Defro Duo Uni 35kW Boiler: Choosing Inflow Pipe Diameter for 6-8 Circuit Manifolds in 240m² Home

niedzwiadek204 wrote:

Hello!
I am building a central heating and hot water system at home, I have a problem with choosing the diameter of the inflow pipes as for the manifolds, the manifold will produce about 6-8 circuits for radiators without underfloor heating, there will be 3 manifolds throughout the house, the pipes connecting the manifold with radiators are 20mm PEX
A one-story house 240m ^ 2, including two rooms in the attic, Defro Duo Uni boiler 35kW

I will try to advise you, first of all, why such a thick pipe for radiators, if each radiator separately from the manifold, a diameter of 16-18 mm is enough. For risers, if steel is one inch or copper 28mm, I have been doing this for many years and my thighs do not complain.

CEZAR67 wrote:

I will try to advise you on something, first of all, why such a thick pipe for radiators, if each radiator separately from the manifold, a diameter of 16-18 mm is enough. For risers, if steel is one inch or copper 28mm, I have been doing this for many years and my thighs do not complain.

First, what risers if a one-story building? 28 risers to two rooms in the attic?

Second: why 28 ???? I can understand it within the boiler, but 28 risers? Complete nonsense.


Back to the topic. In Sweden, no construction manager would endorse an installation that you picked out for yourself. Well, but when you ask, I will answer:
- 16mm tubes are more than enough from the manifold to the individual radiators
-to individual manifolds, I would not give pex for a solid fuel boiler, but if you insist and do not care about safety, give the tube 25.
- copper 28 within the boiler, unless you want to carve steel, it is usually 1 1/4 "..

The diameters depend on the power of the installation.
The scheme is acceptable in total - I allowed myself to make a few corrections.
Most of them are only for the better readability of this diagram.
In this diagram, you have a four-way valve, don't regret the diameter here. (Generally the diameter as the boiler connection, but you can slightly reduce it because such large four-way valves are quite expensive)
On the other hand, the diameter of the manifolds depends on the power that this installation is to give to the radiators.
The diameter of the connections is also recommended for the container. (Of course, it can be slightly reduced, but also in moderation)
With this pex ?16 it is true, but you have to be aware that really large radiators can have problems.

OKAY
It would be good if you gave the power of the radiators and not their dimensions.
It will just be faster to calculate the diameters. (I will not have to search the net)

So:
the first splitter is 11209 W.
the second is 7921 W. and the third is 11059 W.
total 30,189 W. and flow on main branch needs approx. 1300 l / ha. 25 mm pipe (inside diameter) allows flow of approx. 1500 to 1600 l / h at 0.8 m / s.
You have no other option than 28mm copper.
Obviously those few heaters that are around 2000W. you need to connect with a "pex" pipe ?20 mm because ?16 allows about 1900 W.

The reservoir has room for the temperature sensor (in your case, this hole is in the center)
The CO sensor is mounted on the flow.
Optionally, there is a weather sensor and a room thermostat.
The sensors are "clip-on" or as "immersion probes" - but this largely depends on the manufacturer of the controller.
For applications in small domestic boiler houses, the former are rather used.
In the case of poorly "equipped" controllers, differential thermostats are used to avoid cooling down the hot water.
Well ... but here you would have to write something about the driver you have.
Usually, in the driver documentation there is an exemplary connection diagram.
If, however, it was not - ask on the forum.
Colleagues will probably tell you.

ps. Temp. DHW is 55 ° C, but you can set it in your home as you like.
Temp. CO depends on the outside temperature and the preferences of the household.
The four-way valve allows you to set the temperature on the indoor installation
and that's why it is so "cool" that it allows you to maintain a different temperature on the boiler and a different temperature on the internal installation and the controller should "keep an eye on" all this.

Yes, for a full house, it's better not to.
the pump should also be "counted" (there is a formula for calculating the pump capacity). Best check by trial and error.
The ideal pump is with smooth speed control, but it can also be set normally.
Probably it will be in the middle range.
Avoid maximum speed - why should you listen to the noise of the installation at night?

niedzwiadek204 wrote:

Where to install diaphragm expansion vessels? on the water inlet to the tank? on the return what and in what position they should be

Not really "qumam" about this "CO" return - the installation is, after all, an open system, so the vessel at the top is suitable for installation.
You can only put (and should) the vessel in front of the "boiler". according to posted picture.
The position will arise by itself, depending on the vessel used (most often it is hung from the bottom - this way the appropriate part is flooded with water and you do not have to worry that there is air in this undesirable part)

niedzwiadek204 wrote:

(...) and in what position they should be

We read the manual ...

Hello

I have one question about the pump and gravity valve system, shouldn't it be on the return? Apparently this increases the service life.

PS

For laymen, a legend of symbols would be useful

niedzwiadek204 wrote:

Which means that the heater's power is, for example, 2000W at a temperature of 75/65/20

This means that with a supply temperature equal to Tz = 75 * C and a return Tp = 65 * C, your radiator achieves a power of Q = 2000W. These are the so-called design temperatures assumed when designing the central heating system and 20 * C - room temperature.
PS.
As for the diagram, I would consider the EA type anti-contamination valve at least as shown in the diagram below

If you want to have the regulation, it is for the BA boiler room, but it is quite a cost (the 1/2 "BA2760 valve from Danfos is about PLN 900). However, if you want, you can install an EA valve (the cost of such a valve also from Danfos is max 40 PLN).

niedzwiadek204 wrote:

and I would like to have such power at 75/5/26, for example.

How do you want to achieve these parameters?

So.