On Fri, 27 Dec 2002 18:16:19 +0000, JennyC wrote:



1) There had obviously been a short circuit and when we investigated saw
that the wires were sort of dried out (if that makes sense) and frizzled
at the ends. Could this be due to the really hot temperatures in the GH
during the summer months ?? If so what should we do to stop a repeat of
the problem ?? (I do use shading but it still gets HOT)


A short circuit? If there had been a short circuit then a fuse or circuit
breaker should have open circuited and turned off your electricity supply
to your greenhouse before anything dangerous can happen.

Wires can heat up but if you have a correct fuse rating then this safely
protects the wires from short/overloads and therefore cannot heat up from
short or overload.

Dried out and frizzled at the ends? However, where wire connects to
another piece of equipment then a bad connection certainly can result in
very hot temperatures - so you need to make sure that all the conenctions
are good.

Also, you want to keep water away from the electricity supply.

2) Is there special wire one should use?

Mains cable capable of carrying current to your lighting/heater. Look at
the power rating of your lighting/heater - add up the current both take
and ensure your cable can carry this easily.

Generally appliances only state a power rating rather than current. For
example your lighting may be 60W (w stands for watts). With a 240V mains
electricity supply (UK) the current taken by your lighting is 0.25 amps.

(Current in amps is calculated by dividing the rated watts by
the voltage (240 in the UK), 60 divided by 240 = 0.25A. Note that some
applicances are rated in KW (kilowatts) where 1KW = 1000W.)

Get a current for your heating system. Add this to your lighting current
to give you your total current - then make sure your wire can handle
this. Some common wire ratings are 3A, 6A and 10A.


3) or special insulation ?

Must be suitable for mains use. Greenhouse temperatures won't be a
problem.

If you don't know too much about electricity then you could always get an
electrician to look at it from a safety point of view - he /(she) would
be able to tell you if you need to do anything to ensure it is safe in a
couple of minutes.


PT