How to reduce cycling?

Hi There
What are the best ways to reduce cycling - or it also could be, How do I get better Delta T?
Large Buffer
Extended the system with a large volumnizer
Reduce flow

Or do you have a magic solution to it - let us know :slight_smile:


My ways,

Bigger and/or more emitters to deliver the heat produced.

Increase the heat loss, in my case by opening doors and windows

Increase the heat loss by heating additional unheated areas if possible, with more heat loss and more emitters there is somewhere for the heat to go.

Eliminate zoning and trvs, the heat needs to go somewhere so shutting down areas makes that more difficult and cycling is more likely.

Get a smaller heat pump if that is the problem.

Increase the flow temperature so the emitters you have can deliver more heat

A volumiser just adds volume, in my case for the heat pump to use to defrost, as it is insulated and loses little to no heat it won’t prevent or make cycling any less prevalent.

A buffer tank may work but I am no expert, I would imagine that if you don’t extract the heat from a buffer tank in some way the heat pump will still need to cycle as the return temperature rises.


Who’s heat pump are you using and do you have external control stat, also what is the building age?

What do you mean by Delta T? Difference between flow and return pipes? What Delta T do you have now, and what would be “better”?

Heat pumps typically run around 5° ΔT, and can be adjusted by changing the flow rate (i.e. litres/min). Check the minimum flow rate for your model.

Happy New Year Arne :slightly_smiling_face:.

I see that Matt Gregory has given you some excellent thoughts (though deliberately losing energy by opening windows seems a bit drastic).

The AE080 MIM controller has a fairly opaque algorithm which slows the compressor to ~50% speed as LWT approaches weather comp setpoint, then stops it until both 1) LWT falls to ~2degC below this, and 2) ~5 minutes has elapsed, then it restarts it. As far as I can gather we can’t alter any of these parameters. But my identical model only cycles 2-3 times per hour, not the 7 times per hour that you see. Could be that you have a faulty MIM? (With a house as well insulated as yours, I would expect your LWT to fall only very slowly.)

You say you use the MIM roomstat, not a 3rd party one. But my 3rd party roomstat had internal parameters which sent “room temp satisfied” signals to the MIM 6 times per hour which confused the latter’s algorithm into erratic behaviour. I solved this by changing the internal parameter to 3 times per hour. Could it be that you have FSV2093 incorrectly set? (See User Manual p29 in the English section.)

Just for comparison, my AE080 trundles along quite happily with an ASHP deltaT of ~3degC via a 50 litre buffer tank, with a primary circuit flow of 21l/min and a secondary circuit flow of 11l/min. The compressor runs at an average 56% speed (once at steady state) and gives me a CoP within a couple of % of the number in the Samsung Data Book.


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Hi John

I have a Samsung EHS Quiet 8Kw which is too large for my house - and I have the Samsung MIM control Panel. House is from 1976 - good insulation so my annual heat needs is around 13-14 kwh. So installer calculated an 8kw - when I do the calculation today, I get around 4,3- 5,1 kw pump is needed.
So looking for a way to let the 8 kw work more efficient, or at least run for longer periods, and reduce start/stop per 24 hour, which is close to 180 start/stop, currently.

Hi Sarah,

I know that opening windows sounds like a drastic measure but in my case it works.

My heat pump is also too big and it mostly operates at it’s minimum power level.

My minimum power input is around 900w and so I can choose how much heat I want to produce by varying the flow temperature. At about 35c it produces 4,500w of heat at a COP of 5.0

That’s good for my conservatory that looses heat at a greater rate than the rest of the house, it needs the heat, so to keep the heat pump running at it most efficient and stop the house overheating too much I open windows.

It is not really wasteful as I am using no more electricity whether I produce 3,000w or 4,500w - I am already at the minimum input power.

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Hi Arne

I have a 16kw GEN 6 on a 200 sq/m 220 year old solid stone house which despite what people think isn’t to bad for heat loss as long as your stone walls haven’t been repointed with cement as this prevents them drying out and wet walls lose heat quicker than dry walls, that’s another long story

What I do is run with an external stat as this allows you to alter the flow temp by plus or minus 5 degrees as well as being on the weather compensation which I have set to 40 degrees flow at -3 and 20 degrees at 15

Then I have the parameter 2091 Application floor(this gives a DT5) on room signal only basically the compressor and pump will only switch off if the room stat tells it to

So as long as you have enough emitters to raise the room temp slowly(so weather comp needs to be correct or adjust on the display plus or minus 5 degrees) it will run until your stat says stop and then it will not run again until the room stat tells it to

My stat is an EPH digital one that has a hysteresis of +0.2 degrees past set point to stop and then drops -0.2 degrees past set point to restart

So with this you can adjust flow temps to suit to get the run time you want

Have no experience with the new Quiet ones but assume controller is similar, im sure someone will soon tell me if im wrong

As my house is solid stone once its warm it takes ages to drop by nearly half a degrees, I have turned it off at night in the past and the house only drops by 2 degrees in 8 hours or so

Basically the house becomes your thermal store/buffer

Ive never managed to find out by Samsung what the compressors maximum run time is although as they are modulating they may not have one as for the circulators if it’s a Grundfos it will run for years.

Hope this helps, and obviously if you can make your rads larger you can then run at lower flow and gain COP


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Hi Tim

Exactly differnce between flow and return - I mostly run at Delta T between 2,25 and 3,1 - which could be better.

Hi Sarah

I also get quite confused - i literally had no idea I had so severe cycling.

The lowets I have spotted the compressor have been at, is 96% - that is at the end off the 8 minutes cycle, but not each time…
Also I have difficulties with my flow, only at 17,8 to 18 l/min. I guess its because no heat is needed, then it adjust the flow to whats needed.
And yes, CoP was ok the last time we spoke in 23, regarding CoP - I had flow at 23-26 l/min. I have not been there since that day. :frowning:
Currently we have 5-6 degC outside, but in the next few days temp will drop to below 0, so might get better conditions for this unit…
Would love to get the logger system installed, simply just does not have the money for that currently :frowning:


Thanks for the explanation, Matt.

Perhaps I’m just being stupid (often the case :face_with_diagonal_mouth:) but it sounds like your roomstat gets satisfied - and switches off your ASHP - when your conservatory is still too cold, so you open your living room windows to force it to keep going.

Have you considered the economics of installing more radiator area in your conservatory? By keeping it warmer there, you might be able to tease your weather compensator down by a degree or two and thus reduce your living room heat input a bit so you can close your windows.

The improved CoP might just cover the cost of installing the extra rads… :thinking:

Incidentally, are you really running at minimum power? If your controller switches the compressor off for some of the time, your system power consumption will surely be less than 900W…

Hi Sarah,

I haven’t been using a room thermostat.

It just runs continuously only pausing heating to do DHW.

My installer, Octopus, think that my conservatory makes up more than one third of my overall heat loss even though by floor area it is only about 13% of the total.

The conservatory isn’t big enough to fit that many radiators in.

It already has massive radiators and I actually have the windows open in there too at times.

What I originally found with my heat pump was it was cheaper or no more expensive to just leave it running as the COP was much better after the first hour or so of running. I used no more electricity either way.

It gets a COP of 5+ but it takes a while to get there.

I have changed all my radiators now and it performs better so I am now back to running a room thermostat.

I am running at minimum power at 900w, it uses no less than that apart from when in standby when it uses 22w.

When this Daikin 9kW heat pump is heating it’s minimum electrical input is 900w, reducing the flow temperature will only reduce the heat output, it will not reduce the electricity consumption.

At most times is makes no or very little difference to the electricity consumption whether the flow temperature is 30c or 38c, it just affects the heat produced when I go so low that the radiators can no longer deliver the heat produced.

I have also been experimenting, I just wanted to get the best COP I could before I have to settle for less. The cost isn’t really an issue as I don’t care that much and it is coming entirely from solar export payments, still money I know but as long as I don’t use more than I am in credit with my supplier I really don’t care.

Hi Arne,

  1. Try setting FSV2093 to “Room temp only”. This switches off the weather compensator override, so will help diagnose whether there’s a problem with the latter. (Incidentally, the notation given in the Samsung Installer Reference Guide p135 differs from the MIM display, and the English needs a bit of untangling.)

  2. The 96% you mention refers to the water circulation pump, not the compressor. (The MIM display “Inverter Pump” is a bit ambiguous!) Almost certainly your compressor will be operating at 50-60% speed when your LWT is near your Water Law setting.

  3. Can you increase your water circulation rate? Your 18l/min is worryingly close to the 16l/min minimum, and most CH pumps have selectable speeds/flows. Or maybe there are flow restrictions (like TRVs) reducing circulation.

I considered putting a logger system in, but I can’t justify the cost (and I don’t have the brains to use one in any case :face_with_diagonal_mouth:).

Don’t give up yet…

Interesting. My ASHP is the other way round - just reduces power consumption at lower LWT, but heat duty stays more or less the same (except at >50degC). Maybe down to the respective compressor characteristic curves? (Samsung use scroll compressors, maybe Daikins are different).

Hi Sarah

Tried to set it at Room Temp Only… Will measure the cycles over the next hour :slight_smile:

Regarding the 96% - Is it the waterpump? - As you can see on the picture below, it says Inverter pump

Regarding circulation - I have been at 26 l/min, 18 l/min and even 9 l/min and it still said 100% in there - or 96%.
I have no control on the flow - wish I had - If I am right, when outside temperature drops, more heat is needed and circulation will increase to max, which is around 23-26 l/min. For now, the flow rate is around 18 l/min - which also gives med “bad” CoP :slight_smile:
Cleaned the filters - so there should not be anything to prevent it form going up in flow, but it does not :slight_smile:

Hi Sarah,

I am pretty sure it works the same with both our heat pumps.

My heat pump uses less electricity the lower the flow temperature until it is using the least electricity it can.

Once it is using the least electricity possible and the flow temperature decreases all that happens is you get the same or eventually less heat when the circulation pump is at its minimum speed and the radiators can no longer maintain the dT between flow and return.

There comes a point when running a lower flow temperature results in no less electricity being consumed.

It is just with my heat pump, this low point isn’t very low, even though it is a 9kW heat pump its minimum heat output at a COP of 5.0 is 4.5kW. This happens at 35c flow at 7c outside with sufficiently large emitters.

Reducing the flow temperature further achieves nothing. Increasing it a bit does nothing.

So although this topic is not about my Daikin I am trying to illustrate that running lower isn’t always the most efficient and that sometimes more can be gained by lengthening the cycles and improving the COP even if you might need to take what appear to be drastic actions such as opening windows.

Yes Arne, I queried “Inverter Pump” with Samsung Tech Support UK and have an email confirming that this refers to the water circulation pump per the following extract (I’ve italicised the relevant bit).

On 17/11/2023 17:27, Aftersales Technical Support wrote:

Hi Sarah,
Thanks for the email.
Thermo on / off hysteresis for WL flow temperature is around 2K, this combined with an anti-restart timer of around 5 minutes will dictate the off state time before the heat pump starts again.
> The 405 FSV’s are for a PWM circulation pump, it’s called inverter pump in the FSV list,* it’s a type of water circulation pump that can be used on the system that will modulate the flow rate slightly in heating mode. It doesn’t relate to inverter control in the heat pump sorry.
The minimum turn down for your unit 4KW.

But I think you should stop worrying that low water circulation (provided it’s above the minimum) gives a poor CoP. Your ASHP is just trying to get the LWT up to Water Law setpoint, and controls compressor speed to do so. The CoP is a function of LWT (at any given ambient temp), so your objective should be to minimise LWT. Heat duty is not affected by LWT except above about 50degC (see Samsung Data Book tables), so at any given LWT and heat duty the inlet temp will fall at lower circulation rates, but CoP will not be affected noticeably.

What circulation pump do you have?

i Sarah
thanks for the intel :slight_smile:
I have the Samsung Climatehub, 260L which include waterpump, so it is the internal pump I use and controlled by the MIM.

Allthough it makes me wonder… see when the percentage is at 100% - I have had flow at 23-26 l/min.

Today and for a long period the flow is at 17,8-18,5 l/min, also at Inverterpump at 100%.

This equals to about 1100 l/h - which is the reading on my Kamstrup measure device.
When you learned me to calculate “real” CoP - I had a flow at 23,8 - 26,5 l/min. then suddenly it is down to 17,8 -18,5 l/min. but both are at Inverterpump set at 100% - thats strange.

Installer Tech set that Inverterpump at 70% - but on real cold days the heat did not reach the far ends of the system, so I changed it to 100% and the heat got back.
Test today, gives approximately 70% waterflow, around 13 l/min compared to 18,5 l/min at 100% - so this match up ok.

I will call the installer tomorrow to hear status on a repairment of the Climatehub, which is leaking from the DHW - as I understand, they will dissassemble the hole indoor unit and take out the 260 L watertank for inspection and to tighten some pipes, that might cause this. Not really happy about it, because what will happen to the isolation - but we will see…:slight_smile:

If you want to get to the bottom of this, you need to understand whether / how your system is controlling its flow rate.

In my case I have a single circulating pump, which is PWM controlled by the heatpump’s control board. right now my stats (same screen as yours) say “inverterpump” (i.e. water pump) 52%, and flow rate is 15.2lpm. I know (because I monitor flow rate and DT) that the heatpump’s control system modifies the “inverterpump” % value up and down, to try to target a specific DT. this % value is the PWM value sent to the actual circulating pump, this modifies the flow rate in an exactly predictable way (provided there are no changes to the system such as valves / radiators opening / closing)
I believe your system will have a single circulating pump because as per your other thread, its a single loop. If you can find the circulating pump (it won’t be in the outdoor unit, because its samsung, it’ll be inside in your plumbing somewhere) please take detailed photos and should be able to tell if its a PWM type or not. Also, the basic requirement for a PWM pump is that it must have two cables going into it (one for 230VAC power, and a separate one for 12VDC PWM data) so please count the cables… one or two?
It is a bit puzzling that you saw such widely different flow rates, whilst the duty % remained at 100. That suggests to me that you don’t have a PWM setup. In which case the pump may be making its own decision how hard to push - perhaps via an auto-adaptive setting or similar. Again, photos of the circulating pump will help figure this out.

Hi Ian

Thanks for the input - I have the Samsung Climatehub, which have a pump builtin, PWM - see my answer to Sarah above this :slight_smile: