2 weeks ago there were heavy floodings in Austria. A German friend has told me that on several internet forums people reported that their sub-soil ductings (to pre-warm the incoming fresh air in winter time) were flooded.Which led to blockage, which in turn left only the outlet of the HRV unit open. With the consequence that an underpressure was created within the house and CO alarms started to ring them out of bed, the boilers weren't able to transport the combustion gases out of the house. If they hadn't installed the CO alarms that could have ended in a tragedy.Room-sealed stoves and boilers where also effected, same problem: the ducting was flooded.

So - mistakes are being made all over .

Tried and trusted ?

Now - if people don't believe me - fair enough , but I insist I started this thread with cautious enthusiasm for HRV / MVHR . The more I dig the less my enthusiasm grows . The greater the need for caution .

If you are an educated self builder you are most likely to have a basic understanding of your house construction and should therefore be savvy enough to attend to the system maintenance of the machine controlling the air you breath . You may even choose to attend to the fire risks I have drawn attention to .

What if you allow some relatives to mind your house for 3 months when you go away for some reason ? Or What if you are sick and cant attend to basic maintenance ?

What if you are in social housing and you are handicapped , elderly , over whelmed by the burdens of single parenthood - or if you are just one of those types who in general is irresponsible ? How does the specifier legislate for that ? Tell them not to smoke or cook chips ? (You forgot to mention no Christmas Trees Paul http://www.youtube.com/watch?v=t_eHBqVYa8A )

Being referred to now in the 3rd person ( I am still here you know ) - I get the hint guys . I think maybe I will leave the issue be . On this forum anyhow .

Thanks to Sinnerboy for the guide to a happy MVHR on July 8th.
If doing one's own regular maintanence, the system will need re-adjusting even after simple cleaning of the air vents. Anyone in the UK had experience of owning their own anemometer/airflow meter? The model I saw demonstrated by a MVHR manufacturer was £400,or so.A simple anemometer for sailing or weather is only £25 or a posher Martindale AV90 for £129 - usefully measures temperature, too. Anyone had experience of adapting to fit over an air inlet/outlet? Also a formula to convert m/s or knots to L/sec. Will be necessary, anyway, if self installing; can they be hired?
If the proper device is sine qua non perhaps a S Yorks co-op for MVHR owners ( James, Nick, anyone)?

Doc

I used to work in a bank containing some 3000 staff as an air conditioning systems engineer. When offices were reconfigured we used a pitot(?) tube anemometer to set the systems. A vane type instument was tried but turbulence (another complete thread believe me) within the duct work meant it was rarely accurate.

Once set however they didn't require recalibrating or resetting post maintenance - provided nothing else had changed. Once set one only sees imbalance creep in as filters clog or ducts become internally dirty. That said, it tends to happen across the board (very much more quickly if not filtered) so it's the air volumes that change rather than the overall balance of the system. Once maintained that goes back to original or so close as to not warrant further input.

Reading (well trying anyway) the rest of the thread, in any 'well built' commercial setup, fusible link dampers are installed wherever ductwork penetrates a fire barrier period. Part of our maint was to test each one annually!

Certainly in our case, every supply and extract fan was interlinked with the fire alarm system so if it went off EVERYTHING shut down. Of course the extract system could then be set to operate independantly to pull smoke from the building if (as it was once) reqd. Its was also said at the time of that fire it was out quicker by setting the extract on (I by guess pulling air from the space and thereby limiting one of the combustion elements).

HTH

David