Title: Junkers Cerapur 2200W vs GC 2300W: Opinions, Differences, and Heating System Modernization

Hello

I am planning to upgrade my heating and want to replace my old open-chamber combination boiler with a new condensing boiler. I would like to install a Junkers Cerapur 2200W boiler, but I can't find reviews or anything specific about it on the internet. There are similar boilers, such as the GC 2300W model, but it is 1000£ more expensive. I don't know what the differences are between them. Theoretically they have everything the same. The only thing is the power is different. In the cheaper one it is 4.8 - 25 kW, while the more expensive one has a power of 3 - 25kW.
Is there anyone here who could say more about this?

If you can, buy Bosch GC2300. Higher DHW efficiency (stronger secondary exchanger). Greater precision, especially when using the spray. Modulation from 3.0-25.0 kW.

The difference is only 0.6 l / min. Is it that much? I am asking because I am not a specialist.

Which house / flat?

The apartment is 80m2. Old building. Insulated, but on the top floor, where the attic is not insulated. Heaters for a total of 10kW, slightly oversized.

The one with better modulation will be able to work smoother. During the period of lower demand for heat - it will go down to the minimum power and will keep itself warm. The cheaper one - will sometimes "clock" - because its minimum power turns out to be too high. And the performance on domestic hot water - the more expensive has a little better.
Both will work - while the more expensive one will be more "fitted". The cheaper one will be "too big" in some moments and will extinguish the burner, and the idea of a condensing boiler is to work continuously and supply exactly as much heat as your house can take at a given moment.

How the radiator in the whole apartment is sized for about 10kW and the apartment, as I counted in some calculator, has losses of about 9kW. How big / small boiler should I buy? As I understand correctly, the minimum power is of great importance. When buying a boiler with a minimum power of 4kW, where the heaters receive 10kW, at what point will the boiler start clocking and will it do it at all? So what's wrong with timing?
Next question. In the coldest room I have a Euroster 2026TxRx regulator. In the apartment, when no one is there, or at night, the temperature is set to 19 degrees Celsius, and when someone is 21. How much will it affect the boiler's operation?
I am asking because I am a complete layman.

Hello !
@zerthimon

zerthimon wrote:

Hello,

I am planning to modernize the heating system and I want to replace my old combi boiler with an open chamber with a new one, condensing. I would like to install a Junkers Cerapur 2200W boiler, but I cannot find any opinion or anything specific about it on the internet. There are similar boilers, for example the GC 2300W model, but it is PLN 1000 more expensive. I don't know what the differences are between them. Theoretically, they are all the same. The only thing is that the power is different. In the cheaper one it is 4.8 - 25kW, while the more expensive one has a power of 3 - 25kW.
Is there anyone who could say more about it?

Which boiler did you install and how is it doing?
( if it's not a secret )

Regards. Stefan

@ sp3ots
I installed the GC2200W cerapur. I like its appearance, price and work. The heating has only been working for 2 weeks and only a little bit too, but I noticed something interesting. I have the temperature set to 50 degrees and he can sometimes heat the water to 53 with the hook before the burner goes off. It is probably related to the fact that the burner cannot go down below and the boiler hysteresis allows such a margin. We will see how it will be colder, how it will perform. I am surprised how much condensate it produces. In the summer, when it was hot outside and he only heated the tap water, a pretty good amount of water came out of him. And as for work, it is very quiet. Service water heats up quickly, as does the CO.

Thank you for your answer.
If you had any records of daily gas consumption at the current temperature, I would love to see them.

I do not make such notes, but if I do not forget, I will sign it and write it for you. But I can't promise anything.

OK thank you.

Hello, I am also buying this boiler. I don't know what driver to buy for it. I will be grateful for the hints.
Regards

Polanka wrote:

I don't know what driver to buy for it

just a simple ON / OFF, eg Salus RT510RF or other ON / OFF, depending on your aesthetic preferences, etc. There are many companies producing various models of this type of regulators, from wired to wireless.
Wireless ones have the advantage that, if necessary, you can easily move the regulator to another room or to another wall, and nothing clicks in the room when the boiler is turned on.

Just remember that this boiler has a minimum of 5.2kW, so if you want to heat your apartment in an insulated building, there may be problems with the timing of the boiler.
Zerthimon wrote that he has 10kW heaters, but he did not specify the temperature of the boiler water for which, so it does not say much.
Although it already gives some point of reference. My 70/50 water heaters have a power of 9.2kW, and I have a 100m2 flat in an old, non-insulated building, so they can assume that Zerthimon has a bit more powerful heaters than mine, so these 5.2kW are still right.
If you have an apartment in a modern building, and this is what I associate with your login, it is better to buy a boiler with a minimum power of 3-4kW, i.e. Bosch 2300iW, which in the 2-function version offers a minimum power of 3.4kW for 40/30 boiler water .

Installation of what is a set of connected vessels and everything must be harmonized with each other, so it cannot be an accidental purchase of individual elements, because then it can take revenge.

Hello Thank you BUCKS for your valuable advice. It is a complicated matter for me. I will check the power of the radiators and give you more details. Ultimately, you need a stove for a 60m2 apartment, an insulated building. The installation is extended by another 45m2 apartment which is used five times a year for several days. I don't want to have any problems with moisture, so in winter the 45 m2 will only be heated to a minimum. The installer recommended this boiler to me, but I prefer to seek your advice.
Have a nice day.
Regards

If they are steel plates, it is enough to enter their size, i.e. height, length and depth, then I will estimate their power for a given temperature.
But in an insulated building, if the heaters were installed by the developer, I would not expect large ones.
In an insulated, modern building, I would expect twice less heat demand than in my case.
This means that for 100m2 with frosts of -20 you would need approx. 4kW. Since 40 m2 will be heated to lower temperatures, the second apartment will have a smaller share in receiving heat from the boiler.
The installer recommends what he has in stock, what he trades, etc. The boiler is priced around PLN 3500, so the price is acceptable to most people. The installer will not live in this apartment afterwards and will not be overwhelmed by problems with timing of the boiler, etc., so he does not care.

As for me, it is a must-have 2-function boiler with a minimum power of 3-4kW.
With the cheap ones at a level close to 2200, you have, for example, a Termet Silver 20kW, which offers 25kW for domestic hot water, and if the price does not make much difference, you have, for example, Bosch 2300iW 24C.

Hello In total I have 8 Kermi heaters (in both apartments) 3 pcs-600-800, 2 pcs 600-600, 1 pc 600-1600, 1 pc 600-1400, 600-1000. I would like to add that it is a house built in the 1980s in traditional technology, insulated outside with 8 cm graphite polystyrene. As I mentioned, at the moment the heating area is 110 m2. I would like to add that I want to expand the living space by another 60m2 in the near future, therefore the idea of purchasing Cerapur 2200W.
Regards

Polanka wrote:

In total I have 8 Kermi heaters (in both apartments) 3 pcs-600-800, 2 pcs 600-600, 1 pc 600-1600, 1 pc 600-1400, 600-1000.

Together, this is 7.6 meters in length.
If it is type c22, i.e. 2-plate with a thickness of approx. 10cm, the total power for 70/50 boiler water is approx. 9.5kW.
For 40/30 boiler water it will be approx. 2.6 kW.
But since the whole will not heat only 45m2 half a whistle, the real power will be lower.
As you can see, for 40/30 boiler water it is far from 5.2kW, i.e. the minimum power of 2200.
In theory, Termet Silver 20kW fits better.
After expanding it with additional space, it will be different, but in my opinion it is better to have a lower minimum power, because it gives more flexibility.
The maximum power of the boiler makes no difference, because for 70/50 water you have the power of the current radiators about 10kW, so a 24kW boiler will not change anything.

I'll say something from myself. Until now, I had a boiler with an open combustion chamber. The supply temperature of the radiators was set to 63 degrees approx. Now I have this condensing boiler and for China I would not put 40 degrees on it. I've tried it and it's just cold at home. Heaters designed for different temperatures. Maybe in a new building it is enough, but not in an old cottage or with these heaters. I don't know you are wrong with the timing? Everyone demonizes them, but I have not found any specific calculations of how much this affects gas consumption. At least I am now set to 50 degrees on the power supply and I have never experienced this phenomenon. As for the boiler, listen to what will be mounted for you, not to this anonymous guy on the Internet. Because the installer takes responsibility for it. There is a high probability that he knows it. I don't know about your knowledge of boilers, but if something goes wrong, this guy from the internet will continue to give you good advice, but you will pay for it.

zerthimon wrote:

Now I have this condensing boiler and for China I would not put 40 degrees on it. I've tried it and it's just cold at home. Heaters designed for different temperatures.

it's probably a colleague who has no clue how the heater works.
If you would never set 40 degrees, the heat demand changes with the outside temperature, and since the radiator has a constant size, the power can be regulated by changing the temperature of the boiler water.
So you will heat the boiler water less at +10, a little more at 0 and even more at -10, and the strongest at -20 and this is how the so-called weather control that automatically selects the appropriate temperature of the heating water.
For example, at +10, heating the boiler water to 40 degrees is most appropriate, but with your boiler and your radiators it is unrealistic without clocking the boiler.

You wrote that you have radiators that fit 10kW and allegedly your building needs 9kW.
Considering that it is for frosts -20, on average in the season you can assume that you will need about 4kW of constant power.
You did not write at what water temperature you have these 10kW on the radiators, but if this power is 70/50 for water, then the same radiators:
- for 40/30 they will have approx. 2.8 kW,
- for 45/35 they will have approx. 4kW
- for 50/40 they will have approx. 5.5 kW
The moral of this is that only at approx. 50 degrees on the boiler, your boiler will be able to work in continuous mode and possibly it will turn off earlier if the room regulator turns off the heating request and this is confirmed with your opinion:

zerthimon wrote:

At least I am now set to 50 degrees on the power supply and I have never experienced this phenomenon.

The problem is that at e.g. +10 you would only need to heat the water to 40 degrees without timing, it is technically impossible and with timing you cannot count on a continuous, constant 40 degrees on the power supply. You would have a boiler with a minimum power of 3kW, you would heat the water to e.g. 43 degrees and it would be OK, and so you need to heat the water to 50 degrees so that you do not experience timing.

Everyone has a different feeling of thermal comfort, so what suits you would not suit me anymore. If I had no choice, I would get used to it, but if I have a choice, I prefer to have a boiler that will provide more flexibility.
The installer usually does not care about it, because he wants to do the job and delete the cash, and any timing of the boiler is not subject to complaint, because the boiler itself works and the installation heats up. Unless someone would write a contract and include conditions that must be met by the installation, but no one does it, so there is no basis for a complaint.
In the same way, developers can install the Junkers MIDI with a minimum power of 7.5kW, in new terraced buildings that need, for example, 4kW for frosts -20.

zerthimon wrote:

I don't know about your knowledge of boilers, but if something goes wrong, this guy from the internet will continue to give you good advice, but you will pay for it.

Your knowledge of boilers tends to be very little as well, so your advice dude can be taken similarly.

And what is supposed to fall out, what's wrong with my advice that I suggest buying a boiler with the lowest minimum power possible?
Bosch 2200 is a boiler for about PLN 3500, so what is a Mercedes?

In the Junkers Smart 24-5C boiler from Bosch's group, which is more expensive, you can find threads on the net, where people complain about the allegedly entire plastic circulation pump, which if it falls after the warranty, the cost of buying a new one is only PLN 1000 and some suspect that it is one from the weaker elements of this boiler. I had this Junkers in mind myself, but after reading this, I start to wonder if it was the right choice then.
I am not a service technician, so I do not have selective knowledge about which boiler would be the least emergency, but how many people are so many sentences, so there is no 100% certainty.

Each installation is individual and each case should also be approached individually, but the practice is that few installers do this.
You buy a boiler and if you later find that you would need a lower minimum power, you will not do anything, because only in about 10 years, when replacing the boiler, you will be able to fix your mistake.
Yes, not everyone is bothered by too high minimum power, but not everyone has a faint idea about it.
Ultimately, it is everyone who decides what to buy, it is best that it is aware of and accepts the potential defects of a given solution.

You described everything to me nicely, but I still don't know what's wrong with the timing of the boiler?

I have a sense of comfort that I would prefer the boiler to heat non-stop with the power adjusted to the actual demand, and the heater to work with the lowest possible temperature.
Without having adjusted power, you need to heat the water to a higher temperature than it would result from the actual demand and continuous operation of the burner.

If the work of your boiler does not bother you, use it and be satisfied.
I have a different level of requirements.

I do not know if in my apartment a boiler with a minimum power of 5.2kW would give a satisfactory effect for me, so I prefer to install a boiler, e.g. a 2-function boiler with the lowest possible minimum power of 3kW, because then I know that I have chosen the best possible variant and if such a boiler is not for me Satisfy it, I will not wonder what would happen if I bought the one with a lower power.
The greater flexibility of the boiler means a greater chance that it will meet my needs and ensure continuous operation of the burner even at a higher outside temperature.
Until I have such a boiler, I will not see how it will be in practice, and dry calculations and estimates will not replace practice.
The boiler is not a smartphone, so I will not buy a boiler, e.g. 5.2kW, and if it does not suit me, I will not replace it with a 3kW model, because if it is, the next replacement would be only in about 10 years.

Thermal comfort is right, everyone has their own ;-)

In theory, the continuous operation of the burner means a bit less gas consumption, less wear of the boiler elements, etc., but all in all, I mean thermal comfort and not overheating the radiators above the level that would be needed for given weather conditions.
So for me, better comfort will be offered by radiators with, for example, 40-45 degrees, than impulse-heated radiators and water heating up to 50-55 degrees, because it increases the effect of the temperature sinusoid in an uninsulated building.

And so diverging from the discussion a bit and returning to the heart of the question, Castorama offers a version of this Junkers 15 / 25kW boiler. 15 for Co and 25 for CW. Does anyone have information about this boiler, its minimum power and differences in relation to the 20 / 25kW version?

maybe I will refresh, I am also thinking about Junkers Cerapur GC2200W 20 / 25C, only for me the floor covering on 80m2 new construction. Will this boiler work optimally for such an area by buying a weather regulator?

@szczurman let's assume that for frosts of -20 you need 4kW, and the Bosch 2200 has a minimum of 5.2kW, so it will not be optimal.
I saw how Junkers MIDI worked with a minimum power of 7.5kW per 100m2 in a new building, where there was a floor heating in its entirety, I would say that the boiler operation cycles were a failure.
It is true that the 2200 has 2.3kW less, which is 30% less power, but you have 20% less space.
I would rather go, for example, in the 2300 model with a minimum power of 3.4kW in the case of a 2-function boiler, because if I had room for a hot utility water tank, I would install a boiler with a minimum power of 2.3kW.
As I wrote above, the boiler is not a smartphone that can be replaced almost overnight. The boiler is an investment for about 10 years, so it should be as optimal as possible.
Yes, each installation should be treated individually, so maybe it would work for you, because it is said that the floor heating is a kind of heat buffer. But my knowledge is too limited and my experience so far suggests that it may be poor and a bit of a risky trade.
You have to make up your own mind and take a chance, then you can show off and write your opinion on how it works for you.

BUCKS wrote:

I would rather go, for example, in the 2300 model with a minimum power of 3.4kW in the case of a 2-function boiler, because if I had room for a hot utility water tank, I would install a boiler with a minimum power of 2.3kW.

probably a higher budget to this 2300, and do you see any better option in its price?

I do not recommend any boiler directly, because I do not know what I would choose in the end. and I'm just an amateur. I saw Bosch 2200 and plastic fantastic disappointed me a bit, connecting the room regulator to this boiler, I was afraid that the plastic from the lid would break and fall off
Apparently, the Bosch 2300 has a larger plate heat exchanger, so it will be better to heat up the domestic hot water, and this is also important for the comfort of domestic hot water, so you get not only the minimum power.

Hello !

BUCKS wrote:

I do not recommend any boiler directly, because I do not know what I would choose in the end. and I'm just an amateur. I saw Bosch 2200 and plastic fantastic disappointed me a bit, connecting the room regulator to this boiler, I was afraid that the plastic from the lid would break and fall off
Apparently, the Bosch 2300 has a larger plate heat exchanger, so it will be better to heat up the domestic hot water, and this is also important for the comfort of domestic hot water, so you get not only the minimum power.

Quote:
"I saw Bosch 2200 and plastic fantastic disappointed me a bit, connecting the room regulator to this boiler, I was afraid that the plastic on the lid would break and fall off "
What did you mean by writing this?

I used the Junkers MIDI for four years, now a new house, a new Junkers ... 2200 boiler, both of them have a flue gas outlet made of some material.

Every time you write you are picking on the timing of the boiler, but at the price?

sp3ots wrote:

What did you mean by writing this?

What I wrote that when I tried to connect a room regulator, the motherboard cover gave the impression that it would break and fall off.
It does not inspire confidence and you can see the minimization of costs is reaching its zenith. I also read threads where people wrote that Junkers SMART has a plastic pump that likes to burst. So this fantastic plastic becomes an unwanted norm, which makes me doubt the point of buying more expensive boilers.

sp3ots wrote:

Every time you write you are picking on the timing of the boiler, but at the price?

New houses are more and more energy-efficient, so the power demand is decreasing, but it does not go hand in hand with the boiler power, so I believe that the minimum power is important.
For comparison, I have a Termet Gold, e.g. the 20/20 model, which has a minimum of 3.4kW, so having a Bosch 2200 to choose from, I prefer Gold 20/20 or Gold 25kW, because at the same price I get almost 2kW less minimum power. And quality, at this price, I do not expect miracles and my old Vaillant is probably the last boiler that was quite durable from this family.

Everyone makes a choice for himself and chooses what he sees fit.
I only pay attention to details like minimum power. It is important that everyone buys with the awareness that something like minimum power is important and that it is not a parameter that can be completely ignored, and then everyone will judge with their own measure, whether it was important in their case or not.
Unfortunately, I will not set up a boiler with a capacity of, for example, 5.2kW to test it. When I install the condensate, I will try to install a boiler with the lowest possible minimum power, so as not to wonder what would happen if I bought 5.2kW instead of 3.4kW. In my case, greater flexibility will certainly be useful in transitional periods, and since I have a building that is not insulated, continuous operation of the burner is of great importance for me. In an insulated building this may have a lesser effect.
You do not like my comments, do not read them or write a counter-argument that you have higher minimum power works great and you do not recommend boilers with a capacity of 2-3kW

BUCKS wrote:

Polanka wrote:
I don't know what driver to buy for it

simple ON / OFF is enough, eg Salus RT510RF or other ON / OFF at your discretion

ERROR, by no means. Regulators that communicate digitally are the best. CW400 is expensive but CR100 (weekly room) or CW100 (weather) can be inserted. The electronics calculate the burner power on an ongoing basis and adjust it to minimize the timing and optimize the operation of the entire installation. Secondly, it does not require battery replacement - it is powered by the boiler.
ON-OFF regulators work like, for example, in a car the gas pedal pressed down to the stop or released, they will also work. Or else it is like driving a car and braking sharply at each speed limit, and accelerating rapidly when there is no speed limit. The digital regulator reacts in advance to all changes and, having a weather sensor, works much more efficiently and economically. It is important to put the boiler and the regulator in a good position.
Sometimes I meet with the opinion that this boiler works all the time and how much gas it eats ,,,,,,, and this is what is supposed to work all the time and not turn off using a minimum of gas.

Clock Speed - Why Is It Bad?
-increased wear of the boiler components
- higher emissions to the atmosphere (more starts and extinctions of the burner - personally I would not care about it)
- greater temperature fluctuations in the apartment
-increased gas consumption
each boiler start-up is preceded by air purge (the chimney and exchanger are cooled down, then ignition and operation until the appropriate temperature is reached, and shutdown - re-blow - exhaust gas ejection - and subsequent cooling of the chimney and exchanger.
This does not occur in continuous operation. The idea is to supply as much heat to the mixing as is actually lost through the partitions in order to achieve a constant temperature.


The boiler service is annoying - tight, there is nowhere to put your hand in, and during the trainings they show you how to change parts with your back to the room. Of course, this is not a problem for the user, but for the service, but I add more for the service (as in the case of midi).