So with your shuttle valve, have they by any chance fitted the common connection to your tank flow pipe
That’s mine and AB is the rear common one.
That would explain what you’re seeing, as in both cases, heating or hot water, it would flow via the tank.
My common AB is definitely the right way and is the flow from the ashp.
I’ve narrowed it down to the operation of the charge pump causing the problem. The ashp was off for an hour so the charge pump was off, the return pipe out the cylinder was cold to touch. I then forced the charge pump to run (set the operation mode to auto and 1% speed in idle) and the return pipe immediately got hot as hot water was pulled out the cylinder. the flow pipe temperature into the cylinder (a non scientific touch test) doesn’t seem to change which may indicate it’s not leaking past a faulty shuttle valve.
I’ll post some photos of the actual plumbing tomorrow to see if anyone can see something obvious!
Thank you for the ongoing help!
I am really not sure if these photos will help spot the cause of my problems with DHW temperature loss when the ASHP is running a heating cycle. It is a tight plant room with a lot of pipes.
The top photo shows the ASHP flow comes down from the ceiling, round a “U” bend in the pipe work (hidden behind the tank in the photo) to the shuttle valve where it splits off to DHW or CH. The return from the DHW cylinder comes out the top, drops down behind the shuttle valve and connects into a return pipe (shown better on the bottom photo). It is this horizontal return pipe with the auto air bleed valve which is getting very warm with water pulled up out the cylinder coil when the charge pump is running
The bottom photo shows the return pipe coming down from the cylinder, connecting into a T piece on the common return pipe from the buffer tank / radiator / UFH returns before heading back upwards through the charge pump to the ASHP.
Do I have some kind of syphon effect going on? The only solution I can think of is to fit some kind of motorized zone valve or ball valve on the horizontal return out the top of the cylinder which is only open when the shuttle valve is in the DHW position. This would allow water to flow through the DHW charging coil when charging water but prevent any flow through when the charge pump is running with the ASHP in idle mode or CH mode.
I am really not sure if these photos are clear or helpful!
Also below is another graph (my logging is becoming more reliable so getting better representations of what is going on). This is around 24 hours, all is looking well apart from the saw tooth hot water charging (BT6) trace.
You do have quite a lot of Vertical pipe runs which would encourage thermal syphon effects…
If you’re happy the 3-port Diverter valve is good (and you’ve explained why you think it is) then I reckon the best way to be sure there’s no flow through the DHW coil - except when there’s meant to be - is to add a 2-port motorised valve on the return side of the DHW coil, wired in parallel with the ‘DHW’ position on the 3-port valve.
I have changed my mind…I ran another test tonight with the following results (sorry another long post - I hope all useful debug and diagnostic information for someone in the future!)
allowed a hot water cycle to finish and the ASHP turned off as there was no CH demand (positive degree minutes). With the charge pump mode in intermittent nothing was running.
The flow pipe into the cylinder was very hot and remained hot as you expect following the DHW cycle
Switched the charge pump to automatic and ran the minimum speed as 10% with the ASHP in idle mode
The flow pipe into the cylinder very rapidly cooled down (around 10 seconds) and water was obviously being drawn the wrong way (by the charge pump) through the shuttle valve and through the cylinder backwards
I think this explains why the return out the cylinder is getting hot and I am losing heat in the cylinder, I am pulling cooler weather compensated CH water up through the cylinder which in turn cools the cylinder.
I now need to determine if my shuttle valve is faulty or set up wrong.
I can see that the head indicates that flow direction B (which I assume is the default position) should go to the CH but the actual brass valve underneath has this as direction A to the CH (and vice versa for the DHW). I cannot determine if the wiring is inverted to match as I dont quite understand the wiring diagrams and how the SMO40 works for switching this valve.
The SMO40 manual shows to wire the shuttle as follows:
The shuttle valve manual (I think) shows to wire as follows:
My physical wiring (pins 2,3 and 4) on the SMO40 board is:
UPDATE 1: With the heat pump in idle mode pin 4 is live which is the brown wire, according to the shuttle valve head this puts the valve in position B. Looking at the plumbing position B is to the hot water tank. I think this means if the charge pump was running this would allow water through the cylinder.
My reading of the manual (and the diagram on the top of the valve) is that:
So I reckon you can’t infer much from checking only Pin 4; you need to also know if Pin 3 is Live or not. If Pin 3 is not Live then I agree the valve should be in (default) position B.
The puzzle is that your DHW tank is clearly heating up OK, which implies the DHW coil is seeing ‘hot’ Flow from the ASHP when it thinks it’s doing a DHW cycle - and BT25 is seeing ‘warm’ Flow from the ASHP when it thinks it’s doing a CH cycle.
It might help to check what position the grey circular indicator on the top of the valve shows for:
I can confirm my shuttle valve is wired as per yours:
Blue pin2
Black pin 3
Brown pin 4
However from your pic the shuttle valve body is the wrong way around in conjunction with the brass body labels.and the pipe connections are on the wrong sides.
Your pic of the red casing shows A towards DHW and B towards heating
Your pic of the brass connector shows DHW on B and heating on A.
That is mine.
The thing I don’t understand is how you are getting heating and hot water still, given the above.
The way I see it: your shuttle is sending hot flow to the tank as required, but, is also allowing warm flow through the central heating and tank at the same time.
Could the mis matched orientation be allowing that?
Just looked online and the shuttle can allow dual flow the valve is at 30 degrees and not 60. I wonder if this is what has occurred with yours?
When in mode 0 (idle) pin 3 (black) was not live, I also checked that.
I am definitely getting the hot water in the cylinder and the warm water into the buffer. Like a lot of my installation, puzzling.
I shall collect the “live” status for brown and black wires alongside the indicator status for all modes.
Are you able to share the link? I am not sure I understand the 30 and 60 degree set up options
It does seem that this is what is happening. Hopefully the reasons will become clear soon!
Thank you for the help and suggestions!
So it maybe as the motor unit isn’t matched to the brass indicators that the valve actuation is quite correct.
As David mentioned put a CH and DHW cycle on and take pics of the grey indicator on the shuttle and see which way it’s pointing for each.
You can un clip the motor unit from the brass and see what’s what as well.
ASHP idle or ASHP CH
Brown : 240v
Black : 0v
Indicator : B
ASHP DHW
Brown : 240v
Black : 240v
Indicator : A
so according to the plumbing and indicators on the brass fitting this shouldn’t work, but it does (kind of)
At present I think I know that:
When doing DHW the head is at position A but the brass body has position A plumbed to the CH flow. touching the pipes confirms the water is only flowing to the DHW via position B on the fitting and not to the CH.
When idle or CH the head is at position B but the fitting has position B plumbed to the DHW. My current theory is that I’m actually getting CH flow through both A and B but I can’t see how or why.
I’ll get the motor off the brass body and see if I can determine what the actual valve position inside the brass fitting is doing.
I haven’t figured this out yet, but is there an easy way to force CH or DHW rather than waiting for a naturally occurring cycle? I’ve seen the service menu has some forced start options and one of those seems to allow me to just fire the shuttle valve - so maybe this is all I need to move the valve and then take the motor off to take a look.
Yer, forced start should allow you to put a particular mode on.
So you confirmed that during DHW that hot water was going via B. DHW and pipe got hot, and CH pipe did not.
Did you do the same during CH and see if both CH and DHW flows were equal temp?
Once you pop it off the brass, you can manually move the valve and then assure yourself where it should be for a particular position, eg B and then refit the valve body with that in position B.
I don’t know what the internal gubbins are inside, but I wonder if the mismatched orientation could be the issue?
Found online. That looks like it has a rounded edge to determine valve orientation.
So if fitter upside down, the installer would’ve had to rotate the valve 180 degrees to fit the other way around
Yes that 180 degrees rotation seems to be what has occurred. The valve spindle can rotate over 360 degrees so they have moved it through 180 degrees to get the head to fit.
I’m not clear what this 180 degree revolution does to the internal of the valve.
To eliminate it I might just bite the bullet and switch the brass fitting the correct way.
I am going to switch this around, no amount of orientating the spindle seems to correct the problem…I am just going to wait for it to be a little warmer just in case it doesnt all go back together well!
So onto what I think is my next installation problem…hopefully some fellow nibe users with the same setup can confirm how theirs is and if my understanding is correct.
I am getting a failure to reach temperature during my periodic increase of the hot water. This seems to have been happening since I got nibe uplink running so I assume its another installation problem. Something seems wrong with how the immersion is connected to the SMO40 via the Nibe HR10 contactor box.
This suggest the immersion “auto mode” on the nibe HR10 box needs to be connected to pin 6. Mine is connected to pin 2.
I know the immersion works as when I flick the HR10 box to “on” the CT clamp on the circuit feeding the immersion shows it is pulling approximately 3kw.
I am also not clear how this should be set up in the service menu option 5.1.12 and I dont know what step 1, step 2 or step 3 means in terms of additional heat. On my set up I dont have any other sources of additional heat other than the immersion in the DHW tank.
As always any examples from working set up or Nibe general knowledge on this subject is greatly appreciated.
Evening
Mine used to error with that. I then set my periodic increase to start at 3am, which is during the time my DHW is programmed for. Hasn’t errored since.
Additional heat is not linked to the DHW cylinder. It’s to do with whether you have an additional heat source before or after the reversing valve on the CH loop.
Eg mine is programmed in as after the reversing valve and single step, as I have one immersion in the buffer tank.
There are no options to specify DHW additional heat as far as I’m aware.
Re wiring, here is how my tank and buffer is wired:
So pin 6 is for cylinder immersion and pin 2 is for additional heat pre / post shuttle valve
I’ve just started looking at the my uplink data and I’m quite shocked at the behaviour of the heatpump vs what is being report for the buffer / CH circuit!!
Ok, looks like I need to shift my wiring to pin 6 as a start. That’s what I suspected.
Out of interest, how are you scheduling DHW? I can only seem to schedule a comfort level at a specific time.
The data has been invaluable for me to sort a lot of problems, suspect I’ve a few more to go yet. One at a time.
If you can / do graph it then please post, I’m very interested to see how other Nibe units perform. I can see a few other Nibe units on heatpump monitor but those only show flow and return and power. They certainly have different characteristics to mine, mine seems to run like @dMb but more often and with greater power consumption - but then I don’t have a passivhaus and I have a 16kw unit so probably to be expected.
Morning
I schedule a comfort like you do. So I have it as off from 5am - 2am then 2am - 5am I have it as luxury. (50 degrees).
Then I set periodic increase to 3am
What settings do you have in the additional heat menu, as mine I have to specify one - eg before or after shuttle valve. Won’t let me pick none.
The 1,2,3 step is slight confusing tbh. Eg in my menu it’s after shuttle, 1 step, 23amps. Yet my immersion heater is 3kw and on a 16amp MCB. So I think I need to change that.
Personally would rather block it permanently as it’s less efficient. I think my additional heating is blocked until -7 outside anyhow.
Yer, should be pin 6 or it will think it’s an additional heat immersion on CH side.
Here you go
This is the heatpump side - flow, return and pump speed.
This is the buffer side, request flow temp, flow temp and return temp
The latter is all over the place, vs heatpump which looks relatively ok, although it never seems to run a dT7 and pump spends a lot of time at 100%.
This was yesterday, after raising the curve slightly:
