Re: Price of substrate heating

[Bill Wichers <billw at waveform_net>]

> Why do all the websites seem to suggest that substrate heating is 
> expensive? I live in the UK and can buy a Rena Cor heating coil for the 
> aquarium, vivarium or terrarium for a less than £35 even for over 80 UK 
> gallons (96 US gallons).
> (Price for illustration purposes from www.aquatics-online.co.uk

It is for the low-voltage systems which I think are still more common, at 
least in terms of installed systems. Not too many websites I've seen 
mention the relatively new line-voltage heating cables that are available. 
Not sure why... Some people seem to be afraid of them due to the line 
voltage, others seem to think they are somehow less effective (?).

> It could be something to do with the fact they use sealed 240V cables 
> instead of an expensive transformer and low voltage cables. The risk of 
> electrocution is negligble, really, especially if you you a power breaker.

Probably more due to Dupla charging too much :-) Transformers themselves 
aren't terribly expensive. And for the electrocution issue, you need a GFCI 
*and* a ground probe of some sort for proper protection. A flexible plastic 
line buried in the gravel is going to be much more likely to sustain 
non-catostrophic and thus unnoticed damage, so I think it is a bigger issue 
with undergravel cables than it is for the usual glass heater.

> (I think US plugs are stupidly designed anyway, like most of the rest of 
> the world. There's just not enough brass. UK plugs are must harder to pull 
> out and are overdesigned. End of entirely random rant. Sorry. And why no 
> proper earth terminal?)

Remember that most all those plug designs are at least 70-80 years old. 
Before then there were cords with threaded light fittings on the end to 
connect to light sockets, back when it was "electric light", not "electric 
power". There is enough contact area on most of the plugs out there as long 
as proper contact pressures are maintained in the receptacle. The problem 
is that old and cheaply made receptacles tend to either wear out or not 
make a good connection. And of course there is the corrosion problem that 
aquarium people will eventually encounter...

BTW, there is a 3-prong US plug (known as a NEMA 5-15P) with a proper 
ground terminal that makes contact before the other two. It's not terribly 
unlike the UK plug but it is smaller, and it uses the same blades for power 
(ground is a round pin) as the two-prong non-grounded connector which can 
be plugged into a grounded receptacle.

        -Bill


> --
> Andrew McLeod
> thefish at theabyssalplain_freeserve.co.uk


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