Plumbing a radiator

Spannerman7

I did a search but could not find what I'm looking for.
I was at the selfbuild show at the weekend and at one of the seminars there was a part about the most efficient way to plumb a rad, it was said that the way most are done here is just to make it easier for pipe runs and neatness but is not the most efficient. Most I have seen are in and out at the bottom but a better option is meant to be in lower and out upper oposite corner, it makes sense to me but I'd like your views.
I intend to run the pipes through a service cavity so it won't make any odds to me where the supply and return attach.
How do you do yours ?

Joey the lips

Bang on. In bottom out top. Many different reasons it also means sludge stays in the rads and does not get circulated around the system as much.

I aint a plumber though. I was just though this way

makes bleeding easier as well as well because air usually gets cought in the bottle vent.

heinbloed

I'm not a plumber as well....

In a standard situation (normal radiators, pumped system) the hot infed should be positioned at the top and the outlet at the bottom.

The diagonal flow of the water is keeping is distributing the hot water over a larger surface compared to a short-cut solution along the smallest possible surface of the radiator, we agree on this so far.

Having the the inlet at the bottom of the radiator and the outlet at the top will hinder the hot water to spread evenly over the entire surface because it is not only pumped-in but also at the same moment sucked out.
Compare the situation with throwing fluff-balls at a vacuum cleaner.

The other-way around, where the inlet is at the top and the outlet at the bottom, would involve the difference in gravity of the fresh, hot water, the prevalent water in the radiator(cold at the bottom and warm at the top!) to mix the ' jet ' of water better. It wouldn't leave the radator in the shortest possible and lowest resistant way diagonally but would mix with the different layers of the water before it leaves the radiator at the bottom.

Now, with adjusting the heating system correctly (the flow rate of each individual radiator) this would be of a minor problem. But most installed systems aren't. For these the the more logic solution (increasing the 'stay-time' of the fresh hot water flowing through the radiator) the return temperature to the boiler would be lower, the efficiency of the boiler increased.

kay 9

Usually the only reason for BTOE (bottom top opposite end) is used for single pipe system for it to circulate properly. With the 2 pipe system it is just as efficient to use the bottom ends as the flows and returns are seperate. That single pipe system is usually used in hospitals.

Sparkpea

I wouldn't plumb a new system with top and bottom connections.

The only reason I use them is if its a direct replacement radiator.

My wholesalers also don't keep them so I need to order them in so imo they aren't very popular! there is no cost difference etc.