Technical assistance


Frequently asked questions

If you haven’t found the answers you’re looking for in the list below please email us at

My thermostat in my house only has numbers, how to I know what temperature the heating is set at?

If  your thermistastat has number and does not show your heating in 0C then the below links will take you to a simple download that will explain these for your

Hi-Spec ET Thermistastat Graduations 

Modairflow Thermistastat Graduations

Can I fit a smart control system to my heater? What controls are compatible with my heater

'Volt-Free' smart control systems are suitable for use with most of our product ranges. However, the WarmCair heat only range must use the OpenTherm programming language - check before purchasing that your chosen system is OpenTherm capable to ensure it operates the heater correctly.

Installation of any non-OpenTherm control with a WarmCair heat only appliance will invalidate the guarantee.

If your system uses a ModAirFlow thermista-stat, then you can use any Volt-Free controls, however you will lose the increased fan modulation for which the ModAirFlow contol system is designed. This will reduce the overall efficiency of the appliance, causing the fan to run harder and with more on/off cycles. 

If you  have one of our older heaters with the E-T/Eco thermista-stat, only E-T/Eco thermista-stat will be suitable for replacement. Any other thermostatic control will not allow the appliance to operate correctly. 

Using any 240V thermostatic controls will damage the circuit boards of the heater and must not be used

Johnson & Starley Guide to Third Party Controllers

Can I have an Aquair HIU and a heat pump installed together. 

While the Aquair can indeed function with a standard heat pump, it is important to note that the resulting heat output may not meet the householder's expectations due to the lower flow rate temperatures from the heat pump, typically ranging for 45-50C. This observation is particularly applicable to standard heat pumps utilising R32 Gas.  

Consequently, during colder weather conditions, additional heat sources may be necessary to maintain the desired comfort levels. However, it is essential to bear in mind that such a set-up with an additional heat source would constitute a hybrid system, potentially impacting eligibility for the Government grant of £7500.

Alternatively, newer high-output heat pumps employing R290 gas boast a much higher flow rate temperature of 70-75C (according to their manufacturers) This makes that far more suitable for efficient operation alongside the Aquair, albeit Johnson & Starley have not conducted any field trials yet with one of these models. 

Currently, we are also in the process of developing an enhanced range of Aquair HIUs specifically designed to work more effectively and efficiently with standard air-source heat pumps. However, these advancements are still in the development phase, and we anticipate their availability by the end of this year. 

How often should I need to top up the pressure in the heating system. 

Most heating systems only need the pressure topping up once every 6-12 months. If you find that the pressure drops regularly, this indicates a leak on the heating system and must be addressed by your engineer. 

My heating system is constantly losing pressure what should I do?

Constantly losing pressure indicates a leak on the heating system. Contact your heating engineer to investigate and resolve the leak. In the meantime, whilst waiting for an engineer, you can check underneath the boiler and any visible pipework for a sign of leakage, so you can protect your property from any potential damage as a result of the leak. 

How to re-pressurise your QuanTec boiler

If you have an F37 fault on your QuanTec boiler, follow this procedure to re-pressurise the system.

  • Check the pressure gauge underneath the boiler, on the left-most pipe. If this reads less than 0.3bar, the boiler is under pressure and needs refiling. 
  • Turn one of the valves indicated so it is in-line/parallel with the pipe (in the open position)
  • Then follow the same procedure for the second valve.
  • As you turn the second valve, water should begin to fill the system.
  • Wait for the pressure gauge dial to reach between 1 & 1.5bar (needle pointing to 11 O'Clock position)
  • Close both valves previously opened. The boiler will now run an air purge sequence, after which it will return to normal operation. 
  • If you pressure drops again before the next annual service, there is a leak on the heating system. Please contact your heating engineer to identify the cause of the leak and affect a repair. 


Will I receive anything in writing when I have a new boiler/warm air heater installed?

As long as you have correctly registered your new heater for its guarantee then you will receive a letter confirming the date of installation and length of the guarantee. 

It is the homeowners responsibility to ensure that their new heater is registered.

Should I have my heating system treated or cleansed

The system should have been flushed, inhibitor added, and a filter fitted as part of the installation. This is a requirement to maintain the guarantee. However, sometimes this has not taken place, in which case, they system must be flushed immediately, inhibitor added and a filter fitted as soon as possible to protect the appliance

Can I use artificially softened water in the heating circuit with my boiler?

Softened water often contains salts which, when heated, could damage internal components of our appliances. As a result, we do not allow softened water in the heating circuit of our appliances. (For combi boilers, softened water can be run through the hot water system of the boiler, but not the central heating circuit)  

Why does there appear to be a lot of steam coming out of the flue outside from my heater?

This is most likely what is known as 'pluming'. It appears as a white 'steam like' discharge from the flue. Its a result of modern high efficiency heaters running at a cooler temperature than older, less efficient models. 

What sort of shower can I run off my system.

Most showers will be compatible with our appliances. However, some showers do experience issues when fitted with a combi boiler. Please check with the shower manufacturer that your shower is suitable for use with a combi boiler. 

Why is the hot water produced by my boiler sometimes cloudy?

Cloudy hot water is most commonly caused by dissolved oxygen bubbles being released from the water. The water should clear from the bottom up in just a few minutes, if this is not the case then the problem may be caused by sediment and you should contact your Gas Safe Engineer to investigate. 

Can mains water pressure effect my combi boiler.

Excessively low or high mains water pressure could have an effect on the ability of our combi boilers to supply hot water. If the pressure is too low, the system is likely to overheat as it cannot circulate the water fast enough. If the pressure is to high, this may force water through the boiler to fast, not allowing it to heat effectively before reaching your taps. The maximum flow rate of our boilers is 12.2 litres/minute at 350C temperature rise. 

Do you recommend treatment of the central heating water

If you live in a hard water area, a scale reducer must be fitted. If you do not live in a hard water area, then there is no requirement other than the standard flushing, inhibitor and filters. 

I'm selling my house and the buyer's solicitors have asked for a copy of the Building Compliance Certificate for the heater. Can I get a copy from you.

Unfortunately not. This is something that the installer should have completed online at the Gas Safe Register for you when he undertook the installation.

You can get a copy from:


I need an engineer to service my heater, does Johnson & Starley offer servicing work or can you recommend anyone. 

Johnson & Starley are the manufacturers so do not undertake any servicing/repair or installation work. We can help you find qualified Gas Safe Engineers in your area but we do not recommend or approve any registered gas engineers. We do not monitor the work carried out by these engineers and are therefore unable to guarantee the quality of their workmanship. 

Please complete the enquiry form on our homepage for installers in your area. 

Does my heater have asbestos in it

Depending on the age of the heater there is a possibility, although even some heaters that do not contain asbestos in themselves, it may be found in the installation of which Johnson & Starley will have no knowledge of. 

Click here to find out more information. Asbestos in heaters and buildings

Can I transfer the guarantee to the new owner if I sell my house

The guarantees apply to the original retail purchaser and are not transferable.

Why have I only got 3 Cleanflow Filters in my replacement pack and not 6?

The new Cleanflow Filters are now twice as thick, this means you only need to fit one each time your replace the media and not two.  These will last just as long as the original ones.  Click here for more information. 

What is the Buildings Regulations Certificate and do I need one.  

The Building Regulations are designed to make sure buildings are safe to use and inhabit. As part of this aim, in England and Wales local authorities must always be informed when a heat producing appliance is installed in a property, so a Buildings Regulations Compliance Certificate can be issued. 

If you have had a new heat producing product installed in your property then the Gas Safe Engineer must register it with Gas Safe so it complies with the regulations and notifies the relevant local authority.

This should be done within 30 days of installation and it is up to the homeowner, to ensure the Building Regulations are adhered to. Should you at a later date decide to sell the property, this certificate may be asked for by the Solicitors. 

What are the required maintenance schedules for my heater

Any gas appliance should be serviced annually by a correctly qualified Gas Safe Engineer in accordance with the manufacturer's instructions. Failure to have a gas appliance serviced is not only dangerous but will invalidate any guarantee that may have been applied to that heater. 

How do I know if my condensate drainpipe is blocked and what can I do if it is. 

Unfortunately, this can be difficult to identify as condensate drainpipes are commonly installed not to be visible. If your Johnson & Starley appliance has an internal condensate pump, a blocked drainpipe will cause the appliance to shut down and show the relevant error code for an issue with the condensate pump. For externally fitted pumps, please refer to the manufacturer's instructions or contact your heating engineer to investigate. 

What to do if your condensate pipe is frozen. 

If you can see that your condensate drainpipe is frozen, we recommend defrosting this using an external heat source such as a kettle of warm (not boiling) water

How long is my Guarantee for:

The unit must have been registered within 30 days of installation to activate the guarantee. If the unit was not registered it will automatically have defaulted to a 12 month guarantee from date of dispatch from our warehouse. 

To maintain your guarantee the unit must be serviced by a qualified gas safe engineer annually. Failure to adhere to this will result in any guarantee becoming null and void

WarmCair Warmair Heaters

  • 2 years if installed before 02/10/2017
  • 5 years if installed between 03/10/2017 - 31/08/2021
  • *2 + 3 years if installed after 01/09/2021 (years 1-2 Parts and Labour year 3-5 Parts Only)

The fitting of any Non Open-Therm controller to any of the WarmCair C range immediately invalidates the guarantee.

Aquair Heat Interface Units

  • 2 years if installed before 01/02/2015
  • 5 years only if installed with a Quantec boiler between 02/02/2015 - 31/08/2021
  • *2 + 3 years if installed after 01/09/2021 (years 1-2 Parts and Labour year 3-5 Parts Only)

What does my guarantee include

For a full list of the things your guarantee does or doesn't include please refer to the Terms and Conditions that were attached to the confirmation letter when you registered your heater to activate the guarantee.

My filter is making a ticking/clicking sound what is it and is it safe

The noise is most likely being caused by incorrect fitting of the filter pads.  

The pads must be underneath the probes, this allows the probes contact with the screen and will prevent the arcing of static electricity which is causing the ticking/clicking sound that is audible.

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