Carrier 30RA013 cooling past setpoint

[vllkes]

Hi, I have the carrier 30RA013 water chiller with pro-dialog control panel and I have set the setpoint to 0 degrees C (returning water temp). The unit is cooling until -2.7C then cuts off (no alarms). Unit starts cooling again approximately at +0.7 or +0.8C. How can I adjust these limits? There is no such option in the pro dialog manual nor in the user manual (from http://eto.carrier.com/lit.asp).

Is it maybe in service menu? I have the password (113), but I don't know what structure of service menu.

Thanks in advance if anyone can help.

[frank]

It looks like the unit has a 2k Differential (-2.7 to +0.7). The calibration of the sensor may be out.

If you want it to switch off when the return temp = 0C then set your control point to +2C and see how that goes, although the mean temp will be +1C

[vllkes]

It looks like the unit has a 2k Differential (-2.7 to +0.7). The calibration of the sensor may be out.

If you want it to switch off when the return temp = 0C then set your control point to +2C and see how that goes, although the mean temp will be +1C

Hi, I need to set the differential larger, something like 8 degrees to avoid short cycling. With other brand chillers there has always been setting for this but with carrier, it seems you cant set the differential setting?

[frank]

Increasing the differential to 8K is not really the answer. I would suggest that your minimum circuit volume maybe too low.
Looking at the manual, the unit is designed for a return water temp of 12C, which I imagine would give a leaving temp of 6C.
Does your system have glycol?
To prevent 'short cycling' you should install a buffer vessel.

[vllkes]

Increasing the differential to 8K is not really the answer. I would suggest that your minimum circuit volume maybe too low.
Looking at the manual, the unit is designed for a return water temp of 12C, which I imagine would give a leaving temp of 6C.
Does your system have glycol?
To prevent 'short cycling' you should install a buffer vessel.

Hi, thank you for the answer. I'm using this chiller to cool tank in food industry. Using glycol at 33%. I have 200 liters buffer tank already, but I would like that the compressor would not run so often. Currently it runs about 5 mins every 30 mins. Not bad, but it could be less frequent.

[frank]

So what is your priority - maintaining circuit temp for the process or controlling compressor run time?
I must admit that I've never come across a job where the main requirement was for controlling the compressor run time in such a way. All of the projects I've worked on required water temp control as the priority and the compressor ran when required to achieve this.