Domoticz

This is a typical Nefit modulation graph measured on the Out flow of the ground floor (the combination of 5 groups): You see very long cycles of heating, and long cycles of cooling down (= heat loss).
While the room temperature goes down with 0.1C/hr.

On 6 Dec. the average outside temperature in my area was 9.5C.
If the outside temperature is around 15C, there is only one cycle in the 2 days.
Both cases give some discomfort. The room is not too cold, but the floor feels cold.

Heat request is under control of the Moduline400.
The maximum Nefit boiler temperature is limited to 40C.
The floor is consuming most of the heat so the combination of Moduline400 (heat request) and Nefit (modulation on return water) "thinks" that the best heat supply must look like this: The spikes are caused by hot water usage (remaining heat)
Even during the long cycle, the boiler maximum of 40C is not reached.

The floor is heated by water -- the floor heats the air -- the air is measured by the Moduline400 -- on request the boiler heats water -- water heats the floor.

My assumption was that this combination is not optimal in an all floor heating house.
In 1995 that was not so common. At least not for Nefit.
Thanks to Domoticz: Time for a change, see the next post.

So I made a simple Blockly, to control the Thermostat_bypass.
Just an On-Off control: As soon as the floor return temperature is below 23.1C the Thermostat_bypass is switched On until a temperature higher then 25.1C.
The Pump is set to low speed (1 out of 3) just to make sure that it is running.
The normal operation of the Pump is 1 otherwise the return temperature is not representative.

The room temerature is like this (look at the scale!) The concept is that the by-pass takes care of coarse steering while the Moduline400 is degraded to fine steering.
The current stop value in the Blockly leads to a small overheating (the slight positive trend).
I guess a 24.9 would be a good stop value to leave a small job for the Moduline400.

(an other option could be to, to insert an extra "room temperature check" in the first Blockly line)


The next post shows the burn cycles and temperature Input/Output results.

The bypass has this switch behavior: You can see a slight duration and duty-cycle modulation

This leads to an IN flow of the ground floor as this (the boiler on max 40C): The smaller peaks are from the hot water production.

This leads to an OUT flow of the ground floor as this: Take care: the different snaps cover some difference in time.

Average outside temperature on 9 Dec. was 6.9C
Burning cycles with 20-30 minutes duration, per cycle around 0.7m3
Repetition of around every 2 hr.
The impulse response (output reacts on input change) is around 4 min with the Pump on 3, so the flow is already established.

The result? Since 26Nov Gas prognoses for the next 6 months are jumping down, with around 5m3/day.
Potentially 100 - 200m3 / year?
Will keep you informed.
Domosapiens

The return-water controlled thermostat works excellent.

No more complicated delayed measurement from thermostat, to boiler, to floor, to air, to thermostat.
No thermostat PID compensations for undershoot and overshoot, no self learning.
No more boiler assumptions about burn cycles, how to warm (aanwarming in Dutch), heating curves and assumed Delta T optimum.
Assumptions not made for low temperature heating.
No more 2 captains on the ship that understand each other only half.

Just KISS.
A constant floor temperature gives comfort. The room air-temperature is a result of that.
(when a house is rather well isolated).

Domoticz has the lead.
The FIBARO FGBS001 measures the outgoing floor heating water temperature.
Below 23.1C it closes the Philio PAN04-1 relay and that starts the burning cycle on 40C (the max. boiler temperature)
Why the 23.1? To show it is a Float and not Integer, Domoticz does not show the zero in 23.0 for floats (??).

If the outgoing floor heating water temperature comes above 25.1C the PAN04-1 relay opens and the burning cycle stops.

But ... when Domoticz crashes or the Node has no contact anymore, the boiler keeps on burning. That happened 2 times in the last 40 days, so I had to make it more robust.

I have added in-between a delayed OFF relay to prevent cycles longer than 40 minutes (determined empirically).
For less than a whooping 3€ found here: Delay-Turn-off-Switch-Module-with-Timer-DC-12V
That leads to the following diagram: (a big picture so you can read how to adjust the relay, it comes without documentation)

In my case I had an unused contact from the Philio PAN04-1, that also controls a pump for the first-floor heating. The PAN04-1 has no "dry" contact, thats why I used a 230V relay in-between.

Alternatively the PAN06-1 has a "dry" contact, and could switch the 12V directly. Result: more comfort & less gas usage.
Hope this inspire others,
Domosapiens

Your final conclusion does exactly meet my experiences of the last months:
Just KISS.
A constant floor temperature gives comfort. The room air-temperature is a result of that.

I've been investigating a alternative way of heating for the last couple of months for instance by looking at IR-foil heating, as a floor-heating solution, and stumbled at the problem how to regulate temperatures. A 'normal' thermostat switches to off when air temperature is reached, but the resulting effect when in short distance from the heating foil, I had it put up as a wall-heater for testing purposes, is like standing in the sun on a cold day, very nice feeling and then a cloud gets in front of the sun, not that nice.
So I was looking for a solution to get a constant 'sunshine-feeling'.
The problem is the foil I got, 10mtr was 2.2kW, so finding a lightbulb dimmer of that size is a problem. Happily I stumbled on someone asking a somewhat equal question how to reduce the power of a water kettle from 2kW to 1.4kW on electronicaforum.nl and that led me to http://www.ebay.com/sch/i.html?_from=R4 ... er&_sop=15
for less than $10.00 I can now switch on/off within .1 C steps to whatever I want.
I've abandoned the IR-foil solution, electrical heating isn't economical, and now I'm thinking of getting wall-heating, floor-heating but then on the wall, and regulating temperatues the KISS way, sensor of the stc-1000 at return-water-flow and sending that to my Remeha Tzerra and abandoning my 'intelligent' Remeha iSense thermostat.
I've been fighting with that combination because atm I have a mix of 'heavy' radiators and light ones. If the period of on-off is bit long, the light ones are cold and the heavy ones are still warm, but at my working place I'm in the neighborhood of such a light one, which is little bit unpleasant. It took me some time to figure out how the iSense and the Tzerra work together, it more or less resembles your original situation, air temp OK, but an unpleasant cold floor, my back was cold.
Simply measuring the back-temp on the light radiator and sending the CV to heat if it's below a certain level and stop if it's above another level will solve that problem.

Domosapiens wrote: For less than a whooping 3€ found here: Delay-Turn-off-Switch-Module-with-Timer-DC-12V

They also sell those relay boards with a better Omron relay for a similar price.

Thanks for the remark.
Do you have a link?

Hi

Great project you've got here, I've just found this thread and I am impressed.
I have a self- built heating of conventional radiators and a wall heating.
After reading your post I am going to change the controll of my heating system.

I would also like to emphasize the importance of Blockly for this type of project.