HHO

Hi.
I had some spare parts so I wanted to do an HHO experiment. I took large PVC pipes and connectors and made a horseshoe shaped aperatus. I stuffed 100ft of stainless steel cable in each side. I connected tubes to collect oxygen and hydrogen and made sure the whole thing was air tight. I used sodium hydroxide as an electrolyte. I converted 220vac 30 amps to 240vdc using a rectifier and connected it to the aperatus.
After running the experiment for 10 minutes no gas was formed. I checked the anode and cathode on the rectifier with a multimeter and it read 240vdc. I checked the anode and cathode on the aperatus and it read 4 vdc.

Why was this experiment a failure?
My rectifier can handle 1600 volts should I try increasing the voltage? Although I'm scared the electricity will start to arc.

Is HHO really H2 O?

Electrolysis of water only requires 1.23 Volts. If electrolysis isn't happening at 240 volts, then it seems like there is a connection problem...