MVHR: open source logging – brilliant!

Posted by on Nov 17, 2013 in Warm EnerPHit office | Comments Off on MVHR: open source logging – brilliant!

MVHR: open source logging – brilliant!

Just got the MVHR up and running before the cold weather hit. ¬†Good job as I was starting to get really irritated with venting via open windows – I seem to get all the draughts to give others in the office the fresh air ūüôĀ

Anyway, now its been running for a week or two, I decided to get the open source monitoring kit we asked John Canton to make up for us in our old office.  Plugged it all in and it worked!  Logging temps, humiditys , powers straight to the website.  Some pulses ( water, gas) too once we get the reed relays sourced.

Profoundly grateful to all those who have put in effort to the contributors, especially as I’m a complete programming/electronics assembly dumbo. thankyou, Thankyou, Thank you!

Anyway, what good is it?  Well we just set the MVHR up to run without controls at a constant 180 m3/h ( ie about enough for 6 people. our average occupancy) The following trace shows the four temperatures across the unit over the last few days (ignore green, that’s attic temp):

mvhr temps1


I must admit to being surprised at how fast the office cools( the above being a weekend), until I took a look at the gains: We are so good at cutting gains at night and weekend that we only have 80W electrical power, plus a bit of solar on Sat Nov 16th between 10 and 12am. And 40W of that 80W is the MVHR itself.

So my first thought is to reduce this by turning off the vent unit out of office hours. Must be worth a few watts! A quick calc shows this to be right: ¬†reduce from 180 to 50 m3/h(unit minimum) for say 10C avg temp difference assuming 80% heat recovery: ¬†power = (180-50) *0.33 * 10 k * (1-80%) = 85W, so I can effectively double our gains by switching the unit down to minimum, or more if I can switch it off…

This is an example of what commissioning should be about: get some decent monitoring to see what going on, and then adjust, and see the result. ¬†Its what supposed to happen to all our buildings fitted with expensive Building Energy Management Systems, but never happens – probably because once its past hand-over, nobody wants to know. Interesting contrast to Houses too, they have much more regular gains, so they don’t have this issue so much as commercial.

Ill post the next stage once I’ve got this implemented. pete.