MikeGrahamT21 Posted July 17, 2020 Share Posted July 17, 2020 Hi, BPC sent an MVHR installation guide out yesterday, very useful, and one of the things it mentioned was keeping the Radial pipe runs below 15m. From memory I'll have a single supply run to the master bedroom which will either be on the limit or just slightly over. Any implications? Anything I need to do to remedy whatever? Rest of the runs are well below 15m Regards Mike Link to comment Share on other sites More sharing options...
Pete Posted July 17, 2020 Share Posted July 17, 2020 5 minutes ago, MikeGrahamT21 said: Hi, BPC sent an MVHR installation guide out yesterday, very useful, and one of the things it mentioned was keeping the Radial pipe runs below 15m. From memory I'll have a single supply run to the master bedroom which will either be on the limit or just slightly over. Any implications? Anything I need to do to remedy whatever? Rest of the runs are well below 15m Regards Mike Hope not as I have 5 long runs in mine, I think doubling up the pipe run will help enormously Link to comment Share on other sites More sharing options...
Temp Posted July 17, 2020 Share Posted July 17, 2020 The more constricted the pipe the more energy it takes to push air through them. Won't be a hard limit. There could also be an issue with balancing if there is a big difference in pipe runs to different rooms. Link to comment Share on other sites More sharing options...
MikeGrahamT21 Posted July 17, 2020 Author Share Posted July 17, 2020 OK, I can work with that. So potentially as Pete suggested, I may need to run an additional pipe to the room to reduce overall pressure to that outlet if I run into any issues. Its a straight run, just a long one. Link to comment Share on other sites More sharing options...
dpmiller Posted July 17, 2020 Share Posted July 17, 2020 just do two runs and be done with it. 1 Link to comment Share on other sites More sharing options...
joe90 Posted July 17, 2020 Share Posted July 17, 2020 @Jeremy Harris ran two to his kitchen if I remember correctly, thing is you cant instal one later if it’s required ? Link to comment Share on other sites More sharing options...
le-cerveau Posted July 17, 2020 Share Posted July 17, 2020 I had 4 double runs. The two kitchen extracts and the two ground floor long runs. However I have 2 valves in most rooms with singles, could of been a single valve with a double run in many rooms (original ground floor plan) but this was all part of the planning for balancing. Details in my blog Link to comment Share on other sites More sharing options...
MikeGrahamT21 Posted July 17, 2020 Author Share Posted July 17, 2020 After all that the longest run was 13.7m in the very longest way it could possiby go lol! Link to comment Share on other sites More sharing options...
dpmiller Posted July 17, 2020 Share Posted July 17, 2020 and how much shorter are the other runs? I'd put a second length in ... Link to comment Share on other sites More sharing options...
MikeGrahamT21 Posted July 17, 2020 Author Share Posted July 17, 2020 The other supply runs are around 8m each (3no) and then a single short one of around 3m. Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 17, 2020 Share Posted July 17, 2020 I routinely double-up on anything that looks remotely adverse, particularly to bedrooms, and the doubled run also makes for a slightly quieter solution also. Another thing to consider is two runs, but single runs to two ceiling valves instead of two runs to a single valve. I often do that in kitchens where the extract 'area' was large and it was better to cover more area. Again, a quieter solution especially when on boost. Good to remember when the kitchen / bathrooms boost the whole house boosts with it, as there is only one fan group servicing the whole system at a unified speed eg boost rate or trickle rate. 2 Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 17, 2020 Share Posted July 17, 2020 Also consider jumping up to a 92mm duct for any one adverse run for a get out of jail card as it's the resistance that dictates the max length of the run at x dia. 2 Link to comment Share on other sites More sharing options...
MikeGrahamT21 Posted July 17, 2020 Author Share Posted July 17, 2020 Thanks, i'll have a ponder about it. Whole solution has come in quite cheap so far, just a shade under £1000 for everything, and me installing, though this could rise quite a bit if I find the need for a carbon filter! Everything is tweakable as all the pipes are going in the loft, so if its not quite right first time, i've plenty of opportunity to sort it out. Starting clearing the loft in prep for all this, and hoovering all the crap up over the weekend, oh the joys ? Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 17, 2020 Share Posted July 17, 2020 Just now, MikeGrahamT21 said: .....all the pipes are going in the loft, so if its not quite right first time, i've plenty of opportunity to sort it out. Warm or cold attic? Link to comment Share on other sites More sharing options...
MikeGrahamT21 Posted July 17, 2020 Author Share Posted July 17, 2020 Just now, Nickfromwales said: Warm or cold attic? Cold, all pipes are getting buried under 300mm of insulation. Very much doubt it will be a cold attic tomorrow though! 1 Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 17, 2020 Share Posted July 17, 2020 (edited) TLC were the cheapest when I needed some slide-over insulation link Some cheaper on ebay IIRC Edited July 17, 2020 by Nickfromwales Link to comment Share on other sites More sharing options...
MikeGrahamT21 Posted July 17, 2020 Author Share Posted July 17, 2020 7 minutes ago, Nickfromwales said: TLC were the cheapest when I needed some slide-over insulation link Some cheaper on ebay IIRC Yeah thats a good price. I'll need a tiny bit for the odd bits which come out of the insulation, but majority is just going to be buried for ease. Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 17, 2020 Share Posted July 17, 2020 £24 for 10m here ? 1 Link to comment Share on other sites More sharing options...
ProDave Posted July 18, 2020 Share Posted July 18, 2020 I used double runs for all of mine, including the really short ones. Why? Because I thought that was what you were supposed to do. The Architectural Technician that detailed the house drew up the MVHR system plan with it all shown as twin runs. I then bought the kit from BPC and installed it myself, with a few changes to the details of the runs. BPC never said anything. All the celing outlets came ported for 2 pipes, so it all just seemed logical and correct. It was only AFTER doing this I started to read most people only used one run of pipe on anything but the very longest runs. 1 Link to comment Share on other sites More sharing options...
joe90 Posted July 18, 2020 Share Posted July 18, 2020 I only ran single runs even to the longest run which is about 18m, I did this after reading about others and how in reality the flow rates were set below recommended levels . 1 Link to comment Share on other sites More sharing options...
gc100 Posted July 18, 2020 Share Posted July 18, 2020 I have 2 runs at ~25m . I’ve doubled up and have 4 vents with them all for the same large kitchen living area. I didn’t really have any other choice due to the restrictions of my house. Fingers crossed it won’t work the unit too hard. 1 Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 20, 2020 Share Posted July 20, 2020 https://www.electrical2go.co.uk/insulated-aluminium-ducting-100mm-x-10m-fxalins-100.html?utm_source=google_shopping&gclid=EAIaIQobChMI1ubAyLnc6gIVj-vtCh1GlgBoEAQYBSABEgLqkPD_BwE Even cheaper again 1 Link to comment Share on other sites More sharing options...
MikeGrahamT21 Posted July 21, 2020 Author Share Posted July 21, 2020 (edited) I was going to start another topic to ask this, as its not really related, but I'll ask in this one... Rather than going through the external wall for fresh inlet, and stale outlet, I've thought about going through the roof. I see on BPC they sell a 20,000mm2 roof vent, but I want something which is a bit more 'integrated' into the build. How many mm2 of free vent area do I actually require? Clearly the less restriction the better. I was thinking of using something like this: https://klober.co.uk/product/pitched-roofing/pitched-roof-vents/profile-line-15x9-tile-vent These give 10,000mm2, but if I need to get to 20,000mm2 I guess I can just have two of these side by side, and then join the vent pipes from them into the single 125mm ducting? Trying to make it look as invisible as possible, i've got one of these type tiles for an extractor in the utility (not part of the ventilation strategy) and it works very well in terms of performance and looks. Or is it more in terms of resistance? The MVHR i've got has a max flow of 63l/s, which gives the Klober 192pa of resistance, and this one (https://www.hambleside-danelaw.co.uk/wp-content/uploads/2016/08/Datasheet_TV10-Series_July19.pdf) 115pa of resistance. In comparison the 20K universal tile that BPC sell (https://klober.co.uk/product/pitched-roofing/pitched-roof-vents/universal-20k-tile-vent) gives 43pa at the same flow rate. So if I get two of the danelaw tiles, that would give less than 60pa of resistance per tile, which seems acceptable at maximum flow? I think the Klober Profile Line 15x9's are too restricted looking at the specs. Edited July 21, 2020 by MikeGrahamT21 Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 21, 2020 Share Posted July 21, 2020 You’ll be up there every week cleaning those. The proper ones have either no restriction or just a fine 10x10mm mesh. Also, the type you show from BPC is for outlet only. For inlet you need the one that looks like a gas boiler vertical flue, and I believe it’s to do with sucking in excess rain / spray that bounces off the roof in bad weather. ? Link to comment Share on other sites More sharing options...
MikeGrahamT21 Posted July 22, 2020 Author Share Posted July 22, 2020 Ahh ok, didn’t know you needed different one for inlet, good to know. I guess I’ll have to go with the uglier more free flowing solution, or go back to through the gable end Link to comment Share on other sites More sharing options...
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