My heat pump by luck is sized correctly and defrosts hourly.  All you can do is keep the flow temp to the minimum you need and keep it running so you don’t lose any house temp.  With defrosts and HW heating I’ve found that a setback overnight is counter productive if I want to be warm first thing in the morning 

@gary I too have been using night time set back of 2 degrees or so (various ‘degrees of set back since last November as a trial) but have now abandoned this practice.

With minus temperatures, I have found the early morning temperature was a little cooler than we desired in some rooms. I then realised another significant factor in this cool start to the day - our semi detached neighbours have gone to Spain for a week or so and I think they have dropped their heating settings to frost protection only! 😒 Neighbour, come back soon, we miss you! Regards, Toodles.

I must admit with cheap rate overnight, I’m starting to abandon a 2c setback, some rooms take too long to recover. Still playing around trying to find my way

Posted by: @jeegnesh

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I must admit with cheap rate overnight, I’m starting to abandon a 2c setback, some rooms take too long to recover. Still playing around trying to find my way

I am planning on trialling night time 'set forward' to take advantage of cheap rate tarrif.  I have no idea if it will work in practice.  The challenge with this is to stop the bedroom getting too hot.

@jamespa This is the only room in which we have an active TRV, for this very reason. Regards, Toodles.

@jamespa I have a setback of 2C at the moment with a cheap overnight tariff.

To overcome the slow recovery issue I am currently experimenting with the smart grid interface on my Samsung (I have the feeling most if not all machines have it fitted but could be wrong).

I already utilise part of the interface to disable the heat pump when I switch the oil boiler on line but another part allows you to increase the flow temperature of the heatpump by a preset amount, simply by shorting a terminal with a relay.

My strategy is, during the cheap hours drive the heatpump LWT, in my case, 5C hotter to speed up setback recovery then return the LWT to normal during peak electricity hours.

I am setting this up with a simple timer switch to start with but if successful I plan on adding it to my Raspberry Pi energy management project I have in mind.

Back -- So between 2am and 6:30am it's trying to reach a target temp of 40-42c, it's obviously trying to get there and cycling around every 20 minutes, surely thats a bit much outside temp was cold prob around 0 mark OR it cycling likely more frequent when its cold outside - this was the snow day too.

Mine followed a similar general pattern, but the defrosts (I assume the dips are defrosts) were more like once per hour.  The snow day was both very wet and cold, the worst possible conditions for a heat pump.  Mine (which I run 24*7 at least for now) 'kept up', but clearly spent quite a bit of time in defrost mode.  

If yours isn't keeping up there are a couple of questions worth asking

• are you running in 'quiet' mode - you may not be able to in this weather?
• have you got sufficient engaged system volume (TRV/zone valves, if any, all open - this is important because the water in the system supplies the heat for defrost?
• are you running 24*7?

If its not keeping up and all of these are in place, you may need to look at increasing system volume with a volumiser or something else, depending on details of your system.  Im presuming your system is not undersized for the house (which would be unusual, more normally systems are oversized!)

I do not believe it's in quiet mode - what setting is that so I can double check?

I believe the volume should be fine, as I have a 150l Volumiser and TRV are all open

Not quite 24x7, I'm running in expanded mode with 2 thermostats, the reason for this:--

Thermostat 1 0.30 curve - Downstairs UFH in wundaboard insulation and the heat up is quick and it works well on quite a low flow temp (31/32c) (1 thermostat)

Thermostat 2 0.90 curve - Upstairs is all radiators and Kitchen underfloor is in screed likely a bit too much and needs a higher flow temp to be effective 

What this allows me is when thermostat 2 calls for heat it runs at 0.90 curve and if thermostat 1 is at temp it shut off the valves for the wound UFH, if thermostat 1 calls for heat it runs at the lower curve but supplies the whole system, nothing shutoff

Hope that makes sense - I run from 3:30am till around 10am then 1:30pm to 9:30pm however my setback is fairly high so it can come on outside these times if the temp drops.

Any suggestions on how I should run it?

Posted by: @jeegnesh

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I do not believe it's in quiet mode - what setting is that so I can double check?

 

I think you have a Vaillant, in which case (on the sensocomfort) its settings  - installer level - noise reduction mode.  I run mine in noise reduction mode overnight only, during the day NR is off.  During the day the FT usually overshoots on recovery from a defrost cycle, when NR is on it doesn't.  I dont know if the overshoot is by design but it certainly ramps up the compressor speed.

You have an interesting system so its difficult to advise with any certainty how to run it.  With 150l volumiser there should be enough for defrost even if one of the UFH circuits is closed (can they both close simultaneously?)

Is it possible your thermostats are interfering, can you set one of them a few degrees above the target temperature to ensure that there is always a call for heat (which is generally how heat pumps should be run.)

If if its not getting up to temp following a defrost (Im still presuming Im seeing defrosts not cycling because it cant modulate down, you can tell its defrosting by the plume of vapour that rises above it!) then the only real option is to run for more hours and/or try to ensure as much water as possible is available from the system to assist.

Feel free to post some more info if you arent getting a satisfactory heating!

For comparison here is mine today.  The rise in FT at the very end is because its just started its DHW run.

Noise reduction I have no plans so I assume is off always.

Bizarre part I noticed is my heating curve was set to 0.5 - I change it to 0.3 and 0.9 and it is setting it back to 0.5 -- why is it not listening to me?

Think I figured something out for once.  Adaptive heat curve was on, I believe this was adjusting my heat curve automagically, turned it off see if it behaves any better