Danfoss LC13 Temperature Offset

Paul Pankhurst shared this question 9 months ago
Answered

In the old UI there appears to be the ability to define an offset to the Danfoss LC13 setpoint.

Without it it's impossible to get a virtual thermostat to work, as here in the UK the valves are mounted at the bottom of the radiator so there is always at least a 1 or 2C difference between temperature at this height and thermostat height.

Is this value accessible anywhere in the new UI or via the API, or is it safe to set it using the old UI?

Comments (20)

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Hello Paul,

What you are referring to is the thermostats hysteresis settings which you can set on the Virtual Thermostat itself no matter of the device which is used in it.

Please check the screenshot attached:

b4dff8573a2fe9f9b5c741c9ee4a37fb

On more information how the Hysteresis works on thermostat please refer to the link below:

https://asm-air.com/airconditioning/what-is-a-hysteresis-thermostat/

Brgs,

Vedran

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Hi

I think you misunderstand the problem..as I understand it the hysterisis simply stops the thermostat from flipping between on/off when it is close to the set point. In my case, as its set to 0.5, if the setpoint is 21 then it wont go off unless > 21.5 and wont come on unless its < 20.5

My problem is as follows...

Imagine my setpoint is 21C, and the room temperature has risen to 21.5C as measured at the wall thermostat, the rad valve will still be open heating the room because it is detecting a temperature of 19.5 (assuming 2C difference between the two)

If other zones are still calling for heat, then the boiler will still be pumping round hot water and the room will carry on heating up until it reaches 23C because thats the point the LC13 gets to 21. I need a mechanism for applying a permanent offset to the valve so that the valve goes off at the same time as the setpoint is reached on the wall thermostat.

Everything would be fine if the temperature measured by the LC13 and wall thermostat were the same..but they aren't, there is always a differential..as I understand it this less of a problem in Europe as the LC13 would be mounted at the top of the radiator rather than the bottom, so there is very little differential.

Thanks

Paul

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Hey Paul,


You are definitely right, I have indeed misunderstood you.

The thermometer offset which we used in the old dashboard were calculation methods we implemented from our side to bypass the disadvantages of some thermometers which have no temperature offset capabilities on the devices. Unfortunately those calculations are no longer available in the new dashboard.

The device itself supports 3 levels of offset called P1, P2 and P3 which are configurable on the device itself, so this might be of help to you.

In the manual of those valves it is explained how those offsets work, and how to configure them.

If you need my assistance on configuring it, please let me know.


Brgs,

Vedran

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Hi,

Its a shame that feature was removed, as it would be very useful.

I know that the P1, P2 and P3 settings exist on the valve, but my understanding is that these are simply to compensate for oversize or undersize radiators and alter the way the valve modulates the output rather than altering the actual setpoint of the valve..

So...I have found a work around.

I have removed the rad valves from the virtual themostat and added rules to assign the valves setpoint to an adjusted value when the virtual thermostat target value attribute changes as shown in the attached.

It appears to work ok on initial testing, unless you can see a flaw in this solution.

The P1, P2 P3 attributes will be adjusted on the few radiators I have that are over/under sized.

Regards

Paul

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Seems like a decent workaround.We will definitely consider implementing this again as it seems to be very handy from the use case you've provided.

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Hi Paul

i´m also searching for a solution with the missing offset feature. What have you selcted as an output device in your thermostat ?

If nothing is selected the virtuel thermostat does not run.

regards from germany

Chris

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Hi Chris,

I have thermostats in most rooms so I have the rad valves plus thermostat as outputs.

I would check that you have the latest software update as some of the older versions did some really odd things with virtual thermostats.

Regards

Paul

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Hi Paul


thanks for the rapid answer.


I have done many experiments with the virtuel thermostat.


The missing offset is realy a probelm. I discussed this with the Zipato folk many times.

I think in Zagreb they dont have any radiators.

But in my case i have only one Dafoss wave. I selected thes wave as output.

and then i changed the wave temp as you had shown in your program.

after 5 Minutes it jumpes back to the virtuel tmeperature...than the progam overwrites the tempertaure and so on.

The Rad Temperature jumps up and down in 5 Minutes range.


And if the output field is emty the Thermostat does not work. It is alwys off.


do you have any idea what i can select as output ?


regards


Chris

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Hi Chris,

The virtual thermostat is very confusing, and took me a while to understand what the configuration actually does.

There are 3 important settings if you are using the Danfoss Rad Valve:

Heating Outputs - set this to be the Danfoss Rad Valve..the virtual thermostat will set the valves setpoint based on what temperature it thinks is required as a result of schedule or override etc.

Heating Input: set this to be the Danfoss Rad Valve..this allows you to override the temperature setting in the virtual thermostat by manually pressing the buttons on the valve.

Thermometers Input - this needs to be whatever device is being used to measure the room temperature

Hope this helps

Paul

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Well. To have hysteresis, you need virtual thermostats pro for each zone. That is 29 euro per zone.

To be able to use + or - in rules, you need rule creator PRO...

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Hi Attila.. I have actually got rid of the hysterisis as there is already lots built into the system..for example the temperature sensors used as input only update after a specific delta on the temperature or after a specific time period. Equally so the Danfoss valves are non FLIRS so only get updated at the wakeup interval. Extra hysteresis really just makes thing worse. I found it was causing the temperature in the room to go way over the setpoint.

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Hi attila hi Paul


the Hysteresis is not the problem.

I wrote a rule simular to the rule of Paul.

First the Tempertaure is 21° After 5 minutes it changes to 23°. O.k. that might be fine.

After 5 minutes it changes to 25° after 5 to 27° and than back to 25°

Whats that ?

The Danvoss RAD is output and input as Paul has explained.


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Hi Chris,

I think I can see the problem..you have generated a feedback loop!

Assume target temp is 21C

When you set the temperature on the danfoss valve to target+2 (23C) by your rule it will take a while for the danfoss to wake up and get the setting. When it wakes up and receives the setting it will report back its setpoint to the zipato controller as 23C. Since this is an input to the virtual thermostat the target temperature will update to 23C which will cause your rule to execute again and try and set the danfoss to 25C (23+2) and so on...

Just for information..I abandoned the idea of implementing an offset in rules and went in a different direction entirely..

Paul

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Incidentally, I've recently tested out the Eurotronic Spirit, and given a choice would now use this in preference to the Danfoss for several reasons:

1. Supports FLIRS so no need to wait for device to wake up..immediately updates setpoint

2. Supports temperature offset in the configuration

3. Reports back the measured temperature

4. The LCD display can be configured to invert, so valve can be attached in any orientation

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Hi Paul


yes indeed it is a feedback loop. But if the target is 27 the next target is 25 ?


but i think there is another possibility.

If you generate a parameter "virtuel level control" you can select these at "output" in the virtuel Thermostat.

With these parameter you can control the danfoss wave without a loop.


i don´t have a pro license but there is a change that this might be work.


Chris

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I don't think using a virtual meter on the output is going to help. The problem is the input. You could possibly use a virtual meter as a 'temperature input' and set it to whatever the valve setpoint is -2 to provide consistency in both directions.

You could of course do a short term fix by removing the 'temperature input' entirely..all this will do is stop you manually setting the temperature by the valve, which I personally never do.

The best advice I can give is make it as simple as possible and get it stable, then make small incremental changes as I found the system behaviour is complex and difficult to predict. I have 10 virtual thermostats, one for each room. Each room has either a philio multi sensor and/or danfoss thermostat providing inputs. I then have a scheduler that examines each room to work out if there is heat demand and then turns the boiler on/off using a zuno and a custom interface to a Honeywell Smartfit that I designed. Took a while to optimise it, but now performs great, so stick with it, the results are worth it in the end.

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Is the Eurotronic Spirit completly includet ?

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Most of the valves are Danfoss LC-13, I do have a Eurotronic Spirit installed and its fully working without any problems. I have a couple of other Spirit valves that I intend to swap in at some point to replace the Danfoss ones..I'm pretty impressed with them, and they look really cheap on Amazon.de at 41 Euro which is cheaper than distributor pricing!

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Hi Paul


thanks for the information.

You are right. I tried many things with virtuel Sensors and so on. But at least nothing had worked reliable.

So i ordered an Eurotronics Spirit.!!!


thanks


Chris

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Hi Paul


i testet the Eurotronics Spirit now for over a month.


Yes it works with offsett and flirs.

Thaks for the advice. This is the one i searched.

And the Zipato proposal to solve this with the Hysteresis Option.....unbelievable.

I have some open cases with zipato and in all cases zipato is not realy brilliant.

thanks

Chris

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