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Portable Air-Conditioners (Mobiles)


Portable air-conditioners have the advantage of being portable.  Indeed, they are also called 'mobile air-conditioners' or simply 'mobiles.'  They can be wheeled into a room where cooling is required in the warmer months and, when the cooling requirement no longer exists, the unit can be stored away (outside of the room, possibly in a cupboard) during the winter months.  Portable units can be a very practical temporary solution in overheated offices, until funds are available to install 'fixed installation' air-conditioning systems.  There are also cases where planning and landlord restrictions prevent external equipment and the use of portable air-conditioners offers a satisfactory compromise solution.

As a temporary measure, portable units are often called upon to support the cooling requirements of a small/growing Server Room, though they are not suitable for those special applications and normally have operational difficulties.

Some drawbacks with use of portable units, as compared with the installed systems, are:
a) Portables are not as effective as 'fixed installation' systems because the airflow is normally directed from a low position in the room and they tend to have limited penetration into the depth of a room.  Most remove room air to remove the room heat, and this air is made up with outside air, giving an extra cooling load for the room.
b) They can sometimes be rather obtrusive, particularly in a smaller room, occupying valuable floor space and normally need to be close to an openable window (important space in small offices);
c) The trailing electrical cable can be a safety issue; 
d) These inexpensive-to-buy portable units are very expensive to run, compared with the inverter "fixed installation" air-conditioning systems, which uses approx 30% less electricity.  Over a period of, say 4 years, the total cost of a portable unit can work out more expensive than an engineer0installed system, depending on usage.
e) Noise from the unit can be unacceptable in an otherwise quiet room, and certainly too loud for use in a bedroom.  The monoblock unit has the compressor housed inside the Room Unit, which causes the bulk of the noise.  On the other hand, where a room is generally noisy or normally unoccupied this is not normally an issue.

Types of Portable Cooling Units

There are two main types of portable unit available, which can normally be connected to the regular 13A power ring main socket.  Here are some of the important features:

a)  Evaporative Coolers
This type of unit is NOT an air-conditioner; they are more accurately 'air-wetting' units.  Air drawn into the unit is filtered and passed through a water-soaked membrane, which wets the air and lowers the air temperature by up to 5degC.  The wetted air is then returned to the room and in this way the room is cooled.

Being cheap to buy, they are often the first purchase, and soon abandoned for refrigerant air-conditioners when their poor effectiveness becomes apparent.

We do not recommend this type of cooler.

b)  'Hose-Type' Refrigerant Air-Conditioners
These units have one or two hoses that are normally routed out of a nearby window.  The unit draws in room air, filters and passes it through a refrigerant heat exchanger.  The heat exchanger lowers the air temperature by 10-12degC, removes moisture, and then returns the conditioned air to the room. 

The heat removed from the room air is transferred to a second heat exchanger, at the back of the unit (just like a domestic refrigerator).  That unwanted heat is blown out thought an exhaust hose (similar to a laundry tumble-drier).  Importantly, the air used to remove this discharged heat is taken from the room being cooled, which has to made up of new air pulled in from outside.  So the kw-output of the unit is partly wasted in removing the unwanted heat so that a portable unit rated at 3.5kW might in truth only give effective cooling to the room of just 2kW.

In addition to cooling the room air, these units remove moisture and dry the room air (dehumidify).  Condensate collects inside the unit and some units require regular/daily emptying of the internal collection tank.  Some units have an integral condensate pump that removes the condensate water, avoiding the need for daily attention from the staff but the pump requires regular maintenance to avoid breakdown.


We do not recommend portable air-conditioners but would be happy to offer a proposal for an engineer-installed renewable heatpump air-conditioning system as a better installation.