I done some calculations, and reckon that 4 fan units provide an extra 330 W of heat output at Δ20, an increase of 25% on those radiators. This seems in line with independent testing that SpeedComfort mention on their FAQ page, if you extrapolate to the right towards 40C:
[Power increase in % vs. Supply water temperature in °C]
Correlating to some measurements I did of the whole system, this increases the total effective output at Δ50 by 1,500 W (but not real output at that temperature), and drops the overall flow temperature by 0.5 C.
Exactly. Why design for worst case, you are always compromising the other ~90% of the time. Pareto; design for the 80% and mitigate the other 20% in other ways.
@Stephen_Crown Your prior cat5e cabling was fortunate. I installed mine in a IPxx box that was given to me by the Octopus Solar installer when he was clearing his van out (!), running the cable through a handy gap behind the cover. In fact, it’s so much easier to access than inside the HP casing, I’d do it that way in preference. Signal isn’t great (-79dBm), but works. Could be ok for you longer term?
I wanted to go direct to EmonHub/CMS, so changed the MQTT reporting to one data point per message, and modified the MQTT topic, so it is registered automatically in EmonCMS.
What’s the suggestions with the outdoor unit in terms of condensation/excess water? It’d be on a north facing wall, little to no sun in winter, with plumbing available on the internal side of the wall to drain water away if that’s the ‘done thing’?
In terms of heat loss from the survey, ive not had the quote pack back yet but the bathroom and all 3 downstairs rads would be changed. Bedrooms are apparently fine. So removing the conservatory seems to have changed things.
I guess it cant hurt to ‘oversize’ the radiators though? All 4 bedrooms have single panel radiators that could be swapped with double.
This is my thinking on the subject and I hope it makes sense.
I have sized all my radiators in proportion to the heat loss of the room so that whatever flow temperature I run at all the rooms are the same temperature. If you go a bit smaller on rooms such as bedrooms then that is fine. You really don’t want radiators going in and out of play if that makes sense, it will wreak havoc with the efficiency and the feel of your home.
What you don’t what is trvs mucking things up and to that end I have removed all of mine and fitted Danfoss RLV-D lock shields to all radiators.
The trvs are unnecessary if the radiators are the correct size for the room.
Obviously, the bigger the radiators the lower you can go on the flow temperature.
If you can get Octopus to fit the radiators of your choice it will be the cheapest and most convenient option.
I would post up your radiators schedule when you get it so we can all have a look.
I don’t think the siting of the heat pump is of any particular concern, mine is on a south(ish) facing wall but when it is damp outside and cool then it’s damp everywhere.
Octopus are pretty good at actually fitting stuff and they made sure there was adequate drainage around the heat pump, I would have no concerns here.
I would advise you let us know your heat loss, radiator schedule and proposed heat pump so you can get some views on whether it will work well.
Until October 15th we had undersized primaries upstairs restricting 50% of our heating circuit (didn’t notice in the summer for obvious reasons).
The Double DHW is an initial daily schedule to 43 (during cheapest electric period) then every Tuesday 04:00 - 05:00, a legionella cycle to 60 (assisted by the immersion - currently not monitored).
The house is already heating to 21 all day long with a overshoot setting of 4 and a modulation of 5. The night time setback is 19 and the house rarely ever gets near that
Happy to discuss further optimizations but based on daily usage and what I am seeing the heat pump is likely oversized (Believe it should be around 5kw and not 9)
Even with oversized K2 radiators in every room the return temp is still getting to high and turning off the system.
They have done the same with your lounge as mine, included the heat loss in full twice as you have two radiators in the lounge.
What do they say your heat loss is?
The total from the radiator schedule is 7,418w with `both’ lounges included and 5,870w with the lounge only included once.
The 8kW is the correct size in my opinion as the 6kW won’t go any lower than the 8kW as far as I understand things as they use the same compressor.
You might like to check with Octopus, a few of us would like to know.
You have 6,009w of radiator output at a flow of 50c and a delta t of around 30c. I had around 9,000w of radiators at the time of my survey and I am doubling mine right now to cope with the 9kW heat pump! Yours would need to triple.
It’s also interesting that they have assessed your annual heat requirement as 7% more than mine yet you get a much smaller heat pump.
At a flow of 35c you would have radiator output of around 1,500w.
I wonder how low the EDLA08 can run?
I also see it is an EDLA08E2V3 and not and EDLA08E3V3, is that without a back up heater?.
Looking back at my Octopus radiator schedule, it does show one 2-rad room twice, but there isn’t a total heat loss figure quoted. I checked their numbers - with 2 rooms (!) it’s 10.2kW, with 1 actual room it’s 8.4kW. They quoted me for a 9kW HP, so given they could have suggested an 11kW, I suspect that unless you actually have a number from them for total heat loss, the schedule doesn’t actually detail their target heat loss. My rads are rated at 9.9kW post-install. Do you have an actual total heat loss anywhere in the quote? Looking now, I can’t see it in mine.
None of this takes account of the fact that even the 11kW HP actually only delivers 7.5kW at 4C or below, taking into account DHW and defrost cycles, as per @ColinS’s post in this thread. So my 9kW might struggle a bit with the 8.4kW requirement at -2.2!
I assume it knows its the same room as it says 2 radiators, and the total planned radiator output for the room is 1594 vs 1548 heat loss.
Waiting to hear back with install dates now. I think ill miss out on the £250 Daikin offer which is valid on installs between June 21st 2023 and March 31st 2024.
I have no actual heat loss as a single figure from Octopus but the radiator schedule does detail the heat loss of each room in my house.
The total heat loss of all my rooms is 6,350w
My lounge is the same size as the two bedrooms above it.
The heat loss for my bedrooms is 820w but my lounge is 1,441w.
The construction is the same and the window sizes are the same. The lounge obviously gives heat to the bedrooms above but would it be that much different?
I also wonder about how they have calculated air changes per hour, no detail on that.
But at 6,350w my heat loss is not dissimilar to that of @phproxy and I suspect my lounge is smaller looking at the rooms on his radiator schedule but I am guessing a bit based on the bedroom heat losses and there being no dining room.
I am sure my heat loss is overstated but even at was it is I should have an EDLA08 and not an EDLA09, they are miles apart in reality.
I have yet to experience sustained really cold weather so have nothing to add in terms of performance in those conditions. If the 11kW only gives 7.5kW I wonder what the 9kW does?
They have three months to complete the install from the date the grant is awarded (that is how it was for me in June) so you will probably be ok with March 2024.
Out of curiosity how big is your house?
Maybe to give me an idea we have more or less the same heat loss, how big is your lounge?
I can’t believe my lounge heat loss is correct looking at the figures for the rest of the rooms in my house.
I think the schedule knows it is two rooms but I have no idea where they get the total heat loss from, you would think it is the total of the room heat losses.
It is strange that the heat loss of the room is not split between the two radiators.
In my case the total adds up to 7,790w including the lounge twice but only 6,350w if I include the lounge once.
As far as I’m aware, there’s noting in the permitted development legislation that requires MCS installation, only the heat pump unit itself needs to be “MCS compliant or equivalent”. Heat pumps in new build properties generally don’t have MCS since they can’t claim BUS grant. MCS compliant means the unit should be on the MCS product direction, which all A2W heat pumps are. However, as far as I can tell this list does not include A2A heatpumps, but maybe these would fall under “or equivalent” which is a bit a gray area!
Permitted development mentions “the air source heat pump is used solely for heating purposes;”, which I guess excludes mini-splits? But all aircon companies claim that aircon is covered under permitted development, I guess in practice it’s nearly impossible for anyone to tell if a system is capable of cooling or not!
I doubt any council would want the bad press if they demanded someone removed a heat pump if it was being used for cooling.
It looks like our houses are very similar overall in terms of size, heat loss and annual heating requirement.
I expect you will have a much easier time of it than me.
I am guessing but if the 8kW consumes 500w at 7c outside and 35c flow at a COP of 5 the heat output will be 2,500w. That is more than your radiators can output at that flow temperature.
It’s fine if you are not worried about low flow temperatures but if you are you may want to find out what the minimum performance is.
If it bothers you I would upgrade the radiators using Octopus as it will be the cheapest way to do it.
Have you found out what an EDLA08E3V3 is, no back up heater?
I have heard that there is a problem with the back up heater on these models but I don’t know if it is true?
