1993 Buick Century Reduce current to an accessory

1993 Buick Century

Hello,
I have found information on how to build a hydrogen generator, basically electrolysis, and have put it in my car. It does work well, but seems to want to pull more energy than I would like. I have a 20 AMP auto reset circuit breaker and that works well, but after the hydrogen generator warms up it will continually pull more than the 20 AMPS. This causes the breaker to kick on and off every few seconds.
My question is this: What can I do to only allow about 10 to 12 or so AMPS continually even though the hydrogen generator wants to pull more? I put a voltage regulator between the battery and the hydrogen generator and it burnt that up.
I would greatly appreciate some help.
Thank you very much.