It just occurred to me to ask those that have monitoring kit, whether they ever check the Cop from their monitoring kit, with the cop from install to now, on the MMI.
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Hello Terry,
Sorry I haven’t been clearer.
I am not using LWT. I think breadcrumb 2.9 has this option and I have always used “Room Thermostat” - the “use the Madoka” option.
In breadcrumb 2.4 I am using “Weather Dependent”
A few posts ago I started using the qualifier “MCS heat loss” to mean the heat loss stated in the MCS specified survey. This is the figure that our installer designs to. Generally, in these pages we are confident that a typical actual heat loss is smaller than the MCS heat loss. But more specifically, the MCS heat loss only applies when the design conditions exist for longer than an instant. eg. -3C outside and 21/22C inside. I don’t need my house to be quite that warm inside, and the microclimate outside my house hasn’t been that cold for many hours at a time this winter.
So we already have two reductions - the design temps don’t exhibit an in any case I’m not requiring them to be met. The third reduction is that the MCS calculations were amply conservative in the first place, overestimating the actual heat loss.
I share your surprise how little heat has been required to keep my house at a comfortable steady temperature, but happily that’s the way it is 
I have checked my OEM L3 monitoring’s long-term CoP result against the MMI values “from install” and they agree very closely.
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Thanks for the latest reply. I was heartened by the fact that the MMI cop was close to your reporting system cop, as the MMI is really my only tool. Regarding the point above, it was Matt who got me started on my current track, and all the rabbit holes it’s taking me down, when he said it’s delta t, it’s all down to Delta T. And he’s right. So increasing the LWT does two things, by increasing the Mean water temperature it increases the radiators capacity, the Delta T for rads goes up. The second effect and for however long it might last, is to increase the heating Delta T, so the heat pump output goes up. That is until the delta T comes down again. Within that a couple of things can happen. If the delta T increase still keeps it within target , then you simply get the increase in heat that the delta T gives you, but if it takes you over the target, then the pump kicks in to increase the flow rate to get the delta T down to target asap. I’ve seen this a few times on my system now, and it doesn’t hang about. The. Impact of both of those can be that way too much energy is generated for the rads to handle, especially when operating around the low 30’s for LWT. That will of course expedite the drop in delta T as the RWT rapidly rises. At least that’s what the model I’m building tells me. Hoping it will find me the ultimate sweet spot!
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Hi all, just need a little help. It maybe ok , it may not. But all of a sudden the heat pump just starting sucking about 1.8kw which is odd. Consumption had been high around 800w for a little while. So I went down to check theMMI and I couldn’t believe my eyes, leaving water temp was at 35c, that’s over target, RWT was at 29c, so comfortably within delta T 10 target BUT the flow rate, which as I’ve said many times never moves has shot up to 15l/m and just for confirmation there was NO DHW cycle running. I thought back to one of the other guys with the refrigerant leak. Can’t explain this behaviour otherwise, so I’ve switched the system off. Any thoughts, any advice? Thanks , oh and yes I will be calling BG and Daikin, but it’s Saturday and there will be no response. Lines don’t open until 9am, if they open at all.
Hi Terry,
What’s your outside Temperature this morning? My heatpump has been defrosting every half hour which is inevitable given the near-freezing ambient and high humidity 
It draws about the same as you are describing in these conditions.
Is your evaporator side of the heat pump frosting up every so often?
Yesterday was the same - constant defrosting till a little later in the morning when the day warmed up a little. Just now I’ve made my morning switch-on schedule a couple of hours later so that from tomorrow the heatpump doesn’t have to battle through these unfavourable hours.
The system is still working as designed, but I’m thinking why run the pump in these few hours if the house temps don’t need lifting immediately.
Going to have to show my lack of knowledge here, which side is the evaporator side. I haven’t noticed any frosting up, not previously either. Outdoor temp is 2c and it’s been that a few times and I’ve not seen the like of this before. Perhaps this is what has been described as first frost panic! So when it defrosts how long does that last? And does the flow rate zoom up like that? What exactly is it defrosting and is that where all the energy is going ? Yes scheduling it off makes sense, but at present I don’t run any schedules just let it do its thing 7/24, but at a low ish flow rate. Still trying to absorb all the other info we’ve been discussing. I wonder if Matt on his methodology gets the defrost too, I guess we all do? So given I’ve turned it off and today is looking surprisingly sunny I can afford to leave it off until later as it’s going to be a solar gain day. So can you see the peaks of energy use arising from the defrosts. And thanks for responding so promptly to my anguished cry for help.
The evaporator is the radiator grille on the left hand side. Mine faces our kitchen window so it’s easy to monitor.
In these conditions you’ll see it go white with frost every so often and then the heatpump does some kind of reversing that instead of chilling, heats those fins and the frost drips off.
I think the high power draw is a consequence of running in cold weather. It just subtracts from the long-term average performance.
I suppose the only problem with defrosts is that we have periods of time when no heat is being delivered into the house.
@Terry247 at the risk of throwing in a red herring (as it refers to Samsungs rather than Daikins, which are somewhat different in design) you may find some helpful background in Samsung ASHPs: Anatomy of a Defrost. It’s a long read, but perhaps something to pass the time until you can fire up your HP again…
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are you getting defrost cycles ?
you can my 5 defrost cycles in the early hours due to -2 outside temps with high enough humidity
@Chris_Hill , Chris as I don’t have the reporting software and kit I simply don’t know. Unless there is some way I could know, that you could advise me.
when the frost stats to build up on the exchanger keep watching and the fan will stop then the hp will circuit will go in to reverse pulling heated water from the heating circuit and defrost the fins , then you will see a plume of steam as it starts up again , this co insides with the high start up power usage
its worth mentioning that my defrost cycles have dramatically improved with since making the changes @matt-drummer suggests to do , but i am not manually adjusting the WDC its setup and keeping the home warm as we want
you may also see that when the outside temps are below 2 degree C i don’t heat the hot water with the heat pump because this causes a uncontrollable whirlwind of the heat pump doing continuous defrost cycles because it has to work harder and pull more cold damp air through the exchanger which then causes more defrost cycles (never ending )
See pic below, if you mean the front grille, at the back on the left there is no grille and then you have that kind of mesh, where presumably the air is pulled through. I don’t see any, what I would think of as fins. Perhaps I need to have another look at the manual and familiarise myself with the various parts. There is little sign of frosting, but a little time has passed and the sun is up, there is very little water in the tray underneath the pump. My pump sits outside a lobby, that has a window and I do look from time to time wondering if I will see the air plumes that I have seen referenced, but I haven’t as yet seen any. Is that what you see, or is it something less obvious? I know you mentioned the frost.
the exchanger is the fins on the back of the unit, it might not happen now the sun is on the unit
Thanks, so what settings did you choose for your WDC and did you change any others?
getting the flow rate as low as possible as quickly as possible certainly helps to get the het pump settled quicker , there is a thread on here somewhere on the discussion and the journey i took , i will find a link and edited this repsponse with the link to it
link here
Hi Terry,
My heatpump has now settled down into its normal, steady state after the frosting events this morning.
I expect what you were seeing has similar causes so there’s not much for you to worry about. But it does indicate the advantage of having some monitoring to give more information than you can get from the MMI.
Here’s my display for this morning.
https://emoncms.org/app/view?name=Daikin+8kW+ASHP&readkey=c91494900da64f39031be3d94a823710&mode=power&start=1740769650&end=1740823740&flow=1
Let me describe it.
Through the night, (blue line) the pump was running four times an hour for a few mins without doing any heating. This is freeze protection for the outside unit. It runs at your maximum flow rate.
(black line) the inside temperature was falling slowly
(red line) at 6am my schedule started the heatpump and the flow temp increased, still at maximum flow rate. On 3 occasions, the red flow temp goes lower than the green return temp, and this is defrosting. The flow rate stays high.
On a different 3 occasions the flow rate dips to zero and this is the heat pump cycling. I think this is happening because at this high flow rate my radiators cant dissipate enough heat. (From 6am there’s a lot of heat being delivered (yellow shaded area).
Finally, on the RHS, everything starts to calm down. The flow rate drops, the heat drops, the electricity consumed (silver shader area) drops.
I expect this low plateau will now continue through the day.
Thanks, I’ll read those. I note you are using the fancoil setting, and I note you have now increased the dT back to 8 ( as target presumably) mine has been on the rad setting of 10 as target, but varies hugely. I’m yet to be convinced of reasons for lowering it, when I run the modelling it doesn’t appear to be particularly helpful as it reduces output, necessary if the rads can’t cope and temp in rooms is high, but otherwise it seems to be a huge disadvantage. So the target of 10, which on mine is never where it sits seems to work well . Thanks again, as I said I will read those.