Mixergy with a heat pump FAQ
Answers to common questions about using a Mixergy tank with a heat pump.
A heat pump transfers warmth into the water in your tank. This guide covers a Mixergy tank connected to an external heat pump, rather than a Mixergy iHP X with its heat pump built in. Heating is normally slower than with a boiler or direct electric heater.
These answers explain what you are likely to notice. Your installer or housing provider should check faults and change technical settings.
When should I ask for help?
Contact your installer or housing provider if the heat pump shows a fault, heating repeatedly stalls or your household regularly runs short of hot water.
Tell them when the problem happened and what the Mixergy app or gauge showed. Include the exact message on the heat pump’s display. Keep technical settings as installed while they investigate.
Related guides
Choose how your water is heated
Why does your tank heat to full every two weeks?
[IMAGE – HEAT-PUMP FAQ SUMMARY]
Use: Summary showing gradual heating, heating throughout the tank, Boost and configured immersion backup.
Caption: An external heat pump normally heats water throughout the tank in a longer cycle.
Alt text: Summary graphic explaining how a Mixergy tank behaves with an external heat pump.
Common questions
Why is heating slower, and does the heat pump heat the whole tank?
An external heat pump normally warms the water throughout the tank in a longer cycle. This is different from direct electric heating, which can prepare a smaller amount at the top first.
The system helps keep hotter and colder water separated rather than unnecessarily mixing them. That supports steady heat-pump operation. You do not need to adjust this yourself.
Red gauge lights show the amount ready to use, not how much of the tank is currently being warmed. The lights can change slowly while the heat pump runs. What matters is whether enough hot water is ready when you need it.
How do I request a Boost, and can I make it faster?
A Boost is a request to heat extra water. Find the gauge, the slim black panel with lights and buttons on the tank, and press the Boost Up button marked with an up arrow. Green lights show the additional amount requested; they turn red when that water is ready.
With Heat Pump selected, the request starts or continues a hot-water cycle when the heat pump’s controls allow it. It is not instant hot water. See Set hot water levels and use Boost for the app instructions.
Direct electric Boost is only an option if your installer has configured it as a secondary source. The immersion heater is the electric heating element inside the tank. Ask when it should be used rather than switching the heat source to Electric to speed up heating.
Why does heating stop before 100%, or use the immersion heater?
The heat pump can pause because room heating has priority or its hot-water cycle has reached an installer-set limit. Another limit is flow temperature: the temperature of the water leaving the heat pump.
A reading below 100% is not, by itself, a fault. If heating repeatedly stops at the same level and leaves you short, record any message on the heat pump’s display and contact the installer.
The immersion heater can provide configured backup or help complete cleansing. This does not by itself mean the heat pump has failed. Ask your installer to review the setup if it runs frequently and you do not know why.
Why does the cleansing cycle take longer?
Cleansing heats the tank fully to help control Legionella bacteria in stored water. A heat pump works at lower temperatures, so the cycle can take longer or retry later. A configured immersion heater can help reach the required temperature.
Keep cleansing enabled. See Why does your tank heat to full every two weeks? for more about this safety function.
Do I need the app or daily settings changes?
No. Once your installer has set up the system, the tank and heat pump should work together automatically. You can read the red hot-water level lights and request a Boost on the gauge without opening the app.
The app gives access to schedules and settings. Leave the installed heat-source and temperature settings in place unless your installer advises a change.