cooling difference

[aqua_digital]

Thread moved on behalf of Ken Good

http://www.reefcentral.com/forums/showthread.php?t=1811999&goto=newpost

Here is the message that has just been posted:
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Yesterday I was playing with the cooling difference and the hysteris and the chiller was coming on but only cooling until it hit the top of the cooling difference. So instead of coming on every two minutes to chill to 78, it was coming on ever two minutes to chill down to 79. I will try again. Today, I set the hysteris to .3 and the cooling difference to 1.0. My nominal termperature is 78. Does this mean that the chiller should come on at 79 and chill to 78? or does it mean that it will come on at 78.3 and chill down to 78?

[Ken Good]

These are the setting on my profilux. Currently, the profilux is coming on 79.3 and shutting off when the temperature hits 79 (instead of 78). Suggestions.

http://i1011.photobucket.com/albums/af234/kengood45/profilux.jpg

[Ken Good]

I am going to try taking the cooling difference down to zero and changing the hysterisis to 1.00 and see if this gets what I want (which is to allow the temperature to fluctuate one degree so that the chiller is not coming on every 5 minutes).

Ken

[Ken Good]

I am going to try taking the cooling difference down to zero and changing the hysterisis to 1.00 and see if this gets what I want (which is to allow the temperature to fluctuate one degree so that the chiller is not coming on every 5 minutes).

Ken

This is still not quite what I wanted. I would like for the temperature to have a one degree fluctuation. I would like the temperature to come on at 79 and cool to 78. It looks like setting cooling difference to zero and hysteresis to 1 causes the chiller to come on at 79, but to go off at 78.5.

So should I set the nominal temperature to 77.5, cooling difference to zero and hysteresis to 2? Will this get the chiller to come on at 79 and go off at 78? I think I am close.

Ken

[Ken Good]

Nope that is not what I wanted. It now comes on at 79.5. This is why I should have listened in math class when I was in school.

[Ken Good]

I think I may have figured this out. I will try setting nominal to 77.0, cooling difference to 0.00, and hysteresis to 2.0. I think that this will turn it on at 79 and off at 78. I hope it will anyway.

[Ken Good]

It looks like that worked. Why I do not know. But it is coming on at 79 and going off at 78. Can anyone explain why? I understand the coming on at 79. But I do not understand the going off at 78. I would have thought that you would have set nominal to 78, cooling difference to 0 and hysteresis to 2 and this would cause chiller to come on at 79 and go off at 78 and then the heater would come on at 77 and go off at 78.

What do the following settings do for the heater: nominal 77, cooling difference 0 and hysteresis 2?

[Blahenazo]

I didn't test anything yet but according to the hysteresis definition.
it should be in short => how much degrees it should differ before it takes a decision to do something about the temp ( be it heating or cooling )

an example to understand hysteresis with a heater

target is 78 and we have a hysteresis of 1 degree.
current value is 76 => temp to low => heater on => it reaches 78 and then it still heats until it measures 78+1 degree hysterersis. => now the heater is off. then the water cools again and it hits 78 again , it needs to sinks until 78 -1 (hysteresis) before it starts heating again.

+++77***78***79---

+ its always heating
- its does nothing
* heating or doesnothing depending on the trend of the temperatuur (being lowering or warming up)

so in fact you have a 'zone' between 77 - 79 where its either heating or it does nothing but its only on the (target + or - hysteresis) value where it will deside to either stop heating or start heating.

so now you should understand that your hysteresis should be rather low (but not zero, then it will constantly toggle the heating on or off )
if you make it to large you can either overheat or 'underheat' :) your water because your heater /cooler have a certain latency before it have any effect.

For the term cooling diff I don't know how they apply it because it's not a term like hysteresis. but I would expect that it should be and extra threshold 'around' the target before it either cools or heats. or if it starts cooling it cools until the cooling difference is reached (+ hystersis) before it turns the cooler off.

[Matthias]

Hi,

my usual and (maybe unpopular;)) comment:

Please have a look into the manual - nominal value, hysteresis and cool.-diff. are explained there in detail, there is even a calculation example

[Ken Good]

Hi,

my usual and (maybe unpopular;)) comment:

Please have a look into the manual - nominal value, hysteresis and cool.-diff. are explained there in detail, there is even a calculation example

You know I see why this statement would be unpopular and I have seen it before. I have to say, that I researched and read the manual several times before I posted a question. In fact, I tried doing what the manual said (or what I concluded after reading the explanation that in some ways seemed to be in Greek).

Only after I could not get it to do what I thought it said and still could not get it to do what I wanted, then did I post a question. I was hoping for a simple explanation or discourse about a hobby that I love and a new product. If I am having problems, I would think that someone else would be having the same problem and might find it helpful too.

So yes, I do find the comment unpopular and unhelpful. I was asking for help and was sent here for it.

[Ken Good]

Hi,
nominal value, hysteresis and cool.-diff. are explained there in detail, there is even a calculation example

The manual does not have an explanation regarding the shut off point for the cooling feature. Yes it has a calculation example but does not complete the analysis so that you can understand it which is why I wanted further explanation. So for example, if I use a cooling difference of 1 what does that do? If my nominal temperature is 78, it in effect changes the nominal temperature for cooling to 79. But the problem is it also changes the shut off point to 79 too. So if the hysteresis is set to .5, then the chiller comes on every 5 minutes and cools from 79.25 to 79.

Also, the way the manual presents the hysteresis, if I set a hysteresis point of 2, then if the nominal temperature of 78, then the chiller should come on at 79 and chill to 78 and the heater should come on at 77 and heat to 78, but that is not what my unit is doing. That is why I was sent here for a better explanation.

Currently, I have set my nominal temp to 77, cooling difference to 0 and hysteresis to 2. For some reason this is causing my chiller to come on at 79 and chill to 78 (which is what I want). I do not know what it will do to the heater, this is why I asked a question. Where exactly in the manual do I find the answer to this question?

Ken

[Ken Good]

I didn't test anything yet but according to the hysteresis definition.
it should be in short => how much degrees it should differ before it takes a decision to do something about the temp ( be it heating or cooling )

an example to understand hysteresis with a heater

target is 78 and we have a hysteresis of 1 degree.
current value is 76 => temp to low => heater on => it reaches 78 and then it still heats until it measures 78+1 degree hysterersis. => now the heater is off. then the water cools again and it hits 78 again , it needs to sinks until 78 -1 (hysteresis) before it starts heating again.

+++77***78***79---

+ its always heating
- its does nothing
* heating or doesnothing depending on the trend of the temperatuur (being lowering or warming up)

so in fact you have a 'zone' between 77 - 79 where its either heating or it does nothing but its only on the (target + or - hysteresis) value where it will deside to either stop heating or start heating.

so now you should understand that your hysteresis should be rather low (but not zero, then it will constantly toggle the heating on or off )
if you make it to large you can either overheat or 'underheat' :) your water because your heater /cooler have a certain latency before it have any effect.

For the term cooling diff I don't know how they apply it because it's not a term like hysteresis. but I would expect that it should be and extra threshold 'around' the target before it either cools or heats. or if it starts cooling it cools until the cooling difference is reached (+ hystersis) before it turns the cooler off.

Thank you for your detailed explanation. But my tests are getting a different result. I am using the following settings: nominal temp. 77, cooling difference 0, hysteresis 2. It appears that this is getting the chiller to come on 79 and will chill to 78. I believe that my tests show that the heater will come on at below 76, but I am not sure. But this is different than the "vaulted" manual which looks like it was translated from German by someone who needs a few more classes in English.

Ken

[Ken Good]

My apologies for any frustration in my comments. I think I got this to work. I was just trying to get a better understanding of what was going on. Yesterday, I posted on reefcentral.com how much I like the dosing pumps and by the end of the day I was walking another guy through the process for setting up his new Profilux dosing pumps. I was hoping to get a better understanding of the temperature settings. I was not trying to do anything else. If I have offended, I apologize.

[Matthias]

No reason to apologize! Most important is that you got it up and running now.