Interesting to know that. I did wonder whether that might have something to do with it. It wasn't a smelly installation, but there is almost always a mild pong in the vicinity of an oil tank.
Midea 14kW (for now...) ASHP heating both building and DHW
Cathoderay do you know the lowest power output of your HeatPump? On the Ecodan registration plate it states it’s design output but also shows it’s minimum output and maximum output. Eg our system is a Ecodan 8.5 but has a range of outputs from 3.4 to 9.7. So I know that my 21kw rated radiator capacity will cycle if I don’t maintain a full heat exchange of all the radiators.
I haven't seen such a plate with min/max outputs, instead I have been using the Midea Engineering Data manual which has tables of outputs for various OATs and LWTs. These ouputs vary greatly, depending on how favourable or unfavourable the various combinations of OAT and LWT are eg at seriously sub zero OATs with high LWTs the output is shockingly low, at high OATs and low LWT's it becomes reassuringly capable. Here's an extract from the tables for my 14kW heat pump at the sorts of OATs and LWTs I have been considering (CL = 'capacity level', which is not otherwise defined, CAP = capacity ie output in Watts, PI = input in Watts):
Midea 14kW (for now...) ASHP heating both building and DHW
Cathoderay do you know the lowest power output of your HeatPump? On the Ecodan registration plate it states it’s design output but also shows it’s minimum output and maximum output. Eg our system is a Ecodan 8.5 but has a range of outputs from 3.4 to 9.7. So I know that my 21kw rated radiator capacity will cycle if I don’t maintain a full heat exchange of all the radiators.
I haven't seen such a plate with min/max outputs, instead I have been using the Midea Engineering Data manual which has tables of outputs for various OATs and LWTs. These ouputs vary greatly, depending on how favourable or unfavourable the various combinations of OAT and LWT are eg at seriously sub zero OATs with high LWTs the output is shockingly low, at high OATs and low LWT's it becomes reassuringly capable. Here's an extract from the tables for my 14kW heat pump at the sorts of OATs and LWTs I have been considering (CL = 'capacity level', which is not otherwise defined, CAP = capacity ie output in Watts, PI = input in Watts):
Do you have the same info for the 16kW variant? I wonder if the min values are different. Maybe the dip switches just throttle the maximum.
Three clear defrost cycles, each with a marked uptick in OAT. There is also a clear three hour period between 0300 and 0600 when the unit achieved steady running, without cycling. This is interrupted by the third defrost, and then it again continues steady running until 0755, when for some reason the LWT starts to rise, and we get a cycle. Is this triggered by the OAT falling from 3 to 2 degrees? Possibly, the Set LWT can be seen to rise as the OAT fell (as indeed it should). The heat pump then over-shoots, and that triggers the cycle.
OAT sensor spike in readings.
It is difficult to know definitively, without installing additional sensors and recording any variations. I suspect, though I don't have any proof, that in your system it could be a combination thermal energy being emitted by the evaporator, which is in close proximity to the OAT sensor, and also the fact that the supply of cold air coming out of the heat pump has stopped for a short period of time. The sensor is quite small so will react fairly quickly to temperature changes, hence the spike. I do believe other heat pump owners have seen similar spike, but possibly not as pronounced.
Effect of having a PHE.
I am not certain that I clearly explained my concerns in relation to your PHE, so I will see if I can provide a more easily understood explanation. My concern is not about the PHE itself, but on the effect it appears to have upon the operating range of your heat pump, and possibly those of others.
Looking at the manufacturer's data for both the Midea and Ecodan heat pumps reveals the following, for different OAT's and LWT's.
As the data in the tables shows, in virtually all occasions the minimum capacity of the Midea is higher than that of the Ecodan, but more importantly, for some unknown reason, the Midea exhibits quite a large increase in minimum capacity between the 40C LWT values and the 45C LWT values, and this is also shown to occur at all three OAT ranges examined.
So it would appear from the data, that to achieve a lower minimum output capacity with the Midea heat pump it is necessary, if at all possible, to keep the required LWT below 40C.
Having a PHE within the system, which will invariably entail operating the heat pump at higher LWT's, could potentially move the operating parameters above a LWT of 40C, which in turn will increase the likelihood of cycling occurring at lower OAT values.
I hope this is easier to understand than my previous ramblings.
. This winter im running fixed flow@32 and no zones. I reckon the no zones is helping alot and also lower flow temp. I couldn't realistically run24/7 as plant room near my bedroom and the humming would keep me awake. House nice and warm@22 9pm and still21 this morning when i got up @4egOAt@7am. So far im content with my improvements. Would you think its better to run fixed flow if not running24/7? Fixed flow from1pm/9pm usually with 1 hour of that for dhw and thats 33/34l/min cop @5 the meters are telling me
At 32C WC doesn't actually make that much difference, about 10% or less, whereas its more like 20% at 45C. So fixed flow may well be good. The risk is that you may find its just too warm when the OAT is higher, in which case I would turn down the flow temp (manually or using the WC function) rather than let the system return to being principally thermostat on/off controlled. The latter will result in poorer efficiency and also more strain on the heat pump because of the cycling.
4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.
. This winter im running fixed flow@32 and no zones. I reckon the no zones is helping alot and also lower flow temp. I couldn't realistically run24/7 as plant room near my bedroom and the humming would keep me awake. House nice and warm@22 9pm and still21 this morning when i got up @4egOAt@7am. So far im content with my improvements. Would you think its better to run fixed flow if not running24/7? Fixed flow from1pm/9pm usually with 1 hour of that for dhw and thats 33/34l/min cop @5 the meters are telling me
At 32C WC doesn't actually make that much difference, about 10% or less, whereas its more like 20% at 45C. So fixed flow may well be good. The risk is that you may find its just too warm when the OAT is higher, in which case I would turn down the flow temp (manually or using the WC function) rather than let the system return to being principally thermostat on/off controlled. The latter will result in poorer efficiency and also more strain on the heat pump because of the cycling.
Currently the warmest room the kitchen has been getting to 22/23, others 21, i have just been altering length of time heating is on for, probably 1pm-9pm for rest of winter now i hope and house is getting to what i consider ideal temp for us.
Thinking that when i know fixed flow@32 seems to work down to 5deg OAT for the day and below freezing at night time, ill just stick with it, had it @30 fixed flow but upped it to 32 to react bit quicker, not sure how much difference it made. My issue with daikin wc is that its not taking into account my IAT and i know 28deg takes long time to get house up by couple deg heat even in much milder conditions. When its milder then the lwt will go above what i need and sometimes it will be below what i consider responsive enough when using setback. Obviously if i was running24/7 id say the curve would be the way to go. Anybody i know runs stat on/off with wc but i think using curve with that method is possibly worst for consumption.
Why am I getting email notifications that I have been mentioned in a thread when I clearly haven't and neither am I subscribed to said thread? Confused.
"You have been mentioned in a post on "Do setbacks save energy without compromising comfort?" by JamesPa."
"You have been mentioned in a post on "Do setbacks save energy without compromising comfort?" by newhouse87."
Retrofitted 11.2kw Mitsubishi Ecodan to new radiators commissioned November 2021.
14 x 500w Monocrystalline solar panels.
. This winter im running fixed flow@32 and no zones. I reckon the no zones is helping alot and also lower flow temp. I couldn't realistically run24/7 as plant room near my bedroom and the humming would keep me awake. House nice and warm@22 9pm and still21 this morning when i got up @4egOAt@7am. So far im content with my improvements. Would you think its better to run fixed flow if not running24/7? Fixed flow from1pm/9pm usually with 1 hour of that for dhw and thats 33/34l/min cop @5 the meters are telling me
At 32C WC doesn't actually make that much difference, about 10% or less, whereas its more like 20% at 45C. So fixed flow may well be good. The risk is that you may find its just too warm when the OAT is higher, in which case I would turn down the flow temp (manually or using the WC function) rather than let the system return to being principally thermostat on/off controlled. The latter will result in poorer efficiency and also more strain on the heat pump because of the cycling.
Currently the warmest room the kitchen has been getting to 22/23, others 21, i have just been altering length of time heating is on for, probably 1pm-9pm for rest of winter now i hope and house is getting to what i consider ideal temp for us.
Thinking that when i know fixed flow@32 seems to work down to 5deg OAT for the day and below freezing at night time, ill just stick with it, had it @30 fixed flow but upped it to 32 to react bit quicker, not sure how much difference it made. My issue with daikin wc is that its not taking into account my IAT and i know 28deg takes long time to get house up by couple deg heat even in much milder conditions. When its milder then the lwt will go above what i need and sometimes it will be below what i consider responsive enough when using setback. Obviously if i was running24/7 id say the curve would be the way to go. Anybody i know runs stat on/off with wc but i think using curve with that method is possibly worst for consumption.
Best consumption will almost always be obtained by tuning the WC to match the load (ie not on/off except as a temperature limiter when eg solar gain takes over). You do get better responsiveness if the ft is higher, but at the expense of efficiency. I suspect (and the theory says) that your better consumption this year is due to no zones and lower FT, and that you would do better still by switching on the WC, operating for longer hours, then turning the FT down even further. However you may want to let this year settle down first then experiment next year.
4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.
Looking at the manufacturer's data for both the Midea and Ecodan heat pumps reveals the following, for different OAT's and LWT's.
Yes, this confirms that Midea heat pumps lack what I shall call floor room (aka poor modulation depth) compared to Ecodan units. This condemns them to run more like fossil fuel boilers (on/off, aka cycling).
So it would appear from the data, that to achieve a lower minimum output capacity with the Midea heat pump it is necessary, if at all possible, to keep the required LWT below 40C.
A key point is that this is unfortunately not possible without compromising comfort for most of the time. Recall the starting conditions which are constraints: small house, not a lot of wall space. That meant even with the biggest K3 rads I could practically fit, I would still need a high LWT (50-55 degrees, the actual design LWT is 55 degrees) to get enough heat into the building. If I run at lower LWTs I will be cold. I only get to sub 40 degree LWTs when the OAT is in the low teens. The left hand of the WCC is currently at a baseline of 56 @ -4 (design conditions were 55 @ -2), and then as adjusted up to 3 degrees either way by my auto-adaption script. If I set the baseline lower, the house gets cold.
Why am I getting email notifications that I have been mentioned in a thread when I clearly haven't and neither am I subscribed to said thread? Confused.
May I suggest you need to address this to Mars (@editor)?
Midea 14kW (for now...) ASHP heating both building and DHW
@kev-m - here are the data you requested, placed side by side for ease of comparison:
I have to admit that I had not looked at the data sets side by side. Whats is interesting is that the 16kW version not only has a greater output capacity, but allegedly has slightly higher efficiency, certainly in the section shown.
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