Underfloor heating, cold return pipe

22 Jun 2012
Reaction score
United Kingdom
I have a Valiant EcoTec Plus 824 R1 combi boiler, attached to a Uponor underfloor heating system.

There are 4 circuits, each 75m, 2 per thermostat.

The thermostats seem to control the actuators fine, and i can close off onc circuit by turning down one stat.

The boiler generates hot water down the CH flow pipe and i can feel the heat being distrubuted through the manifold to the active circuits under the floor.

However, the rooms never seem to heat up and the CH return pipe remains cold.

The boiler shows the pump running symbol, but enters into ani cycling mode regularly.

The flow guages on the manifold never move.

A plumber had a 10 min look and has told me that its installed wrong and the the pump in the combi boiler has no chance of pushing the water around the system. They told me that I would need to add a seperate pump and valve onto the manifold and that I'm looking at a bill of over £2k to get it done.

Is this true, or should the boiler be able to power the underfloor heating? Why would the return remain cold and the flor guages stay at 0?


Sponsored Links
Could you explain the history of this? Surely it did not just become like this overnight without your knowledge!

He is probably right but has quoted a rather high price for sorting it out.

Could be he was hedging his bets that there may be further problem as well.

I bought this place 6 months ago. The people in the other flats said the the previous owner had complained about the heating being poor before.

It seems to show an pump overrun status quite often. I also noticed that the pressure on the guage was at 0, so i opened the valved to let more water into the system and that has now gone up, but still no heat in the return pipe.

Is it possible there is air in the system?

if i put my ear to the return valve, it sounds a little more hollow, and tapping them gives a slightly different tone. could it be that there is not water travelling around the whole system?

My vaillant manual mentions a test program for bleeding (P.0) - what does this do?

Thanks for all the advice.
Sponsored Links
Thats just an engineers way to run the boiler while removing air from rads etc.

Its impossible to sensibly guess whats wrong with your system without seeing it.

I expect you are going to need to call a professional.

Did the vendor admit the heating system was not working properly?

Sounds like false promotion!


DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local