temperature controlled fan speed

Hello, I have an application where I want to modulated fan speed with VFD to maintain a predetermined temp.how should I go about this?

How about a few more details
What temp, what volume of air, motor size, what will raise or lower temperatur 0f whatever you are trying to control.

If you cant supply this info please send batteries for my crystal ball.

Dan Bentler

leitmotif said:

How about a few more details
What temp, what volume of air, motor size, what will raise or lower temperatur 0f whatever you are trying to control.

If you cant supply this info please send batteries for my crystal ball.

Dan Bentler

Click to expand...

Sorry guess i was vague this is for a 7.5 h.p. cooling tower fan the water is about 74 degrees and we like to cool to 70 degrees .On cool days i do not believe we need full fan speed to get sufficent cooling we currently have thermostat in return water tank and fans are on/off but they never turn off as some cooling is always required

Try PID :nodi:

Can't speak for other manufacturers, but I use Omron's (Yaskawa in the US) E7 inverter for exactly this application. Built-in PID, and the side effect will be a bit of energy saving too.

jeff s said:

Sorry guess i was vague this is for a 7.5 h.p. cooling tower fan the water is about 74 degrees and we like to cool to 70 degrees .On cool days i do not believe we need full fan speed to get sufficent cooling we currently have thermostat in return water tank and fans are on/off but they never turn off as some cooling is always required

Click to expand...

Have done this many times before.
You need a 4-20ma output to control the speed of the cooling tower fan via VFD.CONTROL VARIABLE.
In the cooling water recirculation tank is an RTD to provide the PROCESS VARIABLE.
Now you have a PID control loop.

Trying to make this a little clearer, you need two components. First, a water temperature transducer which mounts on the piping at the point you want to measure and control the temperature. This transducer preferably will have a 4-20ma output and will be powered by the current loop.

Second, you need a VFD with external PID capability. Many have this and many don't. You need to specify that without exception. Many drives with PID capability will also have a 24VDC power supply available to power the transducer loop. If not, you will also need a loop power supply.

Read up on the drive's PID system and build your temperature control system from that information. As mentioned above, this is not an uncommon mode of operation and you will be able to get support from your drive supplier or here on this forum.

Thanks for all your help