It is the
responsibility of every installer (even a DIY installation) of electrical
equipment to ensure that the equipment is fit for the use to which it is being
put and most importantly that it does not pose a threat to health during its
working life. In other words it must be safe!
The Radon Council is concerned that several examples of questionable practice and advice have been observed, that in extreme cases could be hazardous. It is therefore offering these brief guidance notes to assist those involved in the design, specification and installation of electrical equipment (fans), used specifically for radon reduction. These notes are not meant to replace or supersede existing local or national regulations, which must be adhered to, but to illustrate some of the more obvious points to be considered. At the outset a Risk Assessment for any installation should be conducted, with particular reference to the following: -
1) Electrical and Mechanical Safety.
Electrical:
The Institution of Electrical Engineers has for over 100 years published a series of regulations known colloquially as “the IEE Wiring Regs.,” now in their 16th edition. These specify the type of fusing and cable to be used and of particular importance the question of Isolation and Maintenance. Any installation must comply with these regulations and it is strongly recommended that any installation is either connected or at least checked and certified by a qualified electrician.
Isolation specifies that every circuit must be capable of being isolated from the supply. Maintenance requires that the means of isolation (normally a double pole switch) shall be readily accessible; this is to prevent the circuit being accidentally switched on when maintenance, installation or inspection is being carried out. Be careful it happens!
The installation of
a 30mA RCD (Residual Current Detector) should be considered and in certain
cases will be mandatory. It is also important (for fire risk alone) that each
device is fused and that the fuse rating is chosen carefully. Do not use a
value that is too high, if a fuse “blows” check everything carefully and resist
the urge to increase the rating automatically.
Mechanical:
It goes without saying that all equipment must be mounted adequately so that it cannot become detached during normal use or cause injury by contact with moving parts.
Fans that are
fitted inside a property, with internal outlet pipe work, should be located
wherever possible at a high level, usually in the loft. This is to prevent
radon from re-entering the property should any leaks in the pipe work (on the
exhaust side) occur. Particular attention should be paid to fire risk and
noise.
Fans fitted external to a property can be fitted at low level if the exhaust pipe work (exhausting at high level) is also external, any leaks will disperse in free air.
Environmental
considerations:
Fans and any
associated isolation switching, fusing and wiring, mounted external to a
property unless fully waterproofed and certified as such, must be protected
from the elements.
A bad example has been seen of an unprotected fan mounted on a wall, with rainwater pouring over it from a gutter and powered by what appeared to be domestic cable disappearing through a hole in the wall!
A radon reduction system frequently involves the creation of a sump beneath the property with any soil gas present removed by means of a fan. Unfortunately radon may well not be the only soil gas removed, for example methane and other hydro- carbon pollutants can also be present, unlike radon, these hazards are explosive and will also be removed by any fan system. Most fans used for radon reduction (for reasons of cost) have the motor within the fan housing and in contact with any gases present, hence an electrical fault could in a very few cases represent an explosion risk. The likelihood of any explosive gases being present in hazardous concentrations should be included in the risk assessment.
The choice of fan is therefore an important consideration and confirmation of suitability from the manufacturer should be obtained if in doubt.
It
is hoped that these notes, which by their very nature are not fully
comprehensive, will be of assistance in the implementation of a safe and
effective radon reduction system.
If in doubt seek professional guidance.
Brian H Ahern CEng FIEE
Technical Director