By, Ryan Carda
We make web-based ground loop design software, and we are very proud to now say that we have two products in our arsenal:
- LoopLink RLC is for residential & light-commercial applications
- LoopLink PRO is for commercial applications
Both have their place. With the recent addition of LoopLink PRO to our offering, we're now being asked about when it's appropriate to use one over the other. Given the fact that heat transfer in the ground is the same in a residential system as a commercial, which one do you need for a given application?
Even though PRO can be used to design a system of any size and scope (residential or commercial), RLC will make life much easier for the residential designer. This article will help you decide which is better-suited to meet your needs.
What is a “residential” system?
Generally speaking, you can use “residential” ground loop design software on any building where its heating and cooling loads are closely tied to weather conditions. In such a system, there is minimal need for consideration of how the building is being occupied or used. There aren't large amounts of internal gains, occupancy rates, ventilation requirements, industrial processes, etc.
- Any size home, no matter if it is large or small
- Multifamily residential buildings such as apartments or condos
- A large warehouse or storage building with little to no internal gains
- Small office buildings with light occupancy schedules and minimal fresh air requirements
The simple relationship of load to outside air temperature can be used to develop a load profile graph, like this one:
Once the building load profile is generated, it is also a straightforward process to determine how much a heat pump will have to run, how efficient it will be, how much it will cost to operate, how much will required of the ground loop, etc. Because of the predictable behavior of a residential building, RLC can use a small amount of information (peak heating and cooling loads along with project location) and use it to perform a full-fledged energy analysis. It doesn't really matter how big the system is. As long as there is a linear relationship between the building loads and the outside air temperature, the bin method can be used to predict how much heating or cooling will be required.
What is a "commercial" system
For a commercial building, the energy modeling process is quite a bit more involved. The heating and cooling load profile depends on how the building is being used rather than the weather conditions. For example, a manufacturing facility, large office building, or data center would very likely need cooling even when the outdoor air temperature is 40°F. This is a stark contrast to a “residential” application that would definitely need to be heated to maintain thermostat set point at the same temperature. A load profile for a commercial building could look something like this:
Image Courtesy of Ed Lohrenz, GEOptimize
As you can see in the graph, some cooling is required even during the cold winter months. To accurately determine the heating and cooling requirements for a commercial building, you need to consider:
- Occupancy (number of people)
- Occupant activity levels (exercising vs. sitting at a desk, etc.)
- Ventilation (fresh air)
- Light power density
- Internal gains – amount and type depends on the building
- Offices - computers, monitors, copiers, appliances, etc.
- Manufacturing facilities - CNC machines, paint booth, welders, etc.
- Restaurant – range, oven, coolers, etc.
Not only do you need to consider how much each process or component will contribute to the heating and cooling requirements for a building, but you also need to consider when each is used (e.g. – schedule). Attention to detail is critical for this time-consuming process.
There are many programs that are well-suited to model a commercial building. These programs use the hour-by-hour method rather than the bin method for the energy calculations. Here are a few examples:
A good portion of the heavy lifting (e.g. - the energy model) is done outside of ground loop design software. But by decoupling the energy model from the ground loop design calculations, you can analyze a much more complicated system. Each of the programs listed above will export the data in various formats. The outputs are the result of a lot of hard work but are condensed into a usable format that can be directly imported to PRO.
As previously mentioned, PRO could be used to design the ground loop for a residential system. However, it doesn’t perform energy modeling calculations so, you would need to obtain that information elsewhere. For a residential application, it would save a lot of time and effort to use LoopLink RLC for the design because it will perform the energy modeling calculations for you.
It’s all about the energy.
When trying to decide which program is for you, remember the key distinction between residential and commercial applications from a ground loop design standpoint. Ask yourself this question:
Can the heating and cooling requirements for a building be accurately predicted with weather data alone, or do you also need to know something about building usage and its schedule?