I occasionally see the behaviour you're describing, but have never questioned it as an issue.  I just assumed it's a normal part of the cycle to switch between heating and idle modes.

Here's an example from yesterday, where the system has done this on one occasion, but not the other.

On the first occasion, just before 9am, the pump circulation stops at the same time as the heating switches off and the status changes to 'Idle', which is where the background colour changes from yellow to white on the graph.

On the second occasion, at around 11am, there's a 15 minute period after the compressor stops at around 10:48 until the circulation pump stops at 11:03, visible as a small gap where there's no input or output power within the 2nd yellow block shown.  The fact that it's still coloured yellow indicates that the system is still in heating mode at that time, but is not producing any heating power, so that's perhaps the key to understanding it, as it's only when the circulation pump stops that the switch to 'Idle' status occurs.  I don't think it's a bug as such, just something within the internal logic when the system switches modes like this.

I have an energy monitor attached to the smart meter for the heat pump, so am able to see the difference in input power between the two, which is a drop from circa 85W to 15W when the circulation pump stops, so it's not a significant consumption difference.

The other time that I see activity such as this is far more understandable, as it's when the system is running anti-freeze protection (NB: a different process to a defrost cycle) and continuing to keep water circulating through the system at temperatures slightly above freezing.  The above, I think, is an example of the behaviour you're describing, which is different to this.

The Mel Pump interactive graphs are a little clearer in showing this than the one I've included above, but there's an issue with displaying them at present.  They are helpful in also showing the compressor frequency, so it's easier to spot when the system is running in heating mode but with no actual input power being drawn.

Immediately after hitting send on the above, I learned that the Mel Pump issue had been fixed, so I've attached the equivalent data from yesterday.  On the interactive view, look at the difference between what happens between 08:50 and 08:55, when compressor frequency, input power and flow rate all stop simultaneously at the same time as the status bar below this switches from white to grey, indicating the switch from heating mode to idle.

The compare this with the equivalent change between 10:45 and 10:50, where the flow rate continues for a little longer and only stops during the 11:00-11:05 period (the updates are in 5 minute blocks so you don't see the exact time of change in this view) and it is only at this point when the heating status changes to grey.

So, yes, I see similar behaviour to what you're describing but I don't think it's a fault that's causing any significant reduction in efficiency, and therefore requires a fix.

https://melpump.com/public-report/view/019d259f-6a16-7309-b8fc-f34a277f2f08

Hi Sheriff,

Thanks for your reply. I thought it was just mine!

As you say it's not a huge increase in power ~90 watts, 20w quiescent to 109w pump running. In my situation the pump will run for hours, until I intervene or the house has cooled enough for the heat pump to re-start.

More concerning, running the circulating pump is removing heat from the house and dumping it outside. 

@chimpy it sounds like you might have a dip switch configured incorrectly on the main FTC board

Potentially something like the switch for a buffer tank Enabled but none is fitted in your system 

The circ pump running is normal until heat is dissipated and the flow temperature drops, but not for long periods 

Hi, i found this thread because i have a simular problem with my ecodan hp.

I try to figgure out why my primary pump of hp is running all the time. I want to use the SG ready contact to load my buffer (for e.g. to 60c/normally i have 35c feed temp). So fasr so good - the buffer will load to 60c if the sg contact is triggered. But when i release the SG ready contact, compressor will going off and zone pumps are running. BUT primary pump is still running and destroy the layering in the buffer - this make no sence. 

my setup is:

2 zones (z1=unmixed; z2=mixed)

300l buffer tank

DIP 2.6 for butter is ON

Has anyone a idea? 

Sorry for the bad english, i'm from germany. Germany does't have a hugh community for mitsubishi hp.

Thanks

@betaark 

Please try the economy settings for water to be ON
When conditions are met and after a short delay, pumps #1, #2 and #3 are shutdown

@f1p: Pumps are still running. Altrough there is no demand from heat zones (z1 and z2). HP works on static flow mode. 

Maybe i need also a mixer for zone 1?

@f1p

Posted by: @f1p

↑

it sounds like you might have a dip switch configured incorrectly on the main FTC board

Potentially something like the switch for a buffer tank Enabled but none is fitted in your system 

The circ pump running is normal until heat is dissipated and the flow temperature drops, b

This is something that I did not consider when I converted my buffer tank to a volumiser. 

Am I correct in thinking that with my new configuration the dip switch should be OFF?

@davidalgarve 

My comment before should actually say Mixing tank rather than buffer

Dip Switch 2-6 is specifically for mixing and should be OFF if no mixing tank and mix valve is present