UFH no flow normal?

[EdS]

Hi,

 

We have recently had wet UFH installed by a professional - three loops, but acting as a single zone with a single thermometer.  We noticed that the flow meters showed no flow and despite the thermostat being set to 30'C, the floor didn't seem to heat evenly or as hot as we would have expected. 

 

Apologies I have little plumbing experience however started researching and I have some concerns over how it's been plumbed in.  I had understood that a UFH manifest should have a flow block and a return block.  I presume water should be pumped from the flow block (where the flow meters are) through the UFH underfloor piping and back to the return block where the actuators are.  Therefore I assume that normally the pipes connected to the flow block should be warmer than the return pipes.

 

In our set up, we normally see the opposite - the return end of the pipes get hot first and stay hotter than the flow end of the pipes. Also weirdly, if we turn the mixer thermostat to as hot as it will go, and then turn the pump to minimum, we see flow registered.  If we increase the pump speed, the flow registered by. the flow meters decreases

 

So it feels to me that something or several things are reversed and that we're actually pumping water the wrong way round (would flow meters register a reverse flow?).  In other google images of similar setups, I see the output of the mixer plumbed into the flow block, whereas ours is plumbed into the pump which is then plumbed into the return block. 

 

I would be really grateful if someone could look at the attached photos and let me know your thoughts - am I right that the flow is reversed and is there any reason why the plumber would have done this (he's not replying to our messages at the moment which also concerns me!).

 

Thanks in advance

[ProDave]

That looks to be the same manifold system as I have, but it is all mounted upside down compared to mine

 

 

But because yours is upside down, it means your flow and return are backwards, i.e. the manifold leg that comes from the pump is the flow, and the manifold leg that comes from the blending valve is the return.

 

Swap your top and bottom manifold legs over and that will put the actuators at the top and the flow meters at the bottom and it should then work.

 

 

[EdS]

Thanks for your quick response Dave - do you think the pump may also need to swap direction given the weird behaviour I see when I switch the mixer all the way to hot and change the fan speed. It feels like the flow from the hot water is “fighting” against the pump rather than aligning with it.

 

I have looked on the pump chassis and can’t see a flow arrow unfortunately :(

[dpmiller]

the "middle bit" at the back of the pump is the inlet.

[JFDIY]

The flow meters could actually be showing more flow at the lower pump speed because they are being blown shut with higher pump speed.

 

I agree with the suggestion already made, swap top and bottom manifolds, so actuators are at top and flow meters at the bottom and try it again.

 

If the manifolds are the same, it might be less work to swap the flowmeters individually and valves that actuators couple up to. That way you could try one and then see if there is s difference in flow being registered.

 

[JFDIY]

Just had another look and also the main supply and return appear to be swapped compared to @ProDave's set-up. His hot supply in is to the elbow on the blending valve, yours is not if the colour code of the handles is to be believed.

 

So when the blending unit tries to add heat it will cool and vice-versa.

 

Hence the weird things you've seen going on.

Edited August 8, 2020 by JFDIY