2021 Webinar Series - 14 Lisa Meline - Better GSHP Design

Grounded in Reality: Better Ground Source Heat Pump Design

The diligent design engineer has a multitude of design resources available to them. However, even with these resources, engineers are reluctant to tackle the ground loop design portion of a ground-source heat pump system. During this session, Lisa provides a step-by-step approach to developing a good ground-source heat pump system with references for further study and examples to learn from. Goal: Design engineers will build confidence in providing both the “inside” and “outside” designs for their projects through understanding the relationship to each other and to the overall system performance.

Speakers: Lisa Meline / Meline Engineering

 

If you are interested in CEU credits for this session click here


 

Recording

 

 Slides


 

Q&A

  1. Can you use GSHP to heat water for an existing hydronic heating system?
    1. Answered live. Provided two things are possible:  the hot water design temperature is achievable with a heat pump (not 160-180F for example), and that there is a possibility of rejecting heat into the earth from a cooling source to provide an offset to the heat extraction from the earth for heating.  I don’t recommend designing a 1-way heating or cooling system for connection to a ground loop.
  2. Two Vertical loops in series are prone to creating an air trap, have you seen this?
    1. Answered live. Lisa has not seen this, but if you do a good job flushing you should be able to get that air out. It would be rare to have an air trap.
  3. The list of vertical loop types didn't include large-diameter, shallow holes that are created with augers rather than drills. (i.e. GeoColumns, Helical exchangers, etc.). Why weren't short, fat holes included in the description of vertical types?
    1. Answered live. Two reasons, 1 - personal bias because I am familiar with the work that was done at UC Davis and they have (in my opinion) specific applicability because of shallow earth depth & because you really need moisture in the soil to perform well. 2 - Because of my work with codes & standards I am concerned that the AHJ may consider this type of ground heat exchanger a more open pathway for groundwater contamination (than say for a small diameter vertical loop).
  4. To evaluate velocity of water through pipe, does the designer return to the site after the installation? How is the velocity measured, at what point in the closed loop? Is an instrument dropped into the loop.
    1. Answered live. Specify info on drawings - How many gallons per minute of flow is needed to flush heat exchanger and how many loops/circuits is needed in design.  Require a report from the contractor that this is done with the pressure testing information and for commercial projects, a sign off by the general contractor.
  5. What are your thoughts on the various antifreeze choices?
    1. Answered live. I would first not design for antifreeze and then if I need it I would use propylene glycol.
  6. You didn't talk about antifreeze.  What's your feeling about skipping antifreeze in loops where the deep earth is in the mid-50's or higher to save cost and gain some capacity?
    1. Answered live. Typically in California - the authority having jurisdiction will tell you what you can use - propylene glycol is what is allowed. 
  7. Will you provide the recorded versions of sessions later?
    1. Yes.
  8. Are there any free/low cost ground loop calculators that you recommend?
    1. Answered live. If you go to Dr. Steve Kavanaugh’s website - there is a lot of free design tools for anyone to download. https://geokiss.com/
    2. I use his software & Loop Link.
  9. Also, the easiest way to convert a hydronic system to geothermal is with a Double Hybrid heat pump from Energy Catalyst!