Reverse Circulation when HW On

[woodpeckerx]

Boiler feed - is that the boiler flow?

Yes sorry meant flow.

Is that the pump - pumped return system? Never seen one like that but I'm just a DIYer. Or some sort of filter?

It's a Spirotrap magnetic filter.

A pic showing more of the surroundings would help. If there's room maybe the up and downstairs returns could be commoned some distance away, giving room to tee in the cylinder return before the pump.

To get the downstairs return back to upstream of the cylinder so they can all be combined in the right place would mean chopping out that tee and extending the downstairs 22mm return up through the ceiling and under a bedroom floor. I could do it but I'm not filled with ethusiasm due to the resitricted space and time of year.

Looks like a 45° elbow after Tee 3. Is it possible to change to a 90° and connect to a tee on the pump inlet, with the cylinder return into the tee? Or is what looks like blockwork in the way? Fiddly job and need to remove temporarily the "boiler feed" pipe to do it.

The elbows are all 90s and that's not the pump, this is about 4m away in the kitchen, the pump is in the AC which is up through the ceiling and across a bedroom floor.

There are 3x 22mm running across the floor from the boiler area to the AC where the pump and valves are, boiler flow to pump, return which is already combined in the wrong order and the CH flow from CH valve to the downstairs rads. I can' t see anyway to fix it properly without running a fourth 22mm to get the downstairs return to where it should be.

 

[Daveydub]

What type of check valve is it and are you all thermostatic rad valves?

 

[woodpeckerx]

What type of check valve is it and are you all thermostatic rad valves?

Its a Reliance Valves 15mm single check valve, Toolstation code 76666

Rads have TRV4s with Drayton Autobalance valves.

 

[Daveydub]

With T. Rail off and 1 up rad turned to max.does it still chatter ?

 

[woodpeckerx]

With T. Rail off and 1 up rad turned to max.does it still chatter ?

I'll have to report back on that, its my sons house, the chatter comes and goes with different flows. Initially noticed it with all rads on when the system got hot so maybe as TRVs were shutting down.

 

[Daveydub]

Chatter that you can hear if you put your ear to it or from the bottom of the garden?

 

[woodpeckerx]

Chatter that you can hear if you put your ear to it or from the bottom of the garden?

Enough for it to vibrate around all the upstairs rads so pretty bad. Its a fast chatter, like a buzzing sound.

 

[fixitflav]

The elbows are all 90s

OK, my eyes!

I can' t see anyway to fix it properly without running a fourth 22mm to get the downstairs return to where it should be.

Neither can I, but a thought occurs. If you have TRVs on all or nearly all the rads, that should stop most of the reverse flow when room temperature is above TRV setting. I leave my CH on 24/7, so on that basis the TRVs are either closed or a bit of heat from the HW doesn't matter. Different if you only have the CH on for timed periods.

 

[fixitflav]

Another thought on previous post - if you use a timer, having CH times same as HW would be the solution. Unlikely you'll run out of HW during the off period

 

[Daveydub]

if you use a timer, having CH times same as HW would be the solution.

But not in the summer or when room stat is satisfied.

 

[fixitflav]

But not in the summer or when room stat is satisfied.

With the usual set-up, roomstat in a room without a TRV, other rooms controlled by the TRVs, they will be closed when the roomstat is satisfied. In the summer TRVs will be closed. Maybe not a 100% solution, but saves the hassle of rerouting the cylinder return pipe.
Best if the room without a TRV is a small one with a small rad.

 

[Daveydub]

Maybe not a 100% solution,

Definitely not 100% solution.

 

[fixitflav]

Definitely not 100% solution.

Do you have a better suggestion?

 

[Daveydub]

Do you have a better suggestion?

Do it properly or go the check valve route.

 

[fixitflav]

Do it properly or go the check valve route.

Of course the best answer is to re-route the cylinder return, but the OP naturally would like to avoid that. And he's tried a check valve and it wasn't great.
Unless I'm much mistaken, it would need more than one check valve, perhaps 3 or 4, depending on the pipe layout.