Gravity feed to bathroom rad dissappointing

[MarkTravis]

Nothing has been altered other than the radiator swap-out. The hot water heats well and fairly quickly. I have no idea about boiler thermostat calibration - it heats! that's as far as my knowledge on the subject goes!

The boiler thermostat is set at position 3 on a scale of 0-6 and at that setting all the pumped rads get warm enough and the hot water gets hot enough for the wife (too hot for me and most men I think!).

Just for a laugh - like you do - I put the old radiator back on this morning - now here's an odd thing - using a digital thermometer with the reading being taken from middle of the first quarter of the panel, it gets 5c hotter (40c)than the new one which - by-the-way - I omitted from my origianl post is a double-panel radiator, the original being single panel.

The new radiator, was again put back on and that got to 35c. A radiator of a similar size to the new one in the small bedroom, but on the pumped circuit, reaches 48c

It all seems very odd, surely if the water entering the old rad does so at 40c, then you'd have thought a nice shiney new rad would be warmer. The fact the new one is a double shouldn't make any difference to the water temperature in the first quarter of the radiator area - but it does. Switch the heating off and the temperature of the bathrooms new rad rises to around 42c

 

[DeltaT2]

It all 'boils down'(pun intended) to resistance & pipe gradients etc.

If your old rad only reached 40C then I'd say it never worked correctly.

I think we still need a sketch.

 

[MarkTravis]

...not sure I am sufficiently up to making a sketch based on my lack of knowledge as to what is where. One of the problems with this house is that there is pipework everywhere under the bathroom floor.

The Boiler - an Idea Classic Rs50, is downstairs in the kitchen. the two pipes that are gravity F&R are 28mm going directly up into the bathroom above and go through one 90deg turn into the airing cupboard (approx 4 ft then a further 90deg turn up to the Hot water cylinder.

I am not sure where the flow to the radiator comes from, whether is is some kind of T junction where the flow splits cylinder/radiator or if it goes into the rad then the cylinder or visa versa I can't see because this area of pipework is behind the cylinder and probably under it too. you can't get to the back of the cylinder as the cupboard is so small.

A previous occupier seems to have bricked up an all important access area which, in neighbouring houses, is like a loft door on the wall on the turn of the stairs, which would allow you to access pipework behind the cylinder.

Directly above the cylinder in the roof is the header tank.

I have looked at the manual for the boiler and all pipework and distances etc would appear to be correct.

I did mention in one of my posts that the radiator has 15mm pipes connected to the valves fed off a 22mm pipes - I did not measure that pipe so maybe it is 28mm (I assumed 22mm as I didn't realise they made 28mm!). It is definately 28mm F&R into boiler