MikeSharp01

Good thought - I had expected to be able to control the fan speed continuously (so right down to very slow) but if I only have a few fixed settings it may be more difficult I guess.

Have not ordered the unit yet but thought I would go for a good amount of headroom to keep it quiet.

Is that equation right, do I have the units correct - I guess it must be, its definitely me, but I get an odd outcome: So 451m3 x 4 x 15 x 1.012 x 8 = 219077J = 7.6Js-1 = 7.6W of cooling which sounds all wrong - need to go back the Thermodynamics 101, which I hated I seem to recall, - or maybe that 451 should be in l rather than M3 and/or the SHC should be the capacity of the whole volume - what have I missed? 4 ACH is the boost rate for the whole house which I guess you would not object to if you needed cooling.

Yes, we have passive standard insulation and the PHPP gives us only a few days (2% = 7 days) of overheating but that is obviously based on past temp data (2018 was our last update to the PHPP package) so we are not far from comfortable. Our only heating upstairs was to be a towel rail in the family bathroom and let the slab do the but if we have an FCU post the MVHR unit then we have that option as well.

No Loft! Unit is in GF Utility room but I think I can find space to run 4 x 90 rather than 2 x 70 flexi pipes.

Yes maybe for those three rooms. Good thought!

Maybe you could continuously / occasionally recalibrate if there was a portion of the day / fraction of a second when your CT could measure a known load (all dimensions) and then see if the resistance measured current value had moved.

This is a really hot (pardon the pun) topic today. OK so we are at the install stage of the MVHR suppose I double up the pipe runs to the bedrooms and cool the air at the MVHR I wonder if could get close to replicating a fan coil unit in the same place. Appreciate that this will cost but its a toss up given the infrastructure fan coil units need. At this stage much easier to run ducts than highly insulated water pipes and we are squeezed for space in the ceilings. I dimmly recall you @SteamyTea doing some calcs on airs ability to carry cooling but I cannot find them on BH - probably looking in the wrong place. Did find this link which seems to say that if I can get to 2 ACH then it might be effective: https://www.greenbuildingstore.co.uk/can-an-mvhr-system-be-used-for-cooling/

Just posted this on another thread thought it had better be here as well: We have the passive slab, will have the ASHP, so now if I can find some small fan coil units, we have only vaulted ceilings with a small flat spot at the top which has limited room but I found this fan coil unit: Image: https://www.hitachiaircon.com/hk/en/ranges/airside-systems/fan-coil-unit but I cannot find this on any Hitachi / Johnson controls UK site but scaling from the inlet/outlet pipes we might get it into the ceilings. Anybody recognise it?

2 hours - I am in the middle of a heatwave wondering how best to cool the upstairs of the build so this is all very timely. Especially given you feel that your upstairs might be 30deg! We have the passive slab, will have the ASHP, so now if I can find some small fan coil units, we have only vaulted ceilings with a small flat spot at the top which has limited room but I found this fan coil unit: Image: https://www.hitachiaircon.com/hk/en/ranges/airside-systems/fan-coil-unit but I cannot find this on any Hitachi / Johnson controls UK site but scaling from the inlet/outlet pipes we might get it into the ceilings. Anybody recognise it?

Why not use the wire to the consumer unit as your resistor and measure the voltage drop across a length of that.

Yes - sorry should have done that.

So it looks like your code is not using interrupts and this means your counter will miss events if the Pi is busy. There are a number of solutions to this Multitasking or Threading using simple call back interrupts. I found this article which covers the latter case and is probably the easiest if you are wanting to stick with python. It has two call backs (your code could be put in any one of them as they both detect a falling edge.) on different pins (17 & 23) and a wait until pressed on pin 24 (which ends the programme). https://raspi.tv/2013/how-to-use-interrupts-with-python-on-the-raspberry-pi-and-rpi-gpio-part-3 So you set up you GPIO (My example uses Pin 17 and you need global counter variables etc as well) import RPi.GPIO as GPIO GPIO.setmode(GPIO.BCM) GPIO.setup(17, GPIO.IN, pull_up_down=GPIO.PUD_UP) Define a call back function def my_callback(channel): print "falling edge detected on 17" # Put you count code here. Load the trigger for the call back # when a falling edge is detected on port 17, regardless of whatever # else is happening in the program, the function my_callback will be run GPIO.add_event_detect(17, GPIO.FALLING, callback=my_callback) #You don't need bounce time for a photdiode it should be clean. Run the rest of the programme as a loop servicing the saving of the counts. As I am working with WEMOS device I will be using a similar approach but in C rather than python.

I think you could use one of the GPIO counter timers to capture without reference to the software them just read the counter at whatever interval and work out the difference since last interval, and accounting for rollover of the counter at the top - not sure what that is 16 / 32 bits or some such. You don't really need the actual time of each pulse just a number at a given time.

Is it working OK if so not sure it needs refining but also not sure it is reliable - have all the bits now to build a WEMOS d1 mini pro based version but a think I will count pulses and return a figure in 1 minute lumps that means I can store a load of readings on the Wemos and upload the whole lot as needed. I can also just have a start time stamp and keep the whole lot lined up with a NTS so storing much less data. Anyway I will get to that next week. Today we party!

Are you in danger of over thinking this! Perhaps choose an average methodology, worst case or even best case (from whoever's point of view.) and stick it in.

Yep - discourse 101.

None taken - don't worry - its all in good part. Back to WEMOS programming!

I wish I had not started this. An IT earthing system is still an earthing system just not traditional and we are already way away from traditional here - EG Malaysia Airlines fight 370 which is not still flying, has been captured by gravity and therefore is, mostly, now at earth potential somewhere - although I agree that differential metal actions, perhaps in salt water, may well be causing some minor differences in potential of some of the parts. Naturally many other interpretations are possible and Ergo (therefore), ipso facto (by that very act / fact), inter alia (among other things) - I give up!

Do they stay up for ever then - eventually the must come down to earth!

Not a good starting place - every installation needs a good earth somewhere.

Not sure about Velux but we have have Fakro and their insulation detailing on the quad units us great look at their website.might give you.some ideas. Air tightness involves sealing the window frame to the air tight layer - is that your plasterboard or have you got a plastic membrane in there somewhere?

Considered and done this could help the whole damned nation.

Alpha+ to that - I mean the document not the marking rubric!

Is that the Passive house measure at 50% of minimum requirement - that's attention to detail.