Mats Bengtsson

Exchanging radiators in the heating system

Mats Bengtsson mib over the years

Exchanging radiators is easy but information about it is hard to find

Exchanging the radiators turned out to be an interesting operation, there was very little to find around this in ordinary shops. Those knowing about this kind of work live by doing the work for others, very few of them live by selling the parts to do it your self people.

Luckily, a lot has changed in the design of radiators, so a new radiator with double efficency in the heat transfer will not be much bigger than the old radiator. In fact, the measurements of height and length mostly stayed the same, but the thickness increased a bit. This means that the new radiators fit quite well in the house, although changes needed to be made to both piping and wall mounting in order to get them connected.

The effect of the exchange when completed became a huge success, the rooms that previously could not be heated long enough from the heat pump could with the new radiators keep the heat for a longer part of the year. Instead, as expected, other rooms became the rooms that were the first to lose the heat and demand the additional energy from the electrical heater.

Thus we exchanged radiators in the next set of rooms that could not keep the heat up using only the heat pump. This was in fact three rooms (living room, kitchen and cellar) but we calculated that when changing in the living room and in the cellar (which is directly below the kitchen), we would get more heat in the kitchen since the cellar would no longer cool down the kitchen through the kitchen floor, which is in fact the cellar roof. This turned out to be correct, and after these two changes there is no single room that has a distinctively bigger problem keeping the heat than any other room.

Previously the house could be heated with the heat pump alone down to about 11 degreees Celcius. Now the heat pump is sufficient for the whole house down to 5 degrees Celcicus. This has extended the part of the year where the heat pump is sufficient quite a lot.

Reuse and addition of radiators

Currently, we have bought 4 new radiators which have been placed in the house in the rooms where an exchange were needed the most. The old radiators we took down during this operation has been reused. Three of them now supply heat in our basement, which was heated by a single small radiator. Through this change, we also changed the heating of the cellar to follow good practice (radiators by the windows instead of one single radiator in the center of the room) and we also now have a radiator in the washing room in the cellar.Fastening Radiator Cupper Pipe

Fastening the new radiators onto the old pipes means in our case a need to fasten a cupper pipe onto the old iron pipe. First the old pipe is cut off at a suitable height (the more that is left of the old pipe, the safer the threading job). Then the old pipe is threaded where it was cut. Finally a converter, seen in the bottom of the left picture, is screwn onto the threaded old pipe. Then a new cupper pipe is bent and sawn off and inserted into the converter.

The house is from 1958 and the standard size for the pipes then was 3/8 inch (R10). The cupper pipe is 12 mm. So the converter in the picture both changes from inch-measures to mm measures, as well as from metall pipes to cupper pipes.

The radiator, as seen top left in the same picture, has a connection of 1/2 inch (G15). That gives quite thick pipes and parts, which was not needed. Thus, the first connection to the radiator is actually a converter, converting from G15 to G10. Then comes a 3/8 inch connector to the flow control, which itself delivers G10, which is finally converted to a 12 mm cupper pipe through a R10/12 mm converter (the extra screw seen just above the cupper pipe).

The connection from the radiator to the flow control is conical, all other needs pipe thread of some kind in order not to leak.

If the height and bend of the new cupper pipe (on the previous picture the pipe with chrome on it) is done optimal, then nothing has to be done with the upper connection point, more than to fasten the new radiator instead of the old one. If the heights do not fit, then also the upper pipe must be sawn off and extended with a piece of cupper pipe.

The principal is the same as for above, first a converter converting the radiators G15 to G10, and then a connection to the thermostat, which itself contains a conversion to a 12 mm pipe.

Removed Radiator

Adding new radiators in this way was extending what we had to be able to do a little, but not much. And one old radiator was used to replace a broken radiator in my parents home.

The added radiators in the basement provides both a possibility to dry washed items, as well as provides a better temperature in the basement, meaning that the basement roof which also is the first floors floor, has a more convenient temeperature. Probably the new radiators which gives us a warmer cellar actually increase the energy needed in the house since they now heat a part of the house that was previously quite cold, but they do at the same time add to the comfort level.

We were "lucky" in the way that one of the radiators we bought were ill manufactured, and we got a new one on warranty. The ill manufactured radiator is to be used to replace yet another radiator in the house (in the entrance hall), after which we believe that there is very little left to gain by replacing more radiators.

Part description for upper connection to radiator:

  • G15 to G10 converter
  • Radiator to Thermostat bent pipe
  • Thermostat
  • R10 threaded pipe

Part description for lower connection to radiator:

  • G15 to G10 converter
  • Flow control using G10
  • G10 to 12 mm converter
  • 12 mm cupper pipe
  • 12 mm to R10 converter
  • R10 threaded pipe



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