OK so I’m trying to understand the energy integral that my Vaillant Arotherm+ is using.
My basic understanding is that every minute the flow temp is over target by each 1C, it will add 1 to the integral. The integral by default starts at -60, so if you are over flow temp by 1C for one our, it should turn off the heat?
My UFH is very slow to react. So the integral can take a while to build. What I am confused about is here is today data (OEM link below). Current flow temp target is 27C, but its been 28C+ for well over an hour, so why hasn’t it turned off? Its been a bit over target room temp since 10am and continues to climb (albeit very slowly). Is something causing the integral to get reset? Can you see it anywhere but in the Controller? I went out to take a look and as of about 5 minutes ago it was at -8, and now typing this, it looks like its finally cut out. I’m just trying to work out why it hasn’t cut out hours earlier?
Are those flow temperature values off ebus directly from Vaillant or your own heatmeter/sensors? I kind of doubt it as they match so nicely when the compressor is off…. There can be quite the discrepancy with Vaillant’s sensors - the builtin flow temperature sensor could easily have a degree offset. If you’re using ebus you could look at the EnergyIntegral in real time to see what’s going on.
In general, your understanding of the integral is correct.
They’re from the OEM heat meter, so not direct from the unit. I see its been off for a bit then run for ~1hr, and off again for ~30mins and just restarting now, which is more as I’d expect (running with ~27C actual and 26C target). I was just surprised to find it was running so long in the first place at 28C flow, 27/26C target without the integral kicking in as it was over for well over an hour. Guess without ebus and logging it, I’ve no idea what it was up to.
What can reset the integral once its in motion? I hadn’t changed the target room temp since 10am when it dropped down to 20.5C.
Unfortunately I don’t have the ebus adapter, but maybe I need to grab one out of curiosity and get the data into Home Assistant. Doesn’t look like the myVaillant integration in HA has target flow temp or integral data (not surprising).
I’ll see if it happens again tomorrow and nip out now and again and take note of the integral value as well as the flow temp from the controller. Unfortunately its in the plant room round the back of the house and only external access, so a bit of a pain.
It has flow temperature as measured by Vaillant, also the heating curve parameter and outdoor temperature. I posted an equation that will calculate target flow temperature based on heating curve and outdoor temperature here, so you can calculate the current target temperature yourself in HA:
. There can be quite the discrepancy with Vaillant’s sensors - the builtin flow temperature sensor could easily have a degree offset. If you’re using ebus you could look at the EnergyIntegral in real time to see what’s going on.