Overshooting pH with the Tunze 7074/2 controller

Charley2015 · 12/10/2015, 10:56 PM

Hi,

I'm trying to use some Tunze equipment as part of a scientific experiment, but I'm having trouble getting the equipment to do what I need it to do. Any advice you could offer would be a huge help!

I am using a:
*Tunze pH controller (7074/2),
*Tunze CO2 diffuser (7074.50) and
*Tunze CO2 regulator (7077/3).

I want to use the system to inject 100% CO2 into a 12L seawater tank to achieve pH 7.7, but the system keeps over shooting the set pH.

I've tried altering the regulator valve, the motor speed, and the controller timer but nothing seems to work. Any advice on what I am doing wrong?

rvitko · 12/11/2015, 09:34 AM

I would set a very low bubble count of about 1 bubble a second or every 2 seconds. I would set the controller timer to the maximum delay, this way it meters and waits the delay time to gauge the effect. I suspect since the volume of water is so small the residual CO2 in the diffuser is causing this effect. In a worst case scenario I would replace the diffuser with a simple diffuser that does not trap the bubbles (one that is like a very fine airstone) or I would drill a vent hole at the top of the diffuser so the bubbles can escape and do not recirculate for as long.

Charley2015 · 01/29/2016, 01:52 AM

Thanks so much for your help, Roger. I switched to a fine air stone and set the bubbles to a low flow rate as you suggested, and that has solved the problem. Thanks again!

rvitko · 01/29/2016, 09:42 AM

Thank you!

12/10/2015, 10:56 PM	#1
Charley2015 Registered Member Join Date: Sep 2015 Posts: 3	Overshooting pH with the Tunze 7074/2 controller Hi, I'm trying to use some Tunze equipment as part of a scientific experiment, but I'm having trouble getting the equipment to do what I need it to do. Any advice you could offer would be a huge help! I am using a: Tunze pH controller (7074/2), Tunze CO2 diffuser (7074.50) and *Tunze CO2 regulator (7077/3). I want to use the system to inject 100% CO2 into a 12L seawater tank to achieve pH 7.7, but the system keeps over shooting the set pH. I've tried altering the regulator valve, the motor speed, and the controller timer but nothing seems to work. Any advice on what I am doing wrong?

12/11/2015, 09:34 AM	#2
rvitko RC Sponsor Join Date: Apr 2000 Location: Austin Texas USA Posts: 35,785	I would set a very low bubble count of about 1 bubble a second or every 2 seconds. I would set the controller timer to the maximum delay, this way it meters and waits the delay time to gauge the effect. I suspect since the volume of water is so small the residual CO2 in the diffuser is causing this effect. In a worst case scenario I would replace the diffuser with a simple diffuser that does not trap the bubbles (one that is like a very fine airstone) or I would drill a vent hole at the top of the diffuser so the bubbles can escape and do not recirculate for as long. __________________ Roger Vitko Tunze USA "He's for every one of us, stands for every one of us, he'll save every man, woman and child in a mighty Flash!" Current Tank Info: 210 gallon planted tank with Altum Angelfish

01/29/2016, 09:42 AM	#4
rvitko RC Sponsor Join Date: Apr 2000 Location: Austin Texas USA Posts: 35,785	Thank you! __________________ Roger Vitko Tunze USA "He's for every one of us, stands for every one of us, he'll save every man, woman and child in a mighty Flash!" Current Tank Info: 210 gallon planted tank with Altum Angelfish

01/29/2016, 01:52 AM	#3
Charley2015 Registered Member Join Date: Sep 2015 Posts: 3	Thanks so much for your help, Roger. I switched to a fine air stone and set the bubbles to a low flow rate as you suggested, and that has solved the problem. Thanks again!