Flow & Return - Both FLOWING. What Have I Done Wrong??

[3500P5BV8]

Have got a conventional vented boiler, mid pos. valve, cylinder etc in a large cupboard on the top floor of my house. It feeds DHW + 7 radiators on the same floor. There are no rads. downstairs.

Anyway, wife was nagging as kitchen downstairs was cold. I put a Myson Kickspace plinth heater under kitchen cabinets.

To feed this, I tee'd off from the 22mm flow and return pipes with 15mm speedfit pipes, approx 2 feet from the boiler, and fed the 2 pipes down to the kitchen.

Refilled systems,bled everything, and original rads upstairs fine, but nothing from plinth heater. To investigate, I turned off the isolation valves at the end of the two pipes where they go into the back of the plinth heater, and detached the pipes. With the heating on, I opened each of these isolation valves, and I get water flowing from both of them!!! (before you ask, I definitely have tee'd one pipe to flow, and one to retun near boiler)

Any ideas?

 

[Bahco]

I get water flowing from both of them!!

Did you expect only one side to flow out?

Are the valves open on your new heater?

 

[cross thread]

you need to tee them off the flow and return on the rad circuit .if you dont you will upset the way it works

 

[Bahco]

I tee'd off from the 22mm flow and return pipes with 15mm speedfit pipes, approx 2 feet from the boiler,

Just spotted it. You need to tee off the F & R AFTER the motorised valve.

 

[mark.neale]

hj

 

[3500P5BV8]

Thanks for the replies.

I need to clarify a few things;

BAHCO - When I say flows from the 2 pipes, I mean pumped under pressure, and yes I have tee'd after the mid pos. valve. I have teed the two 22mm pipes under the floor in boiler cupboard, approx 2 feet from boiler, valve, pump etc, etc.

GORDONGAS, are you saying that I have tee'd too close to boiler and mid pos valve etc?

 

[Bahco]

Look in the FAQs post 8

 

[scatmanjohn]

Have you bled it?

 

[namsag]

Bet they are both of the flow , one of heating flow after the motorised valve other off main boiler flow

 

[3500P5BV8]

Yes, have bled the plinth heater via bleed screw on unit.

No, I haven't Tee'd into the flow twice, either side of the Motorised valve.

It seems that as all of the water in the heating circuit returns to the boiler via return pipe, it pushes water down the tee instead of drawing it out from the plinth heater. It seems that the flow of returning water overwelmes the return tee from the plinth heater, forcing water down it.

I'm confused??

 

[<DAZ>]

Either side of MV is flows im afraid.

 

[scatmanjohn]

What happens if you turn every other rad off apart from the plinth heater?

owt or nowt?

 

[doitall]

A really clever man would connect the two pipes together

You have used full flow valves and not cheap ballofix type isolating valves