GoGuppy
27th July 2007, 04:08 PM
Hi all
I thought I'd set up a new topic to cover CO2 controllers, as there seems to be some interest in this. This note covers a quick update on my CO2 controller performance and is a follow on from my previous posts on this subject under a different topic heading.
I've carried out a few tests to see if the controller performance (that is the over-shooting effect, or increasing the dead band of the control limit settings) could be improved. As mentioned previously, when the controller was set to a pH value of 6.69, it would switch on when the pH fell to 6.66 and switch off when the pH increased to 6.73 (or there abouts). With the original set up of the diffuser and probe, the pH would actually vary between about 6.63 and 6.76 (note however that you would be hard pressed to see this difference with a pH test kit :wink: !!). One full pH cycle from low to high and back to low would take about 4 hours, or more.
The trials I carried out included:
1. increasing the flow through the Dupla diffuser,
2. increasing the circulation flow thought the tank to see if this caused a better distribution of CO2 and hence a faster response from the controller,
3.placing the CO2 probe right near the diffuser rather than at opposite ends of the tank as per original set up, again to see if this would speed up the response of the controller.
The first trial was achieved by restricting the return flow to the tank a little, which forced more water to divert to the diffuser (there is a tee-piece in the return line which is hooked up to the diffuser). This seemed to help by decreasing the pH cycle time somewhat.
To do the second trial I rigged up a larger filter (a Fluval 304 that I had as a spare, in stead of the 203 I was using). This dramatically increased the flow in the tank, in fact my plants went almost horizontal! Luckily the fish were smart enough to find the still spots in the tank where the flow wasn't too bad. I tried this for about two days, but saw no real change in the pH range indicated by the controller, if anything it went worse, so went back to the old filter.
The third trial made quite a difference and it appears the overall range is now around 6.65 to 6.74 which I am happy with. A full cycle through this range now takes about 3 hours, or less.
Hope this is of interest to some of you, and I'll keep you updated if I make any further refinements to the system.
Cheers
I thought I'd set up a new topic to cover CO2 controllers, as there seems to be some interest in this. This note covers a quick update on my CO2 controller performance and is a follow on from my previous posts on this subject under a different topic heading.
I've carried out a few tests to see if the controller performance (that is the over-shooting effect, or increasing the dead band of the control limit settings) could be improved. As mentioned previously, when the controller was set to a pH value of 6.69, it would switch on when the pH fell to 6.66 and switch off when the pH increased to 6.73 (or there abouts). With the original set up of the diffuser and probe, the pH would actually vary between about 6.63 and 6.76 (note however that you would be hard pressed to see this difference with a pH test kit :wink: !!). One full pH cycle from low to high and back to low would take about 4 hours, or more.
The trials I carried out included:
1. increasing the flow through the Dupla diffuser,
2. increasing the circulation flow thought the tank to see if this caused a better distribution of CO2 and hence a faster response from the controller,
3.placing the CO2 probe right near the diffuser rather than at opposite ends of the tank as per original set up, again to see if this would speed up the response of the controller.
The first trial was achieved by restricting the return flow to the tank a little, which forced more water to divert to the diffuser (there is a tee-piece in the return line which is hooked up to the diffuser). This seemed to help by decreasing the pH cycle time somewhat.
To do the second trial I rigged up a larger filter (a Fluval 304 that I had as a spare, in stead of the 203 I was using). This dramatically increased the flow in the tank, in fact my plants went almost horizontal! Luckily the fish were smart enough to find the still spots in the tank where the flow wasn't too bad. I tried this for about two days, but saw no real change in the pH range indicated by the controller, if anything it went worse, so went back to the old filter.
The third trial made quite a difference and it appears the overall range is now around 6.65 to 6.74 which I am happy with. A full cycle through this range now takes about 3 hours, or less.
Hope this is of interest to some of you, and I'll keep you updated if I make any further refinements to the system.
Cheers