# Re: Yet another DIY substrate heating cable question

```On Tuesday, 6/9/98 Paul Nicholson wrote in response to my question quoted in part
below:

> >According to my calculations (using the formulas set forth in the Resler /
> >Behle
> >article in the March 1995 issue of Aquarium Fish Magazine) I need a 12
> >Volt, 4.5 AMP
> >transformer rated to handle at least 65 watts.  So far, so good.
>
> P = I * E, P = 12 * 5, P = 60 watts.
>
> Something is wrong with your calculations as a 12 volt, 4.5  amp
> transformer is only good for 12 * 4.5 = 54 watts.

Paul,

I can see how you would think that my calculations are off, but I just took the
advise of the Resler/Behle article which said, "...buy a transformer that is rated

to handle a 20 to 30 percent higher wattage than you need."   The actual wattage
needed for my system is 54 watts, but adding 20 to 30 percent brings that to 64.8
to 70.2 watts, thus my 65 watt figure.On Tuesday, 6/9/98 Dave Gomberg also wrote
in response to the same question quoted in part below:

> At 03:48 AM 6/9/98 -0400, Jay Bickford suggested:
> > I don't want to build a system that is unsafe
>
> That's a good point, Jay.  If you don't have the knowledge to pick a
> transformer with the help of a vendor, how in the heck are you going to
> ensure it is safely designed, installed and used?

Dave,

To be sure, the same question has crossed my mind, and that is why I am doing this

research here in the APD, as well as through other sources both on and off the
internet.  One of the things I love to do is to learn new things, so I am trying
to learn about this subject as well. But believe me, if I can't get to a point
where I understand this and feel confident that I can build a safe system, I won't

do it.  However, thanks for the concern.

Now for my 2 cents worth about the APD vs. R.A.F.P. discussion:

Some of you may remember that I was on the APD briefly about 2.5 years ago at
about the same time the reorganization of  *.aquaria was being discussed.  I
dropped off the APD due to a move across country for a new job, and due to a
frequent travel schedule I didn't get around to setting up a new planted aquarium
until now. (My wife wouldn't have appreciated being left with the maintenance
chores of my tanks.) At the time of the reorganization I think it was felt by many

on the APD that R.A.F.P. would take the place of the APD and that the APD would
die a quiet death due to lack of use.  I'm glad to see that that did not take
place.

When I started to get back into the hobby several months ago, the first place I
went was to R.A.F.P..  I thought I would see many of the same old names there that

I had seen in the APD, but few were there.  I also found like some others have
mentioned, that the discussion was not at the same level as on the old APD.  So I
looked up the APD, and to my surprise and pleasure the APD had not gone anywhere,
in fact it was better.  Apparently the APD fills a need for many, for if it did
not, it would have died for lack of use a couple of years ago.

Thanks to all who responded to my DIY heating cable questions.  As always, the
information is of great assistance and is greatly appreciated.

Regards,

Jay Bickford
Savage, MN

```