Levo Posted November 14, 2020 Share Posted November 14, 2020 The problem being in the supply, did you check the filters? The external inlet cowling and the internal filter? Clogging up will reduce flow rates, no? Link to comment Share on other sites More sharing options...
JamesP Posted November 14, 2020 Share Posted November 14, 2020 (edited) @Levo I did check the filters, gave them a good clean before testing. The Vent Axia we have has a maximum airflow of 500m3/h for a maximum house size of up to 260m2. The volume is nearer 750m3 due to high ceilings. Figures below were sent from the supplier last week. The initial supply air figures when purchased were 187m3/h! (2018). Edited November 14, 2020 by JamesP Link to comment Share on other sites More sharing options...
LA3222 Posted November 14, 2020 Share Posted November 14, 2020 (edited) @JamesP the MVHR system is something I'm trying to wrap my head around at the minute as I should be ready to install in December (I have the kit now, from BPC too). Your min boost extract rate is very similar to my own value of 81.3l/s. I am trying to understand how BPC assign each rate to the rooms, I assume it must be a function of the whole rate proportional to the room volume but i haven't got to the stage of playing with figures yet. I have a lot more supply/extracts than you - design done by BPC. I only have one extra en-suite to you but they specified an extract in the hallway too. Ours builds seem similar in terms of size and no. of rooms yet they specified the Vent Axia High Flow and i have 8 extract / 10 supply. Have they underspecified for you in terms of MVHR unit? and is that the source of the issues you are having? I'm no expert, just pondering why our specs are so different. Edited November 14, 2020 by LA3222 Link to comment Share on other sites More sharing options...
JamesP Posted November 14, 2020 Share Posted November 14, 2020 @LA3222 Yes the High Flow has a maximum, FID, airflow 650m3/h. What is FID? It looks as though ours is under specified. I was wondering about how each room is assigned. Both our sitting rooms are of a similar size yet mine has been specified at twice the supply air. I think it is just to balance the figures. The MVHR sits very central in the house so has runs of up to 15 meters in either direction. It works well in the background at 30%, use the boost in the kitchen and the humidity sensors kick in when showering etc. Link to comment Share on other sites More sharing options...
JamesP Posted November 14, 2020 Share Posted November 14, 2020 @LA3222 I used 5 x 50m rolls of 75mm radial ducting and wondering how much you have been specified? Link to comment Share on other sites More sharing options...
LA3222 Posted November 14, 2020 Share Posted November 14, 2020 (edited) 20 minutes ago, JamesP said: @LA3222 I used 5 x 50m rolls of 75mm radial ducting and wondering how much you have been specified? 7, i have 14 port manifolds so a quite a few of my runs are doubled up. Edited November 14, 2020 by LA3222 Link to comment Share on other sites More sharing options...
Levo Posted November 14, 2020 Share Posted November 14, 2020 1 hour ago, JamesP said: @LA3222 Yes the High Flow has a maximum, FID, airflow 650m3/h. What is FID? It looks as though ours is under specified. I was wondering about how each room is assigned. I assume that figure is with very low back pressure, @100Pa the flow drops to 575 according to the BCP specs. That I believe is with G3 filters (ISO 45% Coarse (G3)). As a matter of curiosity, do you have paper filter on the inlet side, I believe this unit supports the M5 filter option (ISO ePM10 50% (M5))? A finer filter will further restrict the air flow capacity. How much is obviously anyone's guess... Link to comment Share on other sites More sharing options...
JamesP Posted November 15, 2020 Share Posted November 15, 2020 @Levo Standard G3 filters fitted both sides. Link to comment Share on other sites More sharing options...
JamesP Posted January 26, 2021 Share Posted January 26, 2021 Quick update as perhaps why the MVHR was not quite meeting the supply demand. I recently removed the external inlet grill and this what I found. Will retest the ventilation rates now. 1 Link to comment Share on other sites More sharing options...
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