[Solved] What is the power limit in the Junkers Cerapur Smart 5C 24kW boiler?

Wojewoda82 wrote:

Now I turned it on specifically for central heating, the boiler fired up at about 70% of the available modulation, i.e. somewhere around 8KW, dropped down to 10% for a moment (i.e. somewhere around 5.5KW) and then spun up to 100%, i.e. 10KW.

Anyway, it started with 70% power, max 8kW. If you didn`t limit it, it would probably run at around 17kW. He went down to mine. and stabilized as needed. If the need is low, around 7-8kW, we waste gas on starting it, but we cannot limit it too much so as not to run out of it in frosty weather.

This is how it was set, in my case I do not have easy access to advanced boiler parameters. The only limitation of power from 20 to 10KW for central heating is a switch on the boiler (if necessary, just switch it, a switch similar to that of room regulators: air conditioning/heating, time/temperature, switch on/off), at minus 10 the boiler rocked for a minimum of 12 hours /day. So the maximum power of 10KW is still plenty.

What`s worse is that if I wanted to change something in the parameters myself (pump overrun, speed, starting power, etc.), I don`t have access like Termets and other boilers have, because for this you need a WiFi transmitter and a program on a laptop (i.e. changes would only be via the website). It is impossible to enter the parameters by pressing a combination of buttons on the boiler (there are only 2 and 2 knobs)

bumble wrote:

The boiler has 24 kW and the burner has 47% of what?

Sometimes manufacturers provide power as a value in kW, and sometimes in percentages, and these percentages are always questionable and it is not entirely clear how much kW exactly is.
But it gives us some idea of what power level we have at a given moment, and with numerical indications we can verify whether the power is increasing or decreasing, etc.
So don`t analyze and don`t pursue the topic of exactly how much this 47% is, because even the Junkers hotline probably doesn`t know it ;-)

bumble wrote:

And if so, if the burner has 12 kW, where does 12 kW come from?

And where it was stated that the burner had 12kW, the photo shows that the minimum power is 12%, not 12kW.
I think you`ve got something wrong too.

As for the actual burner power of 47%, it is in other words the current power with which the boiler is operating at that specific moment and I estimate that 47% means a power of approximately 12kW, not that the burner has 12kW in a boiler with a maximum power of 24kW :D

bumble wrote:

Most boilers ignite at max power.

Most condensing boilers have a defined starting power and it is usually not = nominal (maximum) power.
This was the case with old atmospheric boilers, where the control options were limited, but not always, because my boiler starts with minimum power and only after 2 minutes it switches to intermediate power set in the MENU, i.e. it can be a value between minimum and maximum. (factory setting was set to max).

Added after 15 [minutes]:

bumble wrote:

Anyway, it fired up with 70% power, max 8kW. If you didn`t limit it, it would probably run at around 17kW.

You`re a bit confused.
In old boilers, like my Vaillant VUW 240/2-5, there was no separate parameter to set such as the starting power.
You can set the minimum and maximum power on the gas module.
Then in the MENU you set only the intermediate power, which is also the maximum power for CO, and this is where the setting range ends.

In condensing boilers, you have an additional parameter: starting power, which is set at the appropriate level to ensure that the boiler starts without any problems.
Then, after firing the burner, the boiler begins to modulate to the appropriate level, either up to the maximum if the water is cold or down if the temperature sensor detects too high an increase in the boiler water temperature. There may be minor differences resulting from the programmed program of the boiler operation algorithm and the relevant parameters in the boiler.
But this applies to the variant when you have an ON/OFF regulator.

If you have a regulator that communicates with the boiler, it can control the boiler`s power and then the regulator somehow takes control of the boiler. The way the boiler will operate may depend on the advancement of a given regulator.

bumble wrote:

If the need is low, around 7-8kW, we waste gas on starting it, but we cannot limit it too much so as not to run out of it in frosty weather.

Starting power is the power used only when lighting the burner, so nothing is wasted because it is a short process, usually from a few to several dozen seconds.
There is nothing stopping the boiler from having a starting power of 6kW and then switching to a maximum power of 24kW. There is no point in setting the starting power to 17kW, because usually a level of about 6kW is enough.
You can usually change this starting power in the MENU, but setting it too low may cause ignition problems and only that or that much.
So I don`t really understand where your 17kW for starting power comes from, because there is no need for it. Starting power is not the same as nominal (maximum) power.

BUCKS wrote:

As for the actual burner power of 47%, it is in other words the current power with which the boiler is operating at that specific moment and I estimate that 47% means a power of approximately 12kW, not that the burner has 12kW in a boiler with a maximum power of 24kW

Well, you have to admit that there is a "real" difference, a "current momentary" difference, it`s my fault that I write first and think elsewhere or I don`t read to the end.

BUCKS wrote:

Most condensing boilers have a defined starting power and it is usually not = nominal (maximum) power.
This was the case with old atmospheric boilers, where the control options were limited, but not always, because my boiler starts with minimum power and only after 2 minutes it switches to intermediate power set in the MENU, i.e. it can be a value between minimum and maximum. (factory setting was set to max).

Yes, most of them. But not all of them. The newer ones are probably as you write selection. I don`t know if it was dictated. But to common sense it makes no sense. My friend wrote that he has a floor boiler, so it is low-temperature, and the boiler should work as long as possible, i.e., it should be clocked as little as possible, and on transition days, the lowest possible power is needed.
If there is no mixer, the temperature limit for the floor must not be exceeded, and this is certainly in the condensation range, because that is why we buy such a boiler. Unfortunately, we cannot reduce the minimum power. If it starts at max, we can reduce the max power. That was the original question and I would answer yes. To lower. Additionally, it can somehow protect the underfloor heating system from overheating if there are no mixers in the event of a control failure and the boiler running at max power.

rustin wrote:

Bucks, then there is no point in messing with power in my case, if I understood your post correctly

from what you wrote, the regulator controls your boiler in such a way that you do not need to change the power.
If you want, you can reduce the maximum power as a curiosity and see what the effects will be and, for example, what percentage the regulator will indicate.
I would treat it more as an attempt to expand knowledge about my boiler and regulator than a real need.
Maybe if you change the parameters, you will find settings that will suit you better.

Moreover, the boiler may operate differently in a cold installation than in a warm one, when the water is already heated and has a specific temperature.
But if you have an underfloor heating system, the boiler water temperature is assumed to be low, so the boiler will not have much opportunity to work at high power, otherwise the water temperature in the boiler would rise too quickly and the boiler would probably have to shut down immediately.
Without practical tests, it is difficult for me to assess whether the current operation of the boiler is the result of control by your regulator, or whether it is the effect of the boiler water temperature being close to the set temperature, so the power is automatically reduced to avoid overheating the boiler water.
Each boiler has its own operating characteristics and its own algorithm according to which the power is selected at a given moment, and in addition, you have an additional regulator that controls the operation of the boiler.

Added after 23 [minutes]:

bumble wrote:

Well, you have to admit that there is a "real" difference, a "current momentary" difference, and it`s my fault that I write first and think elsewhere, or I don`t read to the end.

The meaning of the words is one thing, but I guessed what the manufacturer Junkers meant when he used the phrase real power.

bumble wrote:

Yes, most of them. But not all of them.

I know that all condensing boilers which I had the opportunity to study the installation instructions had to set the starting power, so I accept it as standard, but I`m not 100% sure.

bumble wrote:

The newer ones are probably as you write selection. I don`t know if it was dictated. But to common sense it makes no sense.

It is not pointless, because starting the boiler requires slightly different parameters than normal operation.
For me, starting power = minimum power.
As a result, I had to increase the minimum power slightly to ensure that the starting power was at such a level that there would be no problems with ignition. Previously, I had explosive ignitions or the problem of humming coils in the gas module, but now I no longer have such problems.

bumble wrote:

My friend wrote that he has a floor boiler, so it is low-temperature, and the boiler should run as long as possible, i.e., clock as little as possible, and on transition days, the lowest possible power is needed.

After all, nothing will happen if the boiler has a starting power of e.g. 6kW, and after a few seconds the power drops to the appropriate level.
By definition, a boiler aims to heat the water as quickly as possible to the set boiler water temperature, and then reduces the power as low as possible to just maintain this temperature. If the minimum power is too high, it will eventually turn off the burner so as not to overheat the boiler water.
In the case of underfloor heating, the operation of the burner at a power of e.g. 6kW for a few seconds is negligible.
Then you can set other parameters if you want to achieve a specific effect.
The author wrote that the boiler starts at the beginning with a power of 47% and immediately drops down, so this short-term operation with higher power does not matter much.
If he wants, he can try to change the settings, but he wouldn`t expect any drastic changes.
The author did not write that the boiler turns on the burner for 5 minutes and then turns off, so there is no problem with timing to complain about this temporary higher power.

I don`t know the operating characteristics of the boiler and regulator at the author`s, but if he doesn`t need to change anything, he doesn`t have to do it.

I know the operating characteristics of my current boiler. These things are not described in any user manual, but based on trial and error I determined what the "intelligence" of my boiler was. With the ON/OFF regulator, I know in advance what the operating cycle of my boiler will be, so it will no longer surprise me
Only I like to know more, so I try and test to get the most out of the equipment I have, while others are not excited about it and it is enough for them that the heating works and the house is warm.

Someone please explain to him that a mixer is needed for the floor and the condensing boiler like incense for a dead person.
Exceeding the temperature limit for the floor next to a condensing boiler and you need a mixer, it`s shocking how someone can confuse someone`s mind to think like that.
Now how is it possible that my boiler without a mixer supplies water at a temperature of 28 degrees Celsius, and in frosts - 15 degrees Celsius, I saw 38 degrees Celsius temporarily. Witchcraft

rustin wrote:

Cerapur Smart 5C 24kW with underfloor heating

You haven`t mentioned anywhere what type of boiler it is. You didn`t write that you only have underfloor heating, no radiators. Everyone tells you to limit yourself and you don`t. I don`t understand the point of this topic.

No, you are limited. In the first post he writes Cerapur Smart 5C 24kW, so what do you think it is? Not the type and model. Man, stop writing and making fun of yourself

I already know that you have problems with reading and interpretation, so I will help you one last time, no one but you is telling me to limit the power because I control the CW400 well, I can only try to experiment with it, which Bucks also explained. Are you taking or drinking anything?

Added after 2 [minutes]:

Bucks` friend explained everything thoroughly. There is no point in further cluttering the topic