The last tee

[Damon Apple]

Help:

I am an apprentice so was dissapointed at college when my tutor belittled me in front of the entire class rather than explain what id done wrong..

I drew a y plan including cylinder flow and returns yet he said i was causing reverse circulation because of the location of my last tee position( grumbled something about HW).....I did not understand and was not explained how to rectify the fault....

Can anybody explain this in simple detail please

 

[quality]

Possibly referring to the last tee in the return line from the indirect cylinder return connection

 

[brightcrow]

yeah no doubt about it, all heating returns need to be commoned (joined) before the last tee where hot water is joined. There is much debate about the orientation of that Tee but path of least resistance works for me.

 

[Damon Apple]

I am conufused.. all i had was flow into then return out of cylinder and all my heating returns were on the pipe return back to the boiler......whats the HW return...surely the HW just goes down the sink...sorry but i am an apprentice...

 

[brightcrow]

No worries. so there are four connections to indirect cylinder (generally!!) Cold water feed from cold water tank, Hot water draw off to taps/outlets, heating circuit flow connection and heating circuit return.

In this instance, the Heating circuit return should join the last tee on the return to the boiler in your drawing.

Hope this helps but some research on indirect cylinders may be more useful to you.

 

[tamz]

Here are a couple of drawings to explain it a bit.

This drawing is piped correctly and the arrows show where the water would flow when on for hot water only


On heating only the water would flow like this

If you put the tee in the wrong place as in this drawing, the water would flow backwards through the nearest rad(s) and they would heat up (back heat).

How far it travels and how many rads would "back heat" depends on the distances and resistance.
The water will always flow in the path of least resistance.

 

[Simon F]

Not forgetting the bypass, this could well be the last tee.

 

[midge]

Damon, its never nice to be shown up like that, but I bet in all the years to come you won't get caught out by installing a system incorrectly. Take it on the chin and learn from it.

I've lost count of how many systems I have attended over the years where the rads get warm in the summer! Drawings of systems on paper bear little resemblance to peoples houses but once you've a picture in your minds eye of what to look out for it gets easier.

 

[Gray0689]

Or it could be inbuilt into boiler

 

[Mike Jackson]

I've lost count of the number of jobs that I've been to that have been reported as a faulty 3 port valve because the rads get hot in the summer. I think I've had a couple in 28 years where it was a faulty valve, most of the time it's an incorrect cylinder return. The favourite one is where the boiler has been relocated into the airing cupboard and the cylinder and heating returns flow into either end of a tee with the return to the boiler in the centre. It just screams reverse circulation to me.

The best one I had was where a system had been re plumbed because the pipes under the concrete floor had burst. The cylinder return was connected to the return furthest from the boiler. This was reported as a faulty 3 port and I had to run a complete new return from the cylinder back to the boiler.