Geothermal Heat PumpsOpen Loop Water-to-Water
Hydron Module HWT048 Geothermal Heat Pump Manual
Setup, everyday use, maintenance and troubleshooting for the open-loop water-to-water geothermal heat pump, with verified specifications.
- ConfigurationOpen Loop Water-to-Water
- RefrigerantR-410A
About the Hydron Module HWT048
The Hydron Module HWT048 is an open-loop water-to-water geothermal heat pump from the Revolution line. This page covers its ENERGY STAR certified open-loop (groundwater) rating.
The certification record for this configuration does not list EER or COP values, so ask Hydron Module or your installer for the performance data that applies to your loop design and water temperatures.
As a water-to-water unit it heats (and, where the system is designed for it, chills) water for radiant floors, fan coils, low-temperature radiators or a buffer tank rather than blowing air directly.
It is also recognized as ENERGY STAR Most Efficient, the program's designation for the top-performing certified products in a category.
Specifications
| Brand | Hydron Module |
|---|---|
| Model number | HWT048 |
| Model name / series | Revolution |
| Configuration | Open Loop Water-to-Water |
| Product series | Revolution |
| Refrigerant | R-410A |
| ENERGY STAR Most Efficient | Yes |
Certified ratings by application
2 certified rating configurations are listed for the Hydron Module HWT048, sorted by COP. Ratings depend on the application, so compare the row that matches your installation.
| Application | Certified |
|---|---|
| Open Loop Water-to-Water | January 2022 |
| Closed Loop Water-to-Water | January 2022 |
Safety information
- Installation, refrigerant work and electrical connections must be done by a licensed HVAC contractor experienced with geothermal systems, following the manufacturer's instructions and local codes. Most jurisdictions require permits for the heat pump and for drilling or trenching.
- Geothermal heat pumps typically run on a 208/230 V circuit. Switch off the disconnect and the breaker before opening any access panel; capacitors can hold a dangerous charge after power is removed.
- Call 811 (or your local utility-locate service) before any digging so buried gas, electric and water lines are marked.
- Do not operate the unit with access panels or the blower door removed.
- Open-loop systems draw from and return water to an aquifer or surface water. Wells and discharge methods are regulated in most states — use a licensed well driller and follow local discharge and permitting rules.
- If your home also has a fuel-burning furnace, boiler or water heater, keep carbon monoxide alarms on every level and near sleeping areas.
Installation and first-time setup
A geothermal system is only as good as its ground connection. The ratings for the Hydron Module HWT048 assume correct source-side flow and temperatures, so the loop or well design deserves as much attention as the heat pump itself.
- Room-by-room load calculation
Insist on an ACCA Manual J heat-loss and heat-gain calculation. Geothermal equipment and loops are expensive to oversize, and an undersized loop drives entering-water temperatures down in winter, reducing capacity and efficiency.
- Well yield and water quality
An open loop needs a reliable well with enough yield for the heat pump at full load, plus a legal way to return the water (a return well or approved surface discharge). Test the water for iron, hardness, pH and sediment — poor water quality fouls the heat exchanger and may call for a cupronickel coil or a closed loop instead.
- Pump and flow control
The well pump should be sized for the heat pump's required flow, and a flow-control or solenoid valve should stop water flow whenever the compressor is off so you are not pumping water for nothing.
- Hydronic distribution
Design the heating side for the lowest practical supply-water temperature — radiant floors and oversized low-temperature emitters let the heat pump run far more efficiently than high-temperature baseboard. Most installations use a buffer tank to prevent short-cycling, plus an expansion tank, air separator and mixing or limit controls where required.
- Verify water flow
Source-side flow must match the manufacturer's table — closed loops commonly run about 2.5–3 gpm per ton, while open loops often use less. Ask the installer to record flow and the temperature difference across the heat exchanger.
- Commissioning
Ask for a start-up report that records entering and leaving source temperatures, refrigerant pressures, airflow or load-side flow, thermostat and auxiliary-heat settings, and the loop fluid freeze point where applicable.
Using your geothermal heat pump
Thermostat settings
Choose a comfortable setpoint and leave it. Geothermal heat pumps work best holding a steady temperature; large setbacks in heating mode can bring on auxiliary electric heat during recovery, which costs several times more per hour than the compressor. If you use setbacks, keep them to a few degrees or use a thermostat with heat-pump adaptive recovery.
Auxiliary and emergency heat
Hydronic geothermal systems are often paired with a backup boiler or an electric element in the buffer tank. The controls should call for backup heat only when the heat pump cannot keep up; if the backup runs often in mild weather, ask your installer to review the staging settings.
Supply-water temperature
Efficiency falls as the heating supply temperature rises. Use the lowest setting (or the outdoor-reset curve) that keeps the house comfortable, and avoid raising the setpoint to "speed up" warm-up — radiant systems respond slowly by design.
If the system also provides chilled water for cooling, the controls must keep surface and pipe temperatures above the indoor dew point to prevent condensation on radiant floors and uninsulated piping.
Domestic hot water
Many geothermal units can be fitted with a desuperheater that preheats domestic hot water using waste heat from the compressor. If your installation has one, its circulator runs only when the compressor runs, and the water heater still provides final heating — check with your installer whether it was included.
Care and maintenance
Ground loops have no outdoor coil to clean and are largely maintenance-free, but the indoor unit and the source-side fluid still need periodic attention.
| When | What to do |
|---|---|
| Every 3 months | Check system pressure on the hydronic side and listen for air in the piping; bleed air as the installer showed you. |
| Every season | Check that the condensate drain and trap are clear (water-to-air units remove moisture in cooling mode) and that nothing is stored against the unit's access panels. |
| Every year | Professional service: clean any strainer, check well-pump operation and flow, and compare water temperature drop across the heat exchanger. Mineral scaling or iron fouling may call for acid cleaning of the coaxial heat exchanger. |
| Every year | Check the expansion tank pre-charge, buffer-tank temperatures, circulator operation and any mixing valves on the load side. |
| Every 3–5 years | Have the indoor coil and blower (or load-side heat exchanger) inspected and cleaned if airflow or temperature split has dropped. |
Troubleshooting
Geothermal heat pumps protect themselves with pressure and temperature switches, so most "no heat" calls trace back to airflow, water flow or thermostat settings. Work through the checks below before calling a technician.
| Problem | Possible cause | What to try |
|---|---|---|
| No heating or cooling | Thermostat in wrong mode; tripped breaker; disconnect off; unit in safety lockout. | Check mode and setpoint; reset the breaker once. Many units clear a lockout when power is cycled off and on — if it locks out again, call for service. |
| Unit locks out in heating mode | Low source-side flow; entering water too cold; low antifreeze concentration; dirty air filter. | Replace the filter and confirm loop or well pumps run. Repeated low-temperature lockouts point to a flow, antifreeze or loop-sizing problem for a technician. |
| Unit locks out in cooling mode | High head pressure from low water flow, a scaled heat exchanger or poor airflow. | Check the filter and blower; have a technician verify flow and the temperature rise across the heat exchanger. |
| High electric bills in winter | Auxiliary heat running too often; deep thermostat setbacks; loop delivering cold water. | Reduce setbacks and ask your contractor to review auxiliary-heat staging and entering-water temperatures. |
| Air from vents feels lukewarm | Normal heat-pump supply temperature (around 90–105 °F). | Judge comfort by whether the house reaches setpoint, not by the feel of the air. |
| Gurgling or rushing water sounds | Air trapped in the loop or hydronic piping. | A technician should purge the air; persistent air may mean a slow leak. |
| Water near the unit | Clogged condensate drain or trap; leaking fitting. | Turn the unit off, clear the drain and check fittings; call for service if water continues. |
| Rusty or slimy deposits; falling capacity | Iron bacteria, iron or scale from the well water fouling the heat exchanger. | Have the water tested and the heat exchanger cleaned; discuss water treatment or a closed loop if fouling recurs. |
| Some zones not heating | Air in the zone; zone valve or circulator not opening; supply temperature set too low. | Bleed air, check the zone thermostat, and have the controls and circulators tested. |
Frequently asked questions
Can the Hydron Module HWT048 be used with both open and closed loops?
This listing covers its open-loop rating. Manufacturers often certify the same water-source unit separately for closed-loop and open-loop use, each with its own EER and COP, so check the Hydron Module literature (or other listings for model HWT048) for the configuration you plan to install.
What refrigerant does the Hydron Module HWT048 use?
The ENERGY STAR record lists R-410A.
Does the Hydron Module HWT048 heat with forced air or hot water?
Hot water. It is an open-loop water-to-water unit that heats water for radiant floors, fan coils, low-temperature radiators or a buffer tank; it does not blow air on its own.
Is the Hydron Module HWT048 ENERGY STAR certified?
Yes. It appears on the ENERGY STAR certified geothermal heat pump list, with a certification date of January 2022, and it is also designated ENERGY STAR Most Efficient.
Sources and disclaimer
Specifications on this page come from the ENERGY STAR certified geothermal heat pumps dataset published by the U.S. Environmental Protection Agency (record certified January 20, 2022), retrieved October 7, 2026.
The setup, operating, maintenance and troubleshooting guidance is written by ManualHarbor's editors for this specific product type and configuration. It is an independent guide — not a reproduction of the manufacturer's manual — and ManualHarbor is not affiliated with Hydron Module. Always follow the safety instructions, installation requirements and warranty terms supplied with your unit, and contact Hydron Module or an authorized service provider for warranty repairs and replacement parts.
Running-cost figures use assumed U.S. average utility prices and are estimates for comparison only. See our editorial methodology for details.
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