GSHP Review 1

[widstje]

I'm a civil engineer at the city level in Virginia. I review residential construction site plans, among other things. We had our first developer come in with a plan to install a GSHP using a horizontal field. Given I am the only individual in the city with a geotechnical background it seemed fitting I should review the plan.

The state's building code requires residential GSHP designs to be done by a licensed HVAC contractor. Our building official, nor I, have any experience with these systems.

The question is: Should we rely on the designer/installer's (who is certified by IGSHPA for installation) work as long as the load calculations for the home are sufficient for the building official? Or do we hire a consultant to review soil conductivity, length/diameter of pipe, Re, earth temperature, pump size... It would seem possible overkill for a residential.

So far I've asked for the design to be shown on the site plan so I can review for possible interference with the utilities and stormwater BMP. When I asked for calculations to verify the design I was met with resistance, stating other localities have never required those for the HVAC permit. I tried to contact adjacent localites for an answer and they passed me around and I never got an answer.

 

[ChasBean1]

Better you in public service than me! You're overbearing and adding cost if you do, and you're negligent if you don't.

I think your approach is right. Let them do their job, but just make sure they're not planning to drill through a gas main in the process.

If the calculations are off, result would be a thermal comfort issue and probably not a life safety issue, so from a city standpoint I'd let their certification stand in lieu of a peer review.

Probably most "licensed HVAC contractors" will be in the same boat as you and the building official as far as these systems go.

 

[willard3]

There are certainly life-safety issues...consider a refrigerant release and asphyxiation.

If you don't feel competent, hire a Professional Engineer who does ground source heat pumps.

 

[ChasBean1]

There are risks with everything, and if you want to, you can find a way to create a need to officiate everything. Just not with my tax dollars, please.

I didn’t get a refrigerant release asphyxiation certification from a public official with any refrigerator or air conditioner that I ever bought. I personally don’t want my tax money to go to public offices putting guarantee risk free stamps on everything.

As far as your role is concerned, make sure they don’t blow up the neighborhood or screw the community in some regard. Don’t feel like you need to peer review their work.

 

[AbbyNormal]

check that the loop is not closer than say 10 feet to the property line. Make sure it clears water lines, septic fields etc.

Ask for a load calculation, compare equipment heating and cooling capacities to expected loop temperatures that will coincide with dead of winter and late summer. Heating capacity depends on the temperature source that you can extract the heat from.

Ask them for a calculation that proves water flow in the loop will be turbulent.

Ask them for documentation that verifies the length of the loop.



Take the "V" out of HVAC and you are left with a HAC(k) job.

 

[AbbyNormal]

I used to have to submit all of that, as well as a pump head calculation and proposed loop static pressure charge to qualify for rebates in the late 80s. The Canadian Earth Energy Association had an inspector coming behind you to double check the installation prior to the customer getting the rebate.

Take the "V" out of HVAC and you are left with a HAC(k) job.

 

[AbbyNormal]

Anything can look great on paper. I do not see it as asking for info up front adds greatly to the cost.

At least if you have the design documented, you are one quarter the way through the process of having a system that actually works.

Then it requires a proper installation, so there is another 50% of what it takes for a successful system.

The remaining 25% is verifying the install and verifying that the builder built the damn house correctly in the first place.

Take the "V" out of HVAC and you are left with a HAC(k) job.

 

[MintJulep]

When I asked for calculations to verify the design I was met with resistance, stating other localities have never required those for the HVAC permit.

So your reply is "Well here we ALWAYS require them."

 

[ChasBean1]

We were running a study way back when for indoor air quality in buildings. One of the things we recorded each study was barometric pressure. So we were in Denver, Colorado and recorded the value of 24 (plus or minus) inches of mercury. The city’s about a mile high and has about 83% of sea level atmosphere density. As it was a study for the government, our government auditor got airport data to verify our readings. The airport data was corrected to sea level. The auditor concluded that the difference in pressure between the inside and outside of the building we studied was 5 inches of mercury.

Most of us (hopefully) in HVAC engineering understand that this pressure would equal about 70 inches w.c. difference which would absolutely implode the building. They concluded our readings were faulty, which led to additional government attention, which led to additional government attention, which finally reached someone who said “wtf?” which led to the fact that it was a non-issue to begin with, several thousands of dollars later.

The point of this small story is let people do their jobs. Government intervention adds cost but does not always add value. The government’s job should be to stop folks from getting f’d by negligence. It should never be for peer review. That’s too much responsibility for folks who have too many concerns coming from too many angles, with too little funding.

 

[AbbyNormal]

NASA must of crashed a 100 million dollars of probes into Mars because of a propblem with highly educated people mixing up IP and SI.

Ground source jpobs need to be sized right on the money and done properly.

Take your logic of governement intervention then and apply it to the governement entity that is licensing these contractors in the first place.

I think after a few plan reviews and inspections, the OP will have separated the men form the boys so to speak

If everyone did their jobs correctly there would be no need for inspectors at all. There would also not be a need for air balancing or commissioning then either. Should be able to just slap the equipment in, hook up the power, flip the switch and walk away.

Take the "V" out of HVAC and you are left with a HAC(k) job.

 

[widstje]

Thank you for all the comments.

In my job I see way too many state licensed engineers (and this is coming from a PE) produce plans with errors and omissions. You'd hope the professional individuals would only stamp plans that were thoroughly reviewed in-house but it doesn't appear so because mistakes are usually blatant. The local government entity becomes the quality control and in some cases the designer. I believe poor submittals are a function of laziness, greed, lack of knowledge, limited time constraints... It truly is a shame. The part that burns me is when the engineer tells the owner the city is holding up the plans because of review time. If we had a competent engineer with a complete submittal reviews would take a fraction of the time.

With all this said, I don't feel asking for design calculations is a burden that increases the cost to the owner. The designer should have done the engineering and have it readily available when asked. Otherwise, what were they basing the design on?

 

[ChasBean1]

Abby and widstje,

You are both 100% right that many out there are not what they sell themselves to be and produce poor work. Believe me; I’m in a private business working for owners to try to limit this.

My beef: it’s Not the government’s job to peer review. Cited:
“The local government entity becomes the quality control and in some cases the designer”

If there really is a performance concern based on specs or submittals, it’s not a public role to rectify that. If you’re trying to verify whether a ground source heat pump will work or not, you’re in the wrong position. If you’re trying to verify neighbor X won’t be killed by neighbor Y running their new GSHP, that’s a public official’s role.

Again, I agree with both of you in principle, and we all have opinions on what is good and bad, but we all have to play the role that we’re in… The role funded by taxpayer money is not on the peer review level.

 

[cry22]

Asking for calculations is NOT an exagerated request at all.

There is a thing out there that "sizing" of GSHP is a top secret knowledge and should not be shared.

The basic rule of thumb that contractors out there use for GSHP goes like this: 1-ton per bore, between 200 and 300 feet deep depending on soil, 400 SF per bore (20 feet on center) they tend to go a little deeper to make sure there is no need for a cooling tower (that's for the consciencious ones)

Because of length of piping, these systems are typically pumped in series (push/pull).

Make sure that the loop has a "reverse return" piping design.