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Heating question

Discussion in 'Plumbing and Central Heating' started by dormermike, 18 Sep 2020.

  1. dormermike

    dormermike

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    Hello

    Planning some changes and looking for opinions please..

    I'm wondering if combi boilers are decent these days for powering:

    - downstairs bathroom bath
    - downstairs bathroom gravity shower
    - central heating (16 rads)
    - hot water tap upstairs bathroom
    - hot water tap downstairs bathroom
    - hot water tap in utility room (not built yet)

    No need for hot water to kitchen because we are putting an instant heater in.

    Bit of an odd question i know, but we have a Y plan open vent system at the moment with an ancient boiler. It works perfectly and i wouldn't dream of touching it, and had planned to add a unvented pressurised cylinder at some stage, but we are building a utility room early next year and the access will be right through where the boiler currently sits (floor standing ideal mexico).

    Trying to decide whether to get a new system boiler and pressure cylinder, or just put a combi in.

    |Thanks
    Mike
     
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  3. muggles

    muggles

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    You could always put a combi in for now then convert to an unvented cylinder later on. Intergas boilers are great for this as the combi boilers are designed to also work as system boilers, so you can drain the hot water side of their circuits and convert them to a system boiler by changing the parameters when the time comes.
     
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  4. Madrab

    Madrab

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    A combi boiler will only supply one of those HW outlets at one time, 2 at an absolute push with one of the larger combi's that'll feed your 16 rads.
     
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  5. dormermike

    dormermike

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    Thanks for the replies

    So it sounds like if the heating is on, a shower may interrupt that, or someone open a hot tap and interrupts someones hot supply in the shower?

    We often have a bath running alongside the heating (doesnt seem a big ask) and occasionally a shower too. I have an electric shower upstairs already, as a backup.

    This does make me think we need to rethink the combi in favour of converting the vented central heating to unvented with a decent system boiler and also the DHW to pressurised.

    or as Muggles suggests the intergas approach; thanks, wasn't aware of those.

    Its a 1994 central heating system consisting of 10mm microbore to the rad tails, and the "backbone" of the system is 22mm and 15mm copper. It is likely to explode in a black sludge mess if we convert it to pressurised... anyone got experience of that?
     
  6. ianmcd

    ianmcd

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    with a combi boiler , when a HW draw off is activated , then the CH supply is interrupted, but it would be unusuall if you actually noticed, an electric shower will never be affected if you have a decent water supply
     
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  7. Elkato531

    Elkato531

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    For your requirements, an unvented cylinder is probably the best way to go but only if your incoming water supply is good enough. Get the pressure and flow rate checked before committing.
     
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  8. Madrab

    Madrab

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    Just get a well recommended installer in, ask for the system to be checked & pressure tested to see if it will hold if sealed. The system will be flushed before the new boiler goes in, industry standard installation procedure, so there shouldn't be much black left. I'd recommend that the feeds to the rads are up'd to 15mm.

    Intergas boilers are very flexible boilers and can be used in more than one setup - sealed or open vent, would always recommend.

    Bullet proof too it seams, was recently called out to a IG Rapid that wasn't working, arrived and saw water pouring out of the flue :eek:, seems the installer had piped the condensate to a rainwater downpipe without an air gap, the downpipe blocked with moss and during an extended downpour the rainwater backed up, up through the condensate, into the back of the heat exchanger and up and out the flue. Stripped it down, emptied the fan venturi, dried it all out with a hairdryer, all back together and away it went, was well impressed.

    A combi stops the heating as it works on hot water priority but the time the hot is on shouldn't comprise the space heating by too much. Unless you are running a bath as a combi will take a while to do that.
     
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  9. winston1

    winston1

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    I can never understand why anyone with a gas boiler would have an electric shower considering electricity costs four times (yes, 4 times) the cost of gas.
     
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  11. muggles

    muggles

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    People seem to be terrified that their boiler might break down at any moment and they won't be able to wait a day or so for someone to fix it. The fact that electric showers are much less reliable than modern gas boilers, as well as being much more expensive to run, doesn't seem to be part of the equation
     
  12. StephenStephen

    StephenStephen

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    Though it does depend on who you're buying your electricity from, and even these day (for some tariffs) on what time of day: Over the last 12 months, unit prices dropped below 2p / kWh 31 times https://octopus.energy/agile/ (though that probably involves getting up in the middle of the night for a shower!)
     
  13. bernardgreen

    bernardgreen

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    A day or so without a shower.

    First find someone to fix it, the good ones ae always busy, and you do not want a cowboy who is on the door step before you hang up the phone.

    Then spare parts have to be collected from the , well from somewhere...

    It is handy to have that back up electric shower, and a bucket to take hot water to the kitchen for washing up with
     
  14. winston1

    winston1

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    Isn’t this the very reason that traditionally we had a cylinder with 150 litres of hot water in it? The current fad for Combi boilers is the problem.
     
  15. Harry Bloomfield

    Harry Bloomfield

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    I have one and would not even consider swap it for gas heated, even though we have an open vented HW cylinder. It provides for a completely independent system, should the boiler/heating system fail and it costs nowhere near the four times the cost of gas heated water. Gas heated via combi has a long cold run off at the start, stored also has a long cold run off and heat is lost from the cylinder. Electric is almost instant, wastes much less water than either alternative.
     
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  16. winston1

    winston1

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    I can’t argue about your cold run off apart from the fact that is probably less than 10% of your shower time. An electric shower is also cold to start with until the “works” have warmed up. Modern cylinders lose very little heat. I still say you electric shower costs a lot more to run than gas heated.
     
  17. Harry Bloomfield

    Harry Bloomfield

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    I would not call two electric shower units installed in 40 years less reliable than gas. Over the same period our boilers have been replaced three times and suffered a total of around 20 break downs system breakdowns. The first electric shower was simply replaced by a better more capable model ten years ago, the original was still functioning just fine, never needed any repairs.

    Our original old boiler was also working fine, though needing a few simple repairs by me over the years. It was replaced by a very troublesome condensing boiler, which itself I replaced a couple of years ago.

    My electric bills are minimal, two of us and we each take a bath or a shower at least daily. When you factor costs, you have to include everything - cost of gas v electric, cost of water, cost of installation and likewise repairs, plus the value of having a spare system installed should your usual system fail.

    I also have an immersion heater, in case there is a longer gas heating outage, plus my caravan in my drive with its own independent systems.
     
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