Verify this installation

[doitmyself]

I'd like some advise regarding the installation of my boiler. Specifically the close coupled tee arangement to hookup the underfloor heating.

If the installers are not familiar with Primary/Secondary piping using closely spaced Tees, there are some rules which they need to follow. The first diagram should explain everything.

A second factor to consider is water temperature. As piped, with the underfloor pair after the radiator pair, the flow temperature to the underfloor pair will vary depending on how much is taken by the rad circuit. So it could vary between, say, 70C and 50C which is reasonable as UF needs a temperature of about 50C, or less. But you have a thermostat which uses weather compensation to determine the flow temperature. So while the flow temperature to the rads may be OK there is a danger that the flow to the UF circuit could be too low. The way to overcome this is to have the radiator and UF circuits in parallel and not in series. They are then both fed the same temperature water. See the second diagram.

 

[doitmyself]

See where the cc tee is on my pic

Sorry, but I can't see a pair of CC tees anywhere. 😕

 

[squishio]

@Brambles Why is it the mixer should be close to the manifold?
As it stands at the moment (not saying its right!) the mixer is in the loft, and the manifold is two floor down.

@doitmyself That is very helpful, thankyou. I'll re-do my diagram to reflect what you've drawn. Out of interest, what is the relevance of the distance between tees? If you're pulling from one and putting it back in the other, what does the distance between them have to do with it?

 

[ShaunCorbs]

Max 4x the dia of the supply pipe eg 22mm 88mm

 

[squishio]

Max 4x the dia of the supply pipe eg 22mm 88mm

I got that bit, but why does that seperation matter? ie why couldnt it be 12" between the tees?
Or am I asking questions that dont need asking 😉

 

[ShaunCorbs]

I got that bit, but why does that seperation matter? ie why couldnt it be 12" between the tees?
Or am I asking questions that dont need asking 😉

Would be too far apart to work efficiently

 

[doitmyself]

what is the relevance of the distance between tees? If you're pulling from one and putting it back in the other, what does the distance between them have to do with it?

It's all to do with the pressure difference between the flow and return ports. This needs to be as small as possible. If it's too big the water may prefer to travel straight past the port, depriving the rads of any flow..

The distance from ports to any bend (or Tee in a parallel system) in the primary circuit is to reduce turbulence in the flow.