Choosing the Right Bathroom Radiator: Parameters, Brands & Dimensions for Tile Renovation

During the renovation of the bathroom and the replacement of tiles, I wanted to replace the radiator with a new one. I have already talked to the cooperative about draining the water, the whole thing will be installed by a friend of mine, a plumber, but I would like to choose a good radiator and buy accessories in advance. The technical conditions provided by the cooperatives do not say anything about the pressure and temperature of the system, but only provide general information, e.g. that there is to be easy access, that the tiles on the floor are to be non-slip, etc. I called the heat allocator service - the number from the letter from the cooperative (in the bathroom there is no divisor) and the guy told me that I can assume what I want, because it is settled on the volume and not the divisor ... And I'm in the spot. In the photo I am enclosing the appearance of the current radiator. Radiator dimensions: 30x150, connections at the top and bottom.



As there are no allocators, I will want to install valves on the radiator (in case of future renovations). And here's a question for you:
1. What radiator can I install in this place? Is the ladder an option?
2. Where to get any data on an existing installation?
3. If I put, for example, a smaller heater, can I pull the tubes higher or lower than the central heating and everything will work as it should?

The apartment is on the 1st floor of a 4-story block.

Why such a tall radiator? after all, the heat always goes up, so the radiators should be relatively low and placed as low as possible, otherwise there will be Saudi Arabia on the ceiling and Akrtyka on the floor. I would suggest a LOWER radiator - then it will be necessary to correct the spacing of the twigs with tubes (elbows) and it should be done in such a way that the height of the lower twig (return) should be left in the current place, and the power sprig should be lowered with fittings so that it fits the new radiator. The valves need to be installed both on the supply branch (it is strange that there is no valve in the photo, which means that the heater could not be turned off during the entire heating season)) and on the return branch (the latter in order to be able to, for example, remove the radiator for bathroom renovation). A ladder radiator can be selected (there are different types of products available). On the supply, I would suggest a thermostatic valve (ordinary valves may leak under the effect of multiple turns).
If the building is a 4-story building, there should not be too high pressure in the installation, but it is better to ask in the technical department of the administration what the maximum working pressures are there (in such a building it would be enough even 2-2.5at., But it may be so that tall buildings are supplied from the same heat exchanger and then the pressure is higher to provide heating also in these tall buildings). Ladder heaters are provided by the manufacturer for a working pressure within 6at (test 9at), and in residential buildings there are no higher pressures (it would have to be a 16-story high-rise building or even higher).
One more thing. A vent must be installed on the new heater.

Mr. Zbigniew, thank you very much for your answer. The radiator that is currently installed has been there since the beginning (90's). The problem is that when I was in the technical department, I was asked to apply for the technical conditions. In the technical conditions issued to me, there are only general statements without specific figures. It only says: "before buying a new radiator, agree its type with the service technician of the company servicing heat feeders", I called and heard that because there is no allocator on the current radiator, and the entire riser is calculated from the cubic capacity, I can assume what I like. I was amused by the statement - perhaps it is not right that an architect should come (I emphasize the architect) and see what a radiator is now and on this basis indicate which one can replace it ... This is how the technical department in my cooperative works.
Is it possible to direct the tubes to the radiator so that they descend inside? Ie won't it affect the efficiency of the system? Lowering the radiator is pointless because there is a washing machine in that corner anyway, which now covers 1/3 of the radiator. Therefore, I wanted to wear something that would heat well and would not "steal" the warmth of the person living above. The fact is that the bathroom is in the middle of the apartment, only one wall (smaller 140x245) touches the outer wall of the building, and due to the fact that it is the only radiator without a divider, the bathroom is left open in winter to heat the hall.

I found such a heater:
ALFA 300 78x30 cm
with a side approach
519W for the parameter 90/70/20
326W for the parameter 75/65/20
* maximum operating pressure 10 bar
* maximum working temperature 95 ° C

according to In my calculations, a 480W radiator is enough for a 4m2 bathroom, will such a radiator be appropriate? Alternatively, how much bigger can I take a radiator to keep me warm in my apartment and not take away other neighbors' heat?

A larger radiator does not have to "steal" the heat from the neighbors, because there is such a thing as a presetting (corrugation). Tubes (supply and return) can "go in", that is, be arranged converging. Actually, the correct arrangement of the twigs should ensure slight slopes, so that the radiator ventilates more easily (then you do not need a vent, but it is always better to give it). This "going inside" should be understood in such a way that the supply branch LOWERS towards the radiator, while the return branch LOWERS towards the radiator (such "going inside" can also be done with elbows). If the bathroom has no window, you don't even need 400W of power. One more thing that I forgot in the previous post. Namely, sometimes you can still find the central heating supply in blocks using the so-called a hydro-elevator (instead of an exchanger) and this system can cause sudden surges of operating pressure reaching several atmospheres. Therefore, in the People's Republic of Poland, panel radiators often broke in the period of severe frost, when the pressure increased rapidly (when supplying exchangers, the pressure is usually constant, usually not more than 6at). Today, hydroelements are not used and in most heat distribution centers they have been replaced by exchangers, although you can still find them somewhere.

I will add one more thing. A dozen or so years ago, at home (I also live in a block of flats), I changed the radiator in my bathroom from a high cast iron (90 cm tip spacing) to a ladder one. I corrected the spacing of the ends with the help of elbows and pipes (steel, sealing with hemp and thread paste). I gave the valve on the return twig. The heater is working properly.

Great, thanks a lot for the advice, I am currently breaking tiles in the bathroom. On Monday, the guy will come to drain the water from the CO, I will ask about the parameters of the installation. If I know something, I will write it