connection of the condensing furnace to the old installation with a plate heat e

I intend to connect a Junkers cerapur midi condensing oven to the old installation. Currently, the system is operated by a coal-fired furnace with an Elka-type gas furnace, a system without control, circulation forced by a circulation pump mounted on the return. I would like to interfere as little as possible with the old water composition that works well, so I want to leave the circulation pump on the return. I want to connect a gas oven with a sondex sl34-50tl-bb exchanger to 50 plates. Is the layout correct, if not what changes should be made.

jorgus1j wrote:

I intend to connect a Junkers cerapur midi condensing oven to the old installation. Currently, the system is operated by a coal-fired furnace with an Elka-type gas furnace, a system without control, circulation forced by a circulation pump mounted on the return. I would like to interfere as little as possible with the old water composition that works well, so I want to leave the circulation pump on the return. I want to connect a gas oven with a sondex sl34-50tl-bb exchanger to 50 plates. Is the layout correct, if not what changes should be made?

No. Differential valve not in place.

Something wrong with your existing layout what. A differential valve on the supply and a pump on the return are a bad solution. The differential valve does nothing in your installation.
Together with an incorrectly located differential valve, there is an error in connecting the overflow vessel. Valves, pumps and other fittings are not installed on the safety pipe.

First, think about how to correct these errors.

Connecting the heat exchanger to the heating system with another boiler also requires control. It is necessary to separate the work of a coal and gas boiler. Typically, the output from the gas boiler to the room regulator is used. If the temperature in the coal boiler is higher than 45'C, the gas boiler turns off.

Now you just need to think about the installations.
The gas boiler has its own pump and it will work with the exchanger, and you need to install a non-return valve.
A coal-fired boiler requires its pump also with a non-return valve. If the coal boiler goes out, the pump stops working. This prevents the gas boiler from heating the extinguished coal-fired boiler.
The last circuit is heating. next pump.

Finally, it is necessary to solve the work of the coal-fired boiler in the gravitational cycle, if the pumps stop and the boiler is hot.

To all this, you need to attach an overflow vessel to protect the coal boiler and the heating system.

Thank you for the tips, now a few words of explanation, the differential valve does not allow the water heated by the gas stove to heat the coal stove. The return pump has been physically operating for ten years, supporting the operation of both the coal and electric boilers, in this system the water heated by the coal furnace passed through the armored electric heater, both furnaces operated in one open system, however, in manual without automatics. The non-return valve is mounted on the flow coming from the exchanger. The furnace will be equipped with a temperature sensor, probably an ordinary pipe thermostat, which will be connected to the automatics of the gas furnace. Immediately after publishing the diagram, I corrected it because I can move the pump from the return to the riser without any problems and thus the expenditure of funds, and then it should be in accordance with the art in the event of a power outage, a coal furnace can operate on gravity.

Sorry, but I have to bark a little bit.

acc. your schematic, this installation will not work properly. The pump, although turned off, will still flow through it .... So the gas boiler heats the radiators and the extinguished coal boiler.

I've written before... First, give me an idea to convert your existing installation to work SAFE. A badly connected coal boiler is a heating bomb. Yes, according to your scheme.

For inspiration, I advise you to ask uncle google how to connect a fireplace with a water jacket to the heating system.

I recommend the first lines of the Elektroda forum "heating systems"
https://www.elektroda.pl/rtvforum/topic1900517.html

Thank you for the so-called barking, originally I had a non-return valve placed behind the coal boiler pump, but the installer who watched the diagram said that it is unnecessary because hot water will penetrate where there are lower resistances and it is always an additional resistance for the pump, it can be assumed at a low cost. When it comes to the so-called bomb, I will not agree, it is an open system, not a closed one, so when the water boils in the boiler, it simply gurgles in the compensating vessel (and this has happened many times in practice) - even if the differential valve sticks, the pressure can expand back if by some miracle a 2'' pipe got stuck here, it is an automt safety expansion valve

I would do this:



The idea of operation is simple.
1. Coal boiler.
The boiler pump turns on only when the stove reaches 45'C. The 3D thermostatic valve separates the boiler and radiator circuits. It opens only when the water in the short circuit of the boiler reaches the valve opening temperature, e.g. 45'C.
The advantage of this solution are two functions. One is to protect the boiler return temperature and the other is to cut off the boiler circuit after the boiler has cooled down.
2. Gas boiler.
Starting the gas boiler also turns on the heating circuit pump. Of course, I assume that the gas boiler is equipped with a pump and a safety group ...
Starting the gas boiler can be controlled by plugging into the room thermostat output and setting the boiler accordingly. The room thermostat is an ON OFF contact and there is no problem to use a relay, e.g. from the boiler pump.
The gas boiler will not ignite earlier until the coal boiler cools down and the 3D valve cuts off the circuit.

In the event of a failure, the pumps stop. Gas boiler too. If such a situation occurs, the differential valve at the boiler will open the gravitational circuit to the radiators. If the installation is done correctly (pipe diameters, radiators, slopes, radiator valves with increased flow), the system will work. It doesn't have to be the entire installation. It is enough to prepare one riser for gravity, where there are the most radiators.
So, if a failure occurs while burning in a coal-fired boiler and it is solidly fired up, there will be no problem with boiling the boiler.

The circuit of the heat exchanger and gas boiler, if the boiler is not equipped with a non-return valve, it should be used. We will eliminate the risk of heating the boiler by gravity.

I like the idea and thus the scheme itself, and now a small nail from which you should start at the lowest possible cost to modify the existing installation, which is greatly simplified in the attached diagram. In previous diagrams, I moved the pump sections to the riser because it would be too much effort to install a differential valve on the return.

In practice, your installation worked... The fact that with the old type gas boiler and the differential valve cut off the coal boiler circuit when the gas boiler switched on the pump.

If the installation has worked so far, it will continue to work. Instead of the old gas boiler, you climb the exchanger with the new gas boiler, add the pump and it will be as before (your first diagram + connection error of the coal boiler pump). The installation will work.

I do not approve of such a solution, because the coal boiler is connected to the overflow vessel through a differential valve. The next thing is the gravitational effect of the installation. It should work automatically if the pumps are turned off and not after the user has moved the valves on the pump.
The differential valve is not applicable as a check valve... There is no spring and miracles in such a valve. There is only an empty ball. Gravity does the rest. The ball "floats" in the housing and opens the flow to the action of gravity. And the pressure of the pump "pushes" the ball to the flange and closes the flow in the valve.
Such valves are not 100% tight and also wear out.

So your installation has three serious errors. Of course, you are the user and you must be aware of the danger that these errors can have in the consequences.


You write that the differential valve "technically" cannot be mounted on the return to the coal boiler. So there is a pump and differential system on the supply and adding a new pipe from the boiler supply to the overflow vessel.
Would such an operation be possible?

And there is one more option. You cut off the heating system from the overflow vessel and connect a gas boiler to it. You create installations with a closed system. On the other hand, you connect a coal-fired boiler to the installation through a heat exchanger and create an open boiler system. The overflow vessel can then be in the boiler room. There will be no gravity, but if the cauldron boils, nothing will happen to it, because it will be protected.

You can think over the overflow pipe, I also think that in this situation it will be best to move the pump to the riser and fix the error by adding a check valve above the pump vertically. The idea of connecting the boiler to the exchanger is out of the question - it would be a sin to give up gravity when it is efficient and the devil is awake. As for the differential, so far it has effectively cut off the water from the gas wheel, the pipe under it did not even get very warm and the empty ball inside weighs a bit. One more question, which of the check valves put less resistance with a plug or a flap valve

Disc and spring check valves have the greatest resistance. The advantage, however, is that the mounting position is arbitrary and they seal well.

The smallest flow resistance is provided by flap valves without a spring. The only problem is the installation method. There is no problem on the horizontal section of the pipe, but with the riser, care must be taken that the flow direction of the media is upwards.
In turn, swing check valves with a spring can be mounted horizontally and vertically.

I have already seen a flap valve without a spring installed with the pump in the horizontal section of the return from the installation to the coal boiler instead of the differential valve.
The decision to install the valve was made when there was a problem with the operation of the pump with an electronic regulator. The differential valve simply did not close when the pump "slowed down".

The user praised the use of the installation. The same installer who installed the flap valve also replaced the leaking radiator valves with thermostatic valves with increased flow. The owner states that the installation works by gravity and does not even turn on the pump for autumn burnout...

The boiler room was mastered hydraulically, only the problem of controlling the furnaces remained. To switch on the central heating furnace pump, I chose the control with a pipe sensor, a small bonus is the current temperature of the furnace. I chose the Auraton 2030 wireless controller to control the Junkers Cerapur Midi gas stove. Now the key question is how to connect the above-mentioned controllers to the furnace and pumps so that when, for example, the temperature on the central heating furnace drops below 40 degrees, the gas furnace will turn on, of course, when the temperature in the rooms drops below the temperature set on the regulator. I know that I need to use a relay, only what kind and how to connect it to the system.

At the outlet (roses) from the coal boiler, install an adjustable contact thermostat.
Connect Auraton through its contacts.
When the thermostat sees a low temperature at the outlet from the coal boiler, it will short the contacts through which Auraton is connected, and then it will take over the function of controlling the gas boiler.

best regards

Thank you for the hint, but it's probably a bit too simple, there are two more pumps on the way. I posted a list of photos, maybe you can combine the elements so that they harmonize with each other. Regards

The system is already working, unfortunately, I had to use a thermoregulator for each of the pumps because the jumkers cerapur midi stove does not have an additional input to connect the pump and the service technician did not even want to agree to switching it on via a relay. However, there was a small but significant problem, when switching on any of the pumps, there is a dull knock coming from the differential valve - of course, the knock is stronger when the pump is operating at 3rd gear and adequately weaker at lower gears.. (the valve is of the old type, it is about 15 years old) Previously, this was not a problem because the pump was on the return and the valve only cut off the water from the gas furnace so that it did not feed the coal boiler. In this situation, I have a question whether changing the valve to a new one, e.g. 1 1/2 inch because I have one, will help or maybe use a check valve with a mushroom instead of a differential valve.

The system has been working for the third month at the beginning on a coal boiler, now the third month on gas, unfortunately, the black vision contained in one of the posts has proven itself. The differential valve is not 100% tight and in this way the junkers warm the junkie. In addition, the knocking of the differential valve is not very comfortable. I temporarily closed the valve on the return at the coal stove, which is not used, and in this way, of course, I temporarily eliminated the heating of the garbage by the gas and the knocking of the differential valve. In the near future I will have to face the replacement of the differential valve with a check valve, the easiest way would be to use a 2 "spring check valve, however, I am thinking of removing the horizontal section and installing a check valve - what do you think?

Wouldn't it be better to move the radiators to a closed circuit (to a gas one) and there would be only an exchanger in the open circuit of coal?

exor wrote:

Wouldn't it be better to move the radiators to a closed circuit (to a gas one) and there would be only an exchanger in the open circuit of coal?

After 6 years, you reheat such an old cutlet?
For what purpose?

I'm bumping this because I'm interested in this topic.

I kindly welcome Mr. Installers and Specialists in heating systems.
I am also very interested in this topic, because the anti-smog law is just around the corner and enforces ecological combustion of fuels.
Well, as of today, I heat my house with a cast-iron camino limited to a power of about 10KW (after thermomodernization). Installation on thick pipes, works great on gravity without any booster pump together with the CWU-140l exchanger.
I had some ideas for reworking either a completely new one or a closed system (on 2 risers you have to cut pipes with radiators at the top, because they are unused, and on one vent), but I decided to leave the old installation with the current cast iron
(I will thank you for the surcharge, the condition of which is the removal of Cinderella) and I am completing a single-function gas stove with a 100-120l hot water tank through a heat exchanger.
I have an eye on this lady - Buderus logamax plus gb122i-15 th, (my cousin only installed it directly in the system because it has a closed installation with a 100 tank, probably made by Galmet).
Using the resources of the forum, I made a simple diagram of connecting the gas furnace to the existing installation through the exchanger.
I do not plan any larger controllers, only controlling the gas boiler to achieve the set temperature in the house and controlling the P2 pump when switching on the gas stove.
A 3D valve will be used to shut off the coal boiler, which currently either distributes water from the boiler to radiators, a hot water exchanger
and secures the return temperature of the water to the boiler by mixing it, for the summer until the central heating installation is closed and the hot water tank can be heated with the furnace itself.