How to turn on a Dimplex Quantum heater: A winter start-up guide

This Quantum winter start-up guide takes you through the checks that make the biggest difference: power supply, clock and timer settings, room temperature and what to expect over the first few days. 

The menus and display wording can vary slightly between Quantum generations, so use this guide as a confident starting point and refer to the manual for your specific model where needed.

Why your Dimplex Quantum won’t turn on in winter

In most cases, a Quantum that appears not to be heating after summer is not faulty. It may be waiting for its scheduled heating period, waiting to take an overnight off-peak charge or re-learning how much stored heat the room needs. As an example, if the room is already quite warm, the heater may not take much charge at first. Start with these simple checks...

Step 1: Check your wall switches and power supply

Quantum heaters are commonly installed with a continuous supply and an off-peak supply. The continuous supply powers the controls and fan, while the off-peak supply allows the heater to charge at the lower tariff during the periods set by the electricity meter. Depending on the installation, the heater may have one or two supply cables and associated wall switches.

Both switches must be on (including overnight)

If your Quantum has two wall switches, make sure both are switched on. The off-peak supply may only become live overnight, so it can look as though nothing is happening during the day even when the system is working correctly. Leave the switches on overnight so the heater can take its first charge. The heater is designed to be left switched on throughout the heating season. Where very little heat or just basic frost protection is needed during the winter period, we recommend leaving the heater powered and using an appropriate mode, such as ‘Away' or ‘Frost Protect’, rather than switching it off at the wall.

Check your fuse box

Check the consumer unit for a tripped breaker or RCD, particularly after a power cut or other electrical work. If a breaker has tripped, try re-setting the breaker. If it trips again, do not keep resetting it, instead, a qualified electrician should investigate. For a dual-supply installation, ask your electricity provider to confirm that the off-peak circuit is being energised at the correct times if you are unsure.

Step 2: Set the date time and timer mode

The clock and timer tell Quantum when the room should be warm, so a correct date and time are particularly important after the heater has been off for a long time, after a prolonged power interruption or when the clocks change.

How to set the date and time on Dimplex Quantum

On many Quantum models, press “MENU”, then Settings, then Date/Time to check and amend the clock. If the options on your display differ, use the specific operating instructions for your series.

Save your updated date and time before returning to the home screen. On a Quantum RF single-supply installation, the heater also needs to know the correct off-peak charge times. These must match the times provided by the energy supplier. That is accessed by holding “ADVANCE” and “MENU” keys and navigating to Charging then Charge Times.

If you have changed tariff or supplier, it is worth confirming the new off-peak times before winter. This is especially important for single-supply Quantum heaters, as incorrect charge times may prevent the heater from taking the expected overnight charge.

Which mode to use in winter

Choose a timer mode that reflects how the household uses the room, this will also help to reduce running costs of a Quantum heater. ‘Home All Day' can be a useful starting point for a regularly occupied space, while ‘Out All Day’ may suit a room that is empty for much of the daytime. ‘User Timer’ gives more control over the heating periods and target temperatures, and ‘Away’ mode helps maintain a lower background temperature while the property is unoccupied. The right mode is the one that gives warmth at the times the room is used, without running the heater unnecessarily.

Step 3: Set your room temperature and use ‘Advance’

Quantum is designed to follow its timer and temperature settings, rather than heat continuously from the moment the wall switch is turned on. Select a target temperature that suits the household, then make sure it is set within the chosen timer periods. Adjusting the temperature on the home screen can create a temporary change, but it will return to the scheduled target when the next programmed period begins.

Why 'Heating Off’ or ‘Comfort Off’ appears on your display

‘Heating Off’ or ‘Comfort Off’ usually means the heater is currently outside a planned ‘Heating On’ period. It does not necessarily mean that the wall switch is off or that the heater has developed a fault. Check the selected timer mode and the next programmed period before taking further action.

Using the Advance button to turn heating on now

If heat is needed before the next scheduled period, press ‘Advance’. When a timer mode is active, this temporarily brings the next ‘Heating On’ period forward. Pressing ‘Advance’ while the display shows ‘Heating On' can instead end that period early. The heater will return to its normal timer schedule at the next planned change, so ‘Advance’ is useful for a one-off adjustment rather than a replacement for setting the right programme.

Step 4: What to expect over the first 2 to 3 days after switching on

If the heater has been totally powered off, give your Quantum time to get back into its rhythm. Its intelligent charge control learns from recent room conditions, timer settings and room heat loss, then adjusts the amount of stored heat it takes overnight. A cold room and the fabric of the building can also take time to warm through.

Why your Quantum can take up to 72 hours to work normally

It can take two to three days for the heater to re-learn the room and begin storing the most appropriate amount of energy. This is why Dimplex recommends switching Quantum back on a few days before it is needed. During this settling period, keep the wall switches on, make sure the timer is right for the room and avoid changing the settings repeatedly.

Signs your heater is charging and releasing heat correctly

A Quantum will usually take its main charge during the off-peak period, then release stored heat in response to the room temperature and timer. You may not feel immediate heat simply because the wall switch has been turned on during the day. Instead, check that the display is showing the correct time and selected timer mode, leave the heater powered overnight, then assess the room during the following scheduled heating period.

Step 5: Quick checks if your Quantum still is not heating

If the heater has had an overnight charge opportunity and is still not providing the expected warmth, work through these practical checks. They can often resolve common issues without an expert changing any wiring or internal components.

Timer settings check

If the timer is programmed to deliver 2 hours of heat per day into the room at 21C, the heater will take a lower charge, compared to being programmed to deliver 10 hours of heat into a room at 23C. If in doubt, try the default “Home All Day” setting rather than “Out All Day” or “User Timer” and make sure the room temperature setting for each time period and day is set high enough. If you need a really warm room, then the default 21C may need to be increased to deliver the warmth you need. 

Airflow and obstructions check

Keep the heater clear at the front, sides and rear in line with its installation instructions. Do not place clothes, furniture or a decorative cover over the Quantum, as this can interrupt airflow and cause the heater to overheat. If the display is flashing red with no text, switch the heater off, allow it to cool and remove any obstruction. If the issue returns once the heater is clear, contact Dimplex support.

When to reset your Quantum (and how)

A factory reset should be a last practical step. It restores the heater's original settings, so note down any timer and temperature preferences before continuing. For Quantum RF (Series G5 onward), press and hold the “ADVANCED” and “MENU” buttons and select ‘Factory Reset’, then choose ‘Yes' to confirm. Menus vary by model and earlier Quantum generations may use a different route, so check the specific manual for your exact series before resetting. When Factory Resetting a Quantum RF (Series G5 onward), if it is on a single supply, the off-peak times will need to be re-entered into the heater after the reset, by holding “ADVANCED” and “MENU” buttons, then navigating to “Charging” and then “Charge Times”. The charge times need to reflect your energy suppliers off-peak tariff times.

Fault codes and when to contact support

If Quantum shows a fault code, make a note of the complete message or code, the model and series, and when it appeared. Check the manual and Dimplex Help Centre for the relevant code and contact Dimplex support if the code persists, the display remains blank or red after obstructions have been cleared, a breaker continues to trip, or the heater still does not heat after the power, timer and airflow checks.

Best Dimplex Quantum settings for winter comfort and efficiency

A good winter setup should support the household's real routine. Quantum gives you the flexibility to set different times and temperatures across the week, so the aim is not to find one universal setting but to create a schedule that keeps the room comfortable when it is occupied.

Recommended timer and temperature settings for typical homes

Start with the mode that most closely matches the household’s occupancy pattern, then refine the periods and temperatures after a few days of experience. Quantum RF default timer periods are factory set to a 21C target temperature for each heating period in the timer, which can be a useful reference point, but comfort preferences and individual needs vary. If a permanent temperature change is needed, amend it within the timer periods rather than relying only on a temporary adjustment from the home screen. 

• Use ‘Home All Day’ for rooms occupied through much of the daytime.
• Use ‘Out All Day’ where a room is normally empty during working hours.
• Use ‘User Timer’ to build a schedule around the household's actual week.
• Use ‘Away’ mode for an unoccupied property, rather than switching a smart-tariff heater off at the wall.

If your room runs out of heat in the afternoon

Firstly, check whether the selected timer is too limited for how the room is now being used. Moving from ‘Out All Day’ to ‘Home All Day’, extending a relevant heating period or increasing the scheduled target by a small amount may give the heater a better basis for charging. If ‘Boost’ is used regularly, review the timer settings first: Boost can draw on peak-rate electricity, so it is best kept for occasional short-term warmth rather than everyday use.

Still not working? Contact Dimplex support

Dimplex support can help you move from a general check to model-specific guidance. Before getting in touch, have the model number, series, fault code (if shown), details of the selected timer mode and a note of whether the heater has had an overnight off-peak charge opportunity. This helps our support teams and installers understand the issue more quickly.

Use the Dimplex Help Centre for troubleshooting guidance. If you need the manual for your exact model, visit Manuals and Guides. The Dimplex product identification guide can help where the Quantum series is unclear. For a new installation or an issue that requires a qualified professional, use Dimplex's Find an Installer service.