combi versus open vent

Discussion in 'Plumbers' Talk' started by Crooked Feed, Sep 13, 2009.

  1. Crooked Feed

    Crooked Feed New Member

    Apologies if you have done this suject to death but I've done the search and cannot find any previous posts.

    My son has just bought a large three bed semi which requires gutting. The existing CH boiler is an old back boiler which will need replacing in order to fit the kitchen.

    We are planning to install a wall mounted boiler concealed within a kitchen cupboard -gas connections and commisioning to be done by qualified engineer.

    The question is whether to go for a combi or open vent boiler. Existing cold storage tanks, cylinder and immersion heater are all in good nick. As I've yet to come across an electric shower that is anywhere near as good as my gravity fed unit, I'm leaning towards a new open vent system. Am I missing anything obvious?

    Thanks!
  2. Switcher

    Switcher New Member

    Most will either say combi, unvented cylinder or sludge bucket but storage tanks are fine IMO.
  3. Dick Puller

    Dick Puller New Member

    Why not retain the existing indirect cylinder & fit a system boiler & new heating system? If you want high water pressure on hot & cold, convert your existing cylinder to a heat bank. However, if it's only a 3-4 person house, I'd strip the lot out & fit a combi.
  4. JP.

    JP. Screwfix Select

    Surely the open vent boiler must be far superior to a Combi in this situation.,ie you can whip in a power shower like the Aquastream SELV unit and stuff off the DHW cylinder. Would think that the F + E tank would not be used, and instead a pressure vessel (expansion vessel) would be used in the appropriate position.

    If a Combi goes down you have no HW and CH usually..the HW cyl and open vent boiler speaks for itself.

    However this is just aspersions from a non plumber.
  5. tackleburger

    tackleburger New Member

    You'll get a great shower of a combi if that's your only worry then don't. The question you need to ask is what is the hot water demand. In this case one bathroom I assume I'd go for the combi, get a good one a Vaillant or a Viessman you won't go wrong. Still nothing wrong with gravity other than the fact you are storing hot water and the shower will probably be better off the combi.
  6. Crooked Feed

    Crooked Feed New Member

    Thanks for the responses. They have made interesting reading.

    My aversion to Combi systems is the number of posts you see which seem to be complaining about combis going down; whereas my open vent system has been going strong for fifteen years and the guy who services it keeps telling me not to get rid of it!

    My son's house has only one bedroom but it's in a family home and we need to future proof it a bit. Tackleburger, can you really get a decent flow in the shower from a combi boiler? My gravity fed shower has a raised cold water tank in the loft and produces a really good flow.
  7. mantor

    mantor New Member

    listen to the fella who services yours, he's giving you good advice. You will get a good shower off a combi, till someone opens a tap or turns the washing machine on.
    The glow worm hxi's are good open vented boilers, and small. Have a look at them.
  8. Dick Puller

    Dick Puller New Member

    However this is just aspersions from a non plumber.................DaftyDIYers should be banned from this forum!!!

    Nothing wrong with an open vented system - primary or secondary.

    As said you need to work out the number in the household & demand etc etc.

    Combis are great if fitted correctly, but there's loads of untrained/unqualified chancers about, just look at the number of CC/CCCs on here ***!!!
  9. Captain Leaky

    Captain Leaky New Member

    Just about anything is better than a combi!
  10. Crooked Feed

    Crooked Feed New Member

    It's beginning to look like open vented, sealed or combi are all possible.

    What sort of flow would I get on a sealed system and could I put the cylinder up in the loft so that I could use the airing cupboard space for a free standing shower?

    It's a blank canvas because we are gutting the inside and can locate boiler, cylinder and tanks whereever we want. Pipe runs to cylinder/tanks will be more or less vertical.

    Thanks for the help thus far!
  11. mantor

    mantor New Member

    You've said it's a big house and you want to future proof it. Forget the combi, go for an unvented cylinder, which you can put anywhere you like. You may have to upgrade your incoming main if the flow rate isn't up to it.
  12. Statia

    Statia New Member

    I'm not a plumber, but if I had a blank canvas I'd deffo go with a heatbank and an open vented system.

    http://wiki.diyfaq.org.uk/index.php?title=DIY_HeatBank

    You've got the reliability of the non-combi boiler, the mains pressure hot water which will match or better any combi and an immersion heater for backup to ensure you still have hot water in case the boiler breaks down.

    I'd go with a Viessmann Vitodens 100-W heat only boiler.

    I'd also put two futher cylinder jackets over a HW cylinder as the foam on them is insufficent. Overkill some may think, but it really will save you money.

    To me, it's a no brainer.
  13. Dick Puller

    Dick Puller New Member

    I'm not a plumber................Why do all the DaftyDIY'ers write this!! Giving their personal experience of ONE installation.

    Statia son, if you read my post above you'll see I already suggested that!! Too much winking eh!!

    Ban all DaftyDIY'ers!!!
  14. Statia

    Statia New Member

    "Statia son, if you read my post above you'll see I already suggested that!!"

    Get over yourself pal.

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