Geo-Flo Calculators

Geo-Flo’s System Design Calculators are available free of charge to registered users. This comprehensive suite of Calculators provides geothermal and hydronic design tools, concentrating on the hydronic portion of the system. From pressure drop calculation to pump sizing to flushing requirements, the design suite is continually being developed to help customers save time and design better systems. Below is a list of currently available Calculators with an explanation of typical use, as well as notes on using the Calculators.

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Pressure Drop Calculators

Residential/Light Commercial Calculators

Single unit, outside header: This calculator is designed to determine the system pressure drop for a single unit with a single flow center, and an outside header. Pressure drop results are applicable for both pressurized and non-pressurized systems. Usage notes: Observe notes for inputs. Piping is one side only, except for the ground loop circuit. If the two sides are different lengths, use the longer of the two. The ground loop circuit is the total length (from supply header back to return header). Match up the piping color in the drawing to the input boxes below.

Single unit, inside header: This calculator is designed to determine the system pressure drop for a single unit with a single flow center, and an inside header. Pressure drop results are applicable for both pressurized and non-pressurized systems. Usage notes: Observe notes for inputs. Piping is one side only, except for the ground loop circuit. If the two sides are different lengths, use the longer of the two. The ground loop circuit is the total length (from supply header back to return header). Match up the piping color in the drawing to the input boxes below.

Two units, one flow center: This calculator is designed for two units piped in parallel (see diagram in the calculator) and a single flow center. This application is designed for one ground loop for both heat pumps. If there is a loop for each unit, use one of the single unit calculators; if there is a flow center for each heat pump, and both units are on the same loop, use the "Up to 5 units, flow center per unit" Calculator. Match up the piping color in the drawing to the input boxes below.

Dual unit (NPD) flow center: This calculator is designed around the Geo-Flo NP Series Dual Circuit flow center. Many times, it is much easier to use a dual unit flow center than to add Ts, additional piping, check valves, isolation valves, etc. The NPD includes flushing/purging valves, check valves (one for each heat pump), and drain valves. Based upon the non-pressurized design, this flow center compensates for loop fluid expansion (takes the place of an expansion tank) and acts as an air separator. Usage notes: Observe notes for inputs. Piping is one side only, except for the ground loop circuit. If the two sides are different lengths, use the longer of the two. The ground loop circuit is the total length (from supply header back to return header). Match up the piping color in the drawing to the input boxes below. This Calculator is limited to up to 30 GPM (typically 10 tons) and 2” PE pipe. For larger systems, use the NP Series Multi Circuit flow center or use one of the commercial calculators.

Multi unit (NPM) flow center: This calculator is designed around the Geo-Flo NP Series Multi Circuit flow center. For systems with 3 to 5 heat pumps, piping becomes much more difficult. The NPM includes virtually all of the piping (including heat pump manifolds), flushing/purging valves, and pumps/zone valves for 3 to 5 heat pumps as part of a factory assembled package for multi-unit installations up to 30 tons. Based upon the non-pressurized design, this flow center compensates for loop fluid expansion (takes the place of an expansion tank) and acts as an air separator. Usage notes: Observe notes for inputs. Piping is one side only, except for the ground loop circuit. If the two sides are different lengths, use the longer of the two. The ground loop circuit is the total length (from supply header back to return header). Match up the piping color in the drawing to the input boxes below.

Up to 5 units, central pumping: This calculator will allow the use of up to five units piped in parallel (see diagram in the calculator) and a central pump system. This application is designed for one ground loop with multiple units. If there is a loop for each unit, use one of the single unit calculators. Usage notes: Observe notes for inputs. Piping is entered as total length (both sides). The ground loop circuit is also the total length (from supply header back to return header). Match up the piping color in the drawing to the input boxes below.

Up to 5 units, flow center per unit: This calculator will allow the use of up to five units piped in parallel (see diagram in the calculator) and a flow center for each unit. This application is designed for one ground loop with multiple units. If there is a loop for each unit, use one of the single unit calculators. Usage notes: Observe notes for inputs. Piping is entered as total length (both sides). The ground loop circuit is also the total length (from supply header back to return header). Match up the piping color in the drawing to the input boxes below. Care must be taken when using multiple parallel flow centers on a common loop. Available head of multiple flow centers in parallel is the head of only one flow center. It is important to have enough head/flow when all heat pumps are running at full load.

More than 5 units: For more than 5 units or for other pumping applications (e.g. primary-secondary), please use the commercial calculators below.

Commercial Calculators

Pipe segment calculator: This calculator will determine the pressure drop for a geothermal heat pump system that is more complex than the residential/light commercial calculators above. Because every system is different, it is beneficial to look at individual pipe segments when calculating pressure drop. Example diagrams are included in the calculator. Usage notes: The scratch pad at the bottom of the page may be used to keep track of the various pipe segments, totaling all of the calculations at the bottom.

Flow rate-pump affinity laws: This calculator uses the squared relationship of the system curve to calculate pressure drop or flow rate at conditions other than the originally calculated system pressure drop. It is useful for pump sizing and consideration of other operating conditions (e.g. pressure drop at nominal flow, pressure drop at minimum flow, etc.).

Cv Calculator: The Cv Calculator calculates the pressure drop of a ball valve, zone valve, or other system component based upon the Cv of the device. Cv is flow coefficient, which is the flow in U.S. GPM through a component with 1 psi pressure drop across the device. For example, a strainer with a Cv of 20 has a pressure drop of 1 psi (2.31 feet of head) at 20 GPM. Usage notes: Use this calculator when one of the pressure drop Calculators does not include all of the components in the system. Then, add the pressure drop in feet of head to the “Other” section of the Calculator.

Pump Sizing Calculators

Residential/Light Commercial Calculators

Pump Sizing – Flow Centers (up to 100 gpm): The Pump Sizing Calculator will graph the system pressure drop, and plot pump curves to determine the actual flow rate of the system with the selected pump(s). Usage notes: The system pressure drop should include the pressure drop for the entire system (ground loop, heat pump heat exchanger, inside piping, etc.), including antifreeze. Pump selection notes below the system/pump curves explain how the chart may be used. In most cases, heat pump nominal flow rate (typically 3 GPM/ton) should be used for calculating pressure drop. Lower flow rates should also be considered when selecting a pump. For example, if one pump can be used instead of two at 2.5 GPM/ton, but two pumps are needed for 3 GPM/ton; it normally makes more sense to design at the lower flow rate to decrease pump Watts (verify with heat pump manufacturer data before choosing a lower flow rate). With the exception of the GEO Magna (32-140) variable speed pump, the actual flow rate is shown (the point where the pump curve crosses the system curve). The variable speed pump will adjust speed to match the flow rate and pressure drop entered up to the maximum operating point.

Series/Parallel Pump Calculator: More complex systems may have a combination of pumps in series and/or parallel. Pump curves and sizing can become quite complicated, especially when some pumps are in series, and some are in parallel. This calculator allows up to 5 sets of pumps in series to be combined in parallel to determine system operating point (flow rate and head). Usage notes: There are several error checks incorporated into the Calculator. Observe the messages in red font just above the chart.

Reynolds Number Calculator: When designing a system, the number of parallel circuits per ton affects system pressure drop, which affects pump sizing, and ultimately operating costs (pump Watts). However, more circuits per ton (less flow rate per circuit) lowers the Reynolds number (Re), which is a measurement of turbulence. Laminar flow (Re < 2300 ± 200) is characterized by layers of fluid sliding along in the direction of flow without mixing. Historically, the geothermal industry has suggested Re of greater than 2500 at full load operation. Note that laminar flow at lower heat pump (part-load) operation is not problematic since the greater-than-required length of the ground loop more than offsets the possible loss in heat transfer by the lower Re. Therefore, variable speed systems, which can operate at Re less than 2500 in part load, are encouraged, since the system is capable of operating at design flow rates at full load, but can provide energy savings most of the year when the system is in part load.

Commercial Calculators

Pump Sizing – Magna3 (up to 600 gpm): The Magna3 Pump Sizing Calculator is designed around Geo-Flo’s Magna3 insulated pump. Geo-Flo takes a Grundfos Magna3 variable speed pump, and installs it into an insulated cabinet, providing protection from condensation at low fluid temperatures, and also makes the pump much easier to mount on the wall or floor mount. The Geo-Flo Magna3 also provides ball or butterfly isolation valves, and factory programming specific to the application (typically geothermal installations). This Calculator allows input for one or two pumps in constant pressure (differential pressure), delta-T (temperature difference), or constant curve modes. If selecting two pumps, pumps in series or pumps in parallel may be selected to compare system requirements with pump selection, including maximum and average power consumption.

Geothermal Expansion Tank Calculator: This Calculator determines the bladder type expansion tank size for a geothermal heat pump application (systems with HDPE pipe in the ground). For water-source heat pump systems (systems with rigid piping and no ground loop--also called boiler/tower system), the standard ASHRAE calculation is used (none of the piping below may be PE3408/3608 or PE4710). Sizing an expansion tank for a geothermal system requires additional considerations. Although pressure increases as temperature increases for all systems, HDPE pipe expands at a higher rate than the increased pressure, causing the opposite effect in ground loop systems (the system pressure decreases as the loop temperature increases, and increases as the loop temperature decreases). Therefore, expansion tank sizing in this Calculator is based upon the amount of HDPE pipe vs. rigid pipe in the system.

Reynolds Number Calculator: When designing a system, the number of parallel circuits per ton affects system pressure drop, which affects pump sizing, and ultimately operating costs (pump Watts). However, more circuits per ton (less flow rate per circuit) lowers the Reynolds number (Re), which is a measurement of turbulence. Laminar flow (Re < 2300 ±200) is characterized by layers of fluid sliding along in the direction of flow without mixing. Historically, the geothermal industry has suggested Re of greater than 2500 at full load operation. Note that laminar flow at lower heat pump (part-load) operation is not problematic since the greater-than-required length of the ground loop more than offsets the possible loss in heat transfer by the lower Re. Therefore, variable speed systems, which can operate Re less than 2500 in part load, are encouraged, since the system is capable of operating at design flow rates at full load, but can provide energy savings most of the year when the system is in part load.

Flush Cart Calculator

Once the system pressure drop has been calculated, the Flush Cart Calculator may be used to determine if the Geo-Flo flush cart can flush the loop (based upon Geo-Flo model 3563 flush cart with Munro 1.5 HP pump). Usage notes:

  • Flush cart fittings are added to the system pressure drop automatically.
  • The pressure drop calculators may be used to determine flushing requirements.
  • Flushing assumptions are based upon IGSHPA standards including a parallel, close-coupled, reducing header. Other designs may not be flushable with this flush cart.
  • If the flush cart cannot flush the loop, redesign should be considered. The flush cart can typically flush 10 to 12 circuits (3/4" PE). Normally, a maximum of 10 to 12 circuits are connected in parallel. If there are more than 10 to 12 circuits, each set of 10 to 12 circuits can be sub-headered to maintain a system that may be flushed (see Commercial Pressure Drop Calculator for details on headering).

Spaced Pond Coil Calculator

Geo-Flo's spaced Pond Coil Calculator is based upon the ASHRAE 2014 publication, Geothermal Heating and Cooling: Design of Ground-Source Heat Pump Systems, by Kavanaugh and Rafferty, using pond coils assembled with spacers designed and manufactured by Geo-Flo Products Corporation. Other pond coils may perform differently. Once the system information is entered for a geothermal application using Geo-Flo spaced pond loop coils, results are shown in feet of pipe per nominal ton. Usage notes: Calculations are based upon parallel coils. Typically, coils are designed with one coil per ton for 3/4" pipe (3 gpm per ton), and less than one coil per ton for 1" pipe (longer coils). The use of 3/4" or 1" pipe is determined by system pressure drop. Logistics (shipping weight and pallet size for spaced pond coils) may limit the coil length. In cases where more than the available coil length is required, the use of two coils in series may make sense. Pond coil applications with small approach temperatures will be longer and the number of parallel coils should be in the upper range, while coils with larger approach temperatures should be in the lower range of parallel coils per ton.

Hydronic Calculators

Buffer Tank Calculator: This Calculator is used to determine the volume required for a Geo-Flo Hydro-Connect buffer tank used with a water-to-water or combination heat pump, or with a modulating-condensing boiler.

Heat Pump Load Side Pressure Drop Calculator: This calculator is designed to determine the pressure drop in the “load side” piping from a water-to-water heat pump (or combination heat pump or boiler) to the buffer tank. Once pressure drop is calculated, the Pump Sizing Calculator may be used to determine the best pump selection to provide design flow rate to/from the buffer tank.

Radiant Floor/Fan Coil Pressure Drop Calculator: This calculator is designed to determine the system pressure drop for radiant floor and/or fan coil system piping from the buffer tank to the heat emitters or terminal units. Once pressure drop is calculated, the Pump Sizing Calculator may be used to determine the best pump selection to provide design flow rate to/from the buffer tank.

Expansion Tank Calculator-Radiant/Hydronic System: This Calculator determines the bladder type expansion tank size for a hydronic application (not for use for the ground loop piping – see Pump Sizing Calculators), using the standard ASHRAE calculation for systems with PEX, PEX-AL-PEX, or PP-R piping.

Flow Rate Calculator

The Flow Rate Calculator uses the nominal flow rate from the heat pump manufacturer’s catalog, and interpolates/extrapolates based upon the actual measured pressure drop across the heat exchanger to save the technician time when starting up or troubleshooting a geothermal application.

HE-HR Calculator

The HE-HR Calculator is used to determine heat of extraction (HE) in the heating mode or heat of rejection (HR) in the cooling mode for a geothermal application, using the flow rate and temperature difference at the P/T plugs installed at the heat pump.