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We recognise that
our customers/clients may desire a quick solution to condensation problems that
are occurring in their properties. The installation of a dehumidifier for a few
weeks may help a severe condensation problem, but should not be used alone as a
method of condensation control. Other methods of control such as natural ventilation at
source (bathrooms and kitchens), tumble dryers vented to the outside, background
heating, forced electric ventilation, cavity wall or roof insulation should all be used to
obtain the best long term results to reduce condensation in the property.
Therefore, this page on dehumidification should be read in conjunction with that
on Condensation.
What is a dehumidifier ?
A dehumidifier is a machine designed to dry air by removing water vapour from
it. As the air is in contact with all other surfaces (e.g. plaster, timbers,
etc.) these surfaces will tend to dry out too. The machine works by directing a
stream of the air it gathers over refrigerated fins. The temperature of the fins
is usually well below the dew point for the conditions that are set by the
ambient temperature and relative humidity, and so water from the air condenses
on the fins. This liquid water runs off to be collected in a container or
directly to a drainage system. In some machines the cooling of the fins
progresses below the freezing point of water and ice can form on the fins. This
is prevented by warming the fins (reversing the refrigeration process) allowing
any ice on the fins to melt. The machine deals with this automatically in its
operation cycle.
Small dehumidifiers can usually extract about 10 litres of water per day
(full power) and this would suit a 2 to 3 bedroom house. The level of water
extraction can usually be adjusted manually, by a controller provided on the
machine.
Costs - buying or hiring
Machines for a 2 to 3 bedroom house are available for about £80 upwards, but
some DIY stores have them available in 'sales' for about £75 or less. Larger
machines for bigger buildings (industrial applications) are considerably more expensive.
A "professional" type machine can be as much as £650 + vat.
Hiring is an alternative and this a service we provide to our local area
(small machines only). We operate a minimum charge of £60.00 plus vat for the first week
with a pro rata charge per day thereafter. The minimum hire period is 1 week.
We offer to deliver and collect the dehumidifier from the
property concerned, given reasonable access, and depending on location. We will also monitor the condition
of condensation control in the property at the time of delivery and collection
and advise the client accordingly on progress.
The hirer must be responsible for the safe use of the
equipment and should ensure that the equipment is insured with regard to
malicious, accidental, fire damage or theft.
Running Costs
Smaller dehumidifiers are rated at 1.2 to 1.5 Amps. This means that they will
cost about 14 to 18 pence per hour to run - or up to £4.30 per 24 hour day
if left to run at full extraction rate. (Electricity cost taken as 12p/kWh)
General Notes - for domestic dehumidifiers
Before attempting to operate any unit, read the
instruction sheet thoroughly and follow all directions carefully. By doing so
you will ensure the safety of both yourself and others around you, whilst also
ensuring correct and successful operation of the machine.
The machine operates using 240 volts AC power supply
(standard 13 amp plug). Never operate the dehumidifier in an environment where
it is likely that standing water will accumulate around the unit. If this
condition should occur, for your safety unplug the supply cable before stepping
into the water accumulating around the dehumidifier. Do not operate the
dehumidifier if it is in damaged condition and notify the owner immediately of any such
damage. Do not operate the dehumidifier with any covers removed. For additional
safety, operate the equipment connected to the electrical
supply via an earth leakage protection device (RCD).
Choosing a location
Use the dehumidifier in any enclosed room or area such as a
workshop, basement or living area where you want moisture removed. For best
results, keep all external doors and windows closed.
Good airflow is essential for dehumidifying. Make sure that
there is at least 150 mm / 6” of space between the rear of the dehumidifier
and any wall or other obstruction such as furniture or appliances. The
dehumidifier should be in an upright position and on a level surface.
Operating the dehumidifier
Dehumidifiers are equipped with an automatic humidistat
control that will switch the dehumidifier on and off to maintain the chosen
humidity level. When you operate the dehumidifier for the first time in a
particular area, set the humidistat dial on the mid point. Allow the
dehumidifier to operate at this setting for 2 or 3 days. After this time the
amount of dehumidification can be set to suit your requirements, by turning the
setting control up or down.
The cooling coils on the back of the dehumidifier may get
frost/ice covered if the room temperature or the amount of moisture in the air
(relative humidity) is too low. This condition usually happens in cooler
conditions of use. The dehumidifier is designed to remove moisture when
the room temperature is above 8 degrees centigrade. Most units are equipped with
an automatic system to defrost the coils. The defrost cycle operates on a
pre-programmed time and includes an electronic timer allowing coils to be
quickly defrosted about twice per hour, if required.
Disposal of collected water
Small dehumidifier containers have a capacity of about 10
litres (or smaller) and an automatic shut off system to prevent overflow when the receptor
gets full. When the water in the receptor rises to a certain level, a float
switch shuts off the system and turns on a warning light on the front panel. The
water receptor should then be removed and emptied. The dehumidifier should be
switched off when the water receptor is removed and switched on again when the
water receptor has been replaced.
To empty the receptor, turn the control dial to the off
position. Hold the receptor firmly with both hands and carefully slide it out.
Empty the water and replace the receptor in the dehumidifier. Turn the control
dial back on to your desired setting.
Direct delivery of water to a drain from some machines is possible. This is
via a small bore pipe connected to an outlet on the machine. Some machines
require the water collector to remain in position, whilst other require its
removal.
Service and Maintenance
You should not need to carry out any servicing on a dehumidifier. For your
protection always disconnect the dehumidifier
from the electrical outlet and remove the water receptor before maintenance.
Cleaning the cabinet - wipe the exterior with a soft, damp
cloth. Do not use solvents or cleaning agents. Dust may be removed with a brush
attachment of a vacuum cleaner.
Cleaning of the air filter, water receptor and any other
components of the dehumidifier should be carried out as per the manufacturer's
instructions.
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