Setting Up and Operating De Dietrich MRC3 Plus Furnace: Heating and Water Change Cycle

I need help setting up the furnace. Two days ago, there was the first start-up by an authorized representative, there were no objections, it seemed that the stove is running regularly and the power pipes are warm. It was known that heating up and changing the water in the entire system must take place, the service technician said it would be up to 8 hours. Due to the fact that I do not live at home yet, it was only after 24 hours that I checked the heating. Unfortunately, at home, the cold on the stove does not have any errors. Irregular work turns on for about 5 minutes, heats the power felt by the splitter, then, as if it had reached the indicated temperature, it calms down and everything cools down on the return of the cold pipe, the cycle repeats after some time.

I will add that the programmer in the room has the day 22st and night21st programs.
On the boiler, it is set to 30 degrees Celsius, heating of domestic hot water is off.

The question is what could be the problem? It looks like the stove turns off because it is peaking from the power supply and disconnecting. Request for help

If you set the boiler to 30, you will not be warmed because you limit the temperature and the boiler is clocking, set 50-70 temperature on the knob, the i-sense thermostat and so will select the supply temperature

Good morning,

I have had this stove for several weeks, internal sensor control, only oversized radiators - 7 pieces, heating area 80m2.
I have 50 degrees CO on the stove, what should be the maximum boiler temperature in isense? also 50? thank you in advance for your help

@gosia. MM, 7 radiators, but what power do they have for 50 levels of power? Radiator manufacturers usually have radiator power converters for different temperatures on their websites.

If you don't know or can't count, there is another way. Your boiler has a burner power modulation and at temperatures of around 50 degrees Celsius, it has a minimum of 6.1kW
If it is the boiler as in the link:
Link

You set, for example, 40 degrees. If the boiler, after about 25 minutes of continuous operation, does not overheat the CO at the set temperature by more than 1-2 degrees, then you are here. If it overheats, raise it 2 degrees and watch again. If it does not overheat, you can try to go down 2 degrees and check.

This way you will have the minimum and most economical flow temperature (max condensation) that the boiler and radiators allow for transition periods like 5-10 degrees outside. When it gets colder and the boiler, operating non-stop at the set temperature, will not be able to heat the rooms, you will increase the temperature by a few degrees on the supply (this parameter is max, what you ask). It is possible that with oversized radiators the max will be the same as the minimum or a little more.

I have a De Dietrich MCR Home 2 function plus on off controller and for me the minimum is 48 degrees on 67 square meters with furnace modulation from 5kW with 80 ribs 500 / 580mm Faral. The boiler currently (about 5 degrees outside, the apartment is not fully insulated, the boiler is limited to 10kW for CO) turns on in cycles of about 2 hours pause / max half an hour of operation (this is how I set the weekly programmer, mixing the comfort temperature with the night temperature) and I can easily heat up to what I want, often without even working for half an hour. Probably I will not increase the flow temperature in case of frost, but I will increase the number of comfort temperature settings on the room programmer.

@ wigi, maybe you have air on the radiators / floor heating and do not receive hot water from the central heating system. In this way, the stove does not manage to modulate the power of the burner, there is clearly too little heat reception by the radiators / underfloor heating. Bleed the system, replenish the water in the system.

On the other hand, if you only have radiators (which it does not look like), you would have to have entire walls in the radiators so that they would receive 6kW from the stove with work at 30 degrees.

@ wojewoda82, I have buderus heaters: 1 room 16m2 - vc22 1600x600, 2 room 16m2 - vc22 1600x600, kitchen 14m2 - 1200x600, corridor 7m2 - 800x600, vestibule 7m2 - 800x600, bathroom 5 m2 - ladder.

I have 50 degrees CO on the knob on the stove, but e.g. in the morning when the stove turns on, it takes over 3 hours to heat up from 20 degrees to 22 degrees! And during this time, the controller demands 90 degrees from the furnace, the furnace works for a few minutes, turns off over and over again ... that's why I thought that on the isense driver I had to reduce it so that it would not demand such high temperatures and work longer and not with such jumps?

These radiators, however, not so much oversized. Unless you have not specified one room of about 15m2, because that's how much I need for your 80m2. What do you have from the radiators, I do not count the ladder, because I do not know what it is and what its power is, at the installation parameters of 55/45/20, the heaters power is 5250W. With a minimum furnace power of 6.1 kW. Assuming you did not enter one room / radiator for 15m2 with a radiator similar to those in the rooms, it would have resulted in 6600W of radiators power on the installation parameters without a ladder. With a ladder it would give about 6800 / 6900W, which is ok, because it is above the minimum power of the boiler. Here is the calculation for 20 degrees at home, you have a little more, so the power of the radiators will be a bit less)

You have a condensate boiler, so the lower the supply temperature, the more heat is recovered from the steam in the flue gas. By chasing the boiler to 90 degrees, you have no condensation at all, so you lose about 15% of the heat to the chimney. In this case, the boiler works like a normal turbo and not a condensing boiler.

You have to choose between economy (not necessarily with reduced comfort) and fast reheating. I would personally choose economics.

So I would do this:
1) I assume that the boiler operating at 50 degrees in the current conditions (daily average about 0 degrees) is able to maintain the temperature in the cottage, and even can slowly raise it in the morning, I would reduce the difference between day and night from 2 degrees to 1. Night reduction practically it gives no savings, only sleeps a little better.
2) AD 1 temperature, assuming you have this 1 heater more than you specified, I would set the boiler to about 47-50 degrees. The stove will run at minimum power almost all the time, the radiators will be warm almost non-stop (but not hot, they will not mix the dust) which will improve comfort (equal temperature all day long)
3) With the increase of the maximum temperature for CO, I would wait for -10 frosts, etc. If the boiler, despite 24 hours of operation at ~ 50 degrees Celsius, would not be able to maintain the assumed heat in the house, I would suffer a maximum of 55-60 degrees (how much it actually depends on house insulation, etc., it can only be checked practically)
4) If you are bothered by the slow rise in temperature in your home during the transition from night to day, just set the daytime faster.

However, if you only have as many radiators as you wrote, the boiler power at 50 degrees would exceed the power of the radiators, which would overheat the CO water by several degrees and periodically turn off the burner in the boiler. Write if you have it at 50 degrees

Finally, the condensation in a gas condensing furnace (which gives a gain of about 15% compared to a conventional furnace) takes place when the return from the heaters is below 57 degrees. Except that slightly below 57 it is practically non-existent. The return temperature is correlated quite closely with the flow temperature. If you have a 50-degree supply, the return can be around 40-45. At 60 degrees, the return is around 52-45 etc. Something like the chart below, of course the return temperature value is not always the same in every installation, but the graph shows a visible correlation:



Economy punishes you to go as low as possible with the feed, so the return will be lower, and thus also more economical operation of the condensing boiler.

I have 70m2, sorry there was a typo earlier (there is one more room, but without a heater, 5m2 storeroom - 70m2 in total). The ladder is Biotherm EUROPA 530x1150

Now I have 50 degrees on the stove, the stove works for a few / maybe a dozen or so minutes, heats up the radiators and turns off, rests and turns on again for a while, and so on - as you write
the furnace is controlled by the isense controller - why does he require a temperature of 90 degrees from the furnace when heats up from 20 to 22 ??
the daily temperature is 22 degrees (from 6 to 22) and 19.5 (22-6) - but so far during the night it drops by 2 degrees in the room
the furnace starts at 6, the temperature in the room after the night is 20 degrees - today, for example, it warmed up to 22 degrees only at 15.30 ... why does it take so long? :(

what should I do to be okay?

Well, you have too little power of the radiators, they are not too condensate (at 50 degrees they cannot heat up the rooms as quickly). In addition, the minimum modulation of the boiler burner is higher than the power of the radiators at this temperature, hence the burner is extinguished (timing), only the pump works, and after some time the burner turns on again and so on.


Raise the minimum flow temperature to 55 degrees, if it continues to heat for a long time or the stove continues to clock, give 60.

Raising the power to 55 should equal the power of the radiators and the minimum power of the burner (it will not clock), it will also result in faster heating of the house because at 55 degrees, compared to 50 degrees, the radiators have a higher power that will be given to the rooms. Set the maximum CO temperature to 60 for now (for the time being, you will probably need to give more in case of frosts)

Anyway, with such settings, the condensation in the boiler will be small, i.e. a small profit from an advanced boiler.

Now it's mustard after dinner, but the solution would be (each solution is costs, if the radiators and stove are new, it doesn't make sense, or rather they are)
A) Replacing the boiler with a lower minimum power. You'd have good condensation at least during the times when it's in the black outdoors
B) Replacing the radiators with higher power (which usually makes them bigger, longer, thicker) or adding a radiator (only here there is not much where)
C) adding a floor layout to, for example, a kitchen and bathroom (but here breaking the tiles, additional mixers for the floor heating, etc.), i.e. an additional radiator, only surface

Preferably A + B with B would give a better effect.

Finally, I will add that this house is a bit leaky (you have a vestibule, so it's probably a small house). I have 67 meters of an apartment on the high ground floor, insulated only on one side in a building from the 90s, and for me, with a similar radiator power at 50 degrees (and I heat at 48 degrees) with an average daily outside temperature of 0 degrees, the boiler works to keep the temperature inside. more or less now in 40% of the day. It now takes about 120 minutes to raise the temperature by 1 degree from night time.

Now I ask myself: If it is a house with a planned usable attic (but not yet used and not heated), then no investments would be ultimately needed. With 3 bedrooms in the attic, with 3 heaters of 1400W each at 50 degrees, it would solve 2 problems. Too high minimum power of the boiler (3 radiators more would reduce the supply temperature to about 45-50 degrees, good for condensate with radiators) and it would be warmer in the rooms because there would be no heat leakage through the ground floor ceiling (radiators would be more sufficient for lower supply temperatures).

Thank you very much for your help.

The house has insulated walls (10 cm polystyrene), but unfortunately the ceiling and the basement are not .. probably that's where the problems with raising the temperature are from, the heat is escaping quickly, today it was windy and -2 so he could not warm up after the night it is quite a poor house from the 80s ..

I will do as you advised, I will give CO 55 degrees on the stove on the knob and see if the problem with the timing disappears.
On the isense driver also then max. boiler temperature give 55? or min. 55 and max. 60? because from what I understand, isense selects the temperature and therefore screams that it wants 90, but the stove does not allow it because it has a maximum of 50 on the knob?

from your suggestions, for now I could add one more radiator to the bathroom, because this ladder does not heat up but will it change anything?

at the current temperatures (average 0), the stove consumes 5.5 m3 of gas per day .. I'm afraid of what will happen when the frosts come

I will start from the end, 5.5 meters at the moment is not a tragedy (though not a great result either) for a house from the 80s, 5.5 x 30 days plus about 60 zlotys fixed fees (because you will probably catch W3 tariff or you already have it), this gives you a bill of about PLN 380. That's just over 1/3 a ton of good coal (at least in my area). And how much trouble would it be when burning a charging stove. And you would burn this coal with just 300 kg (how to convert the used gas to its carbon equivalent, it does not look so terrible anymore). Of course, in frosts more will go.

Ultimately, insulate the ceiling in the attic, the ceiling above the basement, at least from the bottom (because you probably can't from the top of the house, tiles, panels), because this is where the most escapes.

As for the additional radiator in the bathroom, of course. Since the ladder itself cannot comfortably heat the bathroom, the radiator will improve the situation (in general, the bathroom should have 24 degrees). In addition, an additional heater (even 500W at 50 levels of power supply) will improve the work with the boiler. It will stop clocking on what it has now or it is even possible to slightly lower the temperature in the transitional periods.

As for the maximum temperature of 60 degrees, you can raise it to such a height, but with such parameters there will be practically no condensation (there is not much at 55, but definitely more than at 60). I would leave it for freezing temperatures of -10 etc, unless the furnace continues at 55. It seems that the programmer adjusts and modulates the burner power, but when increasing the temperature from night to day, the programmer will still try to demand the maximum temperature at which you let it.

The most optimal option for a condensing boiler is always to set the temperature on the furnace and select the heaters in such a way that the furnace runs at the lowest temperature (and thus power), preferably all the time, or at least with the second cycles. In your case, the whole lime tree is heaters, there are too few of them and their power at low temperatures is too low for the building's needs (since at 50 degrees they cannot cope with a relatively quick increase in temperature) and the minimum power of the boiler.

Let me know if the stove is still extinguishing the burner every now and then and if the temperature in the building rises faster.

Next year I will insulate the ceiling and the basement. This is my first season of heating with gas, I'm just learning what it is :-)

For now I am away from home, on Friday I will do as you wrote and let me know if it helped.
So far I know that, unfortunately, the heating time to 22 degrees was even longer - today it did not warm up until 10 PM until after 6 PM, and it started at 6, so it took him 12 hours .. (at -2 during the day and -4 at night, quite windy - 28 km / h)

I'm still wondering what you wrote to give smaller differences between night and day .. maybe 21 night, 22 day, but how will it affect fuel consumption ..

I will ask about one more thing - for me the radiators heat only at the top, they are cold at the bottom - maybe they are air-tight and need to be vented? is it supposed to be on gas so that only the top heats?

Switching between night and daytime from 2 to 1 degree will result in unnoticeable losses. When switching from night to day temperature, the boiler must replenish the house's heat losses on an ongoing basis, additionally, it must increase the temperature, i.e. catch up. The balance is practically the same.

As for the radiators, do you have thermostatic heads on the valves? If so, unscrew them a little more, i.e. from 3 to 4. It should improve.

If you do not have thermostatic heads it is not normal for the bottom of the radiator to be cold when the boiler is in operation for some time. The radiator may be slightly cooler at the bottom than at the top, but this should not feel like a cold bottom, just slightly less warm than the top of the radiator. In that case, it would look like you have too little water flow through the radiators. So, for example:
- throttled return on radiators (this is a special allen valve, usually secured with a screw cap, which is located next to the radiator right next to the return pipes)
- too low speed of the water pump in the boiler (it is modulated in your furnace, but it can also be limited in the values of 20-100%) - here change only service

The fact that the bottom of the radiators are cold additionally means that the radiators do not work with the power calculated for a given supply temperature, but with a much lower power. Hence, problems with heating the house may arise.

I don't have thermostatic heads, maybe it's not the fault of the stove and the radiators? because 12 hours to heat the temperature by 2 degrees in a 14m2 room, it is definitely too long

Please explain to me, if this flow is too low, the water flows into the radiator and what next? it flows so slowly that when it comes back it's cold? (forgive me if I write nonsense, but I don't understand what this supply and return temperature in the installation is about)

Yes, when the flow through the radiators is too slow, the hot water flowing in with the power supply will have time to cool down a lot (give the heat back to the room), hence there is always a slightly cooler at the bottom. But cooler doesn't mean cold.

Since you do not have thermostatic heads (they, when you already have a room warmed up for the head setting, they close the supply valve tightly, that the flow through a given radiator is very weak), the problem must be somewhere else. According to the information from you, the problem with the cold bottom of the radiator when the top is warm applies to all radiators. So you have a rather poor flow on all radiators, which rather eliminates the twisted return valve (it's hard to imagine that all return valves would be throttled on all radiators).

If so, my most suspect is:
a) speed of the central heating pump in the boiler. It is possible that the installer or service technician has reduced the max speed of the modulating pump to 20-30%, which is perhaps too low speed for your CO. What for, I don't know. here rather only a service, because there is probably no pump settings option in the programmer
b) it is possible that the oblique filter on the CO return is blocked

If so, it's easy to check. It is enough to close the valve above the filter and under the filter and unscrew the cap to check the condition of the metal strainer, whether it is dirty. A little water will be recommended, you may need to pressurize the boiler slightly after cleaning.


If there were air in the radiators, they would not heat well, but then you would also hear the water overflowing in them. This is probably not the reason, but it is worth checking whether water or air flows after unscrewing the vents on the radiators.

Thank you, you were right with that CO filter on the return! Today I had an installation contractor, he cleaned the filter, I increased the CO temperature on the stove by 2 degrees and it is much better! Radiators keep your home warm. I also changed the hourly program - I set 22 degrees around the clock .. in the coming week in my area it will be freezing -5 during the day and -10 at night, I will see what the gas consumption will be after a week with such settings and outside temperatures. I hope I won't go bankrupt ;-)

Thank you very much again for your time and help!