TBOE connection - good/bad?

Discussion in 'Plumbers' Talk' started by lensman, Nov 1, 2004.

  1. lensman

    lensman New Member

    I'm about to connect a new radiator to an existing central heating system and wondered what the merits of TBOE connection are compared to the usual method of connecting both inlet and outlet pipes to the bottom of the radiator. I don't care about the prettiness of the layout - just how it performs. In particular:

    Is the heat output improved by TBOE connection?

    Does the fact that the water flows diagonally make any difference to air pockets inside the radiator?

    Is it better to have the inlet at the upper or lower
    connection end?

    I've never seen TBOE in domestic installations - is there a reason (other than habit) for this?
  2. jmcbuilders

    jmcbuilders New Member

    Hi I do not understand TBOE but if a system has rads with top feed in and out at the bottom it is prob gravity fed. Is your system ? JMc
  3. devil's advocate

    devil's advocate New Member

    Hi lensman.

    I understand that TBOE is a little more efficient than the now conventional both at bottom connection. With modern, powerfully pumped systems, however, I think any benefit will be marginal.

    I <u>think</u> the flow is fed to the topmost fitting.

    I doubt it'll make any difference to air pockets, as these will always end up at the top and need to be vented.

    Any possible improvement that there might be to the efficiency of the rad will, for most people, be <u>more</u> than offset by the unattractiveness of the visible pipe - I imagine that is why it is simply not seen these days (and many modern rads won't even give you the option!)

    These are my thoughts gleaned from titbits over the years. I am not a 'Pro', however, so requisite pinch of salt could (should?) be added.
  4. Bahco

    Bahco Guest

    Isn't it TEBE...top entry bottom exit.
    Forgive me if I am wrong
  5. devil's advocate

    devil's advocate New Member

    Hi Bahco.

    I'm guessing TBOE stands for something like 'Top-Bottom Opposite Ends', the 'opposite' part being particularly important!

    I think I recall seeing - many moons ago - radiator charts giving the outputs when connected both ways, with TBOE (TEBE!) showing a slightly higher output.

    As lensman is clearly after max output, can you confirm if this <u>is</u> the case?
  6. Bahco

    Bahco Guest

    This was covered at college last year.
    You do get more efficiency doing it this way, but is more commonly found in public buildings i.e. hospitals and halls etc. Normally iron piping is used for durability.
    It is not recommended for domestic especially where kids are around
  7. Bahco

    Bahco Guest

    My Apologies.
    As DA said it is top bottom opposite ends (I have consulted my college notes)
    It has been proven to give a better flow but not recommended for domestic due to risk of damage to pipe and also the height of the valve could injure children.
    My own thoughts are if the system is properly balanced why bother. The increased flow would not be noticed anyway
  8. doitall

    doitall New Member

    Top bottom opposite ends were mostly used for the old gravity and single pipe systems, where steel pipe, pitcher tees etc were used.

    still used in public some buildings and with the cast iron radiators.

    Also a plus where old folks have a problem reaching the bottom valves.

    For the record they work just as well top, bottom same end when on a pumped system.
  9. lensman

    lensman New Member

    Thanks for the replies guys - sorry to take so long getting back into my own thread, but I'm sure you'll all understand the bother of connecting to Screwfix at the moment!

    Various answers to comments:

    it is prob gravity fed. Is your system ?

    My system is conventional pumped - old radiators are all
    fed from opposite bottom ends.

    Opposite Ends'


    TBOE showing a slightly higher output.

    It's also (I believe) the connection system used when manufacturers specify the heat output of their systems - presumably (again I assume) because it maximises the output and makes their gear look better.

    where kids are around

    Afraid I don't understand what kids have to do with this?
    As far as I can see, raising the height of the valves (or the TRV, which is what I intend) ought to lift it out of easy reach of toddlers. Admittedly, it means the radiator acquires a new `bump' higher up, but I'm hoping this is less dangerous than having it lower down - especially if it reduces the chances of kids turning the heat up and burning themselves. Is there something else I haven't thought of here?

    bottom valves.

    Indeed, another reason why I'm thinking about it - my dad can't reach below knee height nowadays.

    Thanks for the comments - it seems there's no over-riding reason to either do or avoid TOBE, so I'll do it wherever it seems useful and avoid it on the rads where it's not.
  10. devil's advocate

    devil's advocate New Member

    Hi lensman.

    It seems clear that there <u>is</u> a slight increase in rad efficiency when using TBOE.

    The only 'drawbacks' I can think of - as touched on above - are: the feed pipe is more exposed and prone to damage; it'll be hot and might cause a few peeps to go "ouch" if they brush against it (it'll hardly burn them, tho', and one of these clip-on decorative plastic covers will do enough to protect it), and that's about it.

    Bear in mind that the TRV will be more greatly affected by the heat given off by the rad and the heat rising from the pipe below it. You may have to open it up a little more to match the flow from when it was in the lower position.
  11. lensman

    lensman New Member

    Bear in mind that the TRV will be more greatly
    affected by the heat given off by the rad and the
    heat rising from the pipe below it. You may have to
    open it up a little more to match the flow from when
    it was in the lower position.

    Yup, borne in mind. Since the TRVs only seem to give settings as 1-5 (or whatever) rather than degrees-C, I suspect I can learn to live with the inaccuracy.

  12. devil's advocate

    devil's advocate New Member

    Lensman, something chust occurred to me having read a recent post by someone else.

    If your rad has a rubber bung installed inside, half way along the bottom rail, I think it'll need to be removed for TBOE fitting. This bung is designed to help the water go 'up 'n' over' when connected with bottom fittings. If left in with TBOE, it could effectively isolate half your rad.

    If this is the case, it is removed by pushing a long bar into one of the valve openings, and shoving it out the other...

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