Geo-Prime

It is an accessory that can be added to a standard flow center to create a non-pressurized flow center system. The Geo-Prime Tank consists of a fluid reservoir, two bypass valves and an air-eliminating dip tube inside of a foam-insulated cabinet. The Tank includes a sealing cap with integrated pressure and vacuum relief to prevent the reservoir from being over-pressurized or collapsing.

You need a Geo-Prime Tank if you want to use your standard flow center as a non-pressurized system or want to add air separation and make-up fluid capabilities to your pressurized system.

The Tank is intended for standard residential systems up to 6 tons or 18 GPM of flow.

Installation instructions are available on our website. Several l heat pump manufacturers also provide installation instructions.

In general, no. Under very specific conditions, it may be possible. However, without using a high-head high-flow pump available on most flush carts, it is nearly impossible to guarantee that all the air as been removed from the loop. Also, see Q6 below.

No. It is extremely common for construction debris, polyethylene pipe shavings, dirt, sand, rocks, etc. to enter the ground loop piping during installation. The wet circulator pumps used during system operation require clean, debris-free fluid to function properly. A small amount of debris left in the ground loop could become lodged between the pump’s rotor and stator housing causing pump failure a few days to a few years after initial installation. This preventable issue is a common mode of failure for circulators. In addition, flush carts are equipped with high-flow/high-head pressure pumps which allow the technician to “dead-head” (i.e. shut off the return valve) the flush cart’s pump and watch for a fluid level drop in the cart’s reservoir. This is the only way for one to determine whether the ground loop is air-free and therefore functioning (transferring heat) as designed. Also, “dead-heading” the flush cart’s pump followed by opening the return valve helps any air trapped in the ground loop to become dislodged and carried into the fluid stream back to the cart’s tank. This is due to the high pressure developed during “dead-heading” which compresses the air into smaller bubbles and the subsequent high velocity surge when the return valve is opened. This process cannot be accomplished with a circulator pump. No matter whether you install a pressurized or non-pressurized flow center, you should always flush the ground loop with a quality flush cart.

Connect an acceptable flush cart to your standard flow center’s integrated flush/purge valves and follow the industry’s recommended flushing procedures. The Geo-Prime Tank has integrated bypass valves that allow the ground loop to be flushed without filling, overflowing, or pressurizing the reservoir. All major heat pump manufactures provide detailed written flushing procedures and most provide hands-on training for this important task.

The Tank assembly includes two bypass valves that allow the ground loop to be flushed without filling, overflowing, or pressurizing the Tank’s fluid reservoir. NOTE: The loop should NOT be flushed with a flush cart through the Tank’s reservoir.

The cap is hand-tightened until you hear an audible “click” similar to your automobile’s gas cap.

Yes. Although the Tank is intended to be part of a non-pressurized flow center, it can be pressurized. The sealing cap has an integrated pressure relief valve rated at 3-5 psig. If the system is pressurized to a level above the 3-5 psig, the valve will open and air and/or fluid will leak through the cap from the reservoir.

Yes. The sealing cap will hold pressure to 13-15 psig. Therefore, the Tank can be mounted up to 30 feet below the loop field or heat pump (13 psig X 2.31 ft-hd/psig= 30 ft).

Yes, but in general you should not need to remove the cap and it should only be removed when absolutely necessary. The cap is intended to seal the ground loop system from the outside atmosphere thereby ensuring a closed system. Caution should be exercised when removing the cap. The reservoir may be slightly pressurized which could cause the fluid in the tank to leak out when the cap’s seal is broken. In addition, we recommend that the cap only be removed when the circulator pump is running. When the circulator starts, the fluid level in the tank may drop slightly allowing you to remove the cap without overflowing the tank. The cap should be removed slowly so that if fluid does begin to exit the reservoir, the cap can be quickly retightened.

First, the installation or service technician can pressurize the reservoir during installation or service of the system. Second, if the tank is located below the ground loop or unit piping, the water column can create head pressure on the reservoir. Third, the reservoir can become pressurized due to the temperature variations of ground loop. Polyethylene pipe expands and contracts during seasonal temperature changes. If the reservoir is filled while the ground loop is warm (i.e. during the summer) and then sealed with the cap, the contraction of the pipe when the loop cools (i.e. during the winter) may slightly pressurize the reservoir.

Fluid can either be removed from the reservoir by removing the cap or through the 3-way valve on the flow center.

Heat pump manufacturers suggest measuring the pressure drop across the heat pump’s heat exchanger via PT ports located at the water connections of the unit. The flow is then determined using the manufacturer’s published tables for pressure drop versus flow. Also, flow can be measured using a removable flow meter.

Although there is little static pressure on the ground loop system, the fluid flow through the system will still result in a pressure differential (drop) across the heat pump’s heat exchanger due to the fluid flow and frictional losses. This pressure drop will be the same whether the system is under high or low static pressure. Therefore, assuming you have an accurate gage capable of reading the relatively low pressure drop across the heat exchanger, you will not need a new gage. Be aware that some gages are more accurate near their mid-range value than the upper or lower ranges.

A gurgling sound inside the tank indicates that air is being released from the fluid into the reservoir. If the gurgling sound continues for more than a few minutes be sure to check the fluid level inside the tank.

Approximately 2.5 gallons.

The fluid level in the tank can vary with the seasonal temperature swings in the ground loop. However, if you find that you are adding fluid on a regular basis you may have a leak somewhere in your system. In this case you should contact your installation contractor.

You should be cautious whenever you decide to remove the Tank’s cap. Many ground loop systems contain water and anti-freeze such as ethanol, methanol, or glycol in a concentration high enough to reach the system’s required freeze protection. Adding a small amount of water may not seriously affect the freeze protection level but adding too much water will affect the freeze protection. In addition, many residential water supplies are high in minerals, contain bacteria, or have an inappropriate Ph level to be used in the ground loop system. Finally, mixing the wrong antifreeze in your ground loop system can cause considerable harm. One method of ensuring you are using the appropriate loop fluid is for the installer to provide the system owner with a pre-mixed solution of loop fluid in a clearly marked, sealed, approved container that is stored in a safe, convenient location.

No. An open system is one in which the fluid is open to the atmosphere. The cap seals the reservoir and prevents interaction between the fluid and the atmosphere.

The Geo-Prime Tank differs from other non-pressured flow centers for the following reasons:

• Allows for pressurized or non-pressurized system operation.
• Allows an industry standard flow center to be used as a non-pressured system. Dealers can offer both pressurized and non-pressurized systems to their customers with the addition of a single accessory (the Geo-Prime Tank).
• Allows system flushing/purging using an industry standard flush cart without additional on-site plumbing via the standard flow center.
• Provides a sealing cap that ensures a closed system and that cannot be blown off the tank.
• Cap provides pressure and vacuum relief.
• Space saving, attractive, wall mounted design.
• Allows fluid level to be monitored without removing the cap.
• Safety: small reservoir opening will not allow hands or foreign objects to be placed in the reservoir. In addition, the mounting height on the wall puts the fluid access (cap) out of the reach of small children.
• Modular system; if there is a problem with the flow center system, you replace only the components that have issues (i.e. the pump, flow center, or the Tank).
• Retrofit-able; a standard pressurized system can be changed to a non-pressurized system without replacing the existing flow center and pumps.
• Provides “one-pass” air separation. The unique reservoir design will not allow air to be drawn into the circulator.
• High impact plastic housing will never corrode.
• Utilizes Flo-Link Double O-ring connections for fast and easy installation.

It’s your choice. However, putting the header inside requires more labor, additional wall penetrations, and does not look as professional as burying the header outside. Some installers header inside to allow each individual loop circuit to be isolated with the expectation each circuit will be flushed with the flow center’s circulator. We do not recommend attempting to flush the loop with the system’s circulator (see “Q6: Should I flush the ground loop with the circulator pump?”).

A patent application for the Geo-Prime Tank has been submitted to the United States Patent and Trademark Office. Therefore, it has “patent pending” status.

The terms “pressurized” and “non-pressurized” when referring to a geothermal ground loop system indicates whether there is static pressure on the ground loop and heat pump system. The circulator pumps used in flow centers require a pressure at their inlet (suction side) that exceeds a minimum level that is established by the pump manufacturer. In technical terms, the net positive suction head available (NPSHa ) of the system must be greater than the net positive suction head required (NPSHr) by the pump. In pressurized systems, this positive pressure is induced and captured in the system during start-up/installation by an external pressure source (usually a high-head pressure pump on a flush cart). In a non-pressurized system positive static pressure is not applied to the ground loop system. Instead, a standing column of water is used to meet the minimum suction pressure requirement of the pump.

A: You will find installation contractors who use exclusively pressurized or non-pressurized flow center systems that claim they never have problems with their installations. The fact is that even the very best system will perform poorly if it is not applied and installed properly. This is true of both pressurized and non-pressurized flow centers. Note that many of the items listed below for a particular system’s advantages are also listed as disadvantages and vice versa. Ultimately, the installation contractor, dealer, or homeowner will decide which system is best for them. The following is a list of advantages and disadvantages of each system:

Pressurized flow centers’ advantages

• Do not require or encourage monitoring or maintenance by the homeowner after initial system start-up.
• Generally much smaller in size thereby requiring less space for installation.
• Ensures a closed system which prevents air and or debris from entering system after installation.
• Include 3-way 4-position dual purpose isolation/flush (purge) valves.
• Sold and supported by all major geothermal heat pump manufacturers (not just flow center manufacturers or distributors) since the inception of the industry.
• Fewer components reduce possibility of component failure or system leaks.
• Fewer limitations on installation locations and orientations. For example, pressurized flow centers have no practical limitation on unit placement below the heat pump or loop field. Also, they can be installed in relatively confined spaces such as a crawlspace, closet, or very small mechanical room. Finally, they can be installed vertically or horizontally (12-, 3-, 6-, and 9-o’clock positions) providing greater installation flexibility.
• Flow centers can be plumbed in series or parallel as needed.
• Single point isolation location between the ground loop and heat pump (via the 3-way valves).
• No limitation on the type of pumps used in the system. Many pumps require (NPSHr) much more than the 1-2 ft of head (NPSHa) that most standing column (non-pressurized) flow centers provide.
• Plumbers and hydronics technicians are very familiar with pressurized systems since most hydronic (i.e. hot water heating, radiant floor hearing, solar hot water, etc.) systems are pressurized.
• Requires the minimum number of field plumbing connections to reduce field labor and the risk of leaks.

Pressurized flow centers’ disadvantages

• No built-in provision for air elimination. Therefore, if the installation technician does a poor job of flushing all air from the ground loop it will remain in the system. This could lead to issues with noise and/or air-lock of the pump under certain circumstances. NOTE: Some contractors choose to install air eliminators to pressurized systems to alleviate this concern.
• Thermal expansion (during cooling season, i.e. summer) and contraction (during heating season, i.e. winter) of the ground loop piping causes pressure fluctuations in the system. The loop pipe will slightly stretch and relax over time which causes a decrease in system pressure. If the initial system start-up pressure is not high enough to overcome this relaxation of the pipe the system pressure can drop below the required suction pressure of the pump (NPSHr) causing pump cavitation which could lead to pump failure. NOTE: Some installers choose to install an expansion tank in pressurized systems to alleviate this concern.
• Poor installation practices (i.e. small leaks in the ground loop or inside plumbing) result in decreases in system pressure over time which can lead to pump cavitation and failure.
• Generally do not allow homeowner maintenance or interaction with system. Fluid/pressure can be added to the system via the PT ports but this is typically performed by a qualified service technician.

Non-pressurized flow centers’ advantages

• Standing column of water provides necessary suction head for pump so that the static pressure on the ground loop is not a concern.
• Column of water on suction side of pump prevents air from being drawn into pump (as long as the fluid level remains at an appropriate level) eliminating the chance of air-locking the pump.
• Provides air elimination function.
• Allows homeowner to add make-up fluid to tank if the level gets low.
• Poor installation practices (incomplete flushing, small leaks in piping, etc.) can be tolerated due to the ability for the homeowner to add make-up fluid.

Non-pressurized flow centers’ disadvantages

• Can be used as a bandage to cover up poor installation practices (incomplete flushing, small leaks in piping, etc.). This is bad both for the homeowner and the industry.
• Requires continuous fluid level monitoring from the homeowner.
• Allows homeowners to access ground loop fluid. This could cause issues with the antifreeze being diluted or the wrong antifreeze being added to the system. Both of these issues could cause serious harm to the heat pump. In addition, contact with the antifreeze solution may be harmful to humans and pets.
• Water level decrease in the flow center tank (standing column) reduces the positive suction head pressure on the pump increasing the chance of pump cavitation and pump failure.
• Larger size requires more space for installation.
• Flush/purge valves not incorporated (in some manufacture’s systems) so they must be field fabricated and/or installed.
• Limited installation locations (distance below the loop field or heat pump) and orientation (flow center tank must remain vertical).
• Requires additional ball valves to be field installed to isolate the heat pump from the ground loop (on some manufacture’s systems).
• In general, cannot be installed in series or parallel.
• Requires more field plumbing connections than pressurized flow centers increasing field labor and the chance of leaks.
• Most manufacturers’ non-pressurized systems are not supported or sold by many industry experts such as major geo-thermal heat pump manufacturers.