Video: Burying Mistakes

Wednesday, March 1, 2017

Duration:

31:45

Description

Industry leader, Lisa Meline, P.E. shares a cautionary tale about what happens when geothermal designers trust but don’t verify. A failure analysis of a system points to a design that was sound in principle but not properly overseen during installation. The result was of course an expensive analysis and repair that could have been avoided.

About the Presenter

Lisa Meline, P.E.
Meline Engineering

Ms. Meline is principal engineer and owner of Meline Engineering. She has 25 years of mechanical engineering experience and over 30 years of experience in the construction industry.

Ms. Meline is a licensed professional engineer in four western states and a Certified Geoexchange Designer. She is Standards Sub-committee Chair for ASHRAE TC6.8, Geothermal Heat Pump and Energy Recovery Applications, Chair of IGSHPA’s Standards Committee, and recently served as Special Expert on the IAPMO Uniform Solar Energy and Hydronics Technical Committee.

Ms. Meline is an ASME Fellow and one of the founders of the California Geothermal Heat Pump Association.

Top 6 Reasons to Install a Geothermal Vault

Monday, February 27, 2017

Although some may argue against the upfront cost, there are many advantages to the use of geothermal vaults in large commercial projects. It can save both the owner and installer time and money over the long haul.

Here are the top six reasons for using a geothermal valve vault in a commercial loopfield according to Stuart Lyle, Director of Geothermal Sales at ISCO Industries.

Photo courtesy of ISCO Industries.

1 Create More Space

A vault can free up valuable area inside of a mechanical room by greatly reducing the number of pipes entering the building.

By utilizing a vault to create a manifold space outside of the building, the system designer can:

  • Maintain the integrity of the building by reducing the number of cored holes that must be drilled through the wall or foundation
  • Create more space for other system components such as pumps and controls
  • Decrease the loopfield contractor’s time inside of the mechanical room, which helps keep the project on schedule by reducing the need to coordinate work times with other trades

2 Separation of Scopes

Vaults not only serve as a central location for circuit piping, they also provide a clean stopping point for the loopfield contractor until system commissioning takes place. In new construction projects, the geothermal scope is often one of the first to get underway and also one of the first to finish. With a vault, geothermal contractors don’t have to wait on the mechanical contractor to finish their scope.

With a vault acting as a stopping point between the loopfield and building:

  • The loopfield contractor can properly pressure test, flush and purge the system without first having to connect to the interior mechanical piping.
  • With an incorporated bypass valve in the vault, the loopfield can remain separated from the supply-return lines that run back to the mechanical room. This allows the mechanical contractor to proceed with the interior installation without compromising the loopfield after it has already been tested.

3 Facilitate Repair

Another advantage of the separation between loopfield and building can be realized when making repairs to a damaged circuit or while searching for leaks. With the loopfield manifold located in the vault (and not in the building), the loopfield contractor won’t need to access the building’s interior to make repairs.

By having butterfly isolation valves on each circuit along with a building bypass, the loopfield contractor can identify the damage or leak, make the repair and complete the pressure test/flush/purge sequence without stepping foot in the building.

In the event that a leak occurs, the vault also prevents spillage or mess inside of the mechanical room, minimizes disruption of activities within the building, and allows the contractor to conserve antifreeze and rust inhibitors by isolating the problem during repair.

4Convenience

Prefabricated vaults offer the contractor a “plug and play” option. Rather than allocating valuable time and labor to building a manifold on site (often while paying prevailing wages), the loopfield contractor can focus on drilling operations and pipe installation while the vault is being made off-site.

Once the vault is on site and in place, the geothermal installer can easily connect the circuits, then sequentially pressure test/flush/purge the circuits, subfields and entire loopfield to prepare the system for operation.

5 Accommodate Larger Distances from the Building

In some cases, the loopfield can be separated from the building by a large distance (500 ft or more). A vault acts as the central point where the combined flow from the field is collected, and a single pair of (larger) supply-return lines are run from that point back to the building. A relatively narrow trench can be excavated to accommodate those lines. Also, supply-returns can be sized for minimal head loss such that distance from the building to the loopfield is a non-factor.

6 Plan for Future Expansion

In some cases, a loopfield may be installed in multiple phases. A vault can be designed with extra circuits to allow for future expansion. In such cases, loopfield expansion can be completed with minimal disturbance inside of the building.

With the many advantages of using a vault as part of a commercial geothermal loopfield design, the first cost can typically be justified.

About the Author

Stuart Lyle
ISCO Industries

Stuart Lyle serves as geothermal sales director and provides technical support for ISCO’s customer base in the United States and Canada. A 10 year veteran of the geothermal industry, Stuart has served in both operations and sales roles. Before joining ISCO Industries, Stuart served as a project manager for a nationwide geothermal installation company. Prior to entering the civilian workforce, Stuart had a prestigious military career in the 3rd Marine Division where he earned a meritorious promotion to the rank of Sergeant and the Navy and Marines Corps Achievement medal for outstanding performance while serving abroad. After completion of his tour in Afghanistan, Stuart continued his military service in the Georgia Army National Guard while simultaneously earning a BS in Physiology and BA in Criminal Justice from the University of Georgia in 2006.

LoopLink RLC Update: Pond Loop GHEX Design

Wednesday, February 22, 2017


Pond loops are closed-loop, surface-water heat exchangers. Regulation permitting, any nearby body of water, such as a lake, stream or pond, can serve as a lower cost heat source/sink for a geothermal heat pump system than conventionally bored or trenched systems. That is of course assuming the pond loop is properly designed and installed.

With our latest update to LoopLink RLC, you now have a simple to use tool to properly design a pond loop.

The RLC Approach

LoopLink RLC uses the calculation methods presented in ASHRAE's Design of Geothermal Systems for Commercial and Institutional Buildings (Kavanaugh and Rafferty, 2014) to perform pond loop design calculations. The calculations account for project location (weather conditions), peak heating and cooling loads, GSHP capacity and efficiency as well as the pond temperature, size and condition (i.e. clean water or muddy).

You have the option of designing pond loops in two configurations:

To make things simple, we assume ASHRAE’s minimum spacing recommmendation of 10 feet for both configurations.

As you work, LoopLink RLC will check that the maximum recommended heating and cooling rates are not exceeded (i.e. the pond is large enough and deep enough to accommodate the load) and will display a warning if necessary. Even with those warnings built in, there are some key things to things to think about when designing a pond loop

Size Matters In Cooling

Rejecting heat to a pond in the summer months even in the warmest of locations is fairly easy due to natural convection and evaporation. The most important thing you need to watch out for is the heat rejection rate.

If the pond (reservoir) is too small, you can change the natural temperature of your pond which is bad for the plants and fish. Plus, you can create excessive amounts of evaporation and run the risk of running your small pond out of water… also bad for the plants and fish.

Size Matters In Heating

Water is pretty amazing. One of the most amazing features of water is its behavior at and near freezing. We won’t get into the physics of water freezing but there are two things you need to know about frozen ponds.

  1. Ice floats
  2. Liquid water is densest at 39.2°F (4­°C)

So, if a lake is frozen at the surface, the temperature of liquid water at the bottom of the lake and it is 39.2°F (4°C). That is of course until we start extracting heat energy out of that water through a long winter.

Size matters in two ways in heating. First and foremost is the fact that if you have too small of a loopfield, you may locally freeze the water around your loops. This will make your loops more buoyant and may lift them off the bottom of the lake causing a host of problems not least of which is the possibility of catastrophic system damage.

The second size issue is the pond itself. If you don’t have a large enough volume of water you may suppress the temperature of the entire body which will again pose a risk to the plants and fish. It is possible to freeze a pond all the way through if the rate of heat extraction is higher than the rate of heat rejection from the soil below the body of water.

ASHRAE Says Size Matters

In any pond loop application, the body of water being used needs to be large enough so that the GSHP system does not alter the natural temperature of the reservoir by more than 1°F. According to ASHRAE, the maximum recommended load for a reservoir is 20 tons/acre in cooling mode and 10 tons/acre in heating mode.

Before designing a pond loop, a detailed study should be performed to ensure that the size of the pond is sufficient given the load and also to find the temperature of the pond in the summer and winter at the installation depth of the loop.

Top 5 Features of Bad Vault Design

Tuesday, February 14, 2017

In Joe Pejsa's experience there are common elements in every bad vault design. Here are his top five things to avoid when specifying the requirements for a geothermal valve vault.

1 Circuit Balancing Valves

The primary issue with circuit balancing valves is the fact that they only control flow under peak flow conditions. Typically, a loopfield only operates at peak capacity for a few hours in a year. For most of the year, the system will operate at part load which means the expensive circuit balancing valves serve no purpose for most, if not all of their installed life.

Circuit balancing valves add considerable cost to a vault, create additional points of failure and increase system head loss and associated pumping power requirements. A better alternative to circuit balancing valves is to simply use butterfly isolation valves to balance flow (when necessary). The butterfly valves will already be incorporated into a good manifold design, and they are about 20% of the cost of a circuit balancing valve.

2 Heaters

The occasional spec calls for a space heater to be installed inside of the vault. Although the circulating water temperatures in a GSHP system can fall as low as 25-30F, the inside temperature of the vault will not fall below 40F. The vault is buried and the surrounding soil will moderate the inside temperatures relative to outside air temperature extremes. Also remember that in cold climates, the entire system will be protected with antifreeze (such as propylene glycol) to freeze point temperatures well below the lowest temperature seen inside of the vault. The inclusion of a heater adds unnecessary cost and increases the complexity of the installation due to the need for electricity.

3 Steel Manifolds

Vault manifolds should be constructed from HDPE rather than steel for several reasons.

Corrosion
During the installation process, moisture is constantly present and depending on location, the air will also be full of humidity. The excess moisture can cause a steel manifold to rust and corrode quickly.
Expansion/Contraction
The expansion/contraction of grooved fittings causes leaks. Routine maintenance is needed to make sure the steel is holding up to the environment and the fittings are tight to the grooved end.
Cost
Labor costs can be very high in certain areas. Steel manifolds are very heavy and for the most part, need to be constructed on site. The use of HDPE allows for the manifold to be fabricated and installed by the vault manufacturer so that when it arrives at the site, it will be completely assembled and ready for installation.

4 Individual Loops to the Vault

Geothermal vaults are typically used when there isn’t adequate space in the mechanical room to accommodate the number of circuits. The size and cost of the vault is directly impacted by the number of connected circuits.

To use a vault as a manifold that provides access to each individual loop in the field is expensive and generally unnecessary. When a vault is needed, the most common and cost effective solution is to join the loops in groups of multiple parallel circuits, and bring each circuit to the manifold inside of the vault.

There are instances where individually connecting the loops to the vault is the best answer (for example: an installation under a building or a parking garage), but most loopfields are installed in green spaces or playing fields and can be repaired easily if a leak occurs. Butterfly valves allow for repairs on a portion of the field without requiring shutdown of the entire system if/when that time comes.

5 Tiny Housings

Geothermal vaults are confined spaces that need to meet OSHA ventilation, entry and electrical standards. Forced air ventilation and ladders are just some of the OSHA regulations that need to be followed. When design features such as bypasses, isolation valves, purge ports, gauges and accessories are included, the space becomes very congested.

Installation workers and maintenance personnel need space to work comfortably and safely. If a situation arises, they need to be able to easily and safely escape from the hazard. Being forced to kneel or crawl into a vault that is too small is at best inconvenient and at worst dangerous. Always remember to consider the ability of a real person to maneuver and work when sizing your vault.

Now that you know what to avoid, read 5 Features of Good Vault Design for pointers on how to improve your next vault design.

About the Author

Joe Pejsa
Uponor

Joe is a Manufacturing Engineer at Uponor Infra. He has been involved in the ground source heat pump industry since July of 2003. His involvement in the industry has included technical support, field service work, estimating, installation, and troubleshooting of all types of geothermal systems. Joe has an extensive background in Geothermal Vault design, manufacturability, product development and confined space issues. Joe graduated with a BS in Manufacturing Engineering from South Dakota State University in 2005.

Top 5 Features of Good Vault Design


As with everything in life, there is right way and a wrong way to design a geothermal valve vault. Here, Joe Pejsa shares his recommendations for the right way based on years of experience and hundreds of installations.

1 Use a Two-Manway System

There are two primary advantages of using two manways in a vault design.

Ventilation
Per OSHA standards, proper ventilation must be provided to safely work in a confined space (i.e. a buried valve vault). Ventilation in a vault is provided with a positive pressurization fan so that fumes from the surface can’t be introduced to the workspace (such as vehicle exhaust). The fan can’t be permanently installed inside of the vault, so it can be stored in the second manway for easy removal and use.
Access
The working space in a vault is limited and it is easy to get crowded. Two-manway systems improve access to flush and fill ports without blocking your exit. If something goes wrong and you need to get out, two access points make a lot of sense.

2 Always Include a Bypass

A bypass is a necessity for every geothermal manifold, including vaults. With vaults, a bypass should be placed in the vault(s) as well as in the building. This allows for segregation of interior and exterior piping, which decreases pumping requirements on your flush cart. Plus you be able to prevent the dirt and chemicals from one side of the piping system from getting into the other while you are prepping the system for operation.

3 Manifolds Need Isolation Valves and PT Ports

Every geothermal manifold should also include means to isolate individual circuits (via butterfly valves) and take performance measurements (via P/T ports). In general, some level of isolation will be necessary for any loopfield with multiple parallel circuits. At some point, there may be a need to:

  • Isolate either the main supply-return lines to the building or the individual loopfield circuits during pressure testing or flushing/purging
  • Make slight flow adjustments to individual circuits in order to balance flow through the entire loopfield
  • Isolate a problem such (as a leak) in order allow for repair while preventing a total shutdown of the system

Butterfly valves are the most common and economical choice for isolation valves in a geothermal manifold.

In addition to isolation valves, the manifold design should include P/T ports to allow for performance measurements. In terms of placement in the manifold, P/T ports should be placed:

  • On each circuit, on the loopfield side of the isolation valve (as opposed to the manifold side of the isolation valve)
  • In one or two locations on the mains, such as the interior and exterior vault bypass.

With proper usage of isolation valves and P/T ports in a geothermal manifold, loopfield flushing, purging pressure testing, commissioning, performance checking, maintenance and repair will be simple and straightforward.

4 Make it Waterproof

A geothermal vault will not be entered on a daily, monthly or yearly basis which makes 100% resistance to water intrusion critical. After all, a slow drip over a year can add up to a significant volume. A leak free vault housing would lower maintenance costs by:

  • Decreasing corrosion of valves and mechanical components
  • Eliminating need to make provisions for electricity and sump pumps inside the vault
  • Saving maintenance personnel time wasted pumping water from the vault prior to entering it to perform a system check or periodic maintenance

Environmentally speaking, a leak free vault would prevent the antifreeze solution from contaminating the surrounding area in the event that a leak occurs in the manifold. This can save you from costly environmental assessment and clean-up in the event of a mechanical component failure.

5 Use HDPE for the Housing

A loopfield should be viewed as an investment in permanent infrastructure on the site. HDPE is used to construct the loopfield in part because it has a service life expectancy of more than 100 years. Even if a building is torn down or somehow destroyed in 75 years, the loopfield will still be there ready for use. The same logic should apply to a geothermal vault. If the vault housing is made of the same material as the loopfield, the vault and loopfield will have the same life expectancy.

Stick to these principles with your next geothermal valve vault for maximum utility and minimal issues. Now that you know what to include, read 5 Features of Bad Vault Design for things to avoid with your next vault design.

About the Author

Joe Pejsa
Uponor

Joe is a Manufacturing Engineer at Uponor Infra. He has been involved in the ground source heat pump industry since July of 2003. His involvement in the industry has included technical support, field service work, estimating, installation, and troubleshooting of all types of geothermal systems. Joe has an extensive background in Geothermal Vault design, manufacturability, product development and confined space issues. Joe graduated with a BS in Manufacturing Engineering from South Dakota State University in 2005.

What is a Geothermal Vault?

Tuesday, February 7, 2017


Simply put, a vault is a buried structure that houses an external manifold for a geothermal loopfield. Think of it as a buried mechanical room where your manifold will go. Simply climb down the ladder through the built-in manway to gain access.

For large systems, it usually does not make sense to connect all of the ground loops with a single pair of supply-return lines without first breaking the field into smaller parallel circuits. For example if you had a 100-bore system, you may decide to to break the field into 10 circuits with 10 bores connected to each circuit (or 5 circuits of 20 bores each for that matter).

By doing so, you can more easily:

  • Flush and purge the ground loop to remove air and particulates prior to system startup
  • Balance flow to each circuit
  • Measure the performance of each circuit (flow, temperature, pressure drop, etc.)
  • Isolate circuits in the event that a problem arises rather than being forced to shut down the entire field for repair

When breaking the field into multiple parallel circuits, proper SDSU-RR header design becomes critical to ensure that adequate flushing velocities and head loss characteristics can be achieved. The Auto-Header tool in LoopLink PRO simplifies this (formerly cumbersome) task.

Manifold Options

With the field broken into multiple circuits, you will need to incorporate a manifold somewhere in the piping system to combine those circuits to a single supply return line before connecting to the circulating pumps (whenever a centralized pumping system is used - a topic for another day).

There are two basic options when it comes to manifold location - placement inside or outside of the building. An inside manifold will typically be located in the mechanical room. An outside manifold is buried and typically located in a vault or valve pit.

Inside Manifold (No Vault)

Outside Manifold (Buried Vault)


Why Use a Vault in the First Place?

Per IGSHPA’s RLC Design & Installation Guide:

In any installation, the exterior portion of the ground loop piping should always remain buried 4-6 feet below the ground surface (which will be the depth of the header trench).

Additionally, per Paragraph 1D.3 in IGSHPA’s Design & Installation Standards:

All mechanical connections must be accessible.

With an inside manifold, this problem takes care of itself. With an outside manifold, all mechanical fittings (such as butterfly valves and P/T ports) being used need to be accessible in some way for maintenance, performance checking, flushing/purging, etc., which is the primary purpose of a vault.

Factors to Weigh

The decision whether or not to use a vault is project-specific. Generally speaking, these are the things you should think about before making your decision:

  • Available space in the mechanical room
  • Distance from the loopfield to the building
  • Cost for labor and materials
  • System operating costs
  • Plans for future addition/expansion

Safety Considerations

There are two primary OSHA Standards that must be considered in every vault design.

If you plan to incorporate a vault into your next geothermal loopfield design, read 5 Features of Good Vault Design to ensure that it is well-suited for the application.

LoopLink RLC Update: Economics of Replacing an Old GSHP

Thursday, February 2, 2017

LoopLink RLC now allows for an economic analysis to be performed that compares a new GSHP to an old one that is ready for replacement. By doing so, we allow the system designer to illustrate the benefits of upgrading to a new GSHP unit from an economic point of view.

Why The Update?

Units that were installed in the 80's and 90's are most likely near the end of their 25-30 year life expectancy. If you couple that with the fact that newer GSHP units are quieter, more reliable, and more efficient than they were 20-30 years ago, you may find yourself on the receiving end of sales contract to replace a unit.

Project Changes

The new option is included on the Operating Cost Summary and Cost of Ownership pages. To perform an economic analysis that includes the estimated operating cost and long term cost of ownership for an older GSHP, you must first check the box to activate the option from the Operating Cost Summary page.

The performance of the old equipment is described by the operating efficiency you specify just as it is for the other comparison technologies. If you have actual operating efficiency averages for the past year (there are homeowners that check) you should use that information. Otherwise, using the old rated efficiency should get you close.

The Annual Operating Cost by Technology and Annual Carbon Dioxide Emissions by Technology graphs will update accordingly as you make changes to the technologies to comare and their operating efficiencies.


After activating the option, you will also be able to perform a long term economic analysis on the Cost of Ownership page to show simple payback as well as long term operating and ownership costs.