Danfoss LC-13: How does it work?

[Dave_H 52]

Hi...I'm a newbie, having got my HC2 only a few months ago, but learning fast (or so I hope).

 

One thing that I'm struggling with, though, is understanding how the Danfoss Living Connect LC-13 is working.  This is the setup that I have:

• One room with 2 Danfoss valves and 1 Secure SRT321 Thermostat
• One room with 2 Danfoss valves and 1 Aeon Labs Multisensor 6 - Gen5
• Two rooms with 1 Danfoss valve and 1 Fibaro FGMS-001 Motion Sensor
• Boiler controlled by a Secure SSR302 Boiler Receiver for heating and hot water

I use the Heating Panel to control the temperature set-points for the valves and the thermostat.  Then I use one scene to turn the boiler on and off, depending on whether any room needs heat, and another scene for switching on the hot water at predetermined times.  Note that I don't use an association between the thermostat to the boiler receiver.

 

What I'm finding is that if I set the temperature set-point of a Danfoss valve to 18C, and the temperature in the room is, let's say, 15C, then the valve is hardly opening and the radiator is only lukewarm.  As a result, the room doesn't warm up, and the boiler stays on.  If I set the valve to 23C, then it opens fully and the radiator gets hot.  I would have expected that if the temperature in the room is less than the set-point, then the valve would open fully and let the hot water through until the temperature in the room reached the set-point, regardless of what value I set the set-point to.  It seems as though the set-point is simply controlling how much the valve is opening.

 

I'm thinking that I might have to change my boiler control scene to also control the set-points of the valves so that they deliver more heat when the room needs it.  My concern with this, though, is that with a 15 minute Wake Up Interval, the devices won't be responsive enough.

 

Am I doing something wrong?

 

Dave

 

[hTiger1 50]

Hi

I do not think you are doing something wrong.

Thermostats is a little slow, especially at first. They need some time to learn when the valve opens.

You can adjust the thermostat to the radiator size.

I have 6 Danfoss which is an older model, they are shown even more lethargic than LC13.

I use scenes to change setpoints. In my bedroom, there must be the thermostat at 15 degrees when I open the windows during the day and 19 degrees at night. Danfoss uses 2 hours from the scene has changed setpoint from 15-19 degrees and radiator heater (if there is cold in the room).

 

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[Dave_H 52]

Many thanks for the info, hTiger1.  I've had the valves in since January, so I was hoping that they would have settled down by now.  I had also set the parameter to say that the radiator was small for the room (P3), on the expectation that that would deliver more heat.

 

The link to the article on domotique-store.fr is an interesting one.  It talks about two scenarios - one where Danfoss valves are used on the radiators in order to support multi-zonal PID temperature regulation, and the second using a Secure SRT321 thermostat to control the boiler, but without the Danfoss valves, and therefore a single zone PID temperature regulation setup.  What I'm not very clear on from this is how the boiler is supposed to be controlled in the first scenario.  What I need is a combination of both examples.  I have avoided using the SRT321 to control the boiler, because it doesn't take into account the heating needs of the other rooms.  Therefore, what I have implemented in my scene is the article's 2a example using hysteresis logic.  I've seen Antonio Maestre and Manuel Pascual's Virtual PID thermostat (

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), which is very impressive, and I might look at implementing some of that logic in my scene, but it isn't really designed for use with Danfoss valves, and I'm not sure how it could work in a multi-zone configuration.

 

It's good to know that the Danfoss valve is using PID logic to regulate the temperature.  So, in theory, the valve should open 100% when the room temperature is, let's say, 2C below the set-point as per the example in this article, and reduce as the room temp gets closer to the target.  My problem is that it doesn't seem to be opening to 100% when I set the set-point to 18C and the room temp is 3C less than this, so I need to explore this further.  Recently, I've been having to set the set-point to 22C in order to get the radiator to warm up.  I've changed it back to 18C so that I can monitor it again tomorrow morning.  I'll report back on the outcome.

 

Dave

[hTiger1 50]

Hi

I probably can not give advice to your setup.

As you probably know, there are Danfoss valves are designed for 1-string systems and for 2 -string systems.

The valves for 1 -string systems, provides a great flow at a low pressure and a small opening on the valve.

[Dave_H 52]

OK Thanks.  The radiator was cold again this morning, although the room temperature was 17C and so probably not a good test, as this is only 1C less than the set-point.  I'll keep an eye on it over the next few mornings...it's going to get cold again at the weekend, so we'll see how it behaves then.

 

It would be helpful if we were able to read the room temperature that the Danfoss valve thinks that it is.  I believe that it also monitors the water temperature, and that would be useful information too.

[petergebruers 1,268]

(..) It would be helpful if we were able to read the room temperature that the Danfoss valve thinks that it is.  I believe that it also monitors the water temperature, and that would be useful information too.

I agree, but that information is not made available by the LC13 (nor by the LC12). So that's something the controller can't fix...

[hTiger1 50]

OK Thanks.  The radiator was cold again this morning, although the room temperature was 17C and so probably not a good test, as this is only 1C less than the set-point.  I'll keep an eye on it over the next few mornings...it's going to get cold again at the weekend, so we'll see how it behaves then.

 

It would be helpful if we were able to read the room temperature that the Danfoss valve thinks that it is.  I believe that it also monitors the water temperature, and that would be useful information too.

Hi

See this thread.

 

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[Dave_H 52]

Yes thanks...think that I might be getting myself a Devolo TRV next time.