Jeremy Harris Posted August 13, 2019 Share Posted August 13, 2019 The insulation is probably something like rockwool or glass fibre I expect. Should be easy enough to remove it to see how to connect a silencer, I think. The main thing is to ensure that the insulation vapour barrier on the outside is taped up, so that condensation can't form inside and make the insulation wet. Link to comment Share on other sites More sharing options...
JamesJJJ Posted August 14, 2019 Author Share Posted August 14, 2019 Can I check my logic here. If I confirm the flow rate from the silent vent is in the normal 8-10l/s range (i.e. same as the other rooms) then the difference in noise must be down to the ducting or the valve? I have already confirmed the valve is the same, so this would effectively prove the flexible ducting is acting as a silencer and essentially confirm I need to add a silencer? Basically I am trying to ascertain whether the noise is airflow or motor... Link to comment Share on other sites More sharing options...
Jeremy Harris Posted August 14, 2019 Share Posted August 14, 2019 I doubt that there's much air flow noise from the ducts at around 7 to 8l/s. Flow noise generally starts to become noticeable at a flow velocity of around 2.5m/s, which equates to the following air flow rates for various internal duct diameters: 63mm (semirigid), 2.5m/s = 7.8l/s 100mm, 2.5m/s = 19.6l/s 125mm, 2.5m/s = 30.7l/s 150mm, 2.5m/s = 44.2l/s You may get flow noise around the terminals when they are closed right up, but they'd have to be pretty near closed for this to be a problem, plus the fans would have to be running at high speed. It's most probable that the noise is fan noise, I think. Link to comment Share on other sites More sharing options...
JamesJJJ Posted August 14, 2019 Author Share Posted August 14, 2019 Thanks, Any idea how you adjust a vent like this? Link to comment Share on other sites More sharing options...
JamesJJJ Posted August 15, 2019 Author Share Posted August 15, 2019 (edited) To answer my previous question I dont think you do. My voyage into the world of mvhr has uncovered some lovely installation/service bodging. I managed to acquire a testo 405 and attempted to balance the house but this proved almost impossible because the bathroom extracts were all near zero. Venturing back into the loft and tracing the extract pipes I quickly realised the bathroom fitting needs 100mm pipe but the t-pieces used were 125mm. Their solution was to use insulation to pad the 100mm pipe up to 125 and tape it in place! I also found the 90deg bends were not attached to the ceiling fittings so all 3 bathroom vents were extracting loft air (well, what could get through the insulation!). I am also not convinced the ceiling fittings are designed for mvhr as opposed to a simple extractor fan with the fan removed! All of the ductwork is beautifully insulated, except the main extract runs from the utility and the kitchen. So the warmest rooms were losing all their heat to the loft! All of the t and y pieces are uninsulated for some reason. It now seems quieter and the extract numbers are way higher. However I notice the main extract duct is attached to the mvhr in a similarly shoddy fashion so must be wasting loads of air velocity there as well. I tested the quiet room up to 13l/s and it was still perfectly quiet, so I think the noise we are hearing is motor related. I have therefore ordered a flexible silencer for the fresh air feed and will install that straight off the unit. Assuming this makes things nice and quiet i will then set about sorting the main extract duct and then go about re-balancing it again. It's really frustrating that this was supposedly serviced a few weeks back and was said to be tip-top when the engineer left... Edited August 15, 2019 by JamesJJJ Link to comment Share on other sites More sharing options...
PeterW Posted August 15, 2019 Share Posted August 15, 2019 On 14/08/2019 at 19:30, JamesJJJ said: Thanks, Any idea how you adjust a vent like this? You don’t ... that’s a shower light extractor..!! Could make a restrictor ring somehow with some thin plastic ..?? Link to comment Share on other sites More sharing options...
PeterW Posted August 15, 2019 Share Posted August 15, 2019 4 minutes ago, JamesJJJ said: Venturing back into the loft and tracing the extract pipes I quickly realised the bathroom fitting needs 100mm pipe but the t-pieces used were 125mm. Their solution was to use insulation to pad the 100mm pipe up to 125 and tape it in place You can buy 125-100 adapters in Screwfix and Toolstation - not expensive. Link to comment Share on other sites More sharing options...
JamesJJJ Posted August 15, 2019 Author Share Posted August 15, 2019 Just now, PeterW said: You can buy 125-100 adapters in Screwfix and Toolstation - not expensive. Thats exactly what I bought, they are now nicely fitted and no insulation in the ducts. 1 Link to comment Share on other sites More sharing options...
Jeremy Harris Posted August 15, 2019 Share Posted August 15, 2019 I mentioned earlier that I suspected some systems probably weren't properly commissioned. I honestly didn't expect that you'd find a horror show like this, though! Link to comment Share on other sites More sharing options...
Oz07 Posted August 16, 2019 Share Posted August 16, 2019 9 hours ago, JSHarris said: I mentioned earlier that I suspected some systems probably weren't properly commissioned. I honestly didn't expect that you'd find a horror show like this, though! On the bright side it all sounds fixable with the help of you guys. Another problem bites the dust! 1 Link to comment Share on other sites More sharing options...
JamesJJJ Posted August 16, 2019 Author Share Posted August 16, 2019 1 hour ago, Oz07 said: On the bright side it all sounds fixable with the help of you guys. Another problem bites the dust! Completely agree. Everybody here has been hugely helpful and it is already way better than it was... Link to comment Share on other sites More sharing options...
PeterW Posted August 16, 2019 Share Posted August 16, 2019 @JamesJJJ is it worth looking at the current pull again if it’s been opened up as the resistance in the system should be less. Link to comment Share on other sites More sharing options...
JamesJJJ Posted August 16, 2019 Author Share Posted August 16, 2019 Yes, I am going to put an energy monitor onto the cable so I can keep a proper eye on it. Link to comment Share on other sites More sharing options...
JamesJJJ Posted August 19, 2019 Author Share Posted August 19, 2019 The acoustic duct arrived today and in Villavent land the only thing which identifies this as different from normal duct is a small green sticker on it. I am therefore guessing the lovely acoustic duct is installed under the insulation on its way to the silent bedroom. It would be far easier if the entire white membrane had a green streak in it to clearly mark it out as a silencer. This was relatively easy to fit and I made sure it went around a bend as per the instructions: After turning the unit back on the only thing to be heard was silence, so noise problem solved! I feel much more confident navigating the unit and ducting now, so decided to tackle the main extract duct at the top of the picture. I knew it wasnt properly connected but removal revealed another horror show: I removed all of this, stretched the semi-rigid duct and smoothed the curve (as much as I could) before reattaching: Powering back on the extract was noticeably more powerful especially into the bathrooms with the incorrect terminals! I managed to balance everything out on Max to the following levels: Extract Flow Rate Inlet Flow Rate Master Bedroom 10 Master En Suite 8 Dressing Room 8 Bedroom 2 6 En Suite 8 Bedroom 3 8 Bedroom 4 8 Bedroom 5 6 Bathroom 8 Hallway Kitchen/Family 13 11 Porch Hallway Dining Room 8 Office 7 WC 8 Utility 10 Total 63 64 It is now lovely and quiet everywhere, even on Max. One thing I have noticed is that the unit is drawing even more power. Despite improving the ductwork significantly it is now consuming 180W on Normal mode and 320W on high! The temps have dropped over the last week or so and it was switched from summer bypass to heat recovery. I noticed the control panel has an error on it indicating the rotor motor has failed. Dismantling this I found the bearing was seized so I managed to loosen this with some WD40. I am not holding out much hope and I think the motor will need to be replaced along with the filters in the coming weeks. This unit was introduced back in 2009 so it is lacking any smart features and the only control is via the wired control panel (which lives in our utility). I have therefore fitted a smart plug and that combined with the air quality monitor, temp/humidity sensor and IFTTT means I can start to automate its usage such as making sure the unit is running if humidity in a bathroom increases, or CO2 in our bedroom starts rising above a threshold. Because of its high power consumption I still think opening windows is preferable at this time of year, so the unit can be left off all day and switch on/off depending on various input conditions. Link to comment Share on other sites More sharing options...
JamesJJJ Posted August 19, 2019 Author Share Posted August 19, 2019 I meant to add, comparing power consumption to flow rates I get the following values: Mode Power Consumption Flow Max 320 100% Normal High 182 92% Normal Low 152 80% Min 95 47% I need to dig back into the unit and see if I can find the elusive dip switches and rotary dial so the speed can be more accurately controlled. Link to comment Share on other sites More sharing options...
SteamyTea Posted August 20, 2019 Share Posted August 20, 2019 15 hours ago, JamesJJJ said: comparing power consumption to flow rates I get the following values It is following a log curve, which is probably correct. Power needed to move air via a fan follows a cube law, multiplied by the efficiency. The efficiency is set by Betz Limit. Link to comment Share on other sites More sharing options...
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