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Below are answers to
the sorts of questions that we are often asked by people looking
to buy their first dehumidifier.
We have divided this section into two, dehumidifiers for
the home and dehumidifiers for unheated
or colder areas (i.e. storage, garages, workshops, boats, caravans,
holiday homes, conservatories etc.)
Dehumidifiers
in the home
How does a dehumidifier work?
A dehumidifier draws the air in from the room
over a filter and passes it over some cold coils similar to the
coils on a fridge. As
the coils are cold water condenses and drips into a bucket.
The air is then reheated to room temperature and blown back
out of the dehumidifier.
Why does water appear on my windows/cupboards/walls?
It is a basic law of physics that if the surface
is cold enough and if there is enough water vapour in the air then
it will condense. This
means in the case of windows whether they are double-glazed or not
that if the windows are cold enough and there is enough moisture
in the air then condensation will occur.
Where does this water come from?
We all produce water as we breath, the boiling
of vegetables, showering, rain, calor gas heating and making cups
of tea all produces moisture.
It is just an on-going process that never stops.
Can I just get rid of it by opening my windows?
This is fine on a nice summers day but in winter
opening your windows will just result in you losing the heat from
your central heating and create draughts.
This is a waste of money and if it is raining will just let
more moisture in. You
might as well just throw fivers out of the window.
Will a dehumidifier do the whole house?
A dehumidifier creates a volume of dry air in
as large a space as its fan can effect.
After that it will be helped by the fact that damp air will
always migrate to dry places.
As long as you leave all of the internal doors open a correctly
sized dehumidifier will prevent condensation from appearing around
the whole house.
What about the black spots of mould on my
window and bathroom sealant?
Mould occurs around 68% humidity, condensation
occurs at 100%. As
you can see from this you can have mould but still have clear windows.
A dehumidifier will prevent the mould from getting any worse
and once you have cleaned the mould away it will stop it from coming
back.
Do I put it in the worst room?
You can if you like put it in the main problem
area to start with and then move it somewhere more convenient when
you feel that the problem is under control.
If it is just condensation on the windows that you are worried
about a dehumidifier in a central position at for example the bottom
of the stairs will cure the problem in the whole house.
Are they expensive to run?
A dehumidifier costs about 2-3p an hour to run.
You should take into consideration the fact that the dehumidifier
will not run all the time, as it will be controlled via its humidistat.
Secondly it is very expensive to heat a damp house and you
will see a reduction in your central heating bill when you start
to use your dehumidifier.
What is the humidistat?
Just as you have a thermostat that you set on
your central heating you have a humidistat on your dehumidifier. This will allow the dehumidifier to turn off and on as required
without you having to worry about it.
Should I turn the dehumidifier on for just
a few hours a day?
No just let the dehumidifier decide when to come
on using its humidistat.
Will they help with allergies?
A dehumidifier will reduce the relative humidity
in the house, which will prevent dust mites and other pests from
breeding. In this way
a dehumidifier can help with allergies.
For more information try our allergy experts www.allergymatters.co.uk
Unheated
areas
Why do unheated areas get separated out?
A dehumidifier that can be found in your local
high street store is designed for use in your home, which is nice
and warm. In a garage,
store, workshop, boat, caravan, holiday home or a conservatory the
temperature will drop a lot lower.
Since a dehumidifier works by reducing the temperature internally
it can easily reduce down to freezing even if the ambient temperature
is 10°C. What you do
not want is for your dehumidifier to form a block of ice or for
you to find a puddle on the floor.
What happens when the temperature in the room
drops down towards freezing?
Most dehumidifiers designed for use in the home
will just stop working and turn themselves off.
Others will try to work and might well suffer from a build
up of ice. Those with
a defrost system are likely to only extract a tiny amount of water.
What is the correct type of dehumidifier to
use in these applications?
You need a machine with a function called hot
gas defrost. If the
dehumidifier does not have this then do not buy it.
How does Hot Gas defrost work?
Hot gas defrost works by reversing the coils
and using the heat from the hot side of the coils to melt the ice
to water. When this
is done the heat is returned to the front of the machine to warm
the air before it is blown back out.
So what temperature will a hot gas defrost
system work down to?
Freezing.
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