Troubleshooting Heat Pumps - Common Problems and Solutions

A guide and tips for troubleshooting heat pumps fast and easy. Check out this repair guide and learn how to deal with the most popular water heater heat pumps in North America: AO Smith, Bradford White, Rheem, State, Kenmore, Reliance, American, GE, and others.

The article deals with the leading causes of heat pump failure, symptoms, error codes, and easy and safe repair recommendations.

Rheem heat pump water heater - hybrid

We will assume that the water heater heat pump, before malfunction, was correctly installed - per codes and manufacturer's instructions. This includes an adequately selected room for the unit, also that the electrical and water connections are in place, so as the air filter and condensate lines, and the tank is filled with water.

The first step in diagnosing the problem and troubleshooting is to disconnect the unit for some time simply (the time depends on the model), resume the power, and determine if the error code is still present or not. If, after resuming the power, an error code is still ON, read further, and find the instructions on how to repair the unit.

To fix the problem fast and correctly, it is good to know the main heat pump parts and what's considered a regular operation.

For example, the average operating temperature of the heat pump is between 32 F and 150 F. All heat pumps are equipped with an electric fan and compressor, so it is normal to hear some noise, but not the abnormal sound.

Some noises can also be heard during the metal part contraction (cooling) and expansion (heating).

Common heat pump problems and solutions

For any issues related to the heat pump, the recommendation is to contact a licensed technician, but if you are planning to deal with the problem, here are the most common issues with the instructions on how to fix them:

Problem: Surrounding air is getting cooler


When the heat pump operates, the room air gets cooler… and that is normal. For the correct and efficient operation, the utility room where the unit is installed should have a recommended size, proper clearances around the unit, and vented correctly, so plenty of air is coming in and through the heat pump.

The heat pump uses the warm air for water heating while releasing the air, which is colder than the surrounding. One way to provide more air for the normal operation is to install the louvered door so that the air can get in from the adjacent room.

Problem: Water is dripping


If the water is dripping down the outside of the water heater, the water connections should be inspected for any loose joints or the heater's condensate drain, as it might be dirty and clogged.

For example, if the water leaks around the elements (a gasket or threads), re-seal or replace the gasket. The best solution for these problems is regular maintenance and unit cleaning.

During the water heater installation, a suitable drain pan should be installed under the unit to catch the condensate or leaky water, and piped to the appropriate drain. Since the leak can damage surrounding objects, installing an automatic leak detector with the shutoff device is recommended.

Problem: No hot water and not enough hot water


This is what needs to be checked and fixed:

The water temperature on the thermostat might be set too low – increase it if required.

If the unit is in Vacation mode – turn it off.

If the temperature is above the maximum or below the minimum recommended in some heating modes, the heat pump won't operate.

If the water heater hasn't been used for two weeks or more, the hydrogen gas can accumulate inside the tank – which is very flammable. Before running any of the electrical devices, open the hot water tap for several minutes.

Check the air filter, and if it is dirty, clean or replace the filter.

When the demand for hot water is high, a heat pump cannot recover fast enough, so waiting for the full or partial recovery is the only option. Sometimes it is needed to change the heating mode due to the higher demand and therefore make the pump more efficient. If the water heater runs out of hot water quickly due to higher demand, the issue might be with the undersized water heater.

Check for the sediment or mineral build-up in the heater's tank or on heating elements – the limescale buildup reduces the heat transfer from the heat source to water. Draining and flushing is usually the best option. Water softeners are useful as prevention.

As the unit operates efficiently only in the suggested air temperature range, so when the air gets colder, the unit cannot heat the water to the desired temperature.

The incoming water is way too cold.

During the wintertime, the hot water loses the heat rapidly through the water pipes, so proper pipe insulation is required. The same problem is if the pipe is too long.

If the unit doesn't work, check the power, fuse, circuit breaker, TCO (manual reset limit), or ECO, requiring resetting. Also, check for the non-functioning temperature sensor – perform the resistance test and replace it if defective. Replace the heating element if burned out.

If the mixing valve is installed, check if it is malfunctioning. Also, make sure water connections are not reversed – incoming cold water gets into the hot water pipe, and outgoing hot gets into the cold side.

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Problem: Water is too hot


The thermostat might be set too high or not snug against the tank. A broken thermostat or shorted heating element can also result in extremely high water temperatures. If the electronic control is malfunctioning – the best is to call a technician. To prevent hot water scald, it is recommended to install a thermostatic mixing valve at each faucet.

Problem: The heat pump is noisy


As said before, some noise from a fan and compressor is normal, but if there is a rumbling noise, then the problem is with the mineral or sediment buildup on the heating elements. The elements have to be cleaned or replaced. The noises such as crackling, gurgling, or popping are usually related to scale or lime buildup, while the pounding sound can be reduced by installing the water hammer arrestor.

Problem: Temperature and pressure relief valve makes a popping sound and is dripping


A TPR valve is a safety element that should open only if there is an excessive pressure buildup within the closed heating system. It might also leak if the debris is stacked inside the valve. During the regular operation, the valve should not leak at all. The thermal expansion is kept under control with the installed thermal expansion tank.

To limit the water pressure inside the house plumbing, it is beneficial to install the pressure reducing valve - PRV. It should be installed on the cold water supply line to keep the pressure from 50 to 60 psi.

Problem: Hot water has a bad smell – the smell of a rotten egg


Due to the high sulfate content in water supplies (usually from a well) and its reaction with the anode rod (especially magnesium type), hot water might have rotten egg odor. One solution is to replace the anode with the kind that is less prone to this reaction (aluminum) or chlorinate the heater thoroughly.

Problem: Discolored water


If milky water is seen, the aerated faucets should be installed to eliminate the buildup gases inside the heating system.

Checking the anode rod regularly or switching to a powered anode can prevent corrosion (that makes the water look muddy or brown), as the metal tank is always protected with the effective element, which doesn't deteriorate over time.

Problem: The compressor is not operating


Replace the broken compressor or check if there is a refrigerant leak. In the case of the AO Smith heat pump, check the run capacitor and look for any damages to the housing. Measure the resistance – if it is indefinite, the element has to be replaced.

Problem: High operating costs


The first things that need to be checked are the set temperature - which might be high, inefficient heating mode, and dirty air filter. Also, if the surrounding air temperature is not in the recommending range, the compressor might have trouble operating correctly.

The above problems are problems found on most of the heat pumps for residential use, but there are many more, of course. Due to the advanced electronics followed by the diagnostic system and small display screen found in almost every new unit, the error codes appear when the problem occurs – making problem diagnosing easy.

For example, an American heat pump uses the error codes such as E20, E21… Bradford White and GE heat pumps use the error codes such as F1, F2… F15, followed by the beeping sound - and each code means something; a faulty heating element, dirty air filter, compressor or air failure, sensor malfunctioning…

Every user manual contains the troubleshooting heat pumps guide with a list of the most common diagnostic codes.

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