Radiator plumbed with return on top

[jacoscar]

I've changed all my radiators a couple of years ago and plumbed them TBOE (top bottom opposite ends) with pipes chased into the walls and coming out horizontally.
Normally you have the flow on top and the return at the bottom at the opposite end.
I just realised I messed up with one of them (downstairs living room) and the flow is at the bottom with the return at the top at the opposite end. It's a 2000m wide and 300mm high double panel.
It still heats up but probably not in an optimal way, the corner below the return valve is always cold; is there a quick way to fix it that I haven't considered:
- breaking the wall where the return pipe is, cut the pipe, add an elbow and replumb as "bottom both ends", involves replastering the small section of wall and painting
- cut a hole in the ceiling and swap the two pipes, involves filling and painting the ceiling

 

[ianmcd]

No magic tricks Im afraid

 

[jacoscar]

No magic tricks Im afraid

I was thinking maybe an internal diverter or something like that; I know they exist for certain applications

 

[ianmcd]

I was thinking maybe an internal diverter or something like that; I know they exist for certain applications

have seen them for vertical designer rads, but not sure if they make one for your application, can you post a pic of the rad in question and let me see what we are dealing with

 

[cross thread]

Access pipes under the floor ? to alter them

 

[jacoscar]

have seen them for vertical designer rads, but not sure if they make one for your application, can you post a pic of the rad in question and let me see what we are dealing with

 

[ianmcd]

Never seen a baffle that would fit in that rad, what you could do is remove the rad and cut an access panel in the plasterboard behing the rad and alter the pipework from there and put both connections to the bottom then re-fit the rad, that way you wouldnt need to redecorate

 

[JohnD]

- breaking the wall where the return pipe is, cut the pipe, add an elbow and replumb as "bottom both ends"

Yes, that.

Tucked away in the corner behind the end of the rad it will not be very noticeable.

 

[Johntheo5]

I've changed all my radiators a couple of years ago and plumbed them TBOE (top bottom opposite ends) with pipes chased into the walls and coming out horizontally.
Normally you have the flow on top and the return at the bottom at the opposite end.
I just realised I messed up with one of them (downstairs living room) and the flow is at the bottom with the return at the top at the opposite end. It's a 2000m wide and 300mm high double panel.
It still heats up but probably not in an optimal way, the corner below the return valve is always cold; is there a quick way to fix it that I haven't considered:
- breaking the wall where the return pipe is, cut the pipe, add an elbow and replumb as "bottom both ends", involves replastering the small section of wall and painting
- cut a hole in the ceiling and swap the two pipes, involves filling and painting the ceiling

I did these test a few years ago on one of my rads, you might get ~ 73% output of the properly piped ones, but far better to plumb up correctly.

 

[JohnD]

A muticutter is superb for cutting a neat hatch out of plasterboard. Use a half moon blade.

It should easily fit back afterwards with a bit of filler in the joints

 

[jacoscar]

A muticutter is superb for cutting a neat hatch out of plasterboard. Use a half moon blade.

It should easily fit back afterwards with a bit of filler in the joints

It’s a solid wall so it would be a bit messier than that

 

[jacoscar]

I did these test a few years ago on one of my rads, you might get ~ 73% output of the properly piped ones, but far better to plumb up correctly.

View attachment 317258

Very interesting. How did you calculate the power? With everything being equal, it should just be proportional to the delta T, right?

 

[Johntheo5]

Very interesting. How did you calculate the power? With everything being equal, it should just be proportional to the delta T, right?

Radiator rated output have been for years now based on a 50 deg rating, this the mean or average radiator temperature minus the required room temperature (generally taken as 20C), the mean rad temperature is generally taken as the (flow temp+return temp)/2. if you have a rad with flow/return temps of 75C/65C then based on a 20C room temperature its then at its rated output (100%), ((75+65)/2)-20, 50C, there is also a exponent involved as rad output isn't linear, if you look at the TBOE rad above, the average rad temp is 59.1C, if it was a linear relationship then that rad output would be (59.1-20)/50 or 78.2% but the exponent that the manufacturers use is 1.3 (to the power of 1.3) so the actual rad output is
((59.1-20)/50)^1.3, 73%, the "error" becomes much more pronounced at lower temperatures.
The mean rad temperature calculated by using (flo+return)/2 is quite accurate for normal plumbed rads like BOE & TBOE but cant be used in a BTOE rad, you can see above that the average rad temp in both the BOE & TBOE rads is almost identical whether you actually average all the temperatures or just use the normal method of (flow+return)/2 but in the BTOE rad the (flow+return)/2 gives a average of 60.5C but the actual average is only 51.5C.
One of the reasons I did the test was because a friend of mine was in a standoff with the managers of a new apartment with a HIU unit where all the rads were plumbed BTOE, I was a bit surprised myself at the big effect this has.