Ventilation fans moving far too much air and therefore energy efficiency is out the window

[DundeeDancer]

Thinking on putting one of these smart D-MEV continuous ventilation fan into the bathroom of a flat I plan to rent out and all the D-MEV fans on minimum settings are way too high in my opinion.

 

The bathroom is 1700 * 2000 * 2300 = 8160 Litres of space.

 

The Scottish Domestic Ventilation 1st Edition states:-

Bathroom / Shower, continuously operating mechanical extract rate needed is equal to 0.5 ACPH with 25-50 boost.

 

So the calculation I come up with is:-

Volume of air to be change in hour = between 50% - 100% of room volume so that is between 4080 - 8160 L

1 hour = 3600 seconds.

 

So per second the rate should be between 1.14 - 2.23 l/s.

 

The lowest throughput fans I can see in the market are 5 l/s.  Which is 440% more air than I want to push out the window, unless I’m overlooking something?

 

Anyone know of any continuously operating bathroom fans that only push 1 to 2 l/s ?

 

Thanks, DD.

Edited August 24, 2017 by DundeeDancer
typo

[MikeSharp01]

Check you sums as I make it 7820 L. Does not help you though. Have a look here: https://www.tlc-direct.co.uk/Technical/Ventilation/Ventilation4.html It does all the work for you and should show you the gap in your thinking - English regs mind!

[DundeeDancer]

Thanks for checking my cals Mike, I had did my first batch with a room height of 240cm which would have given 8160 L of space.

 

Anyway the TLC site gives calculations for intermittent extract fans so a different kettle of fish altogether.

Came out as 43 l/s HAHA it's just the one bathroom I'm trying to vent not every room in the 6 apartment block.

 

I think these fans companies have a deal with Gas and Electricity suppliers the amount of energy they want us to throw out the back end of these vents.

[Temp]

Looks like this one does continuous ventilation adjustable down to <1L/S. Has boost etc..

http://www.greenwood.co.uk/product/18/491/omnique-multifunction-fan.html

Date sheet..

http://www.greenwood.co.uk/uploads/docs/450.pdf

 

 

[DundeeDancer]

8 minutes ago, Temp said:

http://www.greenwood.co.uk/uploads/docs/450.pdf

Hi Temp, you had me excited there for a moment but the trickle flow is 6 l/s maybe it was the 1.1 watts that caught your eye.

[Temp]

4 hours ago, DundeeDancer said:

Hi Temp, you had me excited there for a moment but the trickle flow is 6 l/s maybe it was the 1.1 watts that caught your eye.

 

Yes and no. I assumed 6L/S was the maximum because it says..

 

Omnique’s 100% variable airflow is ideal for installation where there are existing gas appliances as the airflow rates can be reduced and tailored as necessary.

 

Perhaps it's only the kitchen boost (eg max flow rate mode) that can be adjusted?

[Temp]

The installation manual here isn't very clear but the speed adjustment is on page 15..

http://www.greenwood.co.uk/uploads/docs/448.pdf

 

step 3 Press speed adjustment buttons to required level and verify with an airflow meter - re-press Airflow Button to confirm

Edited August 24, 2017 by Temp

[Temp]

Best ask them if it can be reduced below 6L or just increased?