JamesJJJ Posted August 11, 2019 Author Share Posted August 11, 2019 Looking at the engineer report the sum of extract was approx 52l/s and fresh air was approx 90l/s which suggests it is miles off. I seem to remember them changing flow rates but it looks like the report only shows pre-adjustment flow rates. Is there somewhere the anemometers can be rented so I can check this myself? Link to comment Share on other sites More sharing options...
Jeremy Harris Posted August 11, 2019 Share Posted August 11, 2019 20 minutes ago, JamesJJJ said: Looking at the engineer report the sum of extract was approx 52l/s and fresh air was approx 90l/s which suggests it is miles off. I seem to remember them changing flow rates but it looks like the report only shows pre-adjustment flow rates. Is there somewhere the anemometers can be rented so I can check this myself? We have a couple that belong to this forum under the tool loan scheme: https://forum.buildhub.org.uk/forum/167-tool-loan/ From those figures it does seem as if the MVHR just hasn't been set up properly, something I suspect isn't uncommon, as it takes time to do it properly and it's a bit of an iterative process, as making big adjustments to one terminal can have a knock on effect to the others. There's guides as to how to set up an MVHR system here: domestic_ventilation_compliance_guide_2010_edition.pdf NHBC MVHR Commissioning.pdf Link to comment Share on other sites More sharing options...
Gone West Posted August 11, 2019 Share Posted August 11, 2019 @JamesJJJ The latest section in my blog details how I commissioned our MVHR system. It may be of some help. Link to comment Share on other sites More sharing options...
PeterW Posted August 11, 2019 Share Posted August 11, 2019 @JamesJJJ can you find an exact model number or a photo of the control panel ..? Can work things out from there but this sounds like the reason you’re off is that it’s running way out of balance. Link to comment Share on other sites More sharing options...
JamesJJJ Posted August 11, 2019 Author Share Posted August 11, 2019 Yes: Link to comment Share on other sites More sharing options...
PeterW Posted August 11, 2019 Share Posted August 11, 2019 Hmm ... got a screwdriver ..?? Wonder if there is anything on the back of that control panel ..?? Link to comment Share on other sites More sharing options...
JamesJJJ Posted August 11, 2019 Author Share Posted August 11, 2019 Not much: Link to comment Share on other sites More sharing options...
PeterW Posted August 11, 2019 Share Posted August 11, 2019 Ok so refit it, and press the egg timer and the fan down arrow simultaneously. That should make the normal and min lights flash. Then see what the noise is like ... Link to comment Share on other sites More sharing options...
JamesJJJ Posted August 12, 2019 Author Share Posted August 12, 2019 Another fail, quieter but still far too loud for my wife. We have 8 fresh air inlets in our house and 7 extracts. All 7 extracts are essentially silent. 7/8 fresh air inlets are noisy, one is silent and I dont understand why. The instructions said attenuators should be fitted to inlet and extract, is it possible these were missed? How do you tell, all I can see in the loft is a mass of insulated ducting... Thanks, 20190811_230746.mp4 Link to comment Share on other sites More sharing options...
PeterW Posted August 12, 2019 Share Posted August 12, 2019 (edited) What sort of inlets are they ..? Photos would be helpful as if you screw certain ones down tighter they become louder. Also what is the layout - how close to the the bedroom unit is the noisy vent ..? Edited August 12, 2019 by PeterW Hit save too early ! Link to comment Share on other sites More sharing options...
PeterW Posted August 12, 2019 Share Posted August 12, 2019 Ok just watched that again (with sound on...) and it sounds like that is too tight and it’s a whistle across the vent. Can you unscrew it ..?? Link to comment Share on other sites More sharing options...
Jeremy Harris Posted August 12, 2019 Share Posted August 12, 2019 I agree with @PeterW both from the sound and from the image it looks like that mushroom terminal is almost completely closed, hence the noise. If all the fresh air supply vents are opened a bit then the noise should reduce and it should be possible to turn the fan speed down and still get loads of ventilation. Having the vents closed probably explains the CO2 readings as well. Looks like the system was never properly set up or commissioned to me. Link to comment Share on other sites More sharing options...
JamesJJJ Posted August 12, 2019 Author Share Posted August 12, 2019 They are the typical villavent inlets/extracts afaik. I will unscrew them all tonight and see what happens. Have also put my name down for the loan meter so I can set it up properly. In general the vent closest to the unit is loudest (the one in the video). Our bedroom vent is probably the furthest but the quiet vent (which is just as closed) is somewhere in the middle. Link to comment Share on other sites More sharing options...
JamesJJJ Posted August 12, 2019 Author Share Posted August 12, 2019 I have unscrewed them significantly and there is noticeable airflow coming from them all. However, the vents closest to the unit are still noisiest and quite loud. Whilst waiting for the meter to become available I have opened the extract vents a good amount as well. These are still silent, the fresh air inlets are still noisy (except 1 which seems silent). Link to comment Share on other sites More sharing options...
PeterW Posted August 12, 2019 Share Posted August 12, 2019 Fan noise can be due to a few things including blocked filters. Have you tried running without the filter on the inlet to see if it changes the noise ..? Link to comment Share on other sites More sharing options...
JamesJJJ Posted August 12, 2019 Author Share Posted August 12, 2019 Now tried that and it made no difference so whilst the filters are dirty I guess it eliminates them as the cause. I noticed some of the ducting going to the 'quiet' room is different. All of the ducting is like this: But going off to the quiet room there is this: Link to comment Share on other sites More sharing options...
Jeremy Harris Posted August 12, 2019 Share Posted August 12, 2019 Are there silencers fitted to the main duct connections to the MVHR? Silencers look like this, typically: https://www.bpcventilation.com/attenuator-silencer The length of flexible duct (the silver stuff) isn't ideal, as in general it tends to impede flow a fair bit. It may be that, if your system doesn't have silencers fitted that the impeded flow from the bit of flexible duct is working as a bit of a silencer. All MVHR ducting, except for a short length coupling the MVHR to the four main ducts, should either be rigid or semi-rigid, not flexible. Short lengths of flexible duct are normally fitted to the MVHR unit in order to reduce noise and vibration transmission to the main ducts in the house. Link to comment Share on other sites More sharing options...
JamesJJJ Posted August 12, 2019 Author Share Posted August 12, 2019 3 minutes ago, JSHarris said: Are there silencers fitted to the main duct connections to the MVHR? Silencers look like this, typically: https://www.bpcventilation.com/attenuator-silencer The length of flexible duct (the silver stuff) isn't ideal, as in general it tends to impede flow a fair bit. It may be that, if your system doesn't have silencers fitted that the impeded flow from the bit of flexible duct is working as a bit of a silencer. All MVHR ducting, except for a short length coupling the MVHR to the four main ducts, should either be rigid or semi-rigid, not flexible. Short lengths of flexible duct are normally fitted to the MVHR unit in order to reduce noise and vibration transmission to the main ducts in the house. Everything into and out of the unit is insulated and looks the same. Would a silencer typically be left uninsulated and therefore be obvious? Link to comment Share on other sites More sharing options...
Jeremy Harris Posted August 12, 2019 Share Posted August 12, 2019 2 minutes ago, JamesJJJ said: Everything into and out of the unit is insulated and looks the same. Would a silencer typically be left uninsulated and therefore be obvious? Silencers may not be insulated, as the absorption layer tends to provide insulation. They are typically around twice the diameter of the duct, though, so should be noticeable. Link to comment Share on other sites More sharing options...
Gone West Posted August 12, 2019 Share Posted August 12, 2019 @JamesJJJ Our MVHR system installation instructions give a crude setup for the vents prior to fine tuning. 1.Set the fan speeds to the number two setting. 2.Adjust all supply air valves so that the valve which is closest to the unit is open at three turns from the closed position, while the one furthest away is open at eight turns from the closed position. 3.Then open the valves in between at four to seven turns depending on how close they are to the unit. 4. Repeat for the extract air valves. We did this and had it running for a few days before carrying out the fine tuning without any problems. Link to comment Share on other sites More sharing options...
JamesJJJ Posted August 12, 2019 Author Share Posted August 12, 2019 Thanks, I have opened all of the valves significantly and very scientifically; I measured each duct opening as the diammeter of my little finger! Tonight I will try running the system on min to see how CO2 levels rise compared to when the valves were almost closed. Sleeping with it on normal or high isnt going to happen anytime soon. Having looked at the ducting in more detail the first part is solid metal up to the first tee where it branches into 6 noisy rooms and another branch into 1 noisy and 1 quiet (through the flexible ducting). I think the proper place to fit a silencer would be before the branches which would silence all rooms at once. However, I am somewhat nervous taking it apart here. The branch to our room feels like insulated semi-rigid, probably in the realms of 75mm diammeter. As an experiment would it be worth me buying a small silencer, cutting this smaller duct and inserting the silencer into this section? The cost of the silencer seems quite low although I am unsure how I would join 75mm duct to a 125mm silencer? Alternatively, is this a terrible idea? Link to comment Share on other sites More sharing options...
Jeremy Harris Posted August 12, 2019 Share Posted August 12, 2019 Best to fit the silencer as far away from the room terminals as possible. The normal place for them would be within about a metre of the MVHR unit, as that's where they are the most effective. Link to comment Share on other sites More sharing options...
Gone West Posted August 13, 2019 Share Posted August 13, 2019 12 hours ago, JSHarris said: The normal place for them would be within about a metre of the MVHR unit, as that's where they are the most effective. +1 I fitted an attenuator to the supply ducting in the ceiling near the MVHR unit and the supply vents are silent. I didn't fit one for the extract ducting as I thought a little noise in the bathrooms etc wouldn't be a problem. It isn't a problem but it is just audible. Link to comment Share on other sites More sharing options...
joe90 Posted August 13, 2019 Share Posted August 13, 2019 I turned my home made manifold into an attenuator by fitting baffles and acoustic foam inside it. Link to comment Share on other sites More sharing options...
JamesJJJ Posted August 13, 2019 Author Share Posted August 13, 2019 (edited) With the system on min and the vents opened up co2 peaked at 1205 overnight so better. However, the heater within the unit kicked in for some reason and it burned 9Kw of energy despite the house remaining >19c all night. I can see no evidence of that 8Kw in the room temps, they fell slowly and consistently all night... Out of interest, any idea what the white insulation wrapping is around the ducting, am thinking I might remove it to see if I can work out how to fit a silencer in the right place? Edited August 13, 2019 by JamesJJJ Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now