Chiller coming on too often

[Slickdonkey]

Check out this graph -- my chiller is coming on ~20 times a day. I have my program set so that the chiller is off for a minimum 20 minutes each time, but shouldn't it be possible to run a tank so the chiller only comes on a few times per day? Right now I'm running my halides for about 5 hours, from about 5pm to 10pm.

Here are the relevant lines in my AC3Pro program, followed by a graph of what's going on. I'm using the default season table. The resolution in the graph should be 5 minutes.

If Temp > RT+0.2 Then FAN ON
If Temp < RT+0.0 Then FAN OFF
If Temp > RT+0.4 Then CHL ON
If Temp < RT+0.0 Then CHL OFF
Max Change 020 M Then CHL OFF
If Temp < RT+-0.4 Then HT1 ON
If Temp > RT+0.0 Then HT1 OFF
Max Change 002 M Then HT1 OFF
If Temp < RT+-0.4 Then HT2 ON
If Temp > RT+0.0 Then HT2 OFF
Max Change 002 M Then HT2 OFF

 

[KEB]

My chiller recycles often in hot weather too. 2/10 degree is tight control. Try keeping fan on to RT-0.2, maybe if your lucky that will slow down the chiller cycle.

 

[bstone]

You may not have enough flow through your chiller , which could be short cuircuting your it causing it to come on and off a lot. Also, KEB said, increase you control range from on to off..

 

[Aquaduck]

Where is your controller temperature probe, and chilled water outlet located?

 

[Slickdonkey]

The chiller pump and return are in the skimmer compartment. The temperature probes are in the refugium, which overflows into the return compartment like this:

Skimmer -> Return <- Fuge

Part of the return is diverted to the fuge, which in turn overflows into the return.

 

[clp]

You could always increase the Max Change statement or increase the delta between the on/off temperatures of the chiller, if you want less frequent cycling. It is just a trade-off in temperature stability vs cycling time of the chiller. I'd increase the on/off temperatures as they are currently pretty tight. It also helps on the electric bill to have less frequent cycling as chillers are more effcient the longer they run.

Curt

 

[AcroSteve]

<a href=showthread.php?s=&postid=7859883#post7859883 target=_blank>Originally posted</a> by clp
It is just a trade-off in temperature stability vs cycling time of the chiller. I'd increase the on/off temperatures as they are currently pretty tight. It also helps on the electric bill to have less frequent cycling as chillers are more effcient the longer they run.

Curt

Yep!

0.4 is pretty tight. I you want your chiller on/off less frequently you need to increase the spread or decrease the amount of heat you are adding to the tank.

 

[laverda]

Also with that set up you only have to chill a small volume of water that is going to your fuge and not realy drop the temp in the tank that much. If you temp prob was in the tank I bet it would cycle a lot less, but I would also increase the temp spread. Your tank can deal with way more variation in temp then that.

 

[jt_redmist]

Don't mean to highjack this thread, but what temp spread would be good?

JT

 

[AcroSteve]

My chiller comes on at 80.0 and off at 78.5. Heater will come on at 78.3 and off at 78.5