
Purchase high efficiency or Energy Star equipment. Many of the new systems include variable speed drives for fans and compressors. Over the years of ownership this will be paid back many times over. Compare standard efficiency equipment to high efficiency equipment in terms of initial cost and life cycle costs. Any good HVAC company or mechanical engineer can obtain this information.
Consider some form of energy recovery for any air exhausted from the building and use it to condition the incoming fresh air. This is air you have paid to condition, so extracting some of the energy before exhausting it should be a priority.
For large commercial buildings, consider conditioning the outside air with a dedicated outside air unit. This will eliminate any problems related to humidity control in most instances. It will also increase occupant comfort and allow for further downsizing of equipment.
Commercial buildings should consider economizers on their equipment. Most current codes require economizers on equipment over 15 tons in size. Often available at a low incremental cost, these units draw in fresh air from the outside when the temperature (sometimes humidity) outside is lower than the temperature inside.
Home owners and small commercial building owners should install programmable thermostats. Commercial building owners should install a Direct Digital Control (DDC) system. The investment in either of these will pay back more than the cost in a small amount of time. Read more below.
Control Systems
The third step to achieve energy and HVAC system optimization is controlling your system.
Programmable Thermostats-The age of digital controls has made saving energy easy. One of the best investments for the homeowner or small commercial building owner is a programmable thermostat. These are simple to use and incorporate strategies based on time scheduling. Most manufacturers offer 7 day programs and setback/setup programs which will turn the HVAC system on and off to compliment your schedule and desired indoor temperature. This is a great way to ensure HVAC systems are used only when necessary.
DDC Systems-For the large commercial building, I consider this as a must have system. Installation costs have steadily decreased and the performance reliability has steadily increased. They can be integrated into any system and expanded as required. Some of the more popular features of these systems are optimized start/stop of the HVAC system, multiple zone control, multiple temperature sensor locations and ventilation control. The best part of these systems is their ability to be scaled up to the largest of commercial applications. This means you can install a simple system and add more controls later to incorporate your whole HVAC system. Again, the payback is short and well worth the investment.
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