I’m looking for advice on the optimal settings for my heat pump when I’m away for extended periods during the colder months. I have a NIBE S2125-12 outside unit with SMO S40 + RMU 40 inside, installed in early 2024. Unfortunately, my installer went bankrupt during the installation process, so I’m learning as I go.
Here’s my situation:
I’m often away for 14+ days and want to minimize energy consumption during these times. Based on the Smart Guide in MyUplink, I believe I have two main options:
a) Reduce the indoor temperature significantly.
b) Switch Operation Mode to “manual” and turn off heating completely.
In both cases, I keep the hot water demand running, set to “small.”
Option A
Setting the temperature to a low value around 10°C doesn’t seem to reduce the heat pump’s activity much. It still runs most of the day. I suspect the heating curve and outdoor temperature take precedence over the set indoor temperature and still cause the heat pump to jump on?
Option B
This generally works well. The heat pump runs only once a day for hot water. However, when the outdoor temperature drops below ~3°C, the system starts generating “Freeze protection” alarms (EB100-EP14). These alarms fire almost every hour with emails and push notifications. Even though the indoor temperature stays stable at around 16–18°C.
Are those alerts something to worry about or just a big annoyance? I assume the freeze protection solely looks at the outside temperatures and turns itself on. I’m fine with that, I would even turn it on if this would be a setting in the controller, but it’s seems to be not available.
Are there alternative settings or adjustments I could make to prevent these freeze protection alarms while still keeping the system in a low-power consumption state?
Any tips or insights would be greatly appreciated!
The community on this forum is friendly and helpful but there aren’t too many NIBE owners who are active on here and most of those (like me) have the older F-series models rather than the newer, more advanced S-series, so experience with your type of system is limited.
Your description of Option A (greatly reducing the target internal temperature) does indicate the heating curve is taking priority so the system keeps delivering heat even though the room temperature is higher than your 10C target. On older NIBE systems there is a setting to adjust how much effect the internal temperature has on the flow temperature - which would let you alter this behaviour - but my recollection from other discussion threads is that there is no comparable setting for the S40.
If you were to select a different (lower) Heating Curve while you are away, that ought to have the system target a reduced internal temperature, while still operating at a low level.
Have you experimented with the options available in Menu 6 (Scheduling)? I wonder what happens if you add a ‘Blocking’ schedule, which only allows the heating to run for part of the day.
Why is the property remaining at above 16c when the heating is turned off and it is -3 outside?
Is the “freeze protection alarm” forcing an internal temperature above 15c?
Do you have radiators or UFH? Are radators very large? What thermal mass of any UFH system?
Have you experimented with the options available in Menu 6 (Scheduling)? I wonder what happens if you add a ‘Blocking’ schedule, which only allows the heating to run for part of the day.
Yes I experimented with scheduling, but it seems to have the same side-effects as the normal operating mode adjustment. Once below 3 degrees celsius outside, the freeze protection kicks in.
On older NIBE systems there is a setting to adjust how much effect the internal temperature has on the flow temperature - which would let you alter this behaviour - but my recollection from other discussion threads is that there is no comparable setting for the S40.
I think this is correct, I do not see this option on my system. But your input reminded me of a different adjustment I have seen before. Menu 1.30.3.1: Indoor Climate > Advanced > External Adjustment > AUX external input > Temp - heating
I believe this is the maximum outside temperature before heating shuts off. Changing this value to the lowest possible value (5 Degrees), seems to be very close to what I would like to achieve and what the freeze protection would do nonetheless.
@Ringi sorry my initial post should have been clearer: The house stays above 16c for a long time even with the heat pump completely turned off. I would say mostly due to proper insulation and southern exposure.
What the freeze protection is actually doing, is a bit of a mystery to me. Judging from the energy consumption, almost nothing.
The situation of NIBE owners and online communities is pretty dire. I keep finding this community here when searching for issues.
I have a nibe 2040-16 with a SMO40 controller. I agree the online support and Nibe information is none existent - everything I have picked up has been from this forum.
I’m not familiar with your model but for taking a guess at what could be happening, I will assume it works similar to the F series.
What is your configuration? Does it have a buffer tank and any circulating pumps on the heating side? I assume you have a charge pump on the return leg to the outdoor unit?
I’m not familiar with the rmu40 but it looks a little like a digital version of the standard F series room sensor which is used to “offset / influence” the heating curve depending on indoor actual temperature
On another F series Nibe system I managed to help investigate why the heat pump ran central heating cycles multiple times a day despite all room stats not calling for heat and it was the middle of summer. The charge pump on the nibe is by default configured to run all the time and constantly cycle water from inside and through the outside unit. Depending in your inside set up this might also be cycling constantly through your indoor circuits or it might be separated by a LLH or buffer tank. The act of going outside obviously loses heat in the water and if you want the heat pump to do nothing whilst away it’s probably best to disable this cycling of the water (depending on insulation of exterior pipe work etc).
The nibe control system simply compares the temperature of this cycling water to the target temperature from the heat curve for a given outdoor temperature. A room setting of 16 degrees may not significantly offset your target temperature on the curve enough to compensate for the loss of heat from constantly cycling your water outside. So therefore the heat pump sees the water temperature drop below target and runs up until it gets the water back above the target. The cycle then repeats.
I can’t say for sure this is happening on your system without seeing some data from Nibe uplink. However out the box the above behaviour will happen on a F series
This could all be totally wrong on a S series with the RMU of course. I’ve only worked with F series!
Nibe uplink data would tell us and I doubt Nibe have significantly different parameters for a S series
Spot on: There’s a 120l buffer tank + circulation pump on the heating side and the charge pump on the return leg to the outdoor unit.
There’s a sensor immediately before the buffer (I think it’s marked as Supply Line BT12) and one after the charge pump on the way out (Return temperature BT3). I have one additional sensor (Additional Heat BT63) I’m not entirely sure about, but it’s probably somewhere close to the additional electrical heating element. My understanding is indeed that the system compares the target temperature (“Calcul supply temp 1”) with the supply temperature.
Regarding RMU40 I’m not so sure either, but it sounds likely that it only adjusts the heating curve.
The charge pump in my case (Grundfos UPM2 25-70) reports 0% charge pump speed (EB101) via myUplink so I assume it’s off if the heatpump is not running?
For the circulation pump I’m not sure at all, the circulation pump is not showing up anywhere in myUplink.
I think I will need to spend some time and properly set up energy monitor to get more insights
I believe that’s normal; my system is the same. Typically it’s only the Charge pump (Primary Circulation pump) which is connected to the NIBE controller. Any ‘Secondary’ Circulation pumps (on the Emitter side of the Buffer) are controlled by some other means - typically a (separate) room thermostat.
On F-series installations it’s common to have a temperature sensor (BT25) fitted to the Buffer tank. In myUplink that’s called the “External supply line” temperature, and it’s that which is compared to S1, the Calculated target flow temperature, rather than comparing BT12 to S1. I’m not sure if S-series systems also have the option of a BT25 sensor.
It does sound similar to the F series. A few plots of your uplink data should get you some very good insights into why it runs when you’re away.
@dMb has excellent guides on this or it’s quite possible to grant read only access to the data so a few of us on here could maybe help get you the insights. I’ve just done this exact thing for a work colleague (not on the forum) with reasonable success in diagnosing the behaviour.
Yes my BT25 sensor is in the nibe buffer tank. I’ve also seen them on the flow pipe.
You could check the wiring to the controller and see if you have a sensor connected and if so trace the wire to your pipework. I’m not sure how easy that would be on your s40 controller and installation.
Yes read only viewer access. It can then be logged using existing scripts and we can post the plots here so others can take a look at the behaviour and seen if we can help you figure it out.
