Super_Paulie Posted July 28, 2023 Share Posted July 28, 2023 I'm sure you knowledgeable lot can answer this in a jiffy, I can't seem to find the answer online. Boiler in the loft, wiring centre (and UFH gubbins) on the ground floor. Should both of these be powered from the same FSU? Just means they are a long way away from each other in terms of local isolation... Link to comment Share on other sites More sharing options...
MikeSharp01 Posted July 28, 2023 Share Posted July 28, 2023 7 minutes ago, Super_Paulie said: Should both of these be powered from the same FSU Makes sense. You can put a label on either / both saying it must be isolated elsewhere (say where) if adjacent to one or other or neither. Link to comment Share on other sites More sharing options...
ProDave Posted July 28, 2023 Share Posted July 28, 2023 The main feed will be to the wiring centre. so FCU there. From there you will need a minimum of permanent L and N and switched L (call for heat) to the boiler. So use a 3 core and earth for that, and locally a 3 pole fan isolator switch would do the job of local boiler isolation. 1 Link to comment Share on other sites More sharing options...
Super_Paulie Posted July 28, 2023 Author Share Posted July 28, 2023 (edited) I've already got 2 FCUs from the ring final, one at each location. But it dawned on me that when you knock the boiler off it should be knocking the wiring centre/gubbins off at the same time. Or not? Edited July 28, 2023 by Super_Paulie Link to comment Share on other sites More sharing options...
Super_Paulie Posted July 28, 2023 Author Share Posted July 28, 2023 Apologies, phone keeps autocorrecting to FSU for reasons unknown. Link to comment Share on other sites More sharing options...
MikeSharp01 Posted July 28, 2023 Share Posted July 28, 2023 Yes one point of isolation for all of it then no chance of a cross feed from anywhere. Link to comment Share on other sites More sharing options...
Super_Paulie Posted July 28, 2023 Author Share Posted July 28, 2023 If my Baxi needs protecting with a 3a and my Heatmiser a 5a, how can I run these from the same spurred FCU? Davinci level drawing attached. Link to comment Share on other sites More sharing options...
Super_Paulie Posted July 30, 2023 Author Share Posted July 30, 2023 (edited) On 28/07/2023 at 19:46, ProDave said: The main feed will be to the wiring centre. so FCU there. From there you will need a minimum of permanent L and N and switched L (call for heat) to the boiler. So use a 3 core and earth for that, and locally a 3 pole fan isolator switch would do the job of local boiler isolation. Cheers Dave. So like this? (earths omitted for clarity) I assume i wouldnt need to isolate the live return to the Heatmiser as it the live supply is clipped at the 3 pole. Quick couple of points if i may. Without a second isolator down at the wiring centre i wouldnt be able to isolate it without killing the juice to the boiler, so if i had an issue down there it would also cut off my potential for hot water only. Should i add in that secondary isolator or am i just being overly cautious in regards to future issues? The heatmiser needs fused down to 5a and the boiler 3a, what fuse should i be looking at in the FCU? Cheers fella. Im the type of bloke who needs to draw it all out in advance. Makes for slow work but thats all my brain will accept. Edited July 30, 2023 by Super_Paulie Link to comment Share on other sites More sharing options...
JohnMo Posted July 30, 2023 Share Posted July 30, 2023 I would double check your boiler takes a live demand for heat. Ours needed a volt free demand for heat. Link to comment Share on other sites More sharing options...
Super_Paulie Posted July 30, 2023 Author Share Posted July 30, 2023 (edited) 1 hour ago, JohnMo said: I would double check your boiler takes a live demand for heat. Ours needed a volt free demand for heat. its a Baxi 830. To keep it simple im using the "240v control connection" instead of anything OpenTherm as i dont think i need that. Attached picture i found online but mine is the same. The Heatmiser LS (live supply) and the LR (live return) are volt free, so connecting those in place of this yellow loop will call for heat, i believe. Edited July 30, 2023 by Super_Paulie Link to comment Share on other sites More sharing options...
Super_Paulie Posted July 30, 2023 Author Share Posted July 30, 2023 1 hour ago, JohnMo said: I would double check your boiler takes a live demand for heat. Ours needed a volt free demand for heat. so i guess.... thats means i wouldnt need to run the LS though the isolator at all as it is never live. Link to comment Share on other sites More sharing options...
JohnMo Posted July 30, 2023 Share Posted July 30, 2023 It doesn't look like you need to supply a 240v live as it already has it. The jumper just becomes a switch in the wiring centre. So the two wires just go from boiler to wiring centre not in to the isolation switch. If it wrong someone will be along to say I'm wrong Link to comment Share on other sites More sharing options...
Super_Paulie Posted July 30, 2023 Author Share Posted July 30, 2023 12 minutes ago, JohnMo said: It doesn't look like you need to supply a 240v live as it already has it. The jumper just becomes a switch in the wiring centre. So the two wires just go from boiler to wiring centre not in to the isolation switch. If it wrong someone will be along to say I'm wrong i agree, was just drawing that up. Hopefully if we are off the mark someone will advise but im hoping to test this out at some point this afternoon. Link to comment Share on other sites More sharing options...
TonyT Posted July 30, 2023 Share Posted July 30, 2023 (edited) No need for a 3 pole isolator. the fcu is the only isolator required. any thoughts for the boiler on its own circuit? Edited July 30, 2023 by TonyT Link to comment Share on other sites More sharing options...
Super_Paulie Posted July 30, 2023 Author Share Posted July 30, 2023 20 minutes ago, TonyT said: No need for a 3 pole isolator. the fcu is the only isolator required. any thoughts for the boiler on its own circuit? Cheers Tony. But that would mean I have no "local" isolation at the boiler? Guess it doesn't really matter but I was going to go from solid core to flex at loft level so may as well put the "local" isolation in instead of just a junction box. If I don't have isolation down before the wiring centre but after the FCU then I'd have no means to knock that off and keep the combi providing DHW, but how often that situation will come up is anyone's guess. Boiler on its own circuit could happen, the wiring centre is almost at the consumer unit anyways. Link to comment Share on other sites More sharing options...
TonyT Posted July 30, 2023 Share Posted July 30, 2023 (edited) Run a 5 core flex from the wiring centre to the boiler label at boiler to say isolation at wiring centre or if it’s on its own circuit breaker/rcbo. Another isolation point Edited July 30, 2023 by TonyT Link to comment Share on other sites More sharing options...
Super_Paulie Posted July 30, 2023 Author Share Posted July 30, 2023 5 minutes ago, TonyT said: Run a 5 core flex from the wiring centre to the boiler label at boiler to say isolation at wiring centre or if it’s on its own circuit breaker/rcbo. Another isolation point I was under the impression flex is frowned upon over distance? We are looking at 15m maybe from boiler to wiring centre. So ignore the fact I wouldn't get DHW if the wiring centre needs isolating for whatever reason? Probably a situation that would never occur to be fair. Link to comment Share on other sites More sharing options...
TonyT Posted July 30, 2023 Share Posted July 30, 2023 Run 100 m if you want no reg to say otherwise Link to comment Share on other sites More sharing options...
TonyT Posted July 30, 2023 Share Posted July 30, 2023 (edited) And a 2 core to the outdoor sensor for weather compensation direct from the boiler Edited July 30, 2023 by TonyT Link to comment Share on other sites More sharing options...
Super_Paulie Posted July 30, 2023 Author Share Posted July 30, 2023 23 minutes ago, TonyT said: Run 100 m if you want no reg to say otherwise Interesting, id read otherwise. I'll do more research on that. If I have the boiler 3a and the wiring centre 5a from the same FCU, how would I protect both from a single fuse? Link to comment Share on other sites More sharing options...
TonyT Posted July 30, 2023 Share Posted July 30, 2023 Most cables radiate from the wiring centre out ( expect the weather comp that’s direct to the boiler) it’s a cable into the spur, out the the spur into the wiring centre 3a fuse for the lot. you are trying to minimise joints Link to comment Share on other sites More sharing options...
Super_Paulie Posted August 12, 2023 Author Share Posted August 12, 2023 On 30/07/2023 at 18:46, TonyT said: Most cables radiate from the wiring centre out ( expect the weather comp that’s direct to the boiler) it’s a cable into the spur, out the the spur into the wiring centre 3a fuse for the lot. you are trying to minimise joints Ok just to confirm before I crack on. I'm ok to run 5 core flex from the wiring centre/spur downstairs up to the loft to power the boiler? Roughly 15m. It just seems I'm getting really contrasting information from 'the web about running such long flex. Cheers Link to comment Share on other sites More sharing options...
TonyT Posted August 12, 2023 Share Posted August 12, 2023 Yes it’s fine, flex still has to have a conductor size capable of handling the current like fixed wiring. https://www.tlc-direct.co.uk/Products/CA0dot75HR5.html Max 6 amp current Remember to fit 3 amp fuses in the spurs. Brown sleeving/ tape on any conductors used a switched line/live. 1 Link to comment Share on other sites More sharing options...
Super_Paulie Posted August 12, 2023 Author Share Posted August 12, 2023 Cheers gents, I've finished the job. Haven't flipped the switch yet as it's beer o'clock now I think, just want to say cheers for the info. One thing that I just thought though, I cable tied the 5 core flexes together along the run just to keep them neat while I was doing the job. Is that frowned upon or am I just being overly cautious with that? Link to comment Share on other sites More sharing options...
TonyT Posted August 12, 2023 Share Posted August 12, 2023 There is no significant current, I wouldn’t worry about it. 1 Link to comment Share on other sites More sharing options...
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