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MelPump: Heat Pump Guide

Your complete guide to understanding heat pumps

school What is a Heat Pump?

A heat pump is a highly efficient device that transfers heat from one place to another. Instead of generating heat directly (like a gas boiler), it moves existing heat from outside air or ground into your home.

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Did you know? Heat pumps can produce 3-5 times more heat energy than the electrical energy they consume. This makes them one of the most efficient heating systems available.

Types of Heat Pumps

air Air Source (ASHP)

Extracts heat from outside air. Most common type, easier to install. Works even when outdoor temperature is below zero.

landscape Ground Source (GSHP)

Extracts heat from the ground via buried pipes (brine circuit). More efficient but requires more installation work.

How Does It Work?

A heat pump works like a refrigerator in reverse. Here's the simplified process:

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1. Absorb

Refrigerant absorbs heat from outside

compress

2. Compress

Compressor increases temperature

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3. Release

Heat released to your home

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4. Repeat

Cycle continues automatically

remove_circle add_circle Show more technical details

The refrigeration cycle consists of four main components:

Evaporator - Located in outdoor unit, absorbs heat from air/ground
Compressor - The heart of the system, increases refrigerant pressure and temperature
Condenser - Releases heat to your heating water
Expansion valve - Reduces pressure before the cycle repeats

warning The compressor is the most expensive component. Protecting it from frequent starts/stops (short cycling) is essential for longevity.

tune Operation Modes

Your heat pump can operate in different modes depending on current heating or cooling needs:

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Heating

Heat is extracted from outside and transferred into your home. Used during cold months.

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Cooling

Cycle reverses - heat is removed from inside and released outside. Used during warm months.

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Hot Water

Heat pump heats domestic hot water in the storage tank. Can work alongside space heating.

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Idle / Standby

Target temperature reached. Compressor is off, system monitors temperatures.

error Watch Out: Short Cycling

If your heat pump frequently switches between modes or turns on/off every few minutes, this is called "short cycling". It can seriously damage the compressor over time.

Healthy operation: Long, continuous cycles (30+ minutes) with gradual frequency changes. Avoid frequent compressor stops.

remove_circle add_circle What are heating zones?

Many installations have two separate heating zones that can be controlled independently:

Zone 1 - Usually the main heating circuit (e.g., underfloor heating or main radiators)
Zone 2 - Secondary circuit (e.g., upstairs radiators or a different building section)

thermometer Temperature Readings

Understanding temperature readings is key to monitoring your heat pump's performance. Here's what each measurement means:

Water temperature leaving the heat pump and going into the heating system. This is the "output" of your heat pump.

Typical values:

Underfloor heating: 30-40°C
Radiators: 45-55°C

warning Efficiency tip: Lower flow temperature = higher efficiency. Every degree lower saves energy. Use the lowest temperature that keeps your home comfortable.

Water temperature returning to the heat pump after circulating through your heating system. Should be lower than flow temperature.

What to look for: Should be 3-7°C lower than flow temperature.

The difference between flow and return temperatures. Shows how much heat is being transferred to your home.

Ideal values:

Underfloor heating: ~5°C
Radiators: 7-10°C

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Problem signs:

ΔT too small (1-2°C): Water pump may be running too fast, or system not absorbing heat properly
ΔT too large (>12°C): Flow may be restricted - check for blockages, air in system, or pump issues

Outside air temperature measured by the outdoor unit. Used for weather-compensated heating curves.

lightbulb The colder it is outside, the harder the heat pump works and efficiency (COP) decreases. This is normal - extracting heat from very cold air requires more energy.

Current temperature of domestic hot water in the storage tank.

Typical settings:

Daily use: 45-50°C
Legionella prevention: 60°C+ (periodic)

Internal temperature where refrigerant releases heat to the water system. Higher values usually indicate the system is working harder.

warning Very high condensing temperatures reduce efficiency. If consistently high, check if flow temperature can be lowered.

For ground source heat pumps - temperature of fluid in the ground loop entering and leaving the heat pump.

Brine Inlet - Fluid returning from ground (warmer in winter)
Brine Outlet - Fluid going to ground (cooler after heat extracted)

error If brine inlet regularly drops below 0°C, the ground loop may be undersized or there's a problem with the collector.

settings Compressor & Frequency

The compressor is the heart of your heat pump - and also its most expensive component. Understanding how it works helps you optimize settings and extend its lifespan.

Compressor Frequency

Modern heat pumps use inverter compressors that run at variable speeds. The frequency (Hz) indicates how hard the compressor is working:

20-40 Hz

Low demand

Efficient operation, maintaining temperature

40-70 Hz

Medium demand

Normal operation, actively heating

70-120 Hz

High demand

Maximum output, cold weather or recovery

dangerous Short Cycling - The Compressor Killer

Short cycling occurs when the compressor starts and stops frequently (multiple times per hour). This is extremely harmful because:

Each start causes mechanical stress and electrical surge
Startup phase uses more energy than continuous running
Oil doesn't circulate properly in short cycles
Can lead to premature compressor failure

Solutions: Add or enlarge buffer tank, lower target temperatures, adjust heating curve, ensure system is properly sized.

Flow Rate

The flow rate (liters/minute) shows how much water circulates through the system. This is crucial for heat transfer:

Too Low

Heat pump may overheat and shut down. Poor heat distribution throughout the house.

Too High

Delta T becomes too small. Wasted pump energy without efficiency benefit.

Dropping Over Time

May indicate clogged filter, air in system, or water pump degradation.

remove_circle add_circle Other compressor-related parameters

Fan RPM - Speed of outdoor unit fans. Varies with heating demand and defrost needs.
LEV (Expansion Valve) - Controls refrigerant flow. Position changes based on operating conditions.
Water Pump Status - Whether internal circulation pump is running.
3-Way Valve - Directs flow between heating circuit and hot water tank.

eco Efficiency & COP

What is COP?

COP (Coefficient of Performance) measures how efficient your heat pump is. It's the ratio of heat output to electrical input.

COP = Heat Output ÷ Electrical Input

Example: COP of 4 means for every 1 kWh of electricity, you get 4 kWh of heat

What Affects COP?

arrow_upward Higher COP (Better)

Lower flow temperatures
Warmer outdoor temperatures
Underfloor heating systems
Properly sized heat pump
Good insulation

arrow_downward Lower COP (Worse)

Higher flow temperatures
Very cold outdoor conditions
Frequent defrost cycles
Booster heater usage
Oversized or undersized system

Energy Consumed vs Produced

The app shows estimated input power (electricity) and output power (heat). Monitoring these helps you understand real-world efficiency:

Estimated Input Power - Electricity being consumed by the heat pump
Estimated Output Power - Heat being delivered to your home
Estimated COP - Real-time efficiency (Output ÷ Input)

show_chart Track your energy over time to spot trends. A sudden drop in efficiency might indicate a problem needing attention, such as low refrigerant, dirty filters, or sensor issues.

ac_unit Defrost & Booster Heaters

Defrost Mode

In cold, humid conditions, frost builds up on the outdoor unit's heat exchanger. The heat pump periodically runs defrost cycles to remove this ice.

info How Defrost Works

During defrost, the heat pump temporarily reverses - it takes heat from inside your home to melt ice on the outdoor unit. You may notice a brief drop in heating during this time. This is normal.

warning When to Be Concerned

Defrost cycles lasting more than 10-15 minutes
Defrost happening more than 2-3 times per hour in extreme cold
Ice that doesn't clear after defrost
Defrost running when outdoor temperature is above 5°C

Booster Heaters

Heat pumps include electric backup heaters for situations when the compressor alone cannot meet demand:

Booster Heater 1 & 2 - Electric elements in the hydrobox that help heat water
Immersion Heater - Electric element in the hot water tank

bolt Warning: High Energy Cost

Electric backup heaters have COP of 1 - they produce only 1 kWh of heat per 1 kWh of electricity. This is 3-5x less efficient than the heat pump compressor.

Monitor for: If booster heaters run frequently during normal weather, your system may be undersized or settings need adjustment.

Legionella Mode

Periodically heats the hot water tank to 60°C+ to kill Legionella bacteria. This often requires booster heaters since heat pumps are most efficient at lower temperatures.

shield Legionella cycles are important for health safety but are energy-intensive. Most systems run them weekly. Consider scheduling during off-peak electricity hours.

list_alt All Parameters Reference

Below is a complete list of parameters available in the app. Note that not all parameters apply to every heat pump.

info Availability depends on your specific model, installation type (air source vs ground source), and whether you have additional sensors or the WiFi adapter installed.

remove_circle add_circle Click to expand full parameter list

Parameter	Description
`Estado del Compresor`	Muestra si el compresor está funcionando actualmente o inactivo
`Frecuencia del Compresor`	Velocidad del compresor en Hz, valores más altos significan mayor potencia de calefacción o refrigeración
`Modo Descongelación`	Indica cuando la unidad exterior está derritiendo la acumulación de hielo
`Potencia`	Si la bomba de calor está encendida o apagada
`Estado del Calentador Auxiliar 1`	Muestra si el primer calentador eléctrico de respaldo está activo
`Estado del Calentador Auxiliar 2`	Muestra si el segundo calentador eléctrico de respaldo está activo
`Estado del Calentador Auxiliar 3`	Muestra si el tercer calentador eléctrico de respaldo está activo
`Estado de la Resistencia Eléctrica`	Muestra si la resistencia eléctrica dentro del depósito de agua caliente está activa
`Modo de Operación`	Modo actual: calefacción, refrigeración o producción de agua caliente. También puede mostrar otros modos como anticongelante o legionella.
`Modo de Operación #1`	Modo de funcionamiento para la zona de calefacción #1. En la mayoría de las bombas de calor es modo de flujo constante o curva de compensación, pero algunos modelos pueden admitir modos avanzados como auto-adaptación.
`Modo de Operación #2`	Modo de funcionamiento para la zona de calefacción #2. En la mayoría de las bombas de calor es modo de flujo constante o curva de compensación, pero algunos modelos pueden admitir modos avanzados como auto-adaptación.
`Tiene Error`	Indica si el sistema tiene un error activo
`Código de Error`	Código de diagnóstico mostrado cuando hay un problema
`Zona 1 Activa`	Si la zona de calefacción/refrigeración #1 está actualmente activa
`Zona 2 Activa`	Si la zona de calefacción/refrigeración #2 está actualmente activa
`Caudal`	Cantidad de agua que fluye a través del sistema en litros por minuto
`Ventilador 1 RPM`	Velocidad del primer ventilador de la unidad exterior
`Ventilador 2 RPM`	Velocidad del segundo ventilador de la unidad exterior
`Lev A`	Posición de apertura de la válvula de expansión electrónica
`Potencia de Entrada`	Potencia eléctrica estimada consumida
`Potencia de Salida`	Energía térmica estimada producida
`COP`	Relación de eficiencia - potencia térmica dividida por consumo eléctrico
`Estado de la Bomba de Circulación 1`	Muestra si la bomba de circulación de agua está funcionando
`Water Pump 2 Status`	WaterPump2Status
`Water Pump 3 Status`	WaterPump3Status
`Water Pump 4 Status`	WaterPump4Status
`Estado de la Válvula de 3 Vías`	Posición de la válvula que dirige el agua a la calefacción o al depósito de agua caliente
`Temperatura Máxima Agua Caliente`	Ajuste de temperatura máxima permitida del depósito de agua caliente
`Forzar Agua Caliente`	Fuerza el calentamiento inmediato del agua caliente independientemente del programa
`Prohibir Calefacción Zona #1`	Cuando está habilitado, impide la calefacción en la zona #1
`Prohibir Calefacción Zona #2`	Cuando está habilitado, impide la calefacción en la zona #2
`Prohibir Calentamiento de Agua Caliente`	Cuando está habilitado, impide el calentamiento del agua caliente
`Prohibir Refrigeración Zona #1`	Cuando está habilitado, impide la refrigeración en la zona #1
`Prohibir Refrigeración Zona #2`	Cuando está habilitado, impide la refrigeración en la zona #2
`Modo vacaciones`	Modo de operación reducido para ahorrar energía durante las vacaciones
`ACS Modo Eco`	Modo de ahorro de energía que calienta el agua más lentamente usando temperaturas de impulsión más bajas para mejor eficiencia
`Modo de Control App MEL Pump`	Si el sistema está controlado a través del servidor, compatible solo con bombas de calor Mitsubishi
`Código de Servicio`	Código de diagnóstico utilizado por los técnicos de servicio para obtener los detalles de los parámetros de la bomba de calor
`Temp. Interior #1`	Temperatura actual del aire en las habitaciones atendidas por la zona de calefacción #1
`Temp. Interior #2`	Temperatura actual del aire en las habitaciones atendidas por la zona de calefacción #2
`Temp. Exterior`	Temperatura exterior actual medida cerca de la bomba de calor
`Temp. Impulsión`	Temperatura del agua que sale de la bomba de calor y entra en el sistema de calefacción
`Temp. Retorno`	Temperatura del agua que regresa a la bomba de calor desde el sistema de calefacción
`Temp. Impulsión #1`	Temperatura del agua suministrada a la zona de calefacción #1
`Temp. Retorno #1`	Temperatura del agua de retorno de la zona de calefacción #1
`Temp. Impulsión #2`	Temperatura del agua suministrada a la zona de calefacción #2
`Temp. Retorno #2`	Temperatura del agua de retorno de la zona de calefacción #2
`Temp. Termostato #1`	Temperatura ambiente deseada establecida para la zona de calefacción #1
`Temp. Objetivo #1`	Temperatura objetivo del agua para el circuito de calefacción en la zona #1
`Temp. Termostato #2`	Temperatura ambiente deseada establecida para la zona de calefacción #2
`Temp. Objetivo #2`	Temperatura objetivo del agua para el circuito de calefacción en la zona #2
`Delta Temp.`	Diferencia entre el agua que sale y la que retorna a la bomba de calor, usada para mostrar cuánta energía térmica se transfiere
`Temp. ACS`	Temperatura actual del agua caliente sanitaria almacenada en el depósito
`Temp. Condensación`	Temperatura interna de la bomba de calor donde el refrigerante cede calor al sistema de agua; valores más altos suelen significar menor eficiencia
`Temp. agua objetivo del tanque`	Temperatura deseada del depósito de agua caliente sanitaria
`Temp. impulsión fuente auxiliar`	Temperatura del agua que sale de la caldera de apoyo
`Temp. retorno fuente auxiliar`	Temperatura del agua que regresa a la caldera de apoyo
`Temp. agua del tanque de mezcla`	Temperatura del agua dentro del depósito de inercia o de mezcla
`Temperatura de entrada de salmuera`	Temperatura del fluido del circuito geotérmico que entra en la bomba de calor
`Temperatura de salida de salmuera`	Temperatura del fluido del circuito geotérmico que sale de la bomba de calor
`Temp. Línea Líquido`	Temperatura del refrigerante líquido que fluye a través del circuito de refrigeración de la bomba de calor

warning Troubleshooting

Here are some common issues and what to check:

Check if flow temperature is appropriate for your heating system
Verify heating curve settings match your home's heat loss
Check for air in the system (radiators may need bleeding)
Ensure all zone valves are opening correctly
Check if heat pump is undersized for your home

Check how often booster heaters are running - they use a lot of electricity
Review COP values - if consistently below 2.5, investigate
Look for excessive defrost cycles
Consider if flow temperatures can be reduced
Check Legionella cycle frequency and timing

This is short cycling - needs attention to protect compressor
Consider adding or enlarging buffer tank
Reduce target temperatures or adjust heating curve
Check if system is oversized for your heat demand
Ensure minimum flow rate is maintained

Check if hot water mode is enabled
Verify 3-way valve is switching to tank position
Check if immersion heater is working (if equipped)
Review hot water schedule settings
Tank sensor may need checking

Check and clean the system filter
Bleed air from the system
Check water pump operation
Inspect for blockages in pipes
Check system pressure

Check if the integration is active
If you added the integration using a guest account, check if you have granted all required permissions
Check that your heat pump controller is on the main screen - some heat pumps don't send data if you open a submenu and leave it there
After returning to the main screen on the controller, you may need to wait up to 24 hours for data to start flowing again
Check if there is data in the original manufacturer app - if not, your heat pump may not support this feature or may have a sensor misconfiguration

Ready to Monitor Your Heat Pump?

Start tracking all these parameters and optimize your heat pump's performance. Join thousands of users who are saving energy and extending their heat pump's lifespan.

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