My AE080BXYDEG/EU is about 2 x oversized (installer’s conservative MCS calcs, as usual), so cycles every 30min despite a 50 litre buffer tank in the CH circuit.
The ASHP compressor is nominally fixed speed but the manual hints that the one way to force a reduced speed (hence power requirement, hence cycling) is to enable Quiet mode.
Has anybody tried this, and if so does it affect ASHP power (i.e. increase CoP)?
Thanks!
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I have a similar situation with my Daikin, so it’ll be interesting to hear what you find.
I tried quiet mode yesterday and all it seemed to do is restrict the heat pump to the lowest output, which is pretty much what had been happening anyway, 1100w in the case of my 11kw Daikin.
Hopefully you have more luck.
Mitsubishi also has a quiet mode, which I tried for a while. Like Sam says, all it did was reduce the output when it was already running on minimum anyway. May have a bigger impact in deep winter.
I tried quiet mode on my Daikin on Friday as the Daikin employee said it would reduce electricity input and heat produced by 50%.
I can’t see it did anything at all.
I am not sure how it can, if it is heating the water to a set flow temperature and it can do it for less electricity why wouldn’t it already be doing it?
Maybe it cuts the noise when it’s really cold and working hard?
Thanks Sam/Tim.
I’ve been sent this table of “capacity corrections” by my contact at Samsung Support for my model:
The bottom row suggests that the effect is indeed larger in winter, though not a lot.
I’ll give Quiet a try on a cold day, comparing before and after on power consumption and cycle time.
Hi i jave a 16kw Samsung that i feel is also oversized so it often runs at a minimum speed and still overshoots flow temp.
It would be interesting to lnow what flow you have around your circuit
I improved my flow by altering some of the ground floor circuits onto a new feed and this upped my flow by 5 lpm and it improved the running and i also made sure all radiators were outputting there max by using a thermal camera to check the surface temp of each rad to ensure i was getti g max output.
I am going to increase size of two of my rads to see if this would help
I think i could have got away with a 12kw but im not sure that isnt the same u it as the 16 so rhe min speed and output may well be the same.
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Hi John and a warm welcome to the community 
.
I’ve learned a lot since my original post:
- My ASHP compressor actually spends most of its time at minimum speed (~50%) anyway, because my LWT is at/near the weather compensation setpoint. So Quiet Mode would only make a difference when starting from cold (e.g. night time defrost cycles).
- You don’t get something for nothing, and hobbling the compressor by enabling Quiet simply takes it longer to do anything (like heat DHW) - 15 mins @ 3kW costs the same as 30 mins @ 1.5kW.
- If bigger rads allow you to increase your CoP (by reducing LWT a bit) then they are often a cost-effective investment. I did just my living room and that gave me a 2 year payback on the installed cost of doubling the rad area.
- For an 8kW ASHP my primary circulation is ~21 l/min which gives an ASHP deltaT of ~3degC.
- I recently “calibrated” my living room and confirmed that the overall MCS-based OHTCs were reasonably accurate. (The installer’s heat loss calcs included an unrealistic ventilation factor per MCS method, so I too have an oversized ASHP.) This calibration included back-calculating the effective room (m.Cp) so I can estimate the additional sensible heat requirement when starting from cold.
Hi Sarah
I have just replied to someone else about a similar situation
He has troule with cycling to often.
If you have hydraulic separation then if your secondary circuit isnt as high flow its always going to be a problem unless you can manage to increase the flow to match by adding an extra rad or some other emitter
I removed the separation i had as a trual and it does work better but i have also added an extra flow and return so 3 of my downstairs rads are no longer on the original loop. This was quite easy as the pupe ran under the kitchen cupboards back to where the heat pump comes through the wall
Even though my house is 220 years old and solid stone it does keep the heat well so i can use my external room stat to switch off at 20.2 and come back on at 19.8 so my house works as the thermal store. I only need to do this when its above 7 outside as below that i have enough emitters to run at about 32 flow temp so ticks along quite nicely at its minimum speed which absorbs around 700 watts
I am told by my good lady that the tinkering must stop soon as its driving her mad. Its only been going on for three years but i think im about done know
Regards
John
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Hi John.
Between you and me (and your good lady, it seems) I suspect that there are a fair few in this community who have forgotten the “don’t let perfection be the enemy of the good” adage, aka if it ain’t broke, don’t fix it.
In the meantime, I must just finish this spreadsheet… 
Sarah
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