Hi - I have a NIBE F2040 12kw and SMO20 and have been having short cycling, high temp & high pressure alarms and defrosting issues (unfortunately from installation back in 2022). My heat pump uses a NIBE weather compensation curve. It provides space heating and hot water. We’re in a 4 bed late 1980s detached house with good insulation and radiators. We also (thankfully) have a wood burning stove. Last Saturday (11th Jan) the heat pump was struggling - we used over 83 kWh of electricity; our non-heat pump base load is probably around 9 kWh - I don’t have an energy monitor I’m afraid. We also burned a large amount of logs on the stove. I’m interested to hear ideas on how we could try to reduce the short cycling and/or reduce electricity consumption? I’d be interested to hear from other NIBE users on their experiences over the past few weeks of cold & damp weather too.
Hi Katherine,
I’m a (happy) NIBE owner but my installation is not especially useful for comparison with yours since mine is a Ground Source system (so no defrosting) in a more modern and very highly insulated house. My heat pump used 11.8 kWh of electricity on 11th Jan.
83 kWh is a lot of electricity to consume in one day. I wonder if your back-up resistive heater is kicking in…?
Is your system connected to myUplink? That is pretty good at reporting any usage of the back-up heater, along with a lot of other parameters.
David
Hi David - thanks for the reply - as far as I understand my system doesn’t have a back up heater. We do have an immersion heater in the hot water tank. (You kindly had a look at some short cycling data off my system from Uplink a while back).
Just for reference on the 11th my 8kW Samsung running 24/7 used just over 50kWh.
(4 bed detached house)
Hi Katherine
Welcome back, I recall we conversed about your strange DHW behaviour. Did you ever sort that?
My 16kw smo40 controlled F2040 used 56kwh on the 11th January and did a whole load of defrost cycles through the day
Coupled with the heat from the log burner, It does sound excessive for your size unit.
As mentioned by David, do you have any resistive heat / immersion heating in your central heating circuit? Maybe in a buffer tank? I noticed last year that under constant defrost cycles the Nibe controller would think the heat pump alone cannot satisfy the heating demand (shown by an excessively large negative degree minutes value). As a result it would try to pull in some help and energise the controller outputs to switch in a resistive load (immersion heater). I didn’t have any resistive load so the controller got stuck and never recovered the heat defecit. I disabled the use of resistive heat in my settings and it’s been fine ever since. Maybe you have a resistive heat load installed and the controller is calling for it under heavy defrost cycles? This would increase energy usage significantly
It also sounds like you’re not getting the heat into your house if you needed log burners too. Without knowing your exact plumbing set up it’s hard to comment further
When you say it was short cycling, how do you know this? Do you have data plots or something from the nibe app?
To understand what goes on we really need to see nibe uplink data. There are simple ways to grant external people (like me or David) read only access to your system, from there we can take a look at what the nibe is “thinking” and why it might be using so much electricity.
I’ve looked at a few nibe set ups now and usually the settings (it’s highly configurable) don’t integrate well with the installation configuration and things need to be adjusted to suit. This was definitely the case with mine
Out of interest, have you compared your usage to the 12kw f2040 on heatpumpmonitor.org. Whilst the house and plumbing set up might be different it will give you a benchmark to understand if you’re on high usage all the time or just on the really cold days
Hi Sam @etchelsa -
many thanks for the reply - unfortunately not much has happened to sort the problems since eI last posted. The DHW problem remains, and the recent cold damp weather has highlighted the short cycling issues with the heating system as well. Very interesting that your system although a 16kW model used less than my 12kW F2040. I will take a look at the other 12kW system you mentioned and compare peak use. I am certain no other heat source is installed apart from the DHW immersion. However you have a point on making sure the settings match the installation. I have concerns on that point myself and will have another look tomorrow (it’s too cold to go out to the garage tonight to check on the SMO20 which is where it was inconveniently installed).