Air Source Heat
Pump FAQ Technical Hub

E37 Error

The E37 error means your heat pump has detected poor water flow.

Main Causes

1. Low water pressure Your heating system needs to be filled to 1.7 bar. → See this guide: How to top up your heating system using a filling loop.
2. System has a leak
   
   • Ensure that there are no leaks on the system.
3. Zones or radiators shutting down
   
   • Thermostats or zone valves closing off underfloor heating (UFH) or radiator circuits.
   • Very common if all UFH zones are closed.

Quick fix to test: Remove one zone actuator from your main zone so that circuit stays open. This often clears the error immediately.

Your Fjord I cylinder has two operating modes:

• Heating mode
• Heating + Fan mode

Heating + Fan mode keeps the fan running constantly for extra air circulation. The fan symbol will appear on the display if this is activated.

To change which mode you are in, either change it in the APP or by pressing and holding the immersion button (second button from the left) for 5~6 seconds. If this function is enabled the fan will continue working to ventilate the air, when the water temperature reaches the set point and unit is standby.

Important: This mode is only practical if your external exhaust is ducted internally in the property. Otherwise, use normal Heating mode.

Get your heat pump connected for app control in under a minute.

Quick steps:

1. Press and hold the power button for 3 seconds to unlock the display.
2. Press and hold the power button + up button together for 5 seconds.
3. The Wi-Fi symbol will flash when it’s ready to connect.
4. Move onto your phone now and follow our guide on connecting to your phone. (246) How to Connect Your Phone to the Adlar Castra Heat Pump - YouTube

Watch the full video: https://www.youtube.com/watch?v=lBGf72MT5ek

You can control your heat pump from your phone using the Smart Life app.

Step-by-step:

1. Activate WiFi on the heat pump

• Press any button to wake the screen.
• Press and hold the Power button + Up arrow together for 5 seconds.
• You’ll hear a beep and the WiFi symbol will start flashing.

2. Add the device in the Smart Life app

• Open the Smart Life app and sign in.
• Tap the + button to add a device.
• Go to Large Home Appliances → select Heat Pump (WiFi).
• Enter your home WiFi password.
• Wait for the app to connect.

Once connected, you can adjust temperature, change modes, and monitor your system remotely.

Watch the full video on our YouTube channel. (246) How to Connect Your Phone to the Adlar Castra Heat Pump - YouTube

See our guide on getting the heat pump into pairing mode: How to Activate WiFi on Your Adlar Castra UK Heat Pump

You can easily change the heating temperature directly on the heat pump control panel.

How to Adjust Temperature Settings on Your Adlår Castra Heat Pump

Step-by-step:

1. Unlock the display Press and hold the Power button for 3 seconds until you hear a beep (the padlock disappears).

2. Adjust in manual mode Use the Up and Down arrow buttons to set your desired temperature.

3. Use Heat Curve mode (recommended for efficiency)

• Let the screen flash after unlocking.
• Press and hold the M button.
• Choose your curve: HH1 (warmest) to HL8 (lowest).
• Press the Power button to save.

Tip: Heat Curve mode is usually more efficient than a fixed manual temperature.

You can easily change the heating temperature directly on the heat pump control panel.

How to Control Your Adlar Castra Heat Pump from Your Phone

Step-by-step:

1. Unlock the display Press and hold the Power button for 3 seconds until you hear a beep (the padlock disappears).

2. Adjust in manual mode Use the Up and Down arrow buttons to set your desired temperature.

3. Use Heat Curve mode (recommended for efficiency)

• Let the screen flash after unlocking.
• Press and hold the M button.
• Choose your curve: HH1 (warmest) to HL8 (lowest).
• Press the Power button to save.

Tip: Heat Curve mode is usually more efficient than a fixed manual temperature.

If your underfloor heating (UFH) zones stay cold, follow these checks in order:

Quick checks

1. Room thermostats Set the thermostat 2–3°C higher than the current room temperature so the zone calls for heat.
2. Zone actuators Check the actuators on the manifold are opening (you should hear them click). Remove one actuator to manually open the zone for testing.
3. Flow meters Make sure all flow meters on the UFH manifold are fully open. → See: How to adjust flow rates on your Underfloor Heating System
4. Circulation pump Confirm the pump is running (listen for it or check Live Data on the heat pump).
5. Mixer valve Check the UFH mixer valve is set correctly (set to maximum / 50°C).

Extra checks

• System pressure must be around 1.7 bar.
• Bleed any air from the system.
• Make sure the heat pump is running and producing warm water (check flow temperature in Live Data).

Tip: Low flow is a very common cause — see our E37 Error guide if you get that error.

If your home isn’t getting warm enough, follow these simple steps:

1. Check the Sun Symbol Make sure the ☀️ sun symbol is showing in the top left of the display (this means heating mode is active). Tap the M button until the sun appears.

2. Turn the Heat Pump ON

• Press and hold the Power/Lock button for 5 seconds to unlock the display.
• Press the Power button again for 2–3 seconds. The sun symbol should appear and heating will start.

3. Increase the Heat Curve

• Unlock the display.
• Briefly press the Down arrow to enter heat curve mode.
• Press Down to raise the curve (higher number = more heat output).

Important note It can take 24–36 hours for your home to fully warm up after changing the heat curve.

During normal operation your Adlår Castra heat pump display should look like this:

Main numbers

• IN – Return water temperature coming back from your home (example: 38°C)
• SET – Target water temperature (example: 50°C)

Symbols you should see

• ☀️ Sun symbol (top left) – Heating mode is active (this is what you want in winter)
• 📶 WiFi symbol – Connected to your home WiFi
• 🔒 Lock symbol – Display is locked (normal). Hold the Power button for 3–4 seconds to unlock.
• Pump symbol (bottom left) – Circulation pump is running
• Fan + Compressor symbols – The heat pump is working and heating your home
• TIME (bottom right) – Current clock time (example: 08:00)

Tip: If you see the sun, pump, fan and compressor symbols together, your system is operating normally.

How to Set Timers on Your Fjord I Cylinder

Your Fjord I cylinder has a built-in timer for automatic heating.

To set the Clock (current time):

1. Short press the ⏰ Clock/Timer button.
2. Use ▲ and ▼ arrows to set the hour and minute.
3. Press ⏰ to save and exit.

To set the Timer (ON / OFF):

1. Press and hold the ⏰ Clock/Timer button for 5 seconds.
2. Set the Timer ON time:
   
   • Use ▲ and ▼ to set the hour.
   • Press ⏰ to move to minutes and set them.
3. Press ⏰ again to set the Timer OFF time (repeat the steps).
4. Press ⏰ once more to save and exit.

To cancel the timer while programming: While setting Timer ON or Timer OFF, press the Settings (gear) button to cancel.

Notes:

• The timer repeats every day.
• Settings are saved even after a power cut.

Alternative option: Create more flexible schedules using Smart Scenes in the Smart Life app.

How to Create Smart Scenes in the Adlår Castra App (Heating & Hot Water)

Smart Scenes let you automatically control your heat pump and Fjord I cylinder based on time, weather, or other triggers.

(246) How to Create Smart Scenes in the Adlår Castra App (Heating & Hot Water) - YouTube

Step-by-step:

1. Open the Smart Life app and tap Scene (or Smart) at the bottom.
2. Tap the + icon to create a new scene.
3. Choose a trigger (e.g. specific time, sunrise/sunset, or temperature).
4. Add an action:
   
   • Select your Adlår Castra heat pump or Fjord I cylinder.
   • Turn it On/Off, set temperature, choose Heating or Hot Water mode, or activate immersion boost.
5. Name your scene (e.g. “Morning Heat” or “Evening Hot Water”) and tap Save.

Note: Scenes may struggle

Smart Thermostats

You can add smart room temperature sensors to the Smart Life app for automatic, efficient control of your Adlår heat pump.

This is an Example device you can purchase, and add it to your Smart Life app. There are a number of alternatives also available.

How to use it:

1. Pair the sensor in the Smart Life app.
2. Create a Smart Scene that changes the heat curve based on the actual room temperature.

Example scene:

• If room temperature > 21°C → set a lower heat curve (e.g. HL1)
• If room temperature < 21°C → set a higher heat curve (e.g. your normal HH8)

Efficiency tip: Use the thermostat to adjust heat curves rather than turning the heat pump fully on or off. This reduces short cycling and improves efficiency

You can easily share control of your Adlår heat pump and cylinder with family members (or allow Adlår support to check your system remotely).

Step-by-step:

1. Open the Smart Life app and tap Me (bottom right).
2. Tap Home Management.
3. Select your home.
4. Tap Add Member.
5. Choose Administrator or Common Member, then:
   
   • Enter their name + email/phone, or
   • Copy the invitation code/link and send it via message.
6. Your family member opens the app → Me → Home Management → Join a Home.
7. They enter the code/link and accept.

Adlår Support You can add our team the same way so we can remotely monitor and help troubleshoot your system.

Tip: The new member must already have a Smart Life account.

If your Adlår Castra heat pump won’t connect to WiFi, try these common fixes:

1. Move your router closer Poor signal is the most frequent cause.

• Temporarily place your WiFi router nearer to the heat pump.
• Use a wired Ethernet extension cable if needed (no need to move the router permanently).
• Once connected, you can move the router back to its normal position.

2. Use 2.4 GHz WiFi only The heat pump only works on 2.4 GHz networks.

• Log into your router settings and temporarily disable the 5 GHz band.
• After the heat pump connects successfully, you can turn 5 GHz back on.

See also: How to Activate WiFi on Your Heat Pump | How to Connect Your Phone to the Heat Pump

Ready to paste straight into Elementor. Want any tweaks?

Can't See Automations / Smart Scenes in the App

If your automations (Smart Scenes) are not visible in the Smart Life app, you’re probably in the wrong view.

Quick fix:

1. On the home screen, tap Smart at the bottom.
2. At the top of the screen, look at the bar. If Tap to Run is highlighted in bold, tap Automation instead.
3. Your automations and Smart Scenes will now appear.

Tip: “Tap to Run” is for one-off actions. “Automation” is where all your scheduled and automatic scenes live.

See also: How to Create Smart Scenes in the Adlår Castra App

Follow these steps to program the automatic hot water timer on your cylinder:

To set the timer:

1. Press the Power button to wake the display.
2. Press and hold the ⏰ Clock button for 5–6 seconds until “ON” appears.
3. Use the ▲ and ▼ arrows to set your ON time.
4. Press the ⏰ Clock button to confirm and move to minutes, then set the minutes.
5. Press the ⏰ Clock button again – it will switch to “OFF”. Set your OFF time the same way.
6. Press the ⏰ Clock button once more to save. Both ON and OFF times will now be displayed on the screen.

To cancel the timer: Press and hold the ⏰ Clock button (so ON or OFF is selected), then press the Settings (Gear) icon. The timer settings will disappear.

Tip: For easier and more flexible scheduling, use Smart Scenes in the Smart Life app instead.

See also: How to Set Timers on Your Fjord I Cylinder | How to Create Smart Scenes

The E51 error (and often E37) usually means no water flow through the heat pump. This is very common on systems with full zonal control (thermostats or actuators closing off zones).

Quick fixes

1. Set your room thermostats to the highest setting so they are calling for heat.
2. Lower the heat pump’s target temperature to the lowest setting HL7-8.

These keep the zone valves open and prevent the heat pump from shutting down the flow.

Test: Set all thermostats to maximum. If the error disappears, this is the cause.

Long-term solutions

1. Manually open one actuator fully on your largest zone (this ensures constant flow).
2. Add a Smart Life compatible room thermostat in the main zone.
3. Create Smart Scenes in the app:
   
   • Turn the heat pump OFF when room temperature reaches 1°C below your thermostat setting.
   • Turn the heat pump back ON when the room temperature drops again.

This stops the zone valves from closing before the heat pump shuts down.

Unlike many single-mode heat pumps, your Adlår dual heat pump system can provide cooling without any extra parts or upgrades.

Important Condensation Warning:

When the heat pump cools the water, pipes can become cold. Condensation (and dripping water) usually starts on exposed copper pipes when the water temperature is 4–8°C below room air temperature. This risk exists even with underfloor heating if pipes are not fully lagged/insulated and can lead to damp, mould or damage.

Recommended & Safest Method (Most Homes):

Keep the heat pump in Heating mode at all times. On warm days simply set the lowest heat curve (HL8). Even if the set temperature is below ambient air temperature, the heat pump will not provide active cooling — it only circulates water. You may feel a small passive benefit, but it is very limited.

Full Cooling Mode:

You can switch the heat pump into dedicated Cooling mode (CL1–CL8 or CH1–CH8 curves). If you choose to do this:

• Set the water temperature manually with only a small difference (max 4–5°C) from the current room temperature.
• Monitor the system closely.

Liability Note Adlår is not responsible for any condensation, damp or related damage while the system is in cooling mode. As a precaution we strongly advise against using full cooling mode unless you are able to monitor it carefully at all times.

Best practice Stick with HL8 in Heating mode for safe, low-risk summer cooling. You can automate this with a Smart Scene if you wish.

Requires Smart Life compatible thermostat. Here is an example.

This setup gives you a reliable baseline day/night schedule plus an automatic “cold boost” if the house gets too cold during the day, while night setback always takes priority. 

You will create 4 scenes/automations:

1. Aurora Daytime (Scene – schedule-based)

• Runs at your chosen daytime start time (e.g. 06:00)
• Sets your normal comfort heat curve

2. Aurora Nighttime (Scene – schedule-based)

• Runs at your chosen nighttime start time (e.g. 22:30)
• Sets setback / reduced heat curve
• Also disables the two automations below (Cold Boost + Return Normal)

3. Aurora Cold Boost (Automation)

• If: Room temperature drops below 18°C AND it is during daytime hours only
• Then: Set a higher heat curve (or higher target temperature)

4. Aurora Return Normal (Automation)

• If: Room temperature rises above 16.5–17°C AND it is during daytime hours only
• Then: Restore your normal daytime heat curve

Tip Using 16.5–17°C (instead of exactly 16°C) in the Return Normal automation prevents annoying on/off ping-ponging.

Final result

• Daytime: normal comfort + automatic boost if needed
• Nighttime: setback mode always wins (boost automations are disabled)

See also: How to Create Smart Scenes in the Adlår Castra App | Smart Thermostats

Any device on the Smart Life infrastructure can be added to the APP and used to control your heat pump/system. 

A good additional product is a smart life thermostat. Here is one example.

Yes – it is perfectly safe and recommended to leave your Adlår Castra heat pump turned on all year round.

What happens in summer:

When the outside air temperature is higher than your set heat curve, the compressor stays completely off. Only the circulation pump runs occasionally to keep the system ready. This uses very little electricity.

Best practice for summer

• Keep the heat pump in Heating mode.
• Set the lowest heat curve (HL8).

This gives you gentle passive cooling through your underfloor heating or radiators while using almost no energy.

For example, when your flow temperature is lower than the ambient air temperature the heat pump won't operate at all.

See also: Cooling with Your Adlår Castra Heat Pump Heat Curves Explained

Yes – it is perfectly safe and recommended to leave your Adlår Castra heat pump turned on all year round.

What happens in summer:

When the outside air temperature is higher than your set heat curve, the compressor stays completely off. Only the circulation pump runs occasionally to keep the system ready. This uses very little electricity.

Best practice for summer

• Keep the heat pump in Heating mode.
• Set the lowest heat curve (HL8).

This gives you gentle passive cooling through your underfloor heating or radiators while using almost no energy.

For example, when your flow temperature is lower than the ambient air temperature the heat pump won't operate at all.

See also: Cooling with Your Adlår Castra Heat Pump Heat Curves Explained

The P07 error on your Fjord I cylinder usually means the cylinder is not filling with water properly. This is quite rare and is most often caused by a temporary disruption to your incoming mains water at the same time hot water is being used. It can also be triggered by the automatic Legionella cycle.

Quick fixes (try in order):

1. Turn the cylinder off using the power button on the display, wait 30 seconds, then turn it back on. Check if the error clears.
2. Turn the cylinder off at the mains isolator, wait 2 minutes, then turn it back on. After that, make sure you also turn the heat pump ON on the main display.
3. In the Smart Life app, tap on the error message to clear it.

If the error keeps returning:

• Weekly occurrences → This is often linked to the Legionella cycle. Contact the office for a settings adjustment.
• Frequent / daily occurrences → Check that your incoming mains stop cock is fully open (a partially closed valve can restrict water flow to the tank).
• If the error continues after the above steps, please contact the Adlår office on 01252 268 669.

See also: How to Set Hot Water Timer on Your Fjord I Cylinder Smart Thermostats & Smart Scenes

Please read first: Cooling with Your Adlår Castra Heat Pump

Adlår sets a minimum cooling temperature of 15°C (parameter P113) as a safety limit. This prevents condensation on pipes if they are not fully lagged or if the system is used without careful monitoring.

If you are confident your pipework is properly insulated and you want stronger cooling:

1. Watch our video guide: Adlår Castra Control Box: Parameter Settings Guide (For Advised Users)
2. Unlock the heat pump display.
3. Change parameter P113 (Minimum temperature for cooling) to a lower value (e.g. 10°C or below).
   
   • Default: 15°C
   • You can also check P112 (Maximum temperature for cooling) which is normally 22°C.

⚠️ Strong Warning We do not recommend lowering this setting unless you have fully inspected your pipework and are prepared to monitor for condensation. Adlår cannot be held responsible for any damp, mould or damage caused by condensation in cooling mode.

Alternative solution Fan-assisted radiators (or fan convectors) are much better at handling lower water temperatures and greatly reduce condensation risk.

Why the system may cycle on/off quickly The 15°C safety limit means the heat pump reaches its target very quickly in hot weather and then stays off for long periods. Lowering P113 (with caution) allows it to run longer for more noticeable cooling.

See also: Cooling with Your Adlår Castra Heat Pump

Parameter Settings Guide Video

Your Adlår Castra heat pump uses a weather compensation heating curve. This automatically adjusts the water temperature sent to your radiators or underfloor heating based on the outside air temperature — the warmer the water, the warmer your home.

Recommended starting curves

• Good insulation + underfloor heating → HL8 to HL4 (low-temperature curves)
• Radiators with fans → HL4-HL1
• Old radiators without fans → HH8-HH4 or a high-temperature curve (HH4 to HH1)

Your installer will have set an initial curve based on your home during commissioning.

Below are the two detailed graphs showing all available curves:

High Temperature Curves (HH1 – HH8)

Low Temperature Curves (HL1 – HL8)

How to adjust your heat curve

• House still too cold? → Raise the curve one step (e.g. HL6 → HL5 or HL4)
• House too warm? → Lower the curve one step (e.g. HL6 → HL7 or HL8)

Important The heat pump is a slow-responding system. Always wait at least 4 hours (ideally 24 hours) after changing the curve before deciding whether to adjust it again.

See also: Heat Curves Explained How to Adjust Temperature Settings

Your Adlår Castra system may include secondary circulation pumps (for upstairs, downstairs, or different zones). These can be controlled in two ways:

• Directly by the heat pump, or
• By your existing thermostat/zone control system (e.g. Heatmiser, Hive, etc.)

What we normally do

If you already have a working zone control system (such as Heatmiser), we usually leave it in place. Your existing thermostats will continue to open and close zones and turn the secondary pumps on and off as before.

How to optimise your system

1. Set all room thermostats to maximum (or at least 2–3°C above current room temperature). This opens every zone valve and calls for heat, keeping the secondary pumps running continuously.
2. Now fine-tune your heat curve (see our Heat Curves guide). Find the lowest curve that still gives you comfortable warmth throughout the house.
3. Once you’re happy with the heat curve, you can (if you wish) start closing some zones again.

Efficiency tip The most efficient way to run the system is to keep all (or most) zones open and let the heat pump work at the lowest possible temperature. Frequent opening and closing of zones usually means the heat pump is running too hot and less efficiently.

Best practice if you still want to close zones Always keep at least one main zone or a larger/colder zone fully open (always calling for heat). This keeps the secondary pumps running, maintains good flow throughout the system, and lets you run the heat pump at its most efficient temperature while still delivering excellent comfort.

See also: Heat Curves Explained

Your Adlår Castra heat pump offers standard weather-compensation curves (HH1–HH8 and HL1–HL8) as well as the ability to create fully custom heat curves for maximum precision and efficiency.

What are custom heat curves?

Standard curves give you 8 pre-set options. Custom curves let you define your own relationship between outside air temperature and the water temperature delivered to your radiators or underfloor heating. This is ideal if:

• Your home has unusual insulation levels or heat loss
• You have a mix of emitters (UFH + radiators)
• You want the absolute best comfort and lowest running costs

When to use them

Most homes do very well with the standard HL or HH curves (your installer will have chosen a good starting point). Only move to a custom curve once you have lived with the standard settings for a few weeks and want to fine-tune further.

Full guide & diagrams Download the complete Adlår Castra Custom Heat Curves PDF here: https://adlar.co.uk/wp-content/uploads/Adlar-Castra-Custom-Heat-Curves-1.pdf

Tip Always allow at least 24 hours after any curve change for your home to stabilise before making further adjustments.

See also: Heat Curves Explained Which Heat Curve Should I Set? How to Adjust Temperature Settings

Many people coming from traditional gas boilers are used to turning radiators or whole zones off to “save energy”. With an Adlår Castra heat pump, heavily zoning your system is one of the worst things you can do.

Why heavy zoning causes problems

• Closing too many zones or valves dramatically reduces water flow → this is the #1 cause of E37 and E51 errors.
• The heat pump is forced to run hotter and short-cycle (turn on and off frequently) instead of running steadily at low temperature.
• Efficiency drops and your electricity bills can actually go up.
• Heating becomes uneven and less comfortable across the house.

The shocking truth Running with most zones open is far more efficient and comfortable than constantly opening and closing them. Heat pumps are designed for constant, low-temperature flow — not the on/off behaviour that worked with old boilers.

Best practice instead

1. Set all room thermostats high (or 2–3 °C above current room temperature) so most zones stay open.
2. Optimise your heat curve until you achieve the right comfort level (see our Heat Curves guide).
3. Always keep at least one main or larger zone fully open at all times — this maintains good flow and lets the heat pump run at its most efficient setting.

Once you do this, many customers are surprised how much quieter, more even, and cheaper the system becomes.

See also: Secondary Pumps & Zone Control

With a traditional gas boiler it made sense to turn off radiators in unused rooms to save energy.

With your Adlår Castra heat pump it is the opposite — turning off radiators is one of the worst things you can do.

Why you should leave them on

• Closing radiators (or TRVs) reduces water flow through the system → this is the #1 cause of E37 and E51 errors.
• The heat pump is forced to run hotter and short-cycle (constantly switching on and off), which is inefficient.
• Your electricity bills actually go up and the house heats unevenly.

The right way to run your system

1. Set all TRVs and room thermostats high (at least 2–3°C above current room temperature) so most radiators stay open.
2. Optimise your heat curve to the lowest setting that still gives you comfortable warmth.
3. Keep at least one main zone or larger room fully open at all times — this maintains good flow and lets the heat pump run efficiently and quietly.

Once you stop turning radiators off, most customers notice the system becomes quieter, more even, and noticeably cheaper to run.

Bottom line: Heat pumps love constant, gentle flow — not the on/off behaviour that worked with old boilers.

See also: Why You Should NOT Heavily Zone Your Heating E51 and E37 Errors Secondary Pumps & Zone Control Heat Curves Explained

For traditional gas boilers → No. Turning the heating off when you’re out and only turning it on when needed is usually more efficient.

For your Adlår Castra heat pump → Yes – leave it on constantly!

Heat pumps work completely differently to boilers. They are most efficient when they run steadily at low temperature rather than constantly cycling on and off.

Why constant running is better with a heat pump

• The house acts as a thermal battery — it stays warm with far less energy.
• The heat pump can use the lowest possible flow temperatures and best weather-compensation curves.
• No big “catch-up” periods when you come home — the system stays quiet, even, and cheap to run.
• Short-cycling (frequent on/off) actually increases your electricity use and can trigger flow errors (E37/E51).

Best practice for your Adlår system

• Keep the heat pump on all year round (even in summer – see our Summer guide).
• Set a low heat curve (usually HL series) and let it run 24/7.
• Avoid turning zones or radiators off — keep most of them open for steady flow.

Most customers are surprised how much quieter, more comfortable, and cheaper the system becomes once they stop turning the heating off.

See also:

Recommended setting for your Fjord I cylinder: 48–50°C

This is the sweet spot for maximum efficiency with your Adlår Castra heat pump.

Why 48–50°C is best

• Lower storage temperature = significantly lower electricity use
• Your heat pump can produce hot water far more efficiently at these temperatures
• You still get plenty of usable hot water for showers, baths and taps

Legionella Protection – How Adlår Handles It

Your Fjord I cylinder has built-in automatic Legionella protection:

• Once a week the system automatically runs a Legionella cycle, heating the water to over 60°C for a short period to kill any bacteria.
• The electric anode also helps prevent bacterial growth and scale.
• You do not need to keep the cylinder at 60°C all the time.

How to change the temperature

1. On the Fjord I cylinder display, press the Power button to wake it.
2. Use the arrow buttons to set the target temperature to 48–50°C.
3. The Legionella cycle will still run automatically each week.

Tip: If you ever notice the water feels too cool, you can temporarily use the immersion boost (squiggly “N” button) for a one-off top-up to 55–60°C.

Bottom line Keeping your hot water at 48–50°C is safe, highly efficient, and exactly what the Adlår system is designed for. The automatic Legionella cycle takes care of the safety side for you.

See also: How to Set Hot Water Timer on Your Fjord I Cylinder
11 Easy Ways To Reduce Your Energy Bills with Your Adlår Castra Heat Pump

Adlår offers all-inclusive warranty packages designed to give you complete peace of mind with your Castra heat pump and Fjord I cylinder for many years.

Standard Warranty (Included Free with Every System)

• 2 years parts cover for manufacturer defects
• Covers the outdoor unit and indoor components supplied by Adlår
• Does not include annual servicing, maintenance, optimisation, or call-outs

Gold Warranty (Recommended)

• Up to 5 years full parts and labour
• Annual servicing and maintenance included
• System efficiency checks and optimisation
• Priority engineer response
• Full access to the Adlår Castra customer app and support

Platinum Warranty

• Up to 15 years full parts and labour
• Everything included in the Gold package
• Remote system monitoring by Adlår engineers
• Advanced smart controls and ongoing performance optimisation
• The most comprehensive long-term protection available

Warmth Guarantee (Included with All Plans)

If your heating or hot water system does not perform as designed (e.g. the house doesn’t reach the agreed comfort levels), Adlår will return and resolve the issue at no extra cost — this goes beyond a normal parts-only warranty.

Why choose an All-Inclusive plan?

• Predictable running costs with included servicing
• Expert support from the same team that designed and installed your system
• No hidden costs for call-outs or repairs
• Long-term protection (up to 15 years)

All warranties are backed by Adlår’s in-house team — no third-party handovers.

Choosing the right heat curve is one of the most important settings on your Adlår Castra heat pump. It determines the water temperature delivered to your radiators or underfloor heating based on the outside (ambient) temperature.

Unlike traditional boilers that run hot and short (60–80°C for 6–8 hours), heat pumps work best with gentle, continuous circulation at much lower temperatures (typically 24–55°C). This delivers more even, comfortable heat and significantly better efficiency.

Below are the two detailed graphs showing all available curves:

High Temperature Curves (HH1 – HH8)

Low Temperature Curves (HL1 – HL8)

How the Curves Drop (Step Rate Explanation)

Each curve has a different rate of drop — this is how quickly the water temperature reduces as the outside (ambient) temperature rises. This is the key difference between the curves.

High Curves (HH1 – HH8)

Low Curves (HL1 – HL8) – Most Common for Modern Homes