Air Conditioning Terms

Heat Pump
A heat pump is simply a cooling only air conditioning system with the addition of a reversing valve, this is normally in the outdoor unit on the split type unit. When heating is selected the complete refrigeration system reverses, “the indoor unit gets warm and the outdoor unit get cold” If you are selecting an air conditioner as a “heating device” it is always wise to oversize the equipment to allow for low outside temperatures. Disadvantages; Duty falls off as outdoor temperatures drop. Advantages; Probably the cheapest, most efficient method of heating.

Cooling Only
A standard system that will just cool and dehumidify, lots of people select a cooling only unit when they have central heating installed and they simply want to cool a single room like a bedroom for example. Most mobile units are cooling only, some have a built in electric element for heating, this is not to be confused with a heat pump. For the small extra cost involved our view is you might as well buy a heat pump type and use on cool only.

What Size? kilowatts (kw)
There are basic calculations that you can use to determine the size of airconditioner you need, we have our own online calculator that will give you a “ball park” figure for a few different applications. This calculator will not be accurate for someone with a south facing conservatory, glass all round, no blinds, and 35 degree direct sunlight for 6 or more hours, no calculator will do this. But for your standard living room, bedroom, conservatory etc. , it will be near enough. Click on calculator link
Calculator

Noise Levels? d(BA)
Most reference to noise from manufacturers will be in decibels (d(BA) With packaged units all the noise is wherever the unit is sited. With split units you have the indoor noise and the outdoor noise. Indoor noise on split types is just the fan, this noise can be as low as 23 d(BA) on some of the more expensive units, however, we have found indoor noise below 30d (BA) on cheaper units so it does not automatically mean more you pay quieter you get!. Outdoor noise is greater on split types because the condenser also houses the compressor. Most systems under 5kw the outdoor noise cannot be heard from 4 or 5 mtrs away.

The Main Types of Domestic Air Conditioning

Split system type (Indoor unit + Outdoor unit
Indoor unit can be of several different types, the wall mounted type is the most popular and least expensive, the Outdoor unit can be sited up to 25 mtrs from the indoor unit. Between the indoor unit and outdoor unit are two small bore pipes containing refrigerant and a cable.Disadvantage – Has to be installed! Advantages Quiet, only a small hole to be made.
Split Type

Packaged type (Self contained “plug in” )
Most common packaged type is the ” window unit”, this is where both the indoor unit and the outdoor unit are contained in one “box”. Disadvantages ! Large hole to be made, Noisier than split type. Advantages, Can be installed by anyone and up to 3.5 kw simply “plugs in” to a mains supply.
Window Unit

Mobile units (Vent Hose)
Portable unit on wheels that can be moved from room to room, The hot air is rejected via a flexible vent hose normally 1.5 mtrs long and 150mm dia.. Disadvantages ! Most types you have to empty a container when full, Have to have a opening for the hose, Hose length is restrictive, Noisier than split types. Advantages, packaged “plug in” good for spot cooling and small rooms.
Mobile unit

Mobile units (Split type)
Portable unit separated by a flexible hose (usually 4 to 5 mtrs in length) Similar to a split installed unit where the condenser (outdoor) is usually placed out of a window or on a patio and the indoor unit is floor mounted on wheels. Disadvantages! Can be heavy and cumbersome. Noisier than fixed split types because compressor is inside indoor unit. Outdoor condenser is quite large and water from indoor unit is usually pumped to condenser which will drip.
Mobile Split Unit

Muliti types (Several indoor units – One outdoor unit)
Several Indoor units (can be of different types) can be connected to a single outdoor unit which can sited up to 50 mtrs from the indoor units. There is usually no cost saving by installing this type but is ideal when outdoor space is limited. Different manufacturers use various methods of connecting this type, too length to explain here. Disadvantages! Unless it is a very sophisticated system if one unit is in cooling mode then they all have to be in cooling mode. (You cannot have 1 indoor unit heating and others cooling at the same time.)
Muliti Split System
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What is Air conditioning?

Air conditioning is based on the precise control of temperature, humidity, air flow and air cleanliness.Split system air conditioners regulate these elements around the clock to provide you with a comfortable, relaxing atmosphere. Day and night, year after year. Cooling Mode: Excess room heat is absorbed by a special liquid – a refrigerant – sealed within the system. As the refrigerant in the indoor unit absorbs the room heat, it changes into a gas and is carried through small, copper tubes to an outdoor unit which releases heat into the atmosphere.The gas is converted into a liquid again and flows back to the indoor unit where air is fanned over it and out into the room. This cycle is repeated until the pre-set temperature is reached. – Top

What is a Heat Pump?

Heating Mode: Heat pump units also allow the cooling cycle to be reversed.A heat pump extracts “free” heat from the outdoor air, even on the coldest dayswhen the outside temperature may fall as low as -10°C, and transfers the heat indoors.Heat pump units therefore avoid the need for a boiler and allow you to cool and heat with the same unit,with savings in costs and energy throughout the year. A simple principle developed to perfectionAir conditioning works like your refrigerator which removes heat continuously from the cabinet and discharges it into the kitchen. You can feel this “free” heat by touching the coil on the back of your refrigerator.In summer, the heat pump extracts heat from the warm air in your home and pumps it outside. Your home stays comfortable & cool.In winter its the reverse. Natural heat in the outdoor air – even when its freezing – is extracted and moved indoors. Wonderful warmth when you need it. Comfort that costs less Three kilowatts of heat for each kilowatt of electricity used… Heat pumps are up to three times more economical than conventional gas fired or electric central-heating systems. Even in bitter cold snaps you will save money.Installation costs are lower too. With just one system, for cooling in summer and heating in winter, you save on equipment outlay. – Top

Wall Mounted Split Type Air Conditioning

What you should know..

Position of Indoor Unit
This should always be mounted at “high level” due to the design of the unit, mounting at low level will result in drafts and uncomfortable conditions.

Selecting the Wall
The perfect wall is an outside wall and preferably the same wall can be used for mounting the outdoor unit. The advantages to this are several, (1) The 60mm hole for the pipes and services to the outdoor unit can be “hidden” behind the indoor unit. (2) The condense water in summer cooling can gravity directly to a suitable rainwater drain outside. (3) The pipe separation is shorter which means cheaper and quicker to install, (4) The system will perform better.

Can My Outdoor Unit Go Higher?
Yes! The outdoor unit can go higher or lower than the indoor unit but there are limits. For example If you have a manufacturers allowable horizontal of 15 mtr pipe difference and the outdoor unit is to be sited 5 mtrs lower or higher, then this 5 mtrs must be deducted from the allowable horizontal separation making the horizontal distance 10 mtrs. Most small split units maximum “lift” is 5 mtrs.

I Have No Outside Wall!
It can usually be overcome, An example is a high wall mounted unit where the pipes go up into the loft, they go over three rooms and eventually exit at the rear of the house where the outdoor unit is mounted on wall brackets, One problem is the condense water, as water will not flow uphill a lift pump is needed to suck the condense water into the loft space, the pump then forces the water to any suitable drain. There are lots of other ways around installing without a direct outside wall, but it is usually the condense water that is aggravation.

Do I Need a Pump?
This is totally dependent on where you are to mount your wall mounted indoor unit. All air conditioning systems dehumidify as they cool, the amount of water that is produced is dependant on the amount of water vapour in the atmosphere ( humidity). This water drips off the fin coils into a condense tray at the base of your indoor unit and then into a short flexible tube supplied by the manufacturer. Like the water in your sink it gravity drains away, it will not go “upwards” If your indoor unit backs onto an outside wall its easy just extend the short flexible tube and take to a suitable rain water point.

When Do I Need a Pump?
If your indoor unit is mounted on an internal wall and you are to run your pipes and services into a loft or false ceiling above the water needs to be forced (pumped). If your drain is extended or rises at any point you will also need a pump.

If So, Which Pump?
There are lots of pumps, In our view the most reliable is the Peristaltic Pump. The peristaltic pump “lifts” the water from the indoor unit and pumps the water away. Some of these pumps can lift the water to 4 mtrs and have a “pumping head” of 10 mtrs. Other pumps can be fitted directly on the short manufacturers hose and work on “sensing “water which starts the pump, when the water has gone the pump stops. More information on air conditioning water pumps can be found at www.hydron-pumps.com
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Understanding Unit Capacities

The cooling or heating capacity of an air conditioner will vary depending upon the indoor and outdoor temperatures. All manufacturers quote duties for cooling at an indoor temperature of 27C with an outdoor ambient temperature of 35C. For heating they use 20C indoors and 7C outdoors. When sizing a system for use in the UK we have to adjust the capacities to take into account average UK conditions. In general we would usually aim to maintain 21C indoors in an ambient of 27C for cooling. We usually aim, in heating, for 20C indoors with an outdoor temperature of 0C. The following correction factors should be applied to the rated conditions.

UK Total Cooling = Rated Total Cooling x 0.9UK Sensible Cooling = Rated Sensible Cooling x 0.97UK Heating Capacity = Rated Heating Capacity x 0.8Total and Sensible Cooling.

Every air conditioner removes water from the air as well as removing heat. This is why we have to remove condensate from them. When a manufacturer quotes a TOTAL cooling capacity they are referring to the total amount of energy removed from the room, and this includes this water removal. When looking at the amount of HEAT removed from the room, we use a different figure called the SENSIBLE COOLING. The amount of energy removed as moisture is called the LATENT cooling. This figure is the difference between the TOTAL and SENSIBLE cooling capacities. The latent cooling capacity can be used to calculate the amount of water removed from the room. When calculating the size of air conditioner for a room, when you know the amount of heat generated within the room, you should always size upon the SENSIBLE cooling. One would assume that when looking at the capacity of an air conditioner he or she is referring to the TOTAL cooling. Nominal Sensible Cooling = Nominal Total Cooling x 0.67UK Sensible Cooling = UK Nominal Cooling x 0.75Latent Cooling = Total Cooling – Sensible Cooling Moisture Removal (l/hr) = Nominal Total Cooling x 0.45 or Latent Cooling x 1.5.

Pipe Separation Between Indoor and Outdoor Units

Every split system has a maximum pipe separation, which includes a maximum vertical separation (lift). In addition each unit is charged with refrigerant for up to a certain pipe work length, above this length refrigerant must be added to the system for correct operation.

The Effects of Exceeding the Maximum Pipe Separation.
The reason for the maximum pipe separation and vertical lift is to prevent failure of the system. Exceeding these limits will have a detrimental effect on unit performance and also cause failure. No system failure due to exceeding these limits will be considered for warranty by most manufacturers.

Effect of Incorrect System Charging
Any system installed with a pipe separation of less than, or equal to, the length of pipe work it is charged for will not require extra refrigerant. If the pipe work exceeds the length the unit is charged for then extra refrigerant should be added. If this is not carried out then the system will be undercharged and will not operate correctly. The most likely effect of this will be for the compressor to overheat and, eventually, fail.

Effect of Pipe Length on System Performance
All system capacity ratings are based upon a 5 metre pipe separation. Longer separations will result in a capacity loss. In general the capacity loss will be around 20% at the maximum allowable separation. It therefore follows that pipe lengths should be kept a short as possible.

The effect of this on unit selection should not be ignored. For example if you need a cassette unit to provide 10KW then you would normally select a 10.5KW. If you are then told that the pipe separation will be 50 metres then the effect of a 20% capacity reduction is that the 10KW unit will only provide 8.4KW and be undersized. Given this information you would select a 12.5KW because applying the 20% reduction to this will give 10.5KW.

Estimate Your Installation Costs

For a rough estimate of your installation costs for a single room wall mounted split type air conditioning system, please use [This Form].
(This form is for guidance only and The Air Conditioning Shop will not be held liable for any calculations produced without confirmation in writing, please call now for an accurate price based on your specific requirements – Tel: 01200 428888)
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