What flow rate should my MVHR be running at?

[Adsibob]

I have a Brink flair 400 My commissioning certificate says this:

 

 

The options for my system (as commissioned by the supplier) are

 

 level 0.   50m3

 level 1.   180m3

 level 2. 255m3

 level 3. 330m3

 

 When I realised the system was a bit noisier than usual (as mentioned in my recent exchange with @jack), I started investigating what was going on and saw that it was operating at level 2, when I seem to remember that level 1 was recommended for default use. I have turned it down to level 1 and the system is definitely much quieter, hardly audible. I think level 1 is the correct setting I should run it at, but grateful if somebody could confirm this based on the commissioning certificate which definitely counts flow rate at the higher 255 m3/hour value.

[Nickfromwales]

It depends ( is dictated by ) the gross internal space ( volume ), so that will set the commissioned values, but 225 vs 330 seems way to little a differential to me. You can run at the lower ( inaudible ) rate and monitor, room by room, you ppm for assuring that the system is functioning at the minimum basic level, eg removing CO2 / humidity at night when the house is at its lowest demand / adversity. Uplift in number of occupants etc will command what you do from that base value, but will ( and usually is ) then down to some degree of human interaction / forecast for the next level of fan speed required to suit that particular circumstance.

Many run the MVHR much lower than ‘recommended’ without issue, setting the flow rate back for a ‘good nights sleep’ in particular.

[Adsibob]

Thanks @Nickfromwales found some formulae in Approved Doc Part F which are as follows:

 

 

Odd that the approved document doesn’t mention volume, but I guess the building regs are assuming a certain occupancy/per m2 or per bedroom.

 

I have about 180m2 of floor space and volume must be about 470m3. On the Part F calcs, that works out at 194.4m3 per hour (180 x 0.3 x 60 x 60 / 1000).

 

I have 4 bedrooms and a study, but 43 l/s works out at 155m3.

 

So I’m feeling fairly okay with the 180m3 flow rate at the moment, not quite as high as the 194.4m3 but with the boosts throughout the day we must average out at close to 194.4m3.

 

There is a timer in the remote controller (Brink call it the eBus or “Brink Air Control”), so I guess I could use that for a good purge after everyone is up if I think we need it, but kids are little still and many years from puberty, so no BO yet!

[Nickfromwales]

6 minutes ago, Adsibob said:

but kids are little still and many years from puberty, so no BO yet!

It’s not their BO I’m worried about