Right now as well with all the heating on and the house running its regular electricity use. I’m only consuming 2KW per hour. That seems odd. 

current outdoor temp is -2.

So far as I understand it, pressing the up/down has no effect (other than to change the number being shown). In the installation guide:

"Please note: this is not to be used for setting the room temperature control"

I've just adjusted mine (HP currently 'off') and nothing has happened. 

You can only use third party controls to alter the target room temperature. Unless your Grant has been installed in some other way, but I don't think it has been (no programmer slots are showing on your controller).

Depending on your weather compensation settings, disabling WC and reverting to constant leaving water temperature would work. Depends on what outdoor air temperature corresponds to maximum leaving water temperature. I’ve found my 10KW unit falls short of target LWT by 3-4degC when it goes into regular defrost. No issue with the ability of the ASHP to provide high LWT as it can go up to 60degC for HW cylinder charging in the current cold weather.

@marvinator80 your situation mirrors my own, except my consumption is typically 3-4kW under these conditions. And, like @allyfish, my system falls a few degrees short of target once in frequent defrost territory (every 30-40 mins currently) and never really gets the chance to stabilise, although it's perfectly capable of achieving higher LWTs.

So, a less than optimum heat output combines with the house losing heat a little more rapidly to mean the system can just about keep the place comfortable. My only approach has been to keep the system running as 'low & slow' as I can for near 24/7 operation and to keep IAT pretty stable. Climbing back up the hill with low LWTs takes an age so your point about getting to a higher base is valid I think. 

I've recently started Octopus's Cosy tariff and have been experimenting with off-peak boosts. Not really possible to boost at 'low & slow' settings so I end up using weather comp offset to add a few degrees to LWT. Without any auto-adaption this is more manually intensive than I'd like. 

Posted by: @dunlorn

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@marvinator80 a less than optimum heat output combines with the house losing heat a little more rapidly to mean the system can just about keep the place comfortable. My only approach has been to keep the system running as 'low & slow' as I can for near 24/7 operation and to keep IAT pretty stable. Climbing back up the hill with low LWTs takes an age

Ditto here. I can just about keep the house at 19C, but the pain of getting a 1C increase from an overnight setback takes at least 3 hours of daytime, and never quite completes. I think I'll change my setbacks to be higher, and try to run 24/7 with a lower LWT, but that's a change for another day. 

I've given up on setbacks: when it's cold it just takes too long to recover even from a 1c drop and the pump has to work incredibly hard to get the return temp up to around the 4c below flow that lets the pump get into an economical run state.

With weather compensation it's great to see the power consumption drop off rapidly once the outside air gets above about 3c - we get COP of about 4 to 4.5 at that temp or 5 - 6 above 12c, but below 2c it drops below 4 and worsens under 0. Still benefits massively from having the maximum amount of water volume (all zones wide open) and the minimum flow temp you can get away with, let the rooms settle where they settle high or low.

Compared to last year, when we had thermostats shutting off the flow in each room when they hit temp, and Cop was continually below 3.5, it's a transformation.

Yeah it’s the defrost cycle that’s fecking me up for sure. A few parameter adjustments made and going to get it all to a higher base from above zero, then it should maintain ok. I hope. 

house has really been 19.5 during day but waking up to only 18.5 isn’t ideal. Will try to boost the whole place by 1 degree and keep it there.

Posted by: @mikefl

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Posted by: @dunlorn

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@marvinator80 a less than optimum heat output combines with the house losing heat a little more rapidly to mean the system can just about keep the place comfortable. My only approach has been to keep the system running as 'low & slow' as I can for near 24/7 operation and to keep IAT pretty stable. Climbing back up the hill with low LWTs takes an age

Ditto here. I can just about keep the house at 19C, but the pain of getting a 1C increase from an overnight setback takes at least 3 hours of daytime, and never quite completes. I think I'll change my setbacks to be higher, and try to run 24/7 with a lower LWT, but that's a change for another day. 

 

just back from a rare day at the office and checked the temps. 

OAT 1.0

LWT 52!!!!

Return temp 47!!!

Energy use zero difference from yesterday. We shall see. 

Now it’s at -2 and LWT hanging tough at 37. Big difference. The defrost cycle seems to be for 5 mins every 45 mins and that’s why it’s not getting back up there.

-3.5 outside now and indoor temps slowly rising, despite the defrost cycles every 45 mins.

Woke to 17.5 to 18.5 throughout the house. Low of -6 overnight. 

have identified an issue though as the utility room was freezing and no feeling of warmth in the UFC despite blasting the whole night. 

A hatch was cut under the tumble drier for cabling across to our garage/annex. There are HUGE gaps and loads of cold air coming in. Honestly about equal to having had a window open all night in -6. 

now at Screwfix for foam.