Heat Pump Hot Water Problems and What They Mean

A heat pump hot water system that seems to be misbehaving may simply be doing what it was set up to do. The common complaints fall into three groups. Settings: a timer window that is too short, or a unit on an off-peak supply that is switched off when you expect it to heat. Placement: a unit boxed in without airflow, sitting under a bedroom window, or exposed to salt air. Genuine faults: a fault code on the display, a refrigerant leak, a failed fan or controller.

The first two groups are worth checking yourself before anyone visits, because they cost nothing to rule out. The third group is not owner territory. A heat pump combines a hot water tank, an electrical supply and a refrigeration circuit, and work on each of those belongs to a qualified trade. The sections below take each symptom in turn and say where the owner's part stops.

Lukewarm water or a tank that runs out can be a timing or usage problem rather than a broken heat pump. Rheem's owner's guide for one of its heat pump models says plainly that heavy hot water use can leave the water cooler than expected because the unit has not been given enough heating time. A household that uses a lot of hot water in one go, such as several showers back to back, can simply get ahead of the reheat.

Three things to look at. First, the timer: the same Rheem guide tells owners who have set a timer to make sure it allows enough time for the tank to reheat. Second, the tariff: if the unit is connected to a time controlled (off-peak) supply, it cannot run while that supply is off, and Rheem notes this is not a fault. Your Home, the Australian Government's guide to sustainable homes, adds that some heat pumps are not compatible with either controlled load tariff and others only with Controlled Load 2, so it is worth confirming your unit matches its circuit. Third, usage: Rheem's guide tells owners to plan their hot water use on heavy-use occasions, because a tank drawn down faster than it can reheat will run short whatever the settings.

A heat pump that costs more to run than expected may be leaning on its boost element. Your Home explains that many heat pump systems include a boost element that heats water directly in very cold weather or during heavy hot water use, and that running cost may rise if that element is used often. An element heats water the same way a conventional electric tank does, so a heat pump that boosts a lot behaves more like a conventional electric tank.

Timing matters too. Your Home says a heat pump's energy use can be reduced by timing heating to coincide with warmer afternoon air, and that a timer set to use rooftop solar will fall back on grid electricity when there is not enough solar during that window. A timer set for the early morning, before the panels produce much and when the air is coolest, works against both. If the bill jumped after installation, the timer setting, the boost setting and the tariff the unit is on are the first three questions to ask before suspecting a fault.

A heat pump makes some noise when it runs, because it has a fan and a compressor; Your Home notes that heat pumps have a fan that can produce noise. On an integrated unit the noisy part sits on top of the tank, and Your Home points out that this height lets noise carry over fences to neighbours and nearby windows. On a split system, the low outdoor unit helps with noise.

Rheem's guide advises installing its heat pump away from bedroom and living room windows, and asks installers to consider the neighbours' bedrooms and living rooms too. It also warns that the noise level once installed may be higher than the tested figure, because sound reflects off nearby walls and structures. A unit in a narrow side passage between a wall and a fence can therefore sound louder than its specification suggests.

Not every sound is a problem. The same Rheem guide says a short knocking sound when power comes back on is the electronic expansion valve working, and is normal on that model. A new grinding, rattling or squealing that was not there before is different: switch the unit off and have it inspected.

A small amount of water around a running heat pump is most likely condensate, and on its own it is normal. Drawing heat out of humid air condenses moisture on the coil, the same way an air conditioner drips. Rheem's guide for one model says the condensate discharges onto the surface below the heat pump and drains or evaporates away, with no drain line needed.

Because the water simply falls to the ground below the unit, where it lands is worth a thought. Onto a garden bed is fine; across a path is a slip risk. If the condensate outlets block, water can collect where it should not. Rheem's service checklist includes checking that the condensate discharge ports on the underside are clear and not blocked.

Water from the tank, its fittings or the relief valve drain is a separate matter. A steady drip or pooling at the base of the tank is not condensate, and it is a plumbing job.

A fault code on a heat pump's display means the controller has detected a problem, and resetting the unit again and again does not fix the cause. Rheem's owner's guide for one model says that when a fault code is present the heat pump may not operate and the water will not heat, and tells owners to note the code and call for an inspection.

Rheem's guide lists the codes for that model in its own manual, so a code number is most useful alongside the brand and model from the data plate. The useful things to record before calling: the exact code, the brand and model from the label on the unit, when the code first appeared, and whether anything changed beforehand, such as a storm, a power cut or work on the switchboard. A photo of the display and the data plate does the job.

A switch-off and switch-on cycle once is a reasonable thing to try where the manual allows it. If the same code comes back, the sensor, controller, fan or refrigeration circuit needs a qualified person, and repeated resets only delay the repair.

On the coast, salt air is the slow problem. The coil, fan and fixings sit outside in the air the unit is moving, and Rheem's warranty for the model checked here excludes corrosion caused by a corrosive environment such as coastal sea air. Read your own warranty for the same exclusion before assuming a corroded unit is covered.

Airflow is the other placement problem. A heat pump works by drawing heat out of the surrounding air, so blocked grilles cut what it can deliver. Rheem's installation instructions say the air inlet and outlet grilles should be clear of obstructions and shrubbery, its six-monthly owner checks include looking around the grilles for plant growth, and its maintenance schedule recommends the evaporator and refrigeration system be checked every five years, more often in dusty places. Overgrown gardens, stored items and new fences built close to the unit can all get in the way.

Your Home notes that air-source heat pumps work best in relatively warm, humid climates, and that their efficiency drops in colder climates. In a warm coastal climate, then, the problems to watch for are salt, airflow and condensate rather than cold-weather efficiency losses.

Anything inside the refrigerant circuit of a heat pump is work for a trained refrigeration technician, never the owner. The Australian Refrigeration Council explains that integrated heat pumps are sealed systems that need no work on the refrigeration side at installation, while a two-part split system that holds a controlled refrigerant needs a technician with an ARC refrigerant handling licence. The Council also notes that split systems usually join the refrigeration circuit with flared connections, which can be a leak source.

A refrigerant leak matters for more than performance. Your Home warns that refrigerants with a high global warming potential, leaking through faults, poor installation or equipment failure, add to greenhouse emissions, and the Australian Refrigeration Council notes that some systems use refrigerants with safety risks, including highly flammable hydrocarbons and high-pressure CO2.

The other parts of the system have their own licences. ARC states that all heat pump configurations need a licensed plumber to install the water heating unit, and the QBCC gives installing or replacing a heat pump water heater as a common example of notifiable plumbing work in Queensland. Queensland's Electrical Safety Office says to always get a licensed electrician to do any electrical work, and quotes the Electrical Safety Act 2002, under which electrical work includes testing, maintaining, repairing and replacing electrical equipment. Ask whoever you call which part of the job they are licensed for.

The downsides of a heat pump hot water system are real but mostly manageable, and almost all of them come back to cost and placement. Your Home notes that heat pumps can cost more to buy than other electric hot water systems, while using much less energy to run. Whether that trade pays off depends on the model, the tariff and how the household uses hot water.

Placement is the bigger question. The unit needs open air around it, a spot away from bedrooms on both sides of the fence, somewhere sensible for condensate to go, and on the coast, some thought about salt exposure. A block with no good position is a genuine reason to choose something else.

The unit also has more to look after than a plain electric tank: a fan, a controller, grilles to keep clear and, on split systems, a refrigerant circuit that only a qualified technician should open. None of that is a reason to avoid a heat pump, but it is worth knowing before buying rather than after.

An owner's checks stop at what you can see and switch. Rheem's guide lists minor maintenance that the occupant can do, such as looking over the unit, while servicing must be done by qualified personnel. Before calling, it suggests checking the circuit breaker marked hot water or water heater at the switchboard.

Stop and call if a fault code returns after one reset, the circuit breaker trips again, water is leaking from the tank or its fittings rather than dripping as condensate, or the unit makes a new grinding or squealing noise. Do not open the unit's covers, touch the wiring or the refrigerant lines, or adjust valves. A photo of the unit, its data plate and any code on the display lets a plumber work out what is likely before arriving.