Domestic Air Conditioning FAQ

We have compiled a list of the most frequently asked questions regarding Domestic Air Conditioners.  If you have a question that is not covered then please feel free to contact us.

Frequently Asked Questions

How does air conditioning work?

Air conditioning systems transfers heat from the interior of your home / office to outside via an internal evaporator and external condenser utilising refrigerant gas.
Copper tubing connects the outdoor unit (the condenser) to the indoor unit (the evaporator)
The refrigerant gas (R32) is pumped from the condenser to the evaporator coil where it absorbs the excess heat.
The refrigerant is circulated back to the condenser, compressed (this makes it boil where it gives off the heat it collected from inside the building) and then passed back through the evaporator coil to cool.
The temperature and relative humidity are both reduced and the air is filtered to remove particulates such as pollen.

Why should I consider air conditioning?

An air conditioning system provides and distributes cooled or heated and de-humidified air throughout a room or building. Filters remove particulates. 

Air conditioning units improve air quality, providing a comfortable environment for the occupants in the building and in the case of commercial premises, can ensure the smooth operation of sensitive equipment such as servers. So - if you have suffered summer nights of poor sleep, which then affects your day, then it’s time to consider domestic AC. If you or a family member suffers from allergies such as hay fever – then it’s time to consider domestic AC. 

If your office environment is uncomfortably hot during the summer months, then its time to consider commercial AC. 

What is an air conditioning split system?

A split system comprises of two units:- 

1. An outside unit (condenser) 

2. An inside air outlet unit, often called the “wall hung unit” (evaporator) 

The two units are connected by copper pipes that carry the refrigerant A multi-split system has multiple indoor units connected to a single outdoor unit. 

A split-system can be used for both cooling and heating. 

What maintenance is required?

It’s always a good idea to take out a planned maintenance contract with Dorn Ltd. to ensure that the equipment has been used and maintained in accordance with the manufacturer’s specifications and recommendations. This will show that you have taken good care of your unit and keep your warranty valid. 

Regular maintenance (every 12 months) will ensure that your unit will last longer, will run at peak efficiency, and therefore cost you less over time. 

The maintenance schedule will include (minimum) :

-Check, tighten and test all components 

-Wash the condenser 

-Check all the refrigerant lines 

-Check and replace filters, clearing any debris 

-Inspect and test all safety controls 

-Take and record temperatures 

-Other checks to make sure your system is running at top efficiency.

What is an inverter?

An air conditioning system with an inverter continuously adjusts its cooling and heating output to suit the temperature in the room, thus improving comfort levels. 

The inverter reduces system start-up time, so the required room temperature is reached more quickly. As soon as the correct temperature is reached, the inverter ensures that it is constantly maintained. 

This is a very energy efficient system, as because the inverter monitors and adjusts the ambient temperature whenever needed, energy consumption drops by 30% compared with a traditional on/off system. 

Our offered systems include an inverter.

How do I choose which size of air conditioning system I need?


This depends on many variables such as: 

1. Room size 

2. Number of rooms 

3. Occupation

 4. Use of the space etc…… 

Please call/ email your enquiry and we’ll be happy to advise

How often should I replace my air conditioning unit?

Well maintained, AC units can last for many years (10+) Regular cleaning and/or changing the filters will ensure optimum efficiency.

What is R22 and why is it important?

R22 was banned under the Montreal Protocol in 2009 after scientists identified that it was a cause of the ozone layer to be depleted. 

R22 was replaced with new refrigerant R32 in Jan 2015 making it illegal to install or repair units using R22.

What certifications do your engineers hold?

We are NICEIC approved contractors, City & Guilds Level 2 Award in F-Gas and ODS Regulations, registered with Refcom, have the CITB site management safety training.

Do you provide free site surveys?

Yes. All our quotes and site surveys for new installations are free of charge.

How much does air conditioning cost to run?

This is not so easy to give an exact figure due to the many variables that could be at play. These include:

1. The type and efficiency rating of your chosen unit

2. The location of your home and it’s insulation levels

3. The type of room(s) you want to control

4. If you take on a maintenance contract (or maintain it yourself to a high level)

5. If your system has remote control functionality

6. Clever system features such as the Mitsubishi 3D i-see sensor

As a general guide for the most popular types of air conditioning units we offer:

A small room with a 2.5kW unit averages 10 - 12p per hour.
A medium room with a 3.5kW unit averages 14 - 16p per hour.
A large room with a 5kW unit averages 20 - 24p per hour.

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