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Dupla heating cables
> > I recently had the opportunity to pick up some Dupla heating cables at
very
> > good prices due to a local distributor going out of business, so I took
all
> > that were available to me, including a Duplaflex 1000, a 250W 42 V
cable.
>
> If it was a local distributor, ir was probably a 250 Watt, 24 volt cable.
> You should be able to verify it though an ohm meter. Because P = V^2/R,
> a 42 volt, 200 watt cable should have a resistance of 8.8 ohms, while a
24
> volt, 200 watt cable will have a resistance of 2.8 ohms.
No, it is clearly marked on both the box and the actual cable as being for
42V.
> Note though the dramatic difference in output power you get from
operating
> the 42-volt 200 watt cable at 24 volts. 1/3 the power!
Yes, I noticed. I gave up today on finding a 42V tranformer with
sufficient amperage, prompted in part by a message from another list reader
informing me that the reason we use 24V cables in the US and Canada is to
comply with UL and CSA low voltage standards. My current plan is to run a
250W and a 200 W cable in parallel (I have just one of each) at 24V. This
will yield, according to my calculations, 148W in total, which won't keep
the tank warm but will perhaps suffice to warm the roots and create some
micro-currents in the substrate. A 24V 8 amp transformer to do this is
easily obtained locally.
Can anybody confirm for me that Dupla heating cables run on AC?
Frank.
-----
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to an invitation. - Jean Shinoda Bolen
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