Nickfromwales Posted February 25, 2018 Share Posted February 25, 2018 1 hour ago, divorcingjack said: Ha! Our planners do not lower themselves to talk to members of the public who have questions about planning. How utterly ridiculous. I can try and get hold of someone, but it's just another task on the so-long list. I was hoping this would be straightforward. Or at least not as nightmarishly complex as every other sodding thing has been. Can you explain why @ragg987 suggestion of a UVC + buffer + blending valve would leave me out of DHW? Could I just upgrade the size of the cylinder? Size vs expected demand basically. The heat transfer rate of the boiler > coil > UVC wouldn't match the rate at which you could consume it at peak times of DHW demand. Something folk seem to forget / not mention much here is that a correctly sized TS and a chunk of a gas boiler will give you nearly constant DHW...eg bath, after bath, after bath or two - three ADEQUATE showers simultaneously with ease. Basically you look at the TS as a big, wet, high-flow combi boiler. As heat is consumed from a TS its replenished by the boiler. The size of the TS and its target store temperature dictate how long it'll provide 'continuous' DHW for, so are factors applied to each enquiry, as no two are ever exactly the same. A TS is a one tank solution for your requirements here, so capital cost is lower, functionality and simplicity is maximised and loss of valuable space is reduced by not having two cylinders to install. 1 hour ago, ragg987 said: Fair point, might be my ignorance but would a TS be more beneficial in this respect, assuming you are only running UFH? Sorry, my fault for the lack of clarity When I refer to cylinders then for ufh its just a buffer you need. I only refer to a TS when its providing both heating and DHW as otherwise it would just be a 'dumb' buffer. In this instance the TS would be providing space heating ( buffering of ) and DHW via an instantaneous DHW coil inside it. Therefore id size it to match the intended UVC size plus the assumed buffer that would have been required and go for one, prob 500l TS. A few will gasp at the thought of a 500l TS, ( roughly 1800mm H x 660mm Dia ) but going bigger will mean you dont have to keep it at the very high temps it would need to be kept at if it was smaller. Therefore the standing losses would be lower, and the latent heat issues would be reduced. That 500 would be if there was PV. 250-300 without. The next bomb-drop would be just fit a chunky buffer for UFH buffering, and maybe fit a coil in it for DHW pre-heat, and simply fit a Valiant 938 heatstore combi. If theres no PV id go for that in a heartbeat. You'd only be storing water at around 40oC then so very little latent heat loss then too. And another bomb...... DHW flow rates are all dictated by the incoming cold mains performance, so pointless planning a solution for 20+ litres per minute outgoing if you've only got 12 or 14 litres per minute coming in. @divorcingjack, do you know what your static cold mains pressure, and l/p/min flow rate are? Pretty critical base criteria for anyone to suggest a solution. Gas + UFH is the ball-ache here imo, so its making the best of what you've got. Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 25, 2018 Share Posted February 25, 2018 2 minutes ago, JSHarris said: Fitting microinverters under each panel mitigates the partial shading problem and gives you a direct 230 VAC feed from the array. What about achieving grid-tie with that arrangement J? Link to comment Share on other sites More sharing options...
Jeremy Harris Posted February 25, 2018 Share Posted February 25, 2018 2 minutes ago, Nickfromwales said: What about achieving grid-tie with that arrangement J? No problem at all, microinverters grid tie individually. 1 Link to comment Share on other sites More sharing options...
divorcingjack Posted February 25, 2018 Author Share Posted February 25, 2018 Ah ok, this did not come up during our original thinking about PV. I take it this makes the install more expensive? I think they would have to be set flat tbh. Next question - can they be installed on top of an EPDM roof? Also - there hasn't been any structural allowance made for this potential install - is this a problem? Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 25, 2018 Share Posted February 25, 2018 A pic or two of the roof would help with that. An aluminium frame would distribute the negligible weight so all problems that can. be solved. The fall-back solution is the Heatstore combi. Instant, constant high-flow DHW. Not a compromise imo either. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted February 25, 2018 Share Posted February 25, 2018 No problem with fitting them on EPDM, in fact as long as the roof is strong enough fitting can be DIY, using these: This puts the panels at a slight angle (15 deg) to allow them to self-clean, but you just ballast the plastic wedge with a couple of blocks and it just sits on the roof. The panel bolts to the top of the box and you just arrange them to take best advantage of the sun. Link to comment Share on other sites More sharing options...
dpmiller Posted February 25, 2018 Share Posted February 25, 2018 (edited) On top of a flat roof? http://www.pluginsolar.co.uk/?product=plug-in-solar-4kw-4000w-diy-solar-power-kit-with-renusol-console-tubs-for-ground-or-flat-roof edit : @JSHarris beat me to it. Edited February 25, 2018 by dpmiller Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 25, 2018 Share Posted February 25, 2018 4 minutes ago, JSHarris said: No problem with fitting them on EPDM, in fact as long as the roof is strong enough fitting can be DIY, using these: This puts the panels at a slight angle (15 deg) to allow them to self-clean, but you just ballast the plastic wedge with a couple of blocks and it just sits on the roof. The panel bolts to the top of the box and you just arrange them to take best advantage of the sun. Bingo. And no penetrations too. Link to comment Share on other sites More sharing options...
Visti Posted February 25, 2018 Share Posted February 25, 2018 (edited) @JSHarris already covered this, I was slow on the ball! 1 hour ago, Nickfromwales said: Have you done a survey / estimate on the potential yield anyway? If its a flat roof and you smother it, plus use micro inverters, you'll get some yield surely ? Someone posted an online doo-dah to work this out....anyone? I used the online PVGIS tool (recommended to me via the forum) to calculate the potential PV performance for our build in our lite version of a PHPP to review whether it was financially viable. Slope and Azmuth you can calculate from your plans, and the kWp of the system is dependent on how many panels you can fit on the roof, i.e. the roof area, and the kW performance of each panel. Plug in your location, and that gives an estimated kWh/day. Edited February 25, 2018 by Visti 1 1 Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 25, 2018 Share Posted February 25, 2018 Whats the latest on the future of FiT payments? This would be a relatively easy DIY install with the floor mounts and micro inverters. Link to comment Share on other sites More sharing options...
divorcingjack Posted February 25, 2018 Author Share Posted February 25, 2018 Oh, you lot! Buggeration. What are we looking at in terms of cost here? The available roof space is prob about 100 sqm - large skylights plus no panels within 1m of the edge of the roof. Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 25, 2018 Share Posted February 25, 2018 Just now, divorcingjack said: Oh, you lot! Buggeration. Theres always a tin bath and kettle you know 1 Link to comment Share on other sites More sharing options...
Visti Posted February 25, 2018 Share Posted February 25, 2018 2 minutes ago, divorcingjack said: Oh, you lot! Buggeration. What are we looking at in terms of cost here? The available roof space is prob about 100 sqm - large skylights plus no panels within 1m of the edge of the roof. We dismissed PV initially as a 4kWp system cost about £6k, but now we're looking at installing twice that potentially! Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 25, 2018 Share Posted February 25, 2018 75m2 would have roughly enough space for 47 panels so youve got plenty of space !!! Link to comment Share on other sites More sharing options...
Jeremy Harris Posted February 25, 2018 Share Posted February 25, 2018 9 minutes ago, Nickfromwales said: Whats the latest on the future of FiT payments? This would be a relatively easy DIY install with the floor mounts and micro inverters. Dead easy. No wiring connections needed on the roof, as everything has plugs so just plugs together and it's all safe, as the microinverters stay dead until they see the 230 VAC mains coming in, plus you're only ever dealing with a single panel as far as the DC goes, so it's only about 60 VDC at most, a lot less if the panel is covered whilst you plug it in. You just need an electrician to make the 230 VAC connection to the CU, via an isolator switch and generation meter. Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 25, 2018 Share Posted February 25, 2018 1 minute ago, JSHarris said: Dead easy. No wiring connections needed on the roof, as everything has plugs so just plugs together and it's all safe, as the microinverters stay dead until they see the 230 VAC mains coming in, plus you're only ever dealing with a single panel as far as the DC goes, so it's only about 60 VDC at most, a lot less if the panel is covered whilst you plug it in. You just need an electrician to make the 230 VAC connection to the CU, via an isolator switch and generation meter. The sunny boy Micros seem cheap enough on the interweb. Link to comment Share on other sites More sharing options...
PeterW Posted February 25, 2018 Share Posted February 25, 2018 SunnyBoys are expensive ..!!! I can get micro inverters for about £60 IIRC which makes a panel about £140 plus mounts. @divorcingjack if you can make an “upstand” of about 200mm cube in the centre of the roof then you’ve got an easy access for any system coming in and out of the deck. With an overhang you can use IP65 inline connectors and joint them in the roof void and then it’s as per @JSHarris with an isolator, RCBO and generation meter. Link to comment Share on other sites More sharing options...
divorcingjack Posted February 25, 2018 Author Share Posted February 25, 2018 Right. So, our sparky is also an installer, so I will talk about it with him. Assuming you lot have won the PV argument, how does this affect my flaming plumbing? @Nickfromwales, thank you for the explanation of the TS argument, I like that it is a simpler install and am reassured that it wouldn't run out of DHW if paired with a big enough boiler. Are the issues about thermal stores running out of HW normally due to a too-small boiler then? So, what on earth do we do with the PV output that relates to a thermal store? Link to comment Share on other sites More sharing options...
divorcingjack Posted February 25, 2018 Author Share Posted February 25, 2018 2 minutes ago, PeterW said: SunnyBoys are expensive ..!!! I can get micro inverters for about £60 IIRC which makes a panel about £140 plus mounts. @divorcingjack if you can make an “upstand” of about 200mm cube in the centre of the roof then you’ve got an easy access for any system coming in and out of the deck. With an overhang you can use IP65 inline connectors and joint them in the roof void and then it’s as per @JSHarris with an isolator, RCBO and generation meter. Roof is complete and watertight ..... Link to comment Share on other sites More sharing options...
PeterW Posted February 25, 2018 Share Posted February 25, 2018 Ok ...... so any penetrations in it at all ..?? Link to comment Share on other sites More sharing options...
dimpsy Posted February 25, 2018 Share Posted February 25, 2018 We're having panels on our flat garage roof and it's going to be well and truly penetrated using this https://www.nicholsonsts.com/products/rooftrak Link to comment Share on other sites More sharing options...
divorcingjack Posted February 25, 2018 Author Share Posted February 25, 2018 1 hour ago, PeterW said: Ok ...... so any penetrations in it at all ..?? Nope. Well, the skylights, but they already have the EPDM bonded to the upstands. They literally stuck down the last piece last Wednesday! The edging hasn’t been done though, so perhaps under there? We’d have to drill through the MBC kit though. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted February 25, 2018 Share Posted February 25, 2018 36 minutes ago, divorcingjack said: Nope. Well, the skylights, but they already have the EPDM bonded to the upstands. They literally stuck down the last piece last Wednesday! The edging hasn’t been done though, so perhaps under there? We’d have to drill through the MBC kit though. It's unlikely to be a cable that's bigger than 4mm2 so will easily run over the edge and be disguised easily enough, I'd have thought. I ran our 6mm2 inverter cable through a bit of 20mm conduit sealed into the wall then ran it inside to the consumer unit. The AC isolator switch and generation meter are mounted under the consumer unit. Link to comment Share on other sites More sharing options...
CC45 Posted February 25, 2018 Share Posted February 25, 2018 Our uvc coil wont deliver more than 18kw so bit pointless getting a bigger boiler. For reasons known only to the plumber (a friend) we ended up with 24kw. We have a ufh buffer of 90l. Bought both when @Nickfromwales organised the Telford cylinders discount a few months ago. Should get it all working in time for the summer.... Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 25, 2018 Share Posted February 25, 2018 5 minutes ago, CC45 said: Our uvc coil wont deliver more than 18kw so bit pointless getting a bigger boiler. For reasons known only to the plumber (a friend) we ended up with 24kw. We have a ufh buffer of 90l. Bought both when @Nickfromwales organised the Telford cylinders discount a few months ago. Should get it all working in time for the summer.... Your plumber was correct. Pointless going bigger than 24 tbh. Your worst case will be heating the house from cold and fully recharging both tanks so 24 is pretty much spot on. Its only worth going for a huge boiler if its a TS, so you can near constant DHW by matching the TS inout and output Plus it'll module down to prob 6kw too. Link to comment Share on other sites More sharing options...
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