Swimming Pool Temp Control

A

Thread Starter

Ajay H

Hi,

I am implementing a control logic where I have to maintain a swimming pool temperature at 30 DegC. I have two sets of Cold and Hot water heat exchangers. Can anybody tell me what factors I will have to consider in order to avoid oerations of both Hot and cold water heat eccangers at the same time.
 
Is this an outdoor pool in a desert climate where the air temperature is above that of the pool water?

If it isn't, why would you need a cold water heat exchanger? 30° (86°F) is above normal comfortable room temperature. So in an indoor, air conditioned pool, the pool water will be constantly losing heat to the room air above it.

Under those conditions there would be no need to cool the pool water, just limit how much heat is added to make up for loss to the room air.

In any event, devices like single loop controllers with a heat/cool control scheme typically has an adjustable deadband in which neither heat nor cool is issued a call for output, ie. output = 0% for heat and 0% for cool, in order to prevent both being on simultaneously. At least, Honeywell UDC controllers do.

David
 
G

Gerardo Gonzalez

I hope I understood your question correctly. You do not provide details on the operation of the heat exchangers (on-off or regulatory). But a controller with a dead band in the set point would do the trick.

Let's say you set 30 °C and dead band is 1 degree above and under. Then the cold water would only be on (or regulating) above 31°C, the hot water actuates below 29°C and none between 29 and 31. You could adjust the dead band as narrow or wide as required.

Another possibility is a PID control with split range output if you have regulating valves for the hot/cold water in your heat exchangers.
 
Top