Radiator inlet/outlet positions

Hi, I am thinking of buying some old cast iron 4 column type central heating radiators, the ones I am interested in have the inlet valve at the top and the outlet at the bottom diagonally opposite, will this work just as efficiently as having both inlet and outlet at the bottom as modern radiators usually seem to have? I assume the old radiator connections are unlikely to unscrew so I will have to use them in the positions they are in. Thanks

Reply to
Julian
Loading thread data ...

It will work - but it will look very messy! Chances are that the rads were part of a series flow system using quite big threaded pipes - so you'll need to use reducing bushes (maybe several in series) to get them down to 1/2" BSP. These would be far less noticeable at the bottom.

The radiators will almost certainly have four connection points, with blanking plugs in the unused ones. These will be tough - but by no means impossible - to remove. You need to lay the rads down on a flat surface and either clamp them down or get someone to sit on them to hold them in place. Then you need to grip the flats of the fittings with a Stilson - if necessary using a metal tube slid over the handle to get extra leverage. Once they start to turn - having broken through the decades of dried up Boss White - they'll come out quite easily.

Reply to
Roger Mills

In article , Julian writes

That's Top Bottom Opposite End (TBOE) and even on modern radiators they work marginally more efficiently that way (a few percent only). On cast iron radiators where there is a high thermal mass and a wide open channel along the bottom there is a risk in Bottom Bottom Opposite End (BBOE) that the flow passes through at the bottom without initiating the convection required to distribute heat around the rad so I would suggest sticking with TBOE.

On aesthetics I know someone who has a this kind of setup and it looks fine, TRVs are mounted vertically on the feed (high) side and don't look obtrusive.

Watch out for leaks and seized iron fittings, exp bleed screws.

Reply to
fred

Julian writes

marginally more efficiently that way (a few percent

open channel along the bottom there is a risk in

without initiating the convection required to

TRVs are mounted vertically on the feed (high) side

Often wondered about the piping configuration of radiators, I wondered why they weren't plumbed more often to the manifolds at the top and bottom. It surprises me that they work the "normal" way at all.

If you do plumb to the diagonals, is there an advantage in having the flow at the bottom?

Reply to
Graham.

There are four connections on almost all radiators. Diagonal connections work the most efficiently as the water circulates in the best way. The other alternative (both bottom connections) works less well, the water tends to go straight across.

I would say don't buy unless you have a return agreement. When they are manhandled and banged about old cast iron radiators often leak at the many joints. They are virtually impossible to fix if they do leak. (There is a joint between each section assembled by LH/RH thread steel/malleable iron couplings)

You might get the fittings out of the ends, but the interior ones (if it leaks) need a special tool and are usually really well seized up/corroded. Also hard to get the couplings.

Reply to
harryagain

In article , Graham. writes

It's all in the convection and quite a few here have reported problems on tall ladder type towel rail radiators where there is a wide open path at the bottom and the heat is failing to reach the top. IIUC they should have baffles at the bottom to fix this but in modern low water content panel radiators it does not appear to be necessary.

If you mean flow at the bottom and return exiting at the top then that is bad, hot inlet water will rise by convection and exit quickly at the outlet point leaving a cold patch in the bottom corner opposite the flow connection.

Reply to
fred

s

Thanks for all your replies, I'm going to look at the radiators again next week and now I have some more information I will be able to decide whether or not to make a purchase.

Reply to
Julian

Most of the old systems I've seen with cast iron radiators were one pipe systems, where the water circulates in a single pipe; at each radiator a fraction of the total is diverted to the radiator with a special tee, then rejoins the main circulation pipe after the radiator. Although the circulation pipe is quite large (often up to 2 inch in domestic systems, maybe even more if it's a larger building like a school or church hall) the pipes going to the radiator are smaller - most of the radiators I recall from my parents' house would have had a 3/4 inch BSP connection, so only a relatively small reduction to get to 1/2 inch. The diagonal connection was necessary to get the water to circulate in the radiator rather than just passing straight through.

Reply to
docholliday

They were usually connected TBOE, because most started life on gravity circulation heating systems which needed the flow in the top, return out of the opposite bottom connection. I assumed TBOE would give the highest heat output, but the CIBSE Journal published a series with some useful rule-of-thumb estimating figures in the early 80s which gave the BBOE connections about 10% more heat output.

Reply to
Onetap

I think that may be the wrong way up, this is an extract from a CIBSE Guide, Volume B, Installation and Equipment Data of about 1994.

B1-5, Heating

"For the testing of radiators, BS 3528 specifies top and bottom opposite end connections (TBOE). Measurements have shown that other connection arrangements have a marginal effect on heat output. Taking the heat output for TBOE connections as 1·0, the following values can be expected:

top and bottom same end connections (TBSE) 1·04 bottom opposite end connections (BBOE) 0·85"

Interesting that TBSE is higher than TBOE and the difference between TBOE and TBSE is more than I expected, TBOE being greater by 17% when using BBOE as the baseline.

Reply to
fred

HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.