Crofter Posted February 9, 2017 Share Posted February 9, 2017 Seeing as my original question (instant heater or electric shower http://forum.buildhub.org.uk/ipb/topic/1873-electric-shower-vs-instant-water-heater/) ended up being answered with 'neither- fit a UVC', I decided it would be better to start a new thread. I know that these units are not a DIY install and that you need a plumber with a G3 certificate. They are also to be checked annually. Just how much of the install needs to be done by a plumber? Need to know so that I can plan to be at the right stage. I like to do as much work myself as possible so what is the minimum that a G3 plumber would do and be happy to leave me to finish off? I presume he will need the electrics in place, but what if I haven't finished building the actual bathroom and there are no taps or shower in place yet? Will he be happy connecting to pipes that I have already boxed in behind plasterboard? I've also seen reference to 28mm copper pipes... I've only got a 25mm service void and my plan is to run everything through that- tight but doable in 15mm especially if I have no fittings boxed away anywhere. I guess this will be a sort of Q&A with @Nickfromwales so will buy him a virtual pint... Link to comment Share on other sites More sharing options...
ProDave Posted February 9, 2017 Share Posted February 9, 2017 Copied from the other thread, I was just thinking about the discharge pipe for my UVC which has to be installed before my floor goes down. So this is my planned run: It will emerge in the airing cupboard space at floor level, so plenty of room for the 400mm above and below the tundish. From the airing cupboard floor it will drop down inside an internal wall 2.5 metres, bend (in bender) run horizontally (with a slight fall) 1 metre, bend (in bender) 2 metre horizontally (again with a slight fall) which will take it out through the front wall. Bend (solder or compression) to turn it downwards where it will discharge into a French Drain. So if each bend counts as 1/2 a metre that makes a total of "8 metres" so it will be okay. And yes that will all be 28mm copper. I will need to question where and how it actually drains. The easiest would be to take it through under where the front door is, BUT that will get enclosed by the ramp up to the door, so I suspect BC won't like that as you won't be able to see the discharge point. So I guess I have to discharge it a bit to one side so it's visible? Also, will it be okay just discharging onto a lot of stones that make up a French Drain? If not I can put a gulley there and tell BC it goes to a soakaway (which it will as the back of the gulley will discharge to the French drain but underground) Link to comment Share on other sites More sharing options...
Crofter Posted February 9, 2017 Author Share Posted February 9, 2017 My UVC will need to go either in the linen cupboard (need to talk to SWMBO about how much space we can lose there) or in the loft space (warm roof so not a complete waste of heat). Either way, I think the discharge pipe will have to go down through the floor. It could just run onto the stones that I laid over the ground under the house, or could perhaps tee into the drains that will take the gutters. Link to comment Share on other sites More sharing options...
Onoff Posted February 10, 2017 Share Posted February 10, 2017 18 hours ago, Crofter said: I guess this will be a sort of Q&A with @Nickfromwales so will buy him a virtual pint... Why virtual? https://beersbypost.com/?gclid=CLTyi5eqhdICFYK87Qod43ED4A Come to think of it I owe him too... Link to comment Share on other sites More sharing options...
jamiehamy Posted February 10, 2017 Share Posted February 10, 2017 As far as I'm led to believe (from two plumbers I know), the actually connection and certification of the UVC requires a qualified/certified plumber, however in terms of the 'rest' of the piping, there is no requirement for them to install or inspect. I know two people who are plumbers but can't do the whole job - but have said they have no issue with connecting up the UVC and making sure the install is correct. As I'm going down the manifold route, I don't see a dependancy on installing one before the other - either way I'll leave the actual connection until towards the end - I think. Or get the manifolds in place and the UVC connected and then work round each connection at the end at leisure since they can all be isolated at the manifold. Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 10, 2017 Share Posted February 10, 2017 Off point, but have you already plumbed to go with manifolds? I can't think of any reason to install manifolds in such a small house TBH, and there is a saving to be had by just buying 15mm Hepworth and unifying the install. Just have a 22mm 'rail' off the UVC, after the TMV, and take all the 15mm runs off that. Fit regular ballofix Tap isolators ( £1 each ) for primary isolation and your good to go at a fraction of the cost. Am I right in assuming your mates aren't G3 so that's the bit that's missing? Fwiw, my mate let his lapse whilst going through a divorce and I ended up using one of Telfords registered ( accredited ) installers to inspect and 'sign off' the UVC. Cost me around £150 iirc, so to answer one of your questions, I, a non-registered regular Joe, fitted that from start to finish and had it signed off via a 3rd party. Admittedly I have fitted a good few of these under supervision and beyond so I know the 'does and dont's' so all you need to do is ask. . I can bounce your postcode on to Roger @ Telford and see who is 'local' to you as TBH your going to need to have someone who can do the annual inspection anyhoo.? Do you have anyone G3 near you? Yell.com maybe? Link to comment Share on other sites More sharing options...
Onoff Posted February 10, 2017 Share Posted February 10, 2017 I have to consider something like this at some stage. I know @Nickfromwales keeps shouting "UVC" at me. From a quick Google I see a TS is unvented and imparts its heat to mains cold via a heat exchanger. Learnt that in the last 5 minutes. AND seemingly doesn't need to be G3. What then is the advantage/disadvantage of a TS over a UVC? Link to comment Share on other sites More sharing options...
Crofter Posted February 10, 2017 Author Share Posted February 10, 2017 I think a TS and a UVC do fundamentally different jobs. In a UVC, you draw off the water from inside, but in a TS you draw cold water through a coil within the TS, so it acts a bit like a boiler, i.e. it supplies heat but not water. Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 10, 2017 Share Posted February 10, 2017 View a TS as an instant water heater, like an extremely powerful combi. . Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 10, 2017 Share Posted February 10, 2017 27 minutes ago, Onoff said: I have to consider something like this at some stage. I know @Nickfromwales keeps shouting "UVC" at me. From a quick Google I see a TS is unvented and imparts its heat to mains cold via a heat exchanger. Learnt that in the last 5 minutes. AND seemingly doesn't need to be G3. What then is the advantage/disadvantage of a TS over a UVC? You've got oil haven't you? Link to comment Share on other sites More sharing options...
Jeremy Harris Posted February 10, 2017 Share Posted February 10, 2017 36 minutes ago, PeterW said: TS needs to be higher temperature and then runs cold quicker - all to do with stored heat. Somewhere I've got some graphs showing the comparison of two identical capacity tanks, one a thermal store, the other a UVC. Ther thermal store has a heck of a lot less capacity to deliver hot water than a UVC of the same capacity and at the same temperature, because of the way it cools down. A decent UVC should be able to deliver most of its capacity as hot water at the right temperature, which is its big advantage. Link to comment Share on other sites More sharing options...
Onoff Posted February 10, 2017 Share Posted February 10, 2017 15 minutes ago, Nickfromwales said: You've got oil haven't you? Erm....yes? Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 10, 2017 Share Posted February 10, 2017 Ok. In that case, you may be better off with a TS. I do forget ?. Good job you didn't 'rush' out and buy an UVC . With oil and UFH, there is quite a big conflict as the boiler can't modulate. That is usually best dealt with by means of a buffer tank but a TS would be the buffer AND provide DHW it's just down to losses and how the house is occupied. With a TS, you'd typically need it heated according to space heating and DHW consumption, much as with an UVC or your current hot cylinder, but the norm is for it to stay hot pretty much all of the time if the house is occupied other than with 9-5'ers. A TS will ebb heat away much quicker than an UVC, mostly due to the extra connective pipework etc, so is less likely to retain useable DHW through the day unless the time clock is left on constant. The summer is where the TS may fall largely redundant ( as you don't have PV so this info is case specific to you ) so there is an argument for a smallish buffer + UVC vs TS. You keeping the upstairs rads and going all UFH downstairs? An open pipe 'combination' TS won't need G3, but a sealed and pressurised one will. As usual, no easy solution other than the one that suits you best . 1 Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 11, 2017 Share Posted February 11, 2017 To stop this UVC thread drifting any further I've started this one.... Anything other than choosing / fitting an UVC can go there . I'll see about moving the content accordingly. Link to comment Share on other sites More sharing options...
Onoff Posted February 11, 2017 Share Posted February 11, 2017 So a UVC is basically just a "reinforced", traditional hot water cylinder able to cope with mains pressure. Mains in at the bottom instead of from the cold water storage tank above? Does the fact the water is hot increase the pressure by much on top of whatever the mains is at? What's the normal sort of pressure a UVC is run at? PRedV is obligatory I assume? Picked at random I see a copper Grade 1 cylinder rated at 3.65 BAR. My incoming mains is nearly triple that! I can see where the safety concerns are now. Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 11, 2017 Share Posted February 11, 2017 3 hours ago, Onoff said: So a UVC is basically just a "reinforced", traditional hot water cylinder able to cope with mains pressure. Mains in at the bottom instead of from the cold water storage tank above? Does the fact the water is hot increase the pressure by much on top of whatever the mains is at? What's the normal sort of pressure a UVC is run at? PRedV is obligatory I assume? Picked at random I see a copper Grade 1 cylinder rated at 3.65 BAR. My incoming mains is nearly triple that! I can see where the safety concerns are now. The hot water expands into a manufacturer supplied expansion vessel. Your current system does the same via the vent pipe over the CWS. Typically they operate around 3-3.5bar, as dictated by the control group / multiblock. Link That's a combination valve that provides 5-6bar cold mains PRV, a PRedV, a balanced 22mm cold draw off point ( to supply all mixer outlets with balanced hot and cold pressure ) and a, sometimes, a tapping to connect the EV. ( Fyi the EV goes on the uninterrupted side of the cold mains inlet to the cylinder ). Again, that's usually manufacturer supplied with the UVC ( they come with everything needed to complete the installation, less isolation valve ). 1 Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 11, 2017 Share Posted February 11, 2017 (edited) Fyi you MUST fit the multi block within around 500mm of the UVC ( in the same room adjacent will pass TBH but you can't mount that remotely ). To retrofit an UVC it's FAR easier to fit a secondary PRedV directly after the stopcock. ( yes, where you've just done all that lovely plumbing ). That gives higher pressure for the outside tap ( say set the secondary PRedV to 4 bar ( primary being the one at the UVC )) and then all of the existing cold plumbing can stay as is. Edited February 11, 2017 by Nickfromwales Added bold text 1 Link to comment Share on other sites More sharing options...
Crofter Posted April 24, 2017 Author Share Posted April 24, 2017 How much space do I need to leave around a UVC? I'm trying to see if I can squeeze the UVC in beside the washing machine in the same cupboard. Oh and size of UVC... a plumber I spoke to reckoned I ought to go all out and get a 200l tank... give people nice long hot showers... I thought that seemed a bit excessive for a one bedroom house! Sizing guidelines I've read online suggest that sort of size for a four bedroom house. Link to comment Share on other sites More sharing options...
ProDave Posted April 24, 2017 Share Posted April 24, 2017 As long as their is room for the plumbing. Ours is in the airing cupboard, built around it once the tank was in. We have 250L. SWMBO has showered until it went cold, then complained the tank was not big enough. Don't under estimate how long a woman can spend in a shower. 2 Link to comment Share on other sites More sharing options...
Crofter Posted April 24, 2017 Author Share Posted April 24, 2017 Ideally it would be arranged to be a snug fit between the washing machine and the wall, and all the plumbing would be on the front. Of course, like you, I have the luxury of building the walls around the tank. I was looking at the Telford 200l model- at 554mm diameter, it would be pretty damn tight next to a full size washing machine (cupboard is nominally only 1100mm but I can push it to 1200mm without any problems... more than that could get tricky). Link to comment Share on other sites More sharing options...
PeterW Posted April 24, 2017 Share Posted April 24, 2017 Telford do a slimline 200 litre one if its a standard direct you are after..? https://www.cylinders2go.co.uk/shop/stainless-steel-unvented-cylinders/telford-tempest-200-litre-slimline-direct-unvented-cylinder/ 1 Link to comment Share on other sites More sharing options...
Crofter Posted April 24, 2017 Author Share Posted April 24, 2017 Just the ticket, thanks! Link to comment Share on other sites More sharing options...
PeterW Posted April 24, 2017 Share Posted April 24, 2017 They also do a 250 litre which I think is 1800 x 410 but Trevor would know - you get the welsh pie discount if you quote @Nickfromwales ... Link to comment Share on other sites More sharing options...
Nickfromwales Posted April 25, 2017 Share Posted April 25, 2017 Don't be misled by guidelines which don't compare apples with apples for UVC size. Remember that you are having a direct with immersions NOT one fed off a boiler and wet coil. Big difference between the two as the recovery times are worlds apart. Forget about house sizes, "x size UVC for a 4 bed house" etc etc as DHW consumption is unique to each property. If a family stays and all use the shower in rapid succession then you'll even struggle with a 200L TBH, so you need to draw a line somewhere. To reheat from cold with just an immersion takes MUCH longer, and you also get less meaningful input from them whilst the hot water is being consumed eg they can't replace the energy being used as fast as it can / will be used, even more so vs a wet 'high recovery' coil. I'd say allow 70-80L of DHW per shower, and about 10mins worst case 'towel time' between showers ( for recovery ) as a benchmark for your calcs, and you'll be ok. That For starters you'll want a dual immersion tank, ( so you have redundancy / failsafe heater ), and if you go Telford then I know you can also specify 6kw immersions instead of the standard 3kw. With dual 6kw you could get away with a 150L or 180L imo based on an estimated 70/30 split of DHW/DCW consumption. The killer is two long showers back to back, so maybe for you the 180L is the safe limit. You can even buy UVC's with 3x 5kw immersions too, so one of those at 150L would suffice. There are plenty of solutions to this problem, just need to fine tune the criteria and size accordingly. 1 Link to comment Share on other sites More sharing options...
joe90 Posted April 25, 2017 Share Posted April 25, 2017 That info Nick is invaluable for my calculations. Not wishing to hijack this thread but to put my "two penneth worth in" my situation is similar in that most days it's just her and me ( and for a woman she does not take long to shower) so our UVC could be quite modest, however we do expect ( hope) family and friends will visit and I hate having to wait for immersions so plan to have a modulating inline heater as per Jeremy. We will just know that it will cost us for lecky on those occasions. An immersion will be needed for legionella cleansing tho. Link to comment Share on other sites More sharing options...
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