Cooling Difference Clarification

[BeanAnimal]

Hi - setting up chiller to run form P4 along with a heater. The user manual is not clear about the shut off point for cooling and leaves the calculation ambiguous.

Examples:
Nominal: 25
Hysteresis: 1
Cooling Diff: 0

Calculated points
Heat Start: <24.5
Heat Stop: 25.5

Cool Start: (Nominal + (5/6 * Hysteresis) + Cooling Diff)
>25.83

Cooling Stop is it:
1 - Cooling Start - hysteresis = 24.83
2 - Cooling Start - (hysteresis/2) = 25.33
3 - Nominal - (hysteresis/2) = 24.5
??

I feel that the user manual needs to be updated here.
@Vinny@GHLUSA
@Gaël

 

[ingchr1]

I'm fairly certain, cooling shuts off once the temperature drops below the cooling start temperature.

Also, here is how I found the two heating functions to work:

I thought I had a pretty good idea on how the Heater and Substrate Heater Functions operated. So, I decided to perform another test to confirm. For this test I used a water bath and doubled my hysteresis from 0.4F to 0.8F. I performed the test three times, and the results were exactly the same each time.

Settings:

Nominal Value = 77.2F
Hysterysis = 0.8F

Decreasing Temperature

77.0F - Substrate Heater On (my primary heater)
76.8F - Heater On (my backup heater)

Increasing Temperature

77.3F - Heater Off (my backup heater)
77.7F - Substrate Heater Off (my primary heater)

Based on the data I was unsure of the Substrate Heater On point, so I performed additional tests on that function using 1.6F and 3.2F Hysterysis. The On points were 76.9F and 76.6F respectively.

From these results and the ones with my normal 0.4F hysteresis, I think it can be concluded that the heating functions of the Profilux operate as follows:

Heater Function ON = Nominal Value - (0.5)(Hysterysis)
Heater Function OFF = Upon exceeding the Nominal Value

Substrate Heater ON = Nominal Value - (~0.2)(Hysterysis)
Substrate Heater OFF = Nominal Value + (0.5)(Hysterysis)

@Lasse @vinny @Gaël #ghlusers

 

[BeanAnimal]

I'm fairly certain, cooling shuts off once the temperature drops below the cooling start temperature.

Also, here is how I found the two heating functions to work:

I would think there has to be some hysteresis there too, otherwise the cooling would short cycle.

 

[ingchr1]

I would think there has to be some hysteresis there too, otherwise the cooling would short cycle.

One would think so, but that is not what I have observed.

Can you run a test to confirm the operation I observe in my testing? Put the temperature probe into a cup of water and adjust the temperature slowly up and down, by slowly pouring in cool or warm water as needed. Observe when the Heater and Chiller functions turn on and off.

I just ran a test with my settings and the outlet turned on at ~79.0F then back off once it dropped below ~79.0F. I say approximate, give or take 0.1F. It was definitely off well before reaching nominal of 77.18F.

T = 77.18 + (0.83)(0.396) + 1.44

 

[BeanAnimal]

Hi - setting up chiller to run form P4 along with a heater. The user manual is not clear about the shut off point for cooling and leaves the calculation ambiguous.

Examples:
Nominal: 25
Hysteresis: 1
Cooling Diff: 0

Calculated points
Heat Start: <24.5
Heat Stop: 25.5

Cool Start: (Nominal + (5/6 * Hysteresis) + Cooling Diff)
>25.83

Cooling Stop is it:
1 - Cooling Start - hysteresis = 24.83
2 - Cooling Start - (hysteresis/2) = 25.33
3 - Nominal - (hysteresis/2) = 24.5
??

I feel that the user manual needs to be updated here.
@Vinny@GHLUSA
@Gaël

Unfortunately I think I have found my answers. It is option 2 above.

It looks like this (whole numbers to make it easy).
Nominal: 25
Hysteresis: 2
Cooling Difference: 1

Heat Start: 24
Heat Stop: 26
Cooling Start: 28.67
Cooling Stop: 27.67

The problem here is that COOLING never makes it even close to the "nominal" value. This (from my testing) is not implemented well at all.

Cooling should TURN OFF at Nominal + (Hysteresis/2) That still keeps out out of the HEAT START band. and brings cooling within the actual expected temperature range.
The expected (proper setup)
Nominal: 25
Hysteresis: 2
Cooling Difference: 1

Heat Start: 24
Heat Stop: 26
Cooling Start: 28.67
Cooling Stop: 26
OR even NOMINAL (25) as this would STILL not trigger the heating cycle.

As it is setup, all "cooling difference" does is move the cooling "band" further from the nominal value. If you set a cooling difference of 10, then the chiller will turn on 9.something degrees above nominal and then turn off when the temp ticks down by 1/2 hysteresis (1 degree in this example).

Let me put it another way. If you are in a warm month and the chiller needs to run, then bumping the cooling difference from "0" to ".5" or "1" or whatever just allows the tank to run hotter by pushing the chillers cycle further away from the nominal value, it DOES NOT CHANGE the chilling cycle length or timing AT ALL.

I hope this makes sense to anybody following along.

To get the expected result, one needs leave the heat on the primary temp probe and create a virtual probe and run the chiller off if it and tweak the nominal and hysteresis to meet one's needs.