The Third Most Common Mistake Made Designing Geothermal Heat Pump Systems

This is the last part in a three part serious about the three most common errors that geothermal designers make when designing ground source heat pumps system. If you’ve been following, the main concern for a very simple reason, the geothermal industry is small but quickly growing so it’ll be best to minimize any black eyes from poor system design.

In my last two posts, I’ve outlined the first two big mistake made by designers.

1. Underestimating the importance of accurate peak heating and cooling load calculations
2. Not Giving Proper Consideration to Alternatives posted on Heating Help.com

The third mistake is simple, don’t overcomplicate the design.

Overcomplicating matters

GSHP systems are extremely reliable, yet very simple systems. Their reliability is due to a number of factors. A packaged GSHP unit has a relatively easy life because it spends the entirety of its existence tucked away in an indoor mechanical room. It won’t be exposed to adverse weather conditions, dust or salt-laden air or have to deal with the problems caused by grass clippings being blown into the coil during weekly lawn mowing occurrences in the summer.

The true beauty of these systems though, is in their simplicity. When you get down to it, we are dealing with a fairly straightforward process of moving heat from one place to another. Because of this, there aren’t that many complicated components that make up the basic, residential GSHP system.

However, all of the benefits that these systems have to offer can quickly be negated by complex (and inherently confusing) design or controls. When supplemental heating is relied on frequently due to daytime setback on programmable thermostats or improper fresh air system design, operating costs will be higher than they could be. When circulating pumps are oversized (even when VFDs are used), pumping efficiency along with overall system efficiency suffer. If a unit short-cycles frequently due to improper sizing or control, its service life and ability to maintain the comfortable levels inside the home can be reduced.

More than ten years ago, Dr. Steve Kavanaugh (recently retired from the University of Alabama) had this to say in a newsletter:

“The best commercial HVAC system currently possible is a simple one-heat pump, one-loop, one-pump GSHP (that looks very much like a residential system). While some may argue that you can’t always do this in a big building. My philosophy is that good engineers will strive to make his/her design look as much like this as possible.” – Outside the Loop, Summer 2000, Volume 3, Number 2.

I’ll have to admit that I agree with Kavanaugh’s philosophy. That goes double for residential and light-commercial systems. When not implemented properly, complicated controls and piping/pumping arrangements can quickly compromise the many benefits that GSHP systems have to offer. Also, it usually goes that the higher the level of complexity, the higher the price tag will be for your system.

Another thing to keep in mind is that as more complexity is introduced to a system’s overall design, the harder it will be for the installing contractor to match the intentions of your original design. Dr. Kavanaugh said it best with his modified version of the age-old acronym K.I.S.S., “Keep it simple and solid”.