"Interim" UFH

[Onoff]

The "how to" of this was lost with the demise of eBuild along with a lot of @Nickfromwales input sadly so I'm starting from scratch here.

 

Regular readers will know that the big bathroom refurb is downstairs of the bungalow. I've currently an unconnected  UFH loop within the 100mm concrete slab with 150mm pir + 25mm eps underneath.

 

 

The "tails" of this loop come out under the slab edge and are left deliberately overlength.

 

There's provision for a slab sensor in the lone bit of Pex-Al-Pex shown below:

 

 

The downstairs CH system is an old 3/4" nominal bore system than ran around the perimeter walls. When I redid the bathroom I took out the pipework in the bathroom and "bypassed" it down the centre of the room adjacent to the bathroom.

 

I'm this photo then the white 22mm pipe just under the floor slab is the "bypass". New bathroom is to the right, under the stairs to the left:

 

 

 Another view taken a bit further back. The plan is to dig this floor up and build back up with probably 150mm pir underneath. The downstairs UFH manifold will be bolted to the wall under the stairs. 

 

 

At this moment in time is there a "simple" way I can break into this 22mm pipe and feed the UFH loop to the right without running that loop at the high temperature the downstairs rads run at?

 

Presumably I need some sort of "blending" mechanism? The hot for blending comes from this 22mm pipe but where does the "cold" for blending come from?

 

I do have this bought back when this was first being discussed on eBuild:

 

 

Edited October 13, 2018 by Onoff

[Jeremy Harris]

On ours the "cold" is just the UFH return, which has been cooled by running around the loop.

[Nickfromwales]

5 minutes ago, Onoff said:

The "how to" of this was lost with the demise of eBuild along with a lot of @Nickfromwales input sadly so I'm starting from scratch here.

 

Regular readers will know that the big bathroom refurb is downstairs of the bungalow. I've currently an unconnected  UFH loop within the 100mm concrete slab with 150mm pir + 25mm eps underneath.

 

 

The "tails" of this loop come out under the slab edge and are left deliberately overlength.

 

There's provision for a slab sensor in the lone bit of Pex-Al-Pex shown below:

 

 

The downstairs CH system is an old 3/4" nominal bore system than ran around the perimeter walls. When I redid the bathroom I took out the pipework in the bathroom and "bypassed" it down the centre of the room adjacent to the bathroom.

 

I'm this photo then the white 22mm pipe just under the floor slab is the "bypass". New bathroom is to the right, under the stairs to the left:

 

 

 Another view taken a bit further back. The plan is to dig this floor up and build back up with probably 150mm pir underneath. The downstairs UFH manifold will be bolted to the wall under the stairs. 

 

 

At this moment in time is there a "simple" way I can break into this 22mm pipe and feed the UFH loop to the right without running that loop at the high temperature the downstairs rads run at?

 

Presumably I need some sort of "blending" mechanism? The hot for blending comes from this 22mm pipe but where does the "cold" for blending come from?

 

You’ll need to tap off that single pipe system to get a flow and return. That’ll need blending down and then pumping into the UFH loop. 

[Onoff]

36 minutes ago, Nickfromwales said:

You’ll need to tap off that single pipe system to get a flow and return. That’ll need blending down and then pumping into the UFH loop. 

 

Thanks but I'm not getting it!

 

That white pipe (flow direction is out of the door) comes off the first rad in the system en route to feed the second rad. Pretty damn warm it is too. Now covered with carpet tiles it's level with the floor underneath and people joke that   I've already got the UFH going that strip of floor gets so hot!

 

Surely too hot to provide flow AND return?

 

Looking back on the old photos and I've just had a thought. Flow on this rad is 100% right to left in the picture below:

 

 

Only knowing what I know now doesn't this mean it's pumping the wrong way for max efficiency as in hot should come in at the bottom, radiate it's heat and exit, spent at the top?

[Nickfromwales]

Not always. A lot of high level ( entry ) rads seem to have the TRV up top too which seems daft. I’ve neber stopped to think about it tbh as almost 99% of the single pipe systems I’ve cone across have been taken out for a new flow and return based system. 

[PeterW]

1 hour ago, Onoff said:

Surely too hot to provide flow AND return?

 

Nope...

 

You have a mixer valve on that manifold that will only allow the hot to enter the system when it needs it. So as @JSHarris says, the "cold" is the loops coming back from the floor as they will be lower temp than the valve to the point that the valve meets it set temp and the flow is purely within the loops.

 

Is that mixer second hand as it looks like its missing a few bits too...

[Nickfromwales]

@PeterW

Ive got a used 8 port manifold I’ve promised to Clive. It’s got a pump and thermo head / capillary wire doodah so will blend down low and reliably ?   

[Onoff]

7 minutes ago, PeterW said:

 

Nope...

 

You have a mixer valve on that manifold that will only allow the hot to enter the system when it needs it. So as @JSHarris says, the "cold" is the loops coming back from the floor as they will be lower temp than the valve to the point that the valve meets it set temp and the flow is purely within the loops.

 

Is that mixer second hand as it looks like its missing a few bits too...

 

2nd hand yep. One Nick pointed me at on eBay I think way back. Unused old stock as in it's never had water running through it.