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Seattle/Kitap water, Dupla Xformers
> From: Walter & Jeanne Klockers <klock at olynet_com>
> I checked my tap water tonight, with the following results:
>
> pH - 6.6
> KH - 3
> GH - 60 ppm
> CO2 - above 15 mg/l (TetraTest)
>
> I was surprised how soft the water was. Any comments about the water out
> of my tap that might be helpful? Thank you.
Hi Walter, good to see you on the electronic forum. Been enjoying your
drawings for a few years. Our water is blessed here; I think the basic
reason is we get so much rain that the water doesn't sit around in
resevoirs for very long (and thus doesn't get minerals leached into it). I
have to add calcium carbonate and/or baking soda to keep the pH balanced
in the high tech tank. It looks like your tank is balanced quite well, but
if you want it at 7.0 you could add the aforementioned buffers.
> From: "Frank I. Reiter" <FIR at istar_ca>
>
> 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.
> I have searched far and wide, and not yet come up with a 42 volt/200 watt
> transformer. So, I turn to the collective knowledge of the list:
>
> 1) Where can I find transformers for these beasts?
I'd go for surplus electronics.
> 2) What are the issues surrounding running them at some other voltage, like
> 24? How would this affect heat output or transformer sizing for example?
You can use a LOWER voltage transformer on the same wire, but not a higher
one (unless you know for sure the wire can take the higher current).
Without knowing if you have a 8.8 or 2.9 ohm wire, here are the three
possibilities you might have:
| 42 volt transformer | 24 volt transformer
--------------+-------------------------+----------------------------
8.8 ohm cable | Need 5 amp transformer | =65 watts, needs 3-4 amp xformer
--------------+-------------------------+----------------------------
2.9 ohm cable | (DO NOT USE) | Need 10 amp transformer
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!
- Erik
---
Erik Olson
eriko at wrq.com