can't get new radiator to work

[izzyeckerslike]

I recently added a radiator in our small front room, the boiler is on the other side of the wall in the veranda & the main flow & return pipes go up the wall & into the loft but nowhere convenient to run pipes down to the new radiator.
I decided to connect the pipes from the radiator thru the wall directly to the 22mm flow & return pipes, I connected them via a 22mm -15mm tees 2ft above the boiler as this appeared the easy option,lol

However I can't seem to get it to circulate thru the radiator properly, the 15mm return pipe from the rad gets hot rather than the flow & it seems that the return is pushing rather than pulling out & thus pulling in hot from the boiler flow pipe, the 15mm flow to the rad is lukewarm at most.

Where have I gone wrong ? the 15mm pipes to the rad are about 2mtrs long

 

[superdupergasman]

Fully blead of air, rad valves fully open and not restricted??

 

[izzyeckerslike]

Fully blead of air, rad valves fully open and not restricted??

Yes, everything is as it should be, no air in the rad. I'm wondering if it's because it's connected too near the boiler?

 

[yerino]

1) Try turning off all your other radiators, with your heating on and see if the rad then gets hot (it might just be a balancing problem.)

If not...

2) Turn off both the valves to the rad and drain just the rad itself using a small dish.. then open up the valves and see if you have actually got a decent flow rate of water getting to the rad.

Post your findings and we'll go from there.

 

[jas05]

you will need to take the flow for the rad after the pump for
it to circulate assuming it is a conventional boiler you have.

 

[izzyeckerslike]

you will need to take the flow for the rad after the pump for
it to circulate assuming it is a conventional boiler you have.

The flow to the rad is just above the boiler as shown in the picture, the pump is in the loft, it's a Myson Marathon boiler, the pipes go down & then 1.5 mtrs to the left & thru the wall to the radiator,
is this because it's too near the boiler?

Edit: after draining & refilling the rad I can see that it's working back to front & the water from the return pipe to the boiler is being pulled in which means that the rad is then pushing it's cold water into the hot flow straight from the boiler which is no good whatsoever. How can I fix this?

 

[TicklyT]

Think about the order of the connection as water flows round the system. It's normally Boiler - Pump - Radiator- Return, or sometimes Boiler - Radiator - Return - Pump.

Aty the moment you appear to have a connection from Boiler - Radiator - Boiler, without the flow through your new radiator going anywhere near the pump.

As Jas05 has said, if both sides of the rad. are the same side of the pump, there will be little or no flow through the rad, and what little there is will flow backwards, as all that's driving it is the pressure drop across the boiler.

That agrees with your observations.

The rad may shunt enough of the water flow away from the boiler for the heat exchanger to overheat despite the flow and return remaining relatively cool.

You need to connect the flow side to the output side of the pump,
(assuming the pump is in the flow), or connect the return side of the radiator before the pump if the pump is in the return circuit.

 

[mogget]

Also, if you have a motorised valve controlling the radiator circuit, make sure that the flow to the radiator comes after it.

 

[izzyeckerslike]

Thanks for the info guys,
I'm going to look in the loft & trace the 22mm circuit & see what goes where & then I'll come back for more advice

 

[izzyeckerslike]

I've had a look & done a rough sketch, I think I now grasp what my error was, piping after the pump is being pushed whereas piping before the pump is being pulled hence the hot flow pipe pulling water out of my radiator instead of pushing it in my radiator . The junction which feeds off to the 2 dormer rads however is connected before the pump which adds to the confusion

Only problem now is how to fix it, moving the pump & fitting it directly above the boiler may cause problems elsewhere?
The CH flow pipe connects to the side of the hot tank together with the 28mm hot water flow pipe, this is another problem we have in that putting the CH on robs any hot water left in the tank from previous heating & I wonder if fitting the pump below might improve that?