Hello, If the flow pipe is hot and the return is not then it sounds as if water is not getting to the radiator itself, could you check the following:

Were the TRV heads put on correctly? It might be worth taking one off, opening it fully to five then replacing. If the head was put on incorrectly to begin with it will hinder water flow, the pin on the valve may not be making contact with the plunger in the head. This is a fairly common occurrence when people have not put the heads on correctly.

Secondly, was the system balanced correctly when the Strada’s were put on to the heating system? Also, it might be worth checking that the flow and return were piped up correctly to the valves as they are not bi-directional.

Hope this helps

Kind regards

Jaga Heating Products (UK) Ltd.

The water to the radiators is hot for about 30cm. Then it rapidly feels cold within 15cm . The rest of the pipes in the radiator are cold. It is exact;y the same for all three radiators. These radiators worked fine on the old boiler so it isn't the valves as only the boiler was replaced - nothing else was touched. Is this a balancing issue?

Hello, please see comments below:

1. There could be a blockage that has been caused by the change of the boiler. When doing any pipework the full system must be flushed through. This was probably done but it might be worth checking.
2. Balancing can be an issue. It might be that the pump internal to the new boiler is different to the old pump so water is flowing differently. Easy fix might be to turn the pump up.

Hope that the above comments help.

Kind regards.

Jaga Heating Products (UK) Ltd.