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Unvented system with 15l flow

Hello,

My boiler is on its last leg and will need to be changed next year when we build the kitchen side return.

We live in a 4 bedroom terrace house (3 levels) - that has 1 bathroom and 1 ensuite shower on the first floor.

We currently have a traditional vented system - and were recommended against to avoid a combi boiler given the 2 bath/shower rooms.

However, given that our mains pressure is 2bar and flow around 14l per minute, I have read that an unvented system (megaflo type) might not be the best option either due to the limited mains flow.

I would be interested to hear a competent opinion on this as we got 4 plumbers and got pretty much 4 different stories. SO before I sink about £3/4k in a new system, I would like to make sure it will give me what I want :-) Thanks
Total Debt (inc. mortgage)31/12/2012 - £893k31/12/2022 - £1.703m

Comments

  • southcoastrgi
    southcoastrgi Posts: 6,298 Forumite
    Part of the Furniture 1,000 Posts Name Dropper Photogenic
    unvented would work HOWEVER if your fiqures are correct I wouldn't fit one, the best option for you is to stick to the same type of hot water system you have, although I may be be tempted to change the boiler for a sealed system type (not a combi)
    I'm only here while I wait for Corrie to start.

    You get no BS from me & if I think you are wrong I WILL tell you.
  • pgalland
    pgalland Posts: 97 Forumite
    Part of the Furniture 10 Posts Combo Breaker
    the problem is that we need to change the current set-up, as the boiler and the hot water tank sit in the room that we want to convert from a bathroom to back to a bedroom (the previous owner turned the back bedroom into an ugly and very big bathroom)
    Given that there will be some significant pipework to move everything out to another location (tbd for now) - we thought we'd move away from the vented system option, which seems archaic.
    The idea was to put a megaflo in the cellar and be done with the water tank in the attic.
    Total Debt (inc. mortgage)31/12/2012 - £893k31/12/2022 - £1.703m
  • southcoastrgi
    southcoastrgi Posts: 6,298 Forumite
    Part of the Furniture 1,000 Posts Name Dropper Photogenic
    edited 31 March 2013 at 7:17PM
    no you don't need to change it, you want to, there is a difference.

    if you change to an unvented cylinder (& i wouldn't fit a megaflow as they are too dear), you are now feeding the entire house hot & cold on 2 bar & 14 ltrs/min & IMO that isn't good enough, do you want to spend £X thousands putting in an unvented cylinder to have less water coming out of your taps & fittings than you do now ? because that is exactly what will happen.

    the only way you may be able to improve things is by putting a new bigger supply pipe in from the outside mains stop tap & either paying or persuiding your water company to increase the size of their supply pipe to yours, this will increase the flow but will do nothing for the pressure.

    you wanted un-biased opinions & mine is that you will spend alot of money to be worse off
    I'm only here while I wait for Corrie to start.

    You get no BS from me & if I think you are wrong I WILL tell you.
  • pgalland
    pgalland Posts: 97 Forumite
    Part of the Furniture 10 Posts Combo Breaker
    Southcoast - thanks for your input.
    Agreed on the megaflo - other brands are as good and much cheaper. Your points are very valid - never came up from talking to the plumbers who came to see the job (worrying).
    I was really hoping I could fit the whole system in the basement, but I get your point about being worse off.

    If I was to keep a vented (yet sealed to your point) system, is it possible (gravity speaking) to put the boiler in the kitchen, while the hot water tank would be on the 2nd floor landing (2m below the cold water tank in the attic)? Would I lose loads of pressure/flow?
    I really don't want to keep the hot water tank in any of the room on the 1st or 2nd floor as we have no space to spare - so the only alternatives are cellar or 2nd floor landing.
    Thanks again for your valuable input
    Total Debt (inc. mortgage)31/12/2012 - £893k31/12/2022 - £1.703m
  • southcoastrgi
    southcoastrgi Posts: 6,298 Forumite
    Part of the Furniture 1,000 Posts Name Dropper Photogenic
    edited 31 March 2013 at 7:38PM
    if you go for a sealed sytem boiler then you can put it anywhere you want (although i would avoid the loft & the garage as due to the inbuilt frost stat it will be switching itself on to prevent freezing thus wasting gas even if the heating is switched off), if your cylinder is on the 2nd floor atm then you aren't going to change the pressure or flow from what you have now, & it gives you the option of fitting a pump to give you increased flow rates, if you have room in the loft then think about raising the height of the roof tank, if you have room in your new airing cupboard then think about putting the boiler in there above the cylinder, this will give you an extra cupboard space in the kitchen plus all the pipework will already be there (apart from re-routing the gas pipe & finding somewhere to run the condense pipe & safety pipe from the boiler if you go for a sealed system boiler), some installers can't see outside their tunnel vision if it's not a combi or unvented they haven't got a clue, yes a vented system is out dated but until the water co get their fingers out & repair all the leaks in the rd & give everyone a decent supply flow rate & pressure then a tradional system is sometimes the best thing for the customer, btw to fit an unvented cylinder you must have the G3 cert did you check that the ones you had round & recommended unvented had this ?
    I'm only here while I wait for Corrie to start.

    You get no BS from me & if I think you are wrong I WILL tell you.
  • pgalland
    pgalland Posts: 97 Forumite
    Part of the Furniture 10 Posts Combo Breaker
    actually, the current system sits on the 1st floor (except the cold water tank which is under the roof in attic).
    The boiler and the HWT both sit in the cupboard that will be destroyed when the 1st floor bathroom is turned back into a bedroom.
    I am keen to have the boiler closer to the gas supply (kitchen) and leave the HWT above both showers (ie. on the 2nd floor).
    I am happy with the shower pressure today - not great - but I prefer to live with that, rather than fitting a noisy pump.

    Bottom line: 1) all agreed that combi is no good, 2) sounds like not appropriate in my situation... so just need to find the right set-up -locationwise- to replace what I have got.

    Right?
    Total Debt (inc. mortgage)31/12/2012 - £893k31/12/2022 - £1.703m
  • southcoastrgi
    southcoastrgi Posts: 6,298 Forumite
    Part of the Furniture 1,000 Posts Name Dropper Photogenic
    yep, in moving the cylinder up one floor you may notice a drop in pressure but tbh i really don't think it's something you should be overly concerned about, there are thousands of houses like this & they cope perfectly well, if it does become an issue then you have the option in fitting a pump (maybe just for the shower so it's not in constant use) which you wouldn't have if you went unvented as you aren't allowed to pump the mains anymore than 12 ltrs/min
    I'm only here while I wait for Corrie to start.

    You get no BS from me & if I think you are wrong I WILL tell you.
  • pgalland
    pgalland Posts: 97 Forumite
    Part of the Furniture 10 Posts Combo Breaker
    Thanks a lot - btw - have you heard of the salamander / booster pumps? One of the plumbers said they could be fitted right off the main - directly into the unvented cylinder... is that legal?
    Total Debt (inc. mortgage)31/12/2012 - £893k31/12/2022 - £1.703m
  • southcoastrgi
    southcoastrgi Posts: 6,298 Forumite
    Part of the Furniture 1,000 Posts Name Dropper Photogenic
    yes i have & he is right although it is only 12 ltrs/min but you already have 14 ltrs/min & if it is fitted onto the cylinder it will take away water from your other cold outlets so it won't really solve your problem
    I'm only here while I wait for Corrie to start.

    You get no BS from me & if I think you are wrong I WILL tell you.
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