Join Date: Aug 2016
Location: Saigon - Vietnam
A heat sink mounted on a basically cubic valve body that does roughly 4cm² each side...A tricky task....
Basically, most NC solenoid valves are not designed to be open for a long time, but they perfectly withstand frequent on-off. Manufacturers put forward the number of on-off transitions amounting to millions, as a basic specifications. The other specifications being the working pressure and the transition time between on-off states, absorbed electrical power (linked to temp rise) is secondary.
Solenoid valves used for Co2 in aquaria don't need to be fast nor to be reliable through very frequent on-off. But are typically open continuously for hours, and here arises the problem of heat: Mine which theoretically pumps 4.2W, get as hot as at least 60°C in 15'. I have another reputed 3W CKD (Japanese brand) solenoid that gets even hotter in just 10', so hot that it melted the O-ring on the fitting connected to the outlet hole. I don't know the matter the diaphragm is made of, but if it is made of rubber of plastic, the high temperature can seriously impact it.
i don't believe that having the co2 diffused in the water this discontinuous way may disrupt anything. In the wild, plants are not surrounded by a water with constant dissolved co2 rate all day long, they strive though. That being said, I am using a reactor with constant dissolution rate and I maintain an excess of co2 during the open phase (lasting 30"), to dampen the shut phase (30").
My brand new cheap solenoid valve cost me roughly $4, my timer cost me the same price. And there in North America, a used Clippard valve is somewhere above $20.