Combi advice

Discussion in 'Plumbers' Talk' started by Mark Taunton, Apr 13, 2014.

  1. Mark Taunton

    Mark Taunton New Member

    Hi All
    Advice please!
    Just had gas mains fitted in an old townhouse so now need to get moving with sourcing rads and a combi boiler so some questions:

    How do I work out the size of boiler required or is it easier to advise on size by the number of rooms?
    The house has sitting room, dining room, kitchen, downstairs bathroom, two bedrooms on first floor and a further bedroom on the 2nd floor, not particularly big house but would rather go for a larger boiler working less than a smaller boiler, does that make sense?
    Also away a lot so wanted to be able to fire it up on an iphone.

    Can the combi boiler be fitted with only the hot water piped in or do all the radiators have to be connected as well, I wanted to fit it all in stages but get the hot water running for the bath and shower first if possible.

    Is it ok to plumb it all in with poly pipe or do you still use a lot of copper?

    Finally for now the gas meter is at the front of the house and the boiler will be about 15mtrs away in the kitchen, what size and type of pipe should be used and can it be run on the skirting or does it have to be buried?

    That's it for now,any advice much appreciated.


    Thanks

    Mark
     
  2. Hi Mark.

    You'll probably gets lots of thoughts and opinions on here - and that's as it should be. You can then use that info to help in your choice.

    First point - you are right; fit a large boiler. Modern combis 'modulate', which is to say their burners are automatically adjusted to suit the demand. So you can fit a boiler that'll heat a 4-bed hoosie into a 2-bed flat. But, the larger size will give you that extra bit of hot water flow out yer tap - which is what you need.

    So I'd recommend approaching a 38kW jobbie which should give you up to around 16lpm (litres per minute) hot water. But you need to check your cold mains can porvide that first.

    iPad control? Not familiar with that, but see it becoming more and more popular. I suspect, tho', that's it the actual programmer wot's controlled by yer 'Pad and not the akshul boiler directly - so I suspect you are free to choose pretty much whichever boiler you want.

    Gas pipe sizing - 15m isn't an unusual length, but it also comes down to how many bends it'll have, any other demand on gas (hob, fire, etc) and power of boiler. That's worked out with some basic calcs, tho' most GasSafes will just look at it, rub their chins, and say 22mm/28mm or whatever.

    Gas pipes don't have to be 'buried' afaIk, but maaan you really want a big ugly pipe running along yer skirtings?

    Poly-pipe is absolutely fine for radiator and hot water use - in fact it has many advantages over copper. You'll likely find that they recommend running the first metre or so of pipe in copper where it connects to the actual boiler. Also, copper pipe looks much nicer, so you may wish to run the short uprights to the rads in 15mm copper (you can interchange most fittings between them).

    I think you'll need at least a single rad to be plumber in to fire up your boiler for DHW. You could even do a temporary lash-up if you needed - just run 15mm polypipe to a single rad close to the boiler. And make sure the CH side of the system doens't come on...

    Since this is a completely new install, strongly consider fitting a zone valve run by its own programmable room stat to control the upstairs bedrooms - you'll likely only want them on in the late eve and first thing in t'morn.
     
    plumberboy and Mark Taunton like this.
  3. Mark Taunton

    Mark Taunton New Member

    Thanks DA, much appreciated.
     
  4. Dave does Gas

    Dave does Gas Screwfix Select

    First and formost a comi is sized for the water demand of the house not the heat loss for the rooms so given what you've said a a 28 to 30 Kw boiler will more than suffice. Combis work more efficiently working to capacity rather than under capacity so if you oversize a boiler you are paying more for fuel not used efficiently every time you turn a tap on.
    All modern combi's take 22mm tube to allow for the correct gas supply to the boiler and also allow for the 1mb max drop between meter and appliance. In a lot of cases it it worth coming off the meter initially in 28mm. You will be best speaking to your installer on this he will size the gas appropriately for the houses needs.This can be run surface but if you have the chance use Tracpipe and bury it.
    There are several remote computer programs on the market at present at an average cost of £190.00 do some research to suit your needs.
    Yes you can run the system in polypipe or similar but it is prone to sagging when hot so needs a lot more clipping than copper. If it were me installing it I would try and talk you out of it initially but if you insisted I would recommend anything seen on the surface be in copper, purely for aesthetic reasons. DA's suggestion of a zone valve is a good one and is currently part of Document J building regs but is not strictly adhered to in retro fits. But it can be beneficial to the end user for very little additional cost.
     
  5. PJ Wales

    PJ Wales Member

    Iphone apps controlled such as Tado and Hive etc need one thing to be installed which can be omitted in the initial package and that is the boiler heat demand/pump control. This is the device between the boiler and your room thermostat/app. SO when installing your combi boiler be aware you may need to install an external RF/wireless boiler controller.
     
  6. itchyspanner

    itchyspanner Member

    part l has now been updated and zoning has been changed back to pre 2010 regs. Only required above 150m2.wether its a good idea to zone is a different matter, they way the property will be used against the extra cost involved is the main thing to consider.
     
  7. The basic cost of a zone is one 2-port valve, one prog stat and a bit of wire. You'd be nuts not to. Imo.
     
  8. PJ Wales

    PJ Wales Member

    If your are serious about going for zone control and want to use iphone or any phone/tablet devices, then you are best to look into z-waves systems and get yourself some danfoss living TRV and these can be controlled by your devices with ease and best of all you can expand your systems to full automation of your home using z-waves wireless.

    There are several free z-waves apps to control danfoss TRV.
     

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