Olly P Posted December 22, 2021 Share Posted December 22, 2021 (edited) Hi all We have installed vent axia sentinel kinetic plus MVHR. 2 units, 1 upstairs, 1 downstairs. Circa 450 Sqm dormer bungalow. The systems were designed and supplied by BPC and I installed them myself. We are nearing completion on the build and I have had the ground floor MVHR running for a few weeks. I have not commissioned the system yet as I'm yet to get hold of an anemometer but i have set all terminals at 2 turns out. My issue is that when I run a hot shower or create steam in the kitchen by boiling some water the extraction is very poor, even on boost . But the supply to the rooms is very good and you can hear/feel the air being supplied into the rooms. I've altered the boost extract setting to 100% and its still not great. I've cleaned the filters and checked all the ducting all seems good and airtight. Any ideas? I was expecting the same performance as a conventional extractor fan but this is nowhere near that. I am expecting too much?? I have the ducting set up as per the vent axia installation manual but I would like to see if anyone could upload a picture of there vent axia system to confirm I have the ducting correct Edited December 22, 2021 by Olly P Link to comment Share on other sites More sharing options...
ProDave Posted December 22, 2021 Share Posted December 22, 2021 The obvious suggestion has to be open the extract vent terminals a bit more. You won't know anything for sure until you get it balances with an anemometer. Link to comment Share on other sites More sharing options...
Stones Posted December 22, 2021 Share Posted December 22, 2021 59 minutes ago, Olly P said: Hi all We have installed vent axia sentinel kinetic plus MVHR. 2 units, 1 upstairs, 1 downstairs. Circa 450 Sqm dormer bungalow. The systems were designed and supplied by BPC and I installed them myself. We are nearing completion on the build and I have had the ground floor MVHR running for a few weeks. I have not commissioned the system yet as I'm yet to get hold of an anemometer but i have set all terminals at 2 turns out. My issue is that when I run a hot shower or create steam in the kitchen by boiling some water the extraction is very poor, even on boost . But the supply to the rooms is very good and you can hear/feel the air being supplied into the rooms. I've altered the boost extract setting to 100% and its still not great. I've cleaned the filters and checked all the ducting all seems good and airtight. Any ideas? I was expecting the same performance as a conventional extractor fan but this is nowhere near that. I am expecting too much?? I have the ducting set up as per the vent axia installation manual but I would like to see if anyone could upload a picture of there vent axia system to confirm I have the ducting correct Conventional extractor fans are designed to shift large volumes of air quickly. MVHR less so. I think this is probably more a case of your expectations rather than anything wrong with the MVHR unit itself. I take it the steam in bathroom clears, just takes longer than you thought? Link to comment Share on other sites More sharing options...
Olly P Posted December 22, 2021 Author Share Posted December 22, 2021 11 minutes ago, Stones said: Conventional extractor fans are designed to shift large volumes of air quickly. MVHR less so. I think this is probably more a case of your expectations rather than anything wrong with the MVHR unit itself. I take it the steam in bathroom clears, just takes longer than you thought? Thanks for the advise so far. Yes it could be the case I'm maybe expecting too much and the steam did clear in the end. I will order an anemometer tonight and see what's actually happening. It's just strange that the supplying terminals are supplying lots of air yet the extracting ones arent performing the same. Link to comment Share on other sites More sharing options...
jamieled Posted December 22, 2021 Share Posted December 22, 2021 Does it have an inbuilt humidity sensor and if so what threshold is it set to to trigger the boost (or are you triggering the boost manually to test it)? Link to comment Share on other sites More sharing options...
Olly P Posted December 22, 2021 Author Share Posted December 22, 2021 25 minutes ago, jamieled said: Does it have an inbuilt humidity sensor and if so what threshold is it set to to trigger the boost (or are you triggering the boost manually to test it)? It does have an inbuilt humidity sensor and it's set to 70% which is default. I've been manually boosting it to test Link to comment Share on other sites More sharing options...
Roundtuit Posted December 22, 2021 Share Posted December 22, 2021 As above, you can't really tell what's going on until you measure it. From memory, you can set extract and supply fan speeds independently I think, to compensate for differences in resistance in the ducting. For info, we've got a single unit, and the humidity sensor (on factory settings) kicks in within a couple of minutes of turning the shower on; never have to use the manual boost. 1 Link to comment Share on other sites More sharing options...
Stones Posted December 23, 2021 Share Posted December 23, 2021 13 hours ago, Olly P said: Thanks for the advise so far. Yes it could be the case I'm maybe expecting too much and the steam did clear in the end. I will order an anemometer tonight and see what's actually happening. It's just strange that the supplying terminals are supplying lots of air yet the extracting ones arent performing the same. Its very difficult to detect the extract air movement by hand - and in comparison to supply where there is a positive flow it feels like there is very little movement. A very easy way to test that air is being pulled through is to hold a bit of tissue up flat to the extract vent - the extract air flow should pull the tissue up against the terminal and at least reassure you that it is extracting. You could also close all but one extract terminal and see the step change at the one remaining open one, again to show you the total volume of air being extracted. 1 Link to comment Share on other sites More sharing options...
MJNewton Posted December 23, 2021 Share Posted December 23, 2021 Adding to what Stones has said about the misleading perception from using your hand to detect extracted air flows, if you've got access to the exhaust vent (even temporarily removing the ducting to it if need be) you'll get a much better feeling of flow by checking there. Of course it'll represent the total whole-house extraction but it'll still give an indication of things operating as expected (or not!). 1 Link to comment Share on other sites More sharing options...
phatboy Posted December 26, 2021 Share Posted December 26, 2021 You likely have less extract vents than supply, so open them up a bit more! You also need to set the "Ckr Hood Supply" and 'Ckr Hood Extract" to 100%, even though you don't have that installed. (BPC advised me of this) 1 Link to comment Share on other sites More sharing options...
Chris-G Posted January 5 Share Posted January 5 (edited) Hey @Olly P I wondered where you got to with this. I have the exact same system and after replacing the bearings in one of the fans I have noticed my extract seems very weak. I didn't ever fully balance the system when I installed it, but intend to now. It may be that the extract has always been like this. On 'normal airflow 30%' my extract vents only just hold a tissue. Cheers Edited January 5 by Chris-G Link to comment Share on other sites More sharing options...
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