Temperature Control Setup (Profilux 4)

[ingchr1]

I've gone ahead and changed the way I was controlling temperature, to what I think will be a better setup.

Original setup:

Primary Heater: 150W Cobalt Neo-Therm controlled by its internal thermostat. The P4 set as a backup to turn off the heater if temperature got too high.

Backup Heater: Completely independent of the P4, backed up by a Cobalt Neo-Stat. This heater was set 2F below the primary and would turn on if the primary failed (temperature low).

New Setup:

Primary Heater: 125W Eheim controlled by the P4. In the P4 I have this heater set as "Substrate Heater".

Backup Heater: 125W Eheim controlled by the P4. In the P4 I have this heater set as "Heater".

Here's how the P4 controls when Temperature is set as a Two Position Controller, with the above settings.

Decreasing Temperature

78.0F - Substrate Heater ON
77.9F - Heater ON
​

Increasing Temperature
78.2F - Heater OFF
78.3F - Substrate Heater OFF

Reasons for the change.

• In this mode of operation the "Heater" will come on if the "Substrate Heater" cannot maintain temperature. I like this because just the right size heaters can be used and if the primary heater fails temperature will still be maintained near nominal temperature.
• Originally I did want a complete independent backup from the P4. I had one Powerbar and one regular power stip. All backups were on the regular power strip (redundant heater, redundant return pump and a powerhead). I have since change out the regular power strip with another Powerbar. Configuring the switch states on the Powerbars has alleviated concerns with what happens if the Powerbar looses communication with the P4. For example, the heater sockets can be set to turn "off" and the pump sockets to turn "on" if the Powerbar looses communications.
• When I first setup the tank I did try the 125W Eheims, and a single heater was just able to get the tank to 77F - 78F. This left no margin for colder room temperatures as I wanted each heater to be full wattage. We keep the heat in the house set at 64F - 68F. With the new setup the backup heater will come on to supplement the primary if needed. We don't have central air, so in the warmer months one heater at 125W will be enough. We do have a through wall AC unit in the area, but the house will still be at a minimum in the mid-70's.

I was going to try using Pulse Variable for the controller mode like @Lasse does but that controller mode does not use the "Substrate Heater", which I needed to be able to create the backup heater function.

 

[Lasse]

There is another way around this problem that give you the chance to use pulse variable. There is a possibility to use something named virtual probe in order to have two different setpoints and functions connected to the same physical probe. If you want to do this – prepare to that you maybe have to recalibrate some of your other probes. It looks like they have fixed this problem with later FW but I´m not sure. Before you do this – backup your settings and sensors data. In order to handle many probes – GHL use a sensor index for each probe. This figure is from my P3.1T and with only temp and pH in the computer. Normally this type of Profilux 3 computer leave sensor index 3-8 for virtual probes – or probes from the extension cards. The two you see here with sensor index 3 and 4 are virtual probes created from real probes in my expanding box 2 (Sensor index 9 and sensor index 13 (temp and redox) For P3.1 ex and P 4 it use to be sensor index 5-8 that is for virtual probes – however you can create how many virtual probes you want (I have had 8 in one set up) but in this case – it can screw up the sensor index rather much. However – if it screw up your sensor index – just calibrate the sensors again and virtual probes does not needs to be calibrated.

How to create a virtual probe? You have to use the computers own interface if you use P4 – if you use earlier versions – you have a virtual display in GCC. I show with my P3.1 but it is the same for P4 but you have to do it direct on the P4

Press up arrow twice – you will highlight system – press the return key

Pres up arrow till you highlight Virtual probe

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Press return key and chose New Virtual probe with the return key

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Now you will have two options. Copy or awerage. If you want to do a copy od a real probe, accept copy with the return key - if you want to do a virtual probe that show the awerage of two (of the same type) probes - chose awerage. In our case - we want to do a copy - press return key

Noe you have to chose real prob to copy into your new virtual probe. In this example - I chose temp 1

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Accept with return key and change the new option with help of left key if you want to save

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When you have accepted yes - you should have a new temperature probe in your list. If all work well - it will have a sensor index between 5 and 8 in your case (between 3 and 8 in my case. If you use an expansion box and use a real probe from that box - you real probe have change its numbering - you have to check functions that use that sensor in order to see if they have change sensor number too. But the most important thing is that the sensor index is the same. If you only use a P4 without expension cards it should be no problems - both index and numbering will be after the former last probe.

In my case you can see that I use virtual probes for heating änd cooling. I use different set points and different methods. During wintertime - I have a temp difference around 0.1 between day and night.

You can use this for your purpose to. Different set points that start heater 2 if heater 1 not can not withhold the temperature. But I would use heaters of titan and without internal controller.

Sincerely Lasse

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[ingchr1]

….But I would use heaters of titan and without internal controller.

I still like the idea of having the thermostat in the heater as a backup, although the heater is a lot more likely to fail (on or off) than the controller.

I would not use the controller to control a heater with a electronic thermostat, as discussed in the thread I started (Does External Control Adversely Affect Electronic Heaters?).

I have looked and not been able to find a titanium heater in lower wattages. Two 100's should work in my case.

 

[Lasse]

I have one 100 Watts from Aqua Medic. But I live in Europe and I do not know if they work within the US

Sincerely Lasse

 

[ingchr1]

I've added some additional protection for the temperature indication reading a false low value. If this happens the heaters will be on trying to restore temperature to nominal, but actual temperature is going to be hotter than indicated and possibly overheat the tank.

I'm not even sure if this is possible or if the indication is more likely to just fail to an open value. I did a test where I disconnected the temperature probe and the heaters did turn off on the loss of the value.

The more likely scenario where this would come into play is if the temperature probe became no longer submerged in the water. It would end up reading ambient temperature, which in most cases is lower than tank temperature.

I created a virtual probe (Temperature 2) and made the setting for the low alarm to be 76.0F. The upper alarm does not matter as the heaters would be turned off by that point under normal control (Temperature 1).

I then use that alarm in programmable logic for heater control. If the alarm comes in for the virtual probe, the heaters will turn off.
​

Deactivate control in the Temperature 1 alarm settings cannot be used as this would also deactivate control of PropellerBreeze I have tied to that sensor. For Temperature 1 I have the low alarm at 77.1F, so this would also allow for some margin for larger temperature swings. It would probably take special circumstances and time for the tank to get down to 76F on its own with the heaters working. The alarm at 77F should give me time to react as well. If the tank did get that low on it's own, I could just change the settings in the P4 for the heaters to be on.

I'm also protected from overheating by the internal thermostats on the heaters, but we know that those can and do fail.

Temperature 1

Temperature 2 (Virtual Probe)

Programable Logic (G6 and G7)

Powerbar (S1 and s6)

 

[ingchr1]

Deleted - posted in wrong thread

 

[ingchr1]

I've added some additional protection for the temperature indication reading a false low value. If this happens the heaters will be on trying to restore temperature to nominal, but actual temperature is going to be hotter than indicated and possibly overheat the tank.

I'm not even sure if this is possible or if the indication is more likely to just fail to an open value. I did a test where I disconnected the temperature probe and the heaters did turn off on the loss of the value.

The more likely scenario where this would come into play is if the temperature probe became no longer submerged in the water. It would end up reading ambient temperature, which in most cases is lower than tank temperature.

I created a virtual probe (Temperature 2) and made the setting for the low alarm to be 76.0F. The upper alarm does not matter as the heaters would be turned off by that point under normal control (Temperature 1).

I then use that alarm in programmable logic for heater control. If the alarm comes in for the virtual probe, the heaters will turn off.

Deactivate control in the Temperature 1 alarm settings cannot be used as this would also deactivate control of PropellerBreeze I have tied to that sensor. For Temperature 1 I have the low alarm at 77.1F, so this would also allow for some margin for larger temperature swings. It would probably take special circumstances and time for the tank to get down to 76F on its own with the heaters working. The alarm at 77F should give me time to react as well. If the tank did get that low on it's own, I could just change the settings in the P4 for the heaters to be on.

I'm also protected from overheating by the internal thermostats on the heaters, but we know that those can and do fail.

Temperature 1

Temperature 2 (Virtual Probe)

Programable Logic (G6 and G7)

Powerbar (S1 and s6)

Update - I change this to have the protection applied to the backup heater only. I use heaters with internal thermostats so those should provide protection for this type of scenario. This was an added second layer of protection, if the heaters thermostat was to fail. Doing it this way I will still have one functioning heater. My heaters are closely sized to what's needed, so if the thermostat on that heater fails the tank shouldn't get too hot. I may even see if I can go to a lower wattage heater, to provide more margin. Right now I use 125W, thinking of trying 100W. Will see the trend over the winter as we keep the house at 64F when no one is home and at night. If the primary can maintain without the help of the backup (or with minimal help) then I'll go with the 100W.

 

[ingchr1]

Update - I change this to have the protection applied to the backup heater only. I use heaters with internal thermostats so those should provide protection for this type of scenario. This was an added second layer of protection, if the heaters thermostat was to fail. Doing it this way I will still have one functioning heater. My heaters are closely sized to what's needed, so if the thermostat on that heater fails the tank shouldn't get too hot. I may even see if I can go to a lower wattage heater, to provide more margin. Right now I use 125W, thinking of trying 100W. Will see the trend over the winter as we keep the house at 64F when no one is home and at night. If the primary can maintain without the help of the backup (or with minimal help) then I'll go with the 100W.

So what I've done is changed the referenced protection over to the primary heater and changed the backup heater to 50W. I also made the initial state of the backup heater outlet to ON. This way I will still have heat should the primary heater fail or the controller itself.

The 50W will ensure the tank still has heat, give me time to respond, and also minimize the chance of overheating should the internal thermostat also fail on it.

 

[ingchr1]

I did some additional testing (documented in another thread) and 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)​

I wanted to post this here since there appears to some misconception on how these functions actually work, and the Programming Guide doesn't have a clear explanation.