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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
`État du Compresseur`	Indique si le compresseur fonctionne actuellement ou est inactif
`Fréquence du Compresseur`	Vitesse du compresseur en Hz, des valeurs plus élevées signifient plus de puissance de chauffage ou de refroidissement
`Mode Dégivrage`	Indique quand l'unité extérieure fait fondre l'accumulation de glace
`État de la Pompe`	Si la pompe à chaleur est allumée ou éteinte
`État du Chauffage d'Appoint 1`	Indique si le premier chauffage électrique de secours est actif
`État du Chauffage d'Appoint 2`	Indique si le deuxième chauffage électrique de secours est actif
`État du Chauffage d'Appoint 3`	Indique si le troisième chauffage électrique de secours est actif
`État de la Résistance Électrique`	Indique si la résistance électrique à l'intérieur du ballon d'eau chaude est active
`Mode de fonctionnement`	Mode actuel : chauffage, refroidissement ou production d'eau chaude. Peut également afficher d'autres modes comme antigel ou légionelle.
`Mode de Fonctionnement #1`	Mode de fonctionnement pour la zone de chauffage #1. Dans la plupart des pompes à chaleur, il s'agit soit d'un mode à débit constant soit d'une courbe de compensation, mais certains modèles peuvent prendre en charge des modes avancés comme l'auto-adaptation.
`Mode de Fonctionnement #2`	Mode de fonctionnement pour la zone de chauffage #2. Dans la plupart des pompes à chaleur, il s'agit soit d'un mode à débit constant soit d'une courbe de compensation, mais certains modèles peuvent prendre en charge des modes avancés comme l'auto-adaptation.
`A une Erreur`	Indique si le système a une erreur active
`Code d'Erreur`	Code de diagnostic affiché lorsqu'il y a un problème
`Zone 1 Active`	Si la zone de chauffage/refroidissement #1 est actuellement active
`Zone 2 Active`	Si la zone de chauffage/refroidissement #2 est actuellement active
`Débit`	Quantité d'eau circulant dans le système en litres par minute
`Ventilateur 1 RPM`	Vitesse du premier ventilateur de l'unité extérieure
`Ventilateur 2 RPM`	Vitesse du deuxième ventilateur de l'unité extérieure
`Lev A`	Position d'ouverture du détendeur électronique
`Puissance d'Entrée`	Puissance électrique estimée consommée
`Puissance de Sortie`	Énergie thermique estimée produite
`COP`	Rapport d'efficacité - puissance thermique divisée par consommation électrique
`État de la Pompe de Circulation 1`	Indique si la pompe de circulation d'eau fonctionne
`Water Pump 2 Status`	WaterPump2Status
`Water Pump 3 Status`	WaterPump3Status
`Water Pump 4 Status`	WaterPump4Status
`État de la Vanne 3 Voies`	Position de la vanne dirigeant l'eau vers le chauffage ou le ballon d'eau chaude
`Température Max Eau Chaude`	Réglage de température maximale autorisée du ballon d'eau chaude
`Activer l'eau chaude`	Force le chauffage immédiat de l'eau chaude quel que soit le programme
`Interdire le Chauffage Zone #1`	Lorsqu'il est activé, empêche le chauffage dans la zone #1
`Interdire le Chauffage Zone #2`	Lorsqu'il est activé, empêche le chauffage dans la zone #2
`Interdire le Chauffage d'Eau Chaude`	Lorsqu'il est activé, empêche le chauffage de l'eau chaude
`Interdire la zone de refroidissement #1`	Lorsqu'il est activé, empêche le refroidissement dans la zone #1
`Interdire la zone de refroidissement #2`	Lorsqu'il est activé, empêche le refroidissement dans la zone #2
`Mode Vacances`	Mode de fonctionnement réduit pour économiser l'énergie pendant les vacances
`Eau Chaude Éco`	Mode économie d'énergie qui chauffe l'eau plus lentement en utilisant des températures de départ plus basses pour une meilleure efficacité
`Mode de Contrôle App MEL Pump`	Si le système est contrôlé via le serveur, pris en charge uniquement par les pompes à chaleur Mitsubishi
`Code de Service`	Code de diagnostic utilisé par les techniciens de service pour obtenir les détails des paramètres de la pompe à chaleur
`Temp. Intérieure #1`	Température actuelle de l'air dans les pièces desservies par la zone de chauffage #1
`Temp. Intérieure #2`	Température actuelle de l'air dans les pièces desservies par la zone de chauffage #2
`Temp. Extérieure`	Température actuelle de l'air extérieur mesurée près de la pompe à chaleur
`Temp. de Flux`	Température de l'eau quittant la pompe à chaleur et entrant dans le système de chauffage
`Temp. de Retour`	Température de l'eau revenant à la pompe à chaleur depuis le système de chauffage
`Temp. de Flux #1`	Température de l'eau fournie à la zone de chauffage #1
`Temp. de Retour #1`	Température de l'eau de retour de la zone de chauffage #1
`Temp. de Flux #2`	Température de l'eau fournie à la zone de chauffage #2
`Temp. de Retour #2`	Température de l'eau de retour de la zone de chauffage #2
`Temp. Thermostat #1`	Température ambiante souhaitée définie pour la zone de chauffage #1
`Temp. Cible #1`	Température d'eau cible pour le circuit de chauffage dans la zone #1
`Temp. Thermostat #2`	Température ambiante souhaitée définie pour la zone de chauffage #2
`Temp. Cible #2`	Température d'eau cible pour le circuit de chauffage dans la zone #2
`Delta Temp.`	Différence entre l'eau sortante et l'eau de retour vers la pompe à chaleur, utilisée pour montrer combien de chaleur est transférée
`Temp. de l'Eau du Réservoir`	Température actuelle de l'eau chaude sanitaire stockée dans le ballon
`Temp. de condensation`	Température interne de la pompe à chaleur où le fluide frigorigène cède sa chaleur au circuit d'eau, des valeurs plus élevées signifient généralement un rendement plus faible
`Temp. eau du réservoir cible`	Température souhaitée du ballon d'eau chaude sanitaire
`Temp. départ source auxiliaire`	Température de l'eau quittant la chaudière d'appoint
`Temp. retour source auxiliaire`	Température de l'eau retournant à la chaudière d'appoint
`Temp. eau du réservoir de mélange`	Température de l'eau dans le ballon tampon ou le ballon mélangeur
`Température d’entrée de la saumure`	Température du fluide du circuit géothermique entrant dans la pompe à chaleur
`Température de sortie de la saumure`	Température du fluide du circuit géothermique quittant la pompe à chaleur
`Temp. Ligne Liquide`	Température du fluide frigorigène liquide circulant dans le circuit de refroidissement de la pompe à chaleur

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?

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