cooling difference

[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.