heating/cooling

[jbb]

hi can someone explain how the heating cooling should be set up as the chiller switches on and off to quickly.
i am after setpoint of 26 , heating to come on at 25.8 and go off at 26.2 and the cooling to come on at 26.5 and go off at 26.2 . i don,t seem to understand the coolin difference in the program , any help please

 

[AQD_ottawa]

Hi

What do you have the cooling difference ands the hysteresis set to?

 

[jbb]

the hysteresis is set to 0.2 which seems right? and the cooling difference is 0.2

 

[AQD_ottawa]

Argh i have re read your first post, I see what you have done now, you have set up temp 2 for cooling? Am i right? or heating makes no odds

if so the two are fighting each other, you only need temp 1 set up for both and the assign two sockets,, one for heating and one for cooling, both under temp1, then leave the cooling difference etc as is. delete Temp 2

If i am wrong then email me your data file so i can see exactly what you are doing

Regards
Michael

 

[jbb]

they are both set under temp 1 ,i have not setup any virtual points .
i have changed now the cooling diff to 0.3 and it seems a lot better.
Question: if the set point is 26 and the coolling diff is set at 0.0 when would the chiller kick in.

 

[Matthias Gross]

Hi

because the temperature control is not an easy task (cooler, heater, substrate heater and controllable fans have to work together) the on/off levels are calculated by some formulars.
Please have a look into the manual chapter temperature -> hysteresis - there i tried to explain this

 

[jbb]

hi matthias
i have got the heating cracked setpoint 26 hyst at 0.2 which means heating on at 25.9 heating off at 26.1.
cooling diff 0.3 ,does that mean the temp has to rise to 26.4 to switch on then switch off at 26.2.or have i read this all wrong.

 

[Matthias Gross]

Not exactly, let me quote the manual:

3.7.8 Hysteresis
The so-called hysteresis determines the interval between the switching points and is necessary in order to reduce the switching frequency. The hysteresis set here encompasses the interval between the switching on of the normal heating and the switching off of the bottom heating. The nominal temperature lies precisely at the centre of the interval between these two switching points. The setting for the hysteresis can be a value between 0.15°C and 2.0°C.
With the hysteresis set at 0.2°C this means that:
• If the actual temperature drops below the nominal by more than 0.1°C -> the heater will be switched on (the bottom heating will already be on)
• If the nominal temperature is exceeded by more than 0.1°C -> the bottom heating will be switched off (the heater will already be off)
The hysteresis set also affects when the cooling will be active. The point at which the cooling is switched on also depends on the cooling difference (see 3.7.10 Cooling difference) and can be calculated as follows:
T = nominal temperature + 5/6 * hysteresis + cooling difference; in the above example: T = nominal temperature + 0.167°C + cooling difference.
The default hysteresis setting of 0.2 °C should not normally be altered. A reduction in the hysteresis is advisable only when the adjustment precision is to be increased. This will, however, also increase switching frequency. The hysteresis should be increased when, for example, the cooling comes on shortly after heater activity. This is particularly likely where there is a large volume of water and only low current.

 

[jbb]

Hi Matthias
re read it this morning ajusted settings abit now its working spot on.
very happy now, thanks