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Practical DIY Heating Cables

by Scott Moore (rocklobster at

I hope this will help anyone who wants to make his or her own substrate heating system. This is a 150-watt system. Remember to test in water, the wire gets hot fast out in the open with out water cooling it.

Here is a list of parts it took to make a substrate heating cable system for a 90 gallon tank with the dimensions of 48 X 18 X 24.
Home Depot
32 feet ½ PVC pipe 2.80
4 ½ PVC elbows 1.00
16 ½ PVC 90 Degree Elbows 5.60
1 6x6x4 outside PVC box 7.50
2 Package TIE-WRAPS 2.50
1 14 amp Extension Cord 7.50
Radio Shack
1 Package Heat Shrink 1.99
1 240v 10amp SPST switch 1.99
2 Lamp Holders 2.79
2 14v Lamps 0.59
1 Inline Fuse Holder 0.99
1 3 amp slow blow fuses 1.99
1 30 AWG wire 2.99
1 aquarium sealer 3.99
Mail-Order Electronics
1 EM24CT8 24VAC 8 AMP 46.63
TOTAL 90.67

If you can find the transformer at a surplus store you can even save more.

The final size came out to 46” x 16 ½”

I cut small pieces of the pipe to connect 6 Tee’s together. The center 2 tees I had to shorten the sides about ½” on each side to keep the whole thing within specs. I used the aquarium sealer as the glue to hold everything together. The tubes are 2 ¼” apart except in the center where they are 1 ¾”. I needed 8 tubes In order to fit the 33’ of heater wire.

I drilled holes through the side of the main pipes after I cut them to size. This is so you can run the tie wraps through them to hold the wire in place. It is easier to do this now before you glue them into the Tee’s.

I also drilled into the tops of the tubes in random areas in order to let the air bubbles out when it submerges.

The PVC outdoor electric box worked great to house the transformer assembly.


I drilled out holes for the power switch and lights. The reason I have 2 lights is because I used 2 14v in series. I had trouble finding a 24v lamp.


The transformer mounted sideways just fine with space for heat dissipation and switch/lamps hook ups. Note the in-line fuse for safety.

Up to Misc. Tech <- Plants <- The Krib This page was last updated 23 June 1999