Page 20 states:
And so I am thinking that these are the two probes I’ve photographed earlier in the thread. (BT25 and BT63)
Coolio; I’m reporting Return flow correctly.
Here is the junction box that splits the cat5 cables to the two sensors (BT25 and BT63… I think) Just looking at Page 20 of the manual suggests the two tails shouldn’t be wired together (blue/white)
and so I think there is a problem. I’ll get the front off the SMO20 in the morning and post my findings
They will be a common ground probably (both connect to QN10). The Cat 5 is because the installers didn’t have any “twincore with cable area of at least 0.5mm²” handy 
Brian’s right - presumably the Blue&White goes to X2:10 as the Common Ground, whereas the Brown&White / Orange&White go to X2:8 (for BT25) and X2:9 (for BT63) - or possibly to another terminal instead of X2:9 for one of the configurable AUX inputs.
The “Service Info” page on NIBE Uplink lists more sensor readings and is more specific about which BT codes they relate to. It will also show any sensors which are expected to be present but not connected (signified by Value = ‘- -’).
How much of an issue, if any, is the use of cat5? it seems to have been used extensively…
spot on. Doesn’t appear to be any issues with the wiring:
I have examined the service menu on the actual SMO20 and found a flow value that I hadn’t seen referenced in the Uplink UI, BT12: Heat medium flow.
This looks to have a more realistic deltaT with BT3: Heat medium return, although if it is the one I should be importing to emoncms, i’ve no idea why it’s not on the UI more prominently, and why BT25: External flow temp is compared with BT3 in the graphics on the UI…?
Nothing else labelled to Aux pins, off to investigate the UI and whether I can import BT12!
Edited to add: My HA integration with Nibe had somehow mislabelled the register for BT12 (reg 44058) as ‘condenser out’ which is unhelpful. I’ve started to send this to EmonCMS and will see where we can go from there.
Can anyone shed any light on what the climate flow/return on the UI actually mean then and also, why there are so close on this system?
OK, so X2:8 is the Brown&White. Have you traced that through the junction box and checked which of the anonymous black sensor wires that connects to? It needs to be the sensor on top of the Buffer Tank, BT25.
Can’t see that being a problem. It’s a short run (compared to something like an outdoor sensor) and it’s good quality copper.
Indeed, it does.
Looks like your MyHeatpump app is showing a much more plausible deltaT as of about 10:45 this morning. Which parameters is that plotting now - BT3 & BT12?
I’m puzzled by BT25 though; if that is indeed the sensor at the top of the UKV Buffer Tank but it’s closely following the Return temp that seems odd. There’s clearly a T connection above your Buffer Tank, with the sensor on the downward leg into the tank. Where does the right hand leg of the T go - is it to that maroon-coloured pump (and if so, what’s that feeding)?
I’m trying to work out whether the Buffer Tank is a ‘short circuit’ back to the Return to the Heat Pump (i.e. sort of a low-loss header) or ‘in series’ with the Flow.
Yes on our NIBE F2040 and SMO there is a definite difference between the readings from BT25 and BT12 (EB101). The location of these sensors is clearly different (is there a standard way of placing these?). So in our case BT25 is on the rad supply circuit only, hence when the DHW diverter valve is activated then is doesn’t correctly measure the flow temp. Whereas BT12 continues to read the correct flow temp, but presumably quite close or inside the condenser F2040 unit itself.
I’m logging the DeltaT value in HomeAssistant and that is derived from BT12 and BT3
Red is flow, blue is return from what I can gather:
It seems to me that BT25 is measuring the top of the UKV (wired to X2: 8), whilst the lower temp sensor is on the return line and I think is BT63 based on where the wire was traced back to (X2: 9)
I think there is one outbound circuit for rads and another for UFH? All the hot water stuff is over to the right of the picture.
I agree, something is still odd. But since changing the compressor start value from -60 to -430 I am seeing much longer runs at lower energy, albeit we’ve been sat at 8 - 9 degrees outside since I made the change. I expect to see more cycling with lower temps.
I am seeing higher DMS values before the compressor kicks in, but I guess that’s to be expected. Does that just mean the system is working ‘harder’?
Thanks for your help with all this!
Do you have a buffer installed?
BT25 here looks to be before the buffer and T’d off to the rad supply and UFH supply. The radiators definitely need balancing here, the UFH is done but I need to chase some air pockets out so perhaps will see a more accurate reading once that’s complete?
I’ve not actually found the BT12 sensor, and I don’t know where BT3 is either!
No buffer on our system.
Is it just me, or is that buffer tank doing the squareroot of diddly squat (in terms of buffering)?
It seems to me, there are 2 pumps acting on the same fluid when the shuttle valve directs the water to the left (UFH circuit?). That seems odd. There is also nothing to stop that flow from the HP simply going round through the buffer and back out again, depends which pump is stronger. If it did that, you would cycle and get minimal DeltaT.
Are there any non-return values?
A most odd setup (from a purely logical view) - BTW happy for someone to tell me I’m wrong!
[edit]
Just realised there is a third pump for the UFH Manifold.
I have no idea. I know what you mean, it does look suspiciously useless but I know nothing about pluming. There’s been a HeatGeek out to look at it earlier in the year and didn’t raise any concerns other than a possibly low refrigerant levels, which turned out not to be the case.
The blue and red marked pipes aren’t connected at the bottom of the buffer, the feed runs behind the blue marked pipe, but it does look like anything that goes in to the buffer then feeds straight in to return flow piping.
The red box just beneath the buffer is a 3-way switch, perhaps the buffer only comes in to play when the SMO20 decides it’s needed?
I’d love to understand it all a bit more, so would welcome some facts!
Due a cold snap next week and will see what sort of behaviour is experienced then.
I’m still looking to re-fill the UFH loops and chase out some air pockets, balance the upstairs rads and insulate that pipework to a better standard. Incremental gains for sure, if that. But I’d rather give it the best chance of working properly.
Nick hi,
I’m assuming the tape is the 25mm wide, 3mm thick tape over some 25mm tubular Armaflex? I can’t see any 25mm thick tape, or rather Google can’t find anything like that. Ours already has some tubular Armaflex installed but it leaves a lot to be desired in terms of gaps etc.
Simon
Not that it really helps, but the diagram from the F2040 manual link I posted before shows BT12 and BT3 are both within the outdoor unit:
The textual descriptions are slightly more helpful:
Argh! But the SMO20 screen shows:
BT12: Heat medium flow
BT3: Heat medium return
These are the two I’m recording to myHeatPump app… Is that correct?
I’ve done some further digging and I’ve concluded NIBE are just using more friendly terminology in the SMO 20 screen.
My GSHP has both BT12 (condenser out) and BT2 (heat medium flow) - but the readings from those are almost identical. It looks like the ASHPs don’t have a separate BT2 sensor so they use BT12 as a ‘proxy’ for that.
So I reckon that’s all good.
OK, so here’s a hypothesis:
That would explain why BT25, which is confirmed to be correctly wired as the sensor at the top of the buffer tank, is showing ‘return’ temperatures, not ‘flow’ temperatures like it should be.
Note that I’m calling the maroon pump the ‘radiator pump’ because I presume it feeds the radiator circuit - although then I’m not clear on where the UFH loops are plumbed in (with their separate pump) - are they connected downstream of that maroon pump?
One way to test this theory would be to turn off the ‘radiator pump’ and see what happens to the readings from BT25. Is there a separate control for that pump, e.g. a thermostat somewhere?
David, thanks so much for all your input. How do I send you something nice to drink?
OK, the maroon pump is set to speed setting 2 of possible 1 - 3. I don’t see any speed setting on the black charge pump. You’re suggesting to set it to run slower?
The maroon pump seems to feed the pipe labelled ‘flow’ in the below image.
There are separate pipes for UFH flow and return, which branch off from just before the maroon pump:
One thing I’m unsure of is the UFH flow and return seem to be linked by a flow meter, which I’m not sure what it should be set at?..
I could just power off the pump I guess?
Should I look at moving the BT25 sensor in this case?
