No flow through one circuit ...

[CraigS]

Hi

 

I had a UFH system installed a couple of years back. There are three circuits in the living room and I've just noticed that there is no flow (or very little flow) through one of the circuits. I don't know whether it was like that when it was installed.

 

I've tried a few things

 

a) closed all other flow rate meters on the manifold, fully opened the problem one. I see a very small increase in flow rate, but nothing much.

 

b) connected up the hose pipe to the manifold, opened each circuit in turn to flush any air out. I ran the problem circuit for around 15 min. With mains pressure (about 3 bar) I could get around 2l/m. With mains pressure on the other circuits for the living room I can see around 4l/m and 3l/m.

 

c) I checked the actuator pin on the problem circuit for stickiness, nothing obvious

 

So I'm a little stumped now. I was originally thinking I had some air in the pipe however after running the hose through it for 15 mins I am not so sure.

 

The UFH was retrofitted on an existing concrete floor using MDF boards with channels for the pipes to run through. There is wooden flooring glued on top of that now with no chance / desire to take up given the associated cost.

 

The pressure showing on the manifold was originally around 1.5bar. I upped that to 2 bar to see if it made any difference, seems not. 

 

Any suggestions as to what the problem might be / what I can try next?

 

Many thanks

[RHayes]

Sounds like you have tried most options and with mains pressure flushing through I normally recon to get 5plus litres per minute when flushing a loop.  That is with 17mm pipe mind and i guess you have a 10 or 12mm pipe being an overlay system so 4 may be more realistic.

 

Have you tried removing the flow meter to see if there is annything stuck in there.  If you can disconnect the loop first below the flow meter so that any debris that may be caught in the flow meter doesn't disapear down the loop when you remove the flow meter then I'd advise that.

 

Otherwise not sure what else to suggest.  Perhaps run that one loop by itself with heat and then trace the loop with a FLIR see if you can spot a kink or restriction?  Not that it will help if you don't want to take the floor up but it may provide the answer to the problem.

[CraigS]

Hi there and thanks for quick response. Indeed, it's a 12mm pipe. I haven't taken the flow meter off as yet, will give that a shot tomorrow after disconnecting the loop. I do have a FLIR also so can try that. Will post back, thanks again.

[PeterW]

Is this a Nu-Heat overlay system ..?

 

Mark and disconnect all the loops and then take the manifold off the wall. Strip it down on a bench - take the ends off and all the flow regulators out and then flush it with lots of clean water. If you can get a hose on both ends, flush the loop through with mains water and see if you get a better flow - it may be the manifold. 

[CraigS]

Thanks for the responses. Pleased to report some success.

 

I swapped out the flow meter on the problem circuit for another clean one I had hanging around. (interesting to note there were some bits floating around inside the flow meter gauge after I took it  out and turned it upside down).

 

Connected it all back with, flows (fully open) are now 

circuit 1 (original problem circuit): 1.3l/m

circuit 2: 2.4l/m

circuit 3: 1.5l/m

 

Circuit 1 is certainly much better, and not far off circuit 3 now. I figured thought that 1.3-1.5l/m is low so took a look at my Pump (Grundfos UMP3 FLEX AS 25-75 130). I noticed that I had a green LED and two orange LEDs (out of a posssible four), and after a bit more research it seems it is only running at 50% of its max output. I managed to update the config such that it is running at its max (or so I thought), and this bumped the output of the pump up to three orange LEDs, so 75% of its max.

 

flow rates are now as follows:

circuit 1 (original problem circuit): 1.6l/m

circuit 2: 3l/m

circuit 3: 2.2l/m

 

A big improvement and circuits 3 is probably in the correct range, and circuit 2 a bit high, although flow rate can easily be turned down. Circuit 1 is still a bit low.

 

@PeterW, this is an OMNIE Setup (https://omnie.co.uk/lowboard-15/). I can certainly take the manifold off and flush all of the circuits and manifold separately if we think that will help.

 

Thoughts from here:

 

- i wonder how I can get the pump working at 100%? Apparently the UMP3 Flex is PWM controlled. I am quite handy with electrics too and installed a Heatmiser Neo control system myself. All works wonderfully but there is nothing I came across in the setup that talked about PWM control of the pump (nor for the boiler also). Or maybe there is something that I am just unaware of. In the absence of a PWM signal, the manual says that it runs at maximum, subject to the setting (which I believe I set to 100% in the settings mode), but clearly it is not running at 100% at the moment.

 

- I can take the manifold off and flush everything

 

- will altering the manifold pressure have any effect. It is running a little under 2 bar right now. If I were to increase that to 2.5 bar or 3 bar, would that help? 

 

Thank you all