I'm not sure whether it's best to post here, or start another topic. It feels like I'm hijacking someone else's topic, but it's all relevant I guess.
I've not had too much 'fun' testing today (largely a consequence of the heating being off as target temp was reached/exceeded earlier). Auto adapt seems a bit slow in auto-adapt'ing to the fact too much heat is being put in to the building and needs to lower flow temps (although I'm still testing out the 'Interval' period of 60 mins that Derek suggested, feels like that may be too longer a period to sample what's going on). Although.. if it's off it's consuming no electricity so fine with me.
Can I bring up flow rates/delta t. Having read a fair number of forums etc recently there seems to be some consensus that a delta t of 5 is one to aim for, but equally consensus for decent flow rates. The two don't seem to go hand in hand, to increase delta t flow rates would need to be decreased? Although I guess if the system was designed from scratch with the proper pipe sizes etc this 'battle' would not be raising it's head, a retro-fit will for most have compromises.
As a real world example:- My 6kW Ecodan has a published flow rate range of 8.6-17.2 l/min. When I set my circulation pumps to a lower setting I see 11 l/min (as seen via code 540 in the running information), if I set the circulation pumps to an intermediate setting I see 17 l/min - the former flow rate being at the lower end of the published range, the latter right at the top end. Observations over the past week or so show the slower flow rate gives a delta t of about 5, the faster a delta t of about 2.5. The slower rate giving a delta t of 5 sounds perfect..?
..not from looking at these two charts from this morning it isn't (outside ambient temp was mild at 9c)? The one with the two longer cycles is at 17 l/min, the one with the three shorter cycles is at 11 1/min. I can only conclude that LWT is being brought up too quickly so shutting down quicker at the lower flow rate. So despite the fact the slower flow has the 'perfect' delta t, my system is better off running at a higher flow rate with a lower delta t?
From reading posts here and elsewhere, I'm also aware of PWM, but fairly certain there is no PWM'ing going on within my system.
Generally would you agree with my conclusion, or are there a lot of hidden 'it depends' that I'm not aware of yet?
Not sure but it seems to me that your primary return water isn’t rising much at all. Your DT appears to be getting wider and wider as the flow water rises until it becomes unstable. Maybe the higher flow rate is able to overcome the resistance better.
Few Possible causes
Water struggling to get through radiators fast enough or
pipe size at some point not able to carry the heat away fast enough through to the radiators or
Not sure but it seems to me that your primary return water isn’t rising much at all. Your DT appears to be getting wider and wider as the flow water rises until it becomes unstable. Maybe the higher flow rate is able to overcome the resistance better.
Few Possible causes
Water struggling to get through radiators fast enough or
pipe size at some point not able to carry the heat away fast enough through to the radiators or
Debris or air lock restricting flow.
or it could be something completely different.
Thanks. I am though becoming more and more certain that it's a consequence of milder temps, it cannot modulate down enough so is in effect 'stalling'. I should of posted another chart along with those two for wider context - the attached is when running at the slower flow rate of 11 l/min, but at ambient temps of 2 degrees (during the recent cold spell) - as you can see it's linear with no 'stalling' and is holding a near constant 5 delta t.
On a final note do you use Room temperature control (Auto Adapt) or Weather Compensation?.............I have trialed both and the conclusion I am coming to is that weather comp seems to be a bit more costly to run and the pump cycles a bit more frequently.
I've also been trailing room temp versus weather comp - so far my findings reflect yours. i.e. more cycling/energy consumption in weather comp mode at milder temperatures. Once ambient temps get to around zero the cycling stops and I get constant running (just a defrost cycle interrupts things).
I have now got a few more days trialling WC in mild weather and think i am going to revert back to AA.............I am getting some serious cycling as shown on attached shots although the one at 3.00 am shows no cycling?
The ambient at 4.00am was around 7c, 9c & rising at 8.00am and 10c and falling at 3.00pm.
My curve has been at 37@-5 and 25@20..............Pump speed @ 1 giving 12 l/min...........COP been around 2.5 - 2.7
On a final note do you use Room temperature control (Auto Adapt) or Weather Compensation?.............I have trialed both and the conclusion I am coming to is that weather comp seems to be a bit more costly to run and the pump cycles a bit more frequently.
I've also been trailing room temp versus weather comp - so far my findings reflect yours. i.e. more cycling/energy consumption in weather comp mode at milder temperatures. Once ambient temps get to around zero the cycling stops and I get constant running (just a defrost cycle interrupts things).
I have now got a few more days trialling WC in mild weather and think i am going to revert back to AA.............I am getting some serious cycling as shown on attached shots although the one at 3.00 am shows no cycling?
The ambient at 4.00am was around 7c, 9c & rising at 8.00am and 10c and falling at 3.00pm.
My curve has been at 37@-5 and 25@20..............Pump speed @ 1 giving 12 l/min...........COP been around 2.5 - 2.7
The Peak at 4.00am is the DHW cycle
As a test, try setting your system in fixed LWT mode with a setting of 29C or 30C to see if you still experience cycling.
As I am sure that you are aware, your heat pump is producing too much heat energy and is therefore running for a period of time and then shutting down until the temperature falls.
After the above test has been completed, switch back to AA mode as you propose and report back. I have some further ideas to probably reduce the frequency of cycling.
What is the indoor air temperature and is it fluctuating?
I am getting some serious cycling as shown on attached shots although the one at 3.00 am shows no cycling?
The ambient at 4.00am was around 7c, 9c & rising at 8.00am and 10c and falling at 3.00pm.
The 4am chart looks to have two cycles in it, it looks 'smoother' as the scale has been changed due to DHW cycle later in the hour. It therefore looks to me that at 7c at 3-4am it was just about hanging in there, once the outside temps increased to 9 and above it lost it as such.
I've learnt enough now and reviewed a fair bit of data to recognise that my heat pump is producing too much energy. Thinking of ways to 'embrace' that I've decided to trial something else.
I know a flow temp of 36-38c will provide sufficient energy to heat the house at -3c, I have decided to set a fixed LWT of 36c. The rationale is that there will be no cycling at temps around zero and below, little cycling at say zero to +5, the cycling will increase at +5 and above, but at 36c LWT the house will warm up beyond my stat temp and the system will turn off (can't cycle if it's not on). Also from my observations anything below say 34c LWT leads to multiple cycles per hour (4-6). 36c seems to be the sweet spot to trial.
Today for instance has been mild +9. At 36c fixed LWT I'm seeing two cycles per hour, the house has reached target temp a couple of time so the heating has been off for at least 8 hours so far today.
If you are interested, I'll report back how that goes comfort wise and energy use wise.
I have now got a few more days trialling WC in mild weather and think i am going to revert back to AA.............I am getting some serious cycling as shown on attached shots although the one at 3.00 am shows no cycling?
The ambient at 4.00am was around 7c, 9c & rising at 8.00am and 10c and falling at 3.00pm.
My curve has been at 37@-5 and 25@20..............Pump speed @ 1 giving 12 l/min...........COP been around 2.5 - 2.7
The Peak at 4.00am is the DHW cycle
What is the indoor air temperature and is it fluctuating?
@derekm
The house is all at design temperature 21/20/19......
What do you think is different at the 4.00am graph which shows little cycling??
I have set to fixed flow temp of 30c and will report back.
Just on a basic level I have noticed some of my rads are barely open on the lockshields although they are all well balanced....does this mean the return water is too high and causes cycling .... should the balancing be redone starting with all lockshields fully open.....
I am getting some serious cycling as shown on attached shots although the one at 3.00 am shows no cycling?
The ambient at 4.00am was around 7c, 9c & rising at 8.00am and 10c and falling at 3.00pm.
The 4am chart looks to have two cycles in it, it looks 'smoother' as the scale has been changed due to DHW cycle later in the hour. It therefore looks to me that at 7c at 3-4am it was just about hanging in there, once the outside temps increased to 9 and above it lost it as such.
I've learnt enough now and reviewed a fair bit of data to recognise that my heat pump is producing too much energy. Thinking of ways to 'embrace' that I've decided to trial something else.
I know a flow temp of 36-38c will provide sufficient energy to heat the house at -3c, I have decided to set a fixed LWT of 36c. The rationale is that there will be no cycling at temps around zero and below, little cycling at say zero to +5, the cycling will increase at +5 and above, but at 36c LWT the house will warm up beyond my stat temp and the system will turn off (can't cycle if it's not on). Also from my observations anything below say 34c LWT leads to multiple cycles per hour (4-6). 36c seems to be the sweet spot to trial.
Today for instance has been mild +9. At 36c fixed LWT I'm seeing two cycles per hour, the house has reached target temp a couple of time so the heating has been off for at least 8 hours so far today.
If you are interested, I'll report back how that goes comfort wise and energy use wise.
,,@gottashp.... that sounds a sensible trial...I am trying the lower fixed LWT of 30c as Derek suggested..... would be good to know your findings
The 4:00am graph does show 2 cycles prior to hot water production. The heat demand at 4:00am will probably be slightly greater, since the external fabric of the building will have cooled. Once direct sunlight starts to hit the external areas of your home the heat demand will start to reduce, hence causing more cycling.
I remember reading that the Ecodan controller has a time setting which delays the heat pump restarting, this could be one way to extend the period between cycles, though it may cause fluctuations of the indoor air temperature.
If you have a room thermostat with a hysteresis of 1C, it may be possible to adjust the warm end setting of the WC curve to say 30C LWT at 7C outside air temperature and above. Then set the thermostat to 1C above the desired temperature. As the outside air temperature increases, and the heat demand reduces, the room temperature will start to increase until the heat pump is switched off by the thermostat, it will therefore take some time for the room temperature to fall and the thermostat to reset and restart the heat pump. This should hopefully reduce the cycling frequency.
If you have the time, you could try re-balancing your radiators, though it is not a 5 minute job.
The 4:00am graph does show 2 cycles prior to hot water production. The heat demand at 4:00am will probably be slightly greater, since the external fabric of the building will have cooled. Once direct sunlight starts to hit the external areas of your home the heat demand will start to reduce, hence causing more cycling.
I remember reading that the Ecodan controller has a time setting which delays the heat pump restarting, this could be one way to extend the period between cycles, though it may cause fluctuations of the indoor air temperature.
If you have a room thermostat with a hysteresis of 1C, it may be possible to adjust the warm end setting of the WC curve to say 30C LWT at 7C outside air temperature and above. Then set the thermostat to 1C above the desired temperature. As the outside air temperature increases, and the heat demand reduces, the room temperature will start to increase until the heat pump is switched off by the thermostat, it will therefore take some time for the room temperature to fall and the thermostat to reset and restart the heat pump. This should hopefully reduce the cycling frequency.
If you have the time, you could try re-balancing your radiators, though it is not a 5 minute job.
@derekM,@gotaashp............Reporting back on previous posts, I tried Derek's ideas above but just had a constant 6 cycles an hour and a COP of about 2.3.
I have reverted back to Auto Adapt with all TRV's open except our bedroom as just can't get that balanced down at the moment and been overheating in bed.
Room Stat set at 20c most of the day, 21C evening and 19C setback overnight.
This has been giving a virtually constant hourly graph as shown attached with typically one cycle per hour and consumed 10KWh with 33kwh delivered which as a COP of 3,3 is the best I have ever recorded over the experimental exercises and one I am reasonably happy with.
I think I am going to try now on a constant set temperature of 20C and see how that performs (hopefully the weather will stall settled).
Concluding I am convinced with my system that in warm milder weather Auto Adapt is to be favoured, when we get a really cold spell I think I will try WC again when hopefully cycling may not be the issue?
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