If you low side pressure shown on the regulator gauge is
zero when the solenoid is open, then you have virtually no
resistance to gas flow. It's like the regulator is trying
to maintain pressure in a balloon with a giant hole in it.
At 20 psi, I'd expect the metering valve to be restricting
the gas flow enough so that the pressure doesn't drop a
whole lot -- it will drop a little if the line is opened at
all, even with resistance -- in the trade they call it
"droop". But if it's going down to zero, then the metering
valve is not actually metering. If your controller is set
at, say, 6.8, then it will trip on at 6.9 and trip off at
6.7. You don't need the system to bounce back up to 6.9
rapidly -- if the solenoid runs open for half hour or more
at a time, that's fine. Then, if your aquarium isn't
shedding CO2 too quickly, it will probably take an hor or
more to drop back down to 6.7.
sh
=====
Christel Kasselmann,
author of the best current authoritative text on aquatic plants
will be a featured speaker at
The Northeast Council of Aquarium Societies 30th Annual Convention.
March 18-20, 2005 at the Marriott Hotel, Farmington, CT
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