2021 Webinar Series - 16 Lisa Meline - Burying Mistakes
Burying Mistakes: When a GSHP Designer Trusts but Does Not Verify
Geothermal design engineers should be actively engaged in their projects from conceptualization to commissioning in order to ensure that the intent of their designs are fulfilled and operating as planned. It is very important for an engineer to oversee the beginning of construction after receiving a building permit by participating in meetings, submittal reviews, site inspections, and system start-up. The risk of delegating this responsibility to others has many implications including the possibility for litigation.
- Can you summarize the financial settlement or repair costs from the legal review of this project?
- The insurer of the project construction ended up awarding the District funding to repair the resulting damage. I do not recall the amount of the award but it was sufficient to pay for all the repairs described in the presentation 2013-14, except the cost of pulling out the y-strainers on the suction side of the geothermal heat pumps.
- Is it Lisa's position or opinion that vaults are not good after seeing what happened here?
- I am advocate for not using vaults but understand that there are times when the site conditions warrant them. Vaults add cost to a project and require confined access permits to enter them.
- Wow!!! That story should be made into a Lifetime TV movie. So scary and dramatic. Very well told. I like the conclusion about the importance of relationships. Would feel better if there was a happy ending photo at the end?
- Thank you for that excellent suggestion. I will find a happy photo to include at the end of this presentation should I be invited to give it again in the future.
- Can you explain the purpose of the coupon rack again?
- The coupon rack is used to monitor the rate of corrosion. It is a place to put samples of the metals used in the piping system in contact with the circulating fluid. By passing the hydronic fluid over the samples any corrosion in the system will also impact the corrosion of the samples. For this project we had a coupon off copper and one of steel. An initial weight is logged for each sample and then monthly the samples are removed and weighed. If there is a loss of mass (weight) corrosion is present. Based on the amount of loss, the corrosion inhibitor percentage in the hydronic fluid is adjusted.
- Are there engineer-based mechanisms to identify the likelihood that saturated soil will sink a vault?
- The soils report or geotechnical report is probably the best information to guide the vault installation. It is not clear to me who would provide that installation specification, but it seems like a good place to start a conversation between the loop field designer and the vault manufacturer - and perhaps bring in the civil/structural engineer when appropriate for support and pipe/trench detailing.
- If vaults are used as originally designed for this project, could/should some type of flexible connection be installed where the field piping connects to the vaults.
- I’m not sure what that flexible connection would look like. HDPE is already somewhat flexible and so perhaps unique to that vault/site configuration there is a piping design or routing up to the vault that would provide additional flexibility between pipe and vault should there be some movement post construction. Think about the placement of pipe loops in steel pipe to help with expansion/contraction.
- You did an extent job showing problems vs. best practices; but how about TAB issues (Testing, Adjusting and Balancing)
- The system was returned to its original configuration. The distribution piping between the building and the five loop fields was direct return; however, the piping in each slinky circuit was reverse-return. All the valves were left wide open so the flow was ‘whatever it is.’ To my knowledge there have never been any flow problems. There is likely not equal flow to each ground loop but is it sufficiently different to cause a problem? Unknown. In general, I advocate for reverse-return in all cases so that balancing is not a concern. It also eliminates the need for circuit-setters, etc. which add cost to the project. Having said that, I also do realize that there may be certain site or logistical issues that would require the addition of balancing valves. I’m not sure that I answered your question.
- Was it Calcium Orthophosphate?
- MCT501 by Cannon Water. Orthophosphate.
- Just to be clear . . . . . the piping leaks/failures were a result of settling of the vaults? Even with 36" of concrete base? Our position is that the vaults ‘sunk’ due to the additional weight of the concrete base (in moist soil) which was specified to be 12 inches by the vault manufacturer and was set to 36 inches in the field.
- Should a qualified structural engineer be involved in the vault design and construction to examine the substrate to prevent concrete vaults settling down from weight?
- See question 5 above.
- Did you have to install “new” balancing valves to rebalance?
- No. See question 7 above.
- Dilemna: of the projects that I was called to diagnose and help with lack of operation performance, I discovered a significant lack of attention to detail in geothermal "holistic" approach to the ground loop, pumping and distribution location and building equipment piping and control. When I confronted (very diplomatically) of the "shortcomings" of the design, implementation and oversight of the initial project, all of the PE's projected the responsibility of the performance and glitches to the mechanical contractors. When the contractors were approached, they said, they built it as it was depicted. I don't understand why and how engineering firms in their contractual specifications, eventually deflect "operation, installation and performance" to the installing contractor. So what is the engineer's responsibility supposed to be? Very frustrating. Also, in my personal opinion, ground vaults should only be installed underground in an absolutely last, last ditch effort due to lack of above ground space for pumping...and distribution systems.
- We need better training for engineers and for installers. We also need to look at our contracting practices. In some instances Design-Bid-Build contracts set up an adversarial dynamic because any error the engineer makes can be used to bill for a change by the contractor. And bad designs and poor specification language puts too much responsibility back on the contractor. The end result is that low bid can often lead to a higher project cost and systems that do not perform well. I don’t have an answer other than to work on building relationships and teamwork which improves the geothermal industry for everyone including building owners (our clients).
- Synopsis, someone needs to take totally responsibility of the the total design, installation and operational performance. If not there will only be finger pointing and "not my problem" will result. I personally take total responsibility of all of it. Because 44 years of experience can do that.
- The engineer needs to take responsibility for the design (inside the building and outside the building). They need to work to provide a design that meets the Owner’s Project Requirements. The point of this presentation is that engineers also need to oversee their designs during construction to head off some of the installation issues I shared as examples. See question 12 above. Including working as an engineering tech during college I only have 38 years of experience!
- Has the system had any flow issues since re commissioned? I've seen 8-12" strainers in hospitals/schools, get clogged enough to stop a 30 ton chiller in its tracks. I agree with you, the 8" strainers should have been cleaned and re oriented for regular service as a priority
- Other than the sticky poly valves I mentioned, I have not been made aware of any problems. In this business no news is good news. We typically only hear about problems -- not when things are going well.
- MCT 501C is a phosphate blend - no need to further elucidate - it was just idle curiosity.
- Yes, see 8 above.