Frequently Asked Questions
If you have a question, please ask it via our ‘contact page’ and we’ll do our best to answer it.
How much would it cost to install a DIY mini-split air-con in my office or workshop?
Typical equipment costings are:
- A basic mini-split air-con system from a good manufacturer like Mitsubishi Electric, Mitsubishi Heavy Industries (a separate company), Fujitsu etc costs around £540 to £570 for a 2.5kW unit. Other manufacturers such as Daikin and Panasonic can cost a little more.
- Approx. £60 for 15m copper tubing in both 1/4 inch and 3/8 inch.
- Approx. £40 for matching pipe insulation.
- Approx. £50 for outdoor unit wall mount.
- Plus £10 for clips, fixings etc.
This comes to around £700 for a basic but good 2.5kW unit. Allow £50 to £75 more for a 3.5kW unit.
Then add the Checkmark connecting, testing, commissioning and certifying fee - see the ‘Booking section’ for details.
You can add optional extras, such as outdoor and indoor trunking depending on your requirements. You may need much less than 15m of copper tubing - some places sell by the metre, or 6m length, but that doesn’t always work out much cheaper.
These prices were checked early 2024. The best prices tend to be from the on-line suppliers. Please note that Checkmark has no affiliation with and does not recommend particular vendors. However, we do encourage you to buy from specialist suppliers rather than a general appliance stores. Some starting points include:
Saturn Sales 
AC One
Orion Air
Carlton Services
Air Con Spares
Prices vary considerably: it pays to shop around.
When it comes to making your system purchase, the supplier should ask you who your installer is (they are required to by law). Checkmark will give you our installer number when you contact us.
How long does a visit to connect, test, commission and certify my install take?
Typically, three to four hours:
- 30 minutes to one hour to make the flares and connect
- An hour to pressure test with oxygen free nitrogen
- An hour to vacuum the system and further test
- 30 minutes to commission and do the final leak tests
- plus a short time to do the paperwork
If any of the tests show that further work has to be done then the visit may be extended. Checkmark doesn’t rush - we like to get it right.
Can I run multiple indoor units off one external unit?
Yes, look for ‘multi-split’ units. Typically, they have several pairs of connections on the outdoor unit and you run a line set to each indoor unit. When sizing the unit, you have to bear in mind the total heating/cooling required, and how often both units would be running simultaneously.
Install under ‘permitted development’ isn’t possible if you have more than one outdoor unit, so a multi-split single outdoor unit can make a lot of sense - but be sure to check the overall dimensions/physical volume of the outdoor unit.
Checkmark can help you with the connecting, testing, commissioning and certifying. The pricing depends on complexity and anticipated time taken, but it’s normally lower than multiple separate installations. Please ‘contact us’ to discuss.
I have an old air-con that doesn’t work. Can you re-gas it?
Maybe! The answer depends on a number of things;
- Which refrigerant it contains. Certain older refrigerants like R22 are now banned and the unit would have to be safely decommissioned.
- If it is a newer unit using a gas like R410A then it is possible to re-gas. The system, would have to be emptied of existing gas, leak tested (to establish why it lost gas?), repaired and re-charged by weight. Whether this is economical depends on the age and condition of the unit.
Please ‘contact us’ us for advice.