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Replacement boiler has changed flow direction, help!

Discussion in 'Plumbing and Central Heating' started by Mattbelfast23, 1 Dec 2013.

  1. Mattbelfast23

    Mattbelfast23

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    Hi guys,

    First time here so be gentle.

    My System is sealed with a Y plan running 13 rads 10 of which are double panel.

    I have recently replaced a standard efficiency warmflow mid-20kw ish oil boiler with a firebird high efficiency 35kw condensing oil boiler. Looking to get better heat and save cash.

    Pretty pleased with this, however the flow direction has changed. The old fittings at the boiler matched really well so were not changed ie no pipe work. However, The hot flow now comes out of the boiler at the bottom on what used to be the return. To deal with this it was suggested that i change the direction of the pump which i have done. I have several questions/worries though:

    Was it a good idea to change the pump direction?

    What negatives could this have?

    Im now getting a lot of noise out of my rads, why would this be?

    Do i need to move the TRVs onto the flow side of the rads? I doubt they are bi directional as they are pretty old and most of them did not work anyway. Stuck pins etc. Id like them to function so would replace broken ones.

    As an aside, Should i get a bigger circulating pump? Over the past few years ive been changing my rads to doubles. 0 to 10 now. My current pump is pretty old and is 5m head

    Thanks for any help or suggestions.

    Matt
     
  2. ChrisR

    ChrisR

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    Even "bidirectional" TRVs are inclined to rattle on the return end. Even expensive ones.

    The flow has to be the right way through your boiler, and OUGHT to be the right way through your 3 port valve though I've seen plenty that were on the return and working.

    I assume this is a sealed system , otherwise your vent etc will be in the wrong place...

    Pump - well does it work ;) Condensing boilers work with a higher temperature differential than oldies so are happy with lower flow rates. (Like 20ยบ rather than 10, for gas. I assume oil is the same but never touched oil)
     
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  4. Galoka

    Galoka

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    Sigh, so the plumber gets it's wrong, and then bodges it...

    Could ring the manufacturers first if you want to see what they say, but seems to me the plumber should be called back to do it properly (at their cost)

    Condensing boilers have a secondary heat exchanger, the return water passes through this first, to remove more heat from the flue gases, before being heated in the main heat exchanger (hence the condensing bit, as the flue gases get cooled more than in a non - condensing boiler).

    If the flow through the boiler is reversed then surely this won't happen as it will go through the main heat exchanger first, so hitting the boilers efficiency at the very least
     
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  5. Mattbelfast23

    Mattbelfast23

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    Thanks for the advice on the pump :)

    Galoka, that was my original worry when the boiler was installed. Would it even do its condensing? So they changed the pump direction. With my limited knowledge i reckon this will probably work for condensing.

    Im really concerned what effects this reverse flow will have on the rest of the system. The system is sealed.

    Will the Y plan motorised valve even do its job anymore?
    Will i need to change the sides of every lock shield and TRV for every rad?

    Thanks
     
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  7. Galoka

    Galoka

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    Can't see how the condensing secondary heat exchanger can work, as it's going to have hot water straight out of the main heat exchanger - though I've never looked into the internals of a condensing boiler to see how it is arranged. There may be other aspects of the internal water flow through the boiler that are important for proper functioning that aren't obvious

    It will invalidate the boiler warranty as well iimagine

    Left as it was, then no I can't see that the mid position valve will work properly either, though it will probably work after a fashion as the routes through the tank and CH will still be open at the right time. But the reverse flow might push the valve open a bit.

    Don't forget that the flow through the cylinder is reversed as well.

    You might need to swap the TRV's over depends on the TRV's I guess.

    You have probably spent what? a couple of grand on the new boiler?I don't really understand why you want to consider this palaver? (ending up with a system that doesn't work properly and to it's full efficiency, and invalidate the boiler warranty). How can it be any easier/better than re-jigging the pipework around the boiler, which surely would have been a pretty straight forward job.

    He should have known better (Assuming that it wasn't your idea that he went along with), it's a bodge, he should sort it.
     
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