Commercial Water HeatersElectric Heat Pump
Rheem RMHPHDA120VD000 Commercial Water Heater Manual
Setup, everyday use, maintenance and troubleshooting for the commercial heat pump water heater, with verified specifications.
- COP4.5
- Electric input35.0 kW
- FuelElectric (heat pump)
About the Rheem RMHPHDA120VD000
This guide covers the Rheem RMHPHDA120VD000, a commercial heat pump water heater listed as ENERGY STAR certified. It has a rated coefficient of performance (COP) of 4.5, meaning it delivers about 4.5 units of heat for every unit of electricity it uses. That COP is higher than 68% of the 67 Electric Heat Pump models in our database.
It has an electric input of 35.0 kW (about 537,000 Btu/h of heat output at the rated COP) and an internal water volume of only 1 gallons, so it is normally piped to separate storage tanks.
Compared with electric-resistance water heating (a COP of 1), a COP of 4.5 means the unit needs only about 22% as much electricity to deliver the same amount of heat.
Specifications
| Brand | Rheem |
|---|---|
| Model number | RMHPHDA120VD000 |
| Type | Electric Heat Pump |
| Fuel | Electric |
| Coefficient of performance (COP) | 4.5 |
| Electric input | 35.0 kW |
| Storage volume | 1 gal |
Safety information
- Have the electrical supply installed by a licensed electrician on a circuit that matches the nameplate voltage, phase and current, with the disconnect and overcurrent protection the manual specifies.
- Heat pump units contain refrigerant under pressure. Sealed-system service must be performed by a certified refrigeration technician.
- Water above 120 °F (49 °C) can scald. Where water is stored hotter for sanitation or Legionella control, install thermostatic mixing valves to temper water delivered to fixtures.
- Turn off the fuel or power supply and close the water valves before servicing.
Installation and first-time setup
Heat pump water heaters move heat from a source — typically the surrounding or outdoor air, or a water loop, depending on the design — into the water, so the location and source conditions directly affect capacity and efficiency. Follow the manufacturer's application guide for source temperature limits, clearances and airflow. The unit's electrical input is 35.0 kW, so plan the electrical service accordingly.
- Plan the system
Design the system with the storage tanks, circulators and controls shown in the manufacturer's piping diagrams; small-volume heat pump units rely on separate storage to meet peak demand.
- Make the water connections
Install isolation valves, unions and any strainers specified, and add an expansion tank where the system is closed.
- Connect the condensate drain
Heat pumps produce condensate from the evaporator; pipe it to a drain and protect it from freezing.
- Wire the unit
Have an electrician connect the supply with a disconnect within sight of the unit, as required by code and the manual.
- Commission
A qualified technician verifies refrigerant operation, water flow, control settings and any backup heating before the system is put into service.
Using your commercial water heater
Setting the water temperature
Choose the storage or outlet temperature for the application and the facility's water-management plan. Common practice for Legionella control is to store water at 140 °F (60 °C) or higher and deliver it to hand sinks and showers through thermostatic mixing valves at a safe temperature. Commercial dishwashers usually need 140 °F supply water, with a booster heater for a high-temperature sanitizing rinse.
Recovery capacity
Based on its rated output, this unit can heat roughly the following amounts of water per hour (calculated estimates; the manufacturer's recovery table governs):
| Temperature rise | Approximate recovery |
|---|---|
| 40 °F | 1,613 gal/h |
| 70 °F | 922 gal/h |
| 100 °F | 645 gal/h |
Getting the best efficiency
The rated COP of 4.5 applies at test conditions. Efficiency falls as the source gets colder or the required water temperature rises, so keep setpoints no higher than the application needs and keep source air or water within the manufacturer's range.
Care and maintenance
| When | What to do |
|---|---|
| Every 3 months | Clean air filters or source-water strainers and check the condensate drain. |
| Every year | Have a refrigeration technician check refrigerant operation, coils and controls, and flush the tank or heat exchanger as recommended. |
Follow the maintenance schedule in your manufacturer's manual — intervals depend heavily on water hardness and usage — and keep a service log; it is often a warranty requirement.
Troubleshooting
Check fuel or power, water valves and settings first. Anything involving gas controls, combustion, venting or electrical components should be handled by a qualified technician.
| Problem | Possible cause | What to try |
|---|---|---|
| Not enough hot water | Source conditions outside the rated range; dirty filters or strainers; demand exceeds capacity. | Check source temperature and airflow or water flow; clean filters; review system sizing. |
| Unit runs but heats slowly | Low refrigerant charge; iced or dirty evaporator; low water flow. | Clean coils and filters; call a refrigeration technician to check the sealed system. |
| Water around the unit | Blocked condensate drain; leaking fitting. | Clear the condensate line; tighten or repair fittings. |
| Error code displayed | Brand-specific diagnostic code. | Error codes are not standardized; consult the code table in your manufacturer's manual before resetting. |
Energy use and running costs
Heating 1,000 gallons of water by 70 °F takes about 583 thousand Btu. At its rated COP of 4.5, the Rheem RMHPHDA120VD000 needs roughly 38 kWh — about $6.46 at $0.17 per kWh. Electric-resistance heating would need about 171 kWh ($29.05) for the same job.
| Hot water per day | Electricity per year | Cost per year |
|---|---|---|
| 250 gal | 3,465 kWh | $589 |
| 500 gal | 6,931 kWh | $1,178 |
| 1,000 gal | 13,862 kWh | $2,356 |
| 2,000 gal | 27,723 kWh | $4,713 |
Real-world COP varies with source temperature and setpoint, so actual costs can be higher in cold conditions or at high outlet temperatures.
Frequently asked questions
What is the COP of the Rheem RMHPHDA120VD000?
Its rated coefficient of performance is 4.5, meaning it delivers roughly 4.5 times as much heat as the electricity it consumes under test conditions.
What is the recovery rate of the Rheem RMHPHDA120VD000?
Calculated from its rated output, it can heat about 645 gallons per hour at a 100 °F rise, or about 922 gallons per hour at 70 °F. Check the manufacturer's published recovery table for exact figures.
How much electricity does the Rheem RMHPHDA120VD000 save compared with an electric water heater?
With a rated COP of 4.5, it uses roughly 22% of the electricity an electric-resistance water heater would need for the same hot-water output — about 78% less — at the rating conditions.
Does the Rheem RMHPHDA120VD000 need a separate storage tank?
Yes, in most applications. Its internal water volume is only 1 gallons, so it is normally piped to separate storage tanks sized for the building's peak demand, following the manufacturer's piping diagrams.
How much does it cost to heat water with the Rheem RMHPHDA120VD000?
At its rated COP of 4.5, heating 1,000 gallons by 70 °F takes about 38 kWh — roughly $6.46 at $0.17 per kWh.
Is the Rheem RMHPHDA120VD000 ENERGY STAR certified?
Yes. It appears on the ENERGY STAR list of certified commercial water heaters, with a certification date of January 2026.
Sources and disclaimer
Specifications on this page come from the ENERGY STAR certified commercial water heaters dataset published by the U.S. Environmental Protection Agency (record certified January 1, 2026), 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 Rheem. Always follow the safety instructions, installation requirements and warranty terms supplied with your unit, and contact Rheem 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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