Samsung Gen 7 EHS Mono Quiet R32 ASHP Series – a few beginner’s observations

If you are considering installing a Samsung ASHP (Outdoor Unit), I offer a few observations/realisations which may help your decision:

  1. This range is available in 8kW, 12kW and14kW (heat generation) sizes. All three models have the same compressor, but the 12/14 units have larger heat exchangers (Freon to circulating fluid) and fans/motors. The normal ASHP controller (Samsung MIM-E03EN) can be installed standalone (with or without a separate hot water cylinder) or integrally with a Samsung Indoor Unit.

  2. Based on my own house heat loss calculations (4kW at -4degC outside), I specified the 8kW size (to cover initial daily house warm-up and exceptional outside temps), and re-used my existing DHW tank, but left the circuit design details to my selected installer. He proposed a 50 litre 4-connection buffer tank with separate primary circulating and secondary CH pumps, and he calculated house heat loss (using the conservative MCS methodology) to be 7kW, so the 8kW choice looked good. I upsized a couple of living room radiators, but all others were retained.

  3. Installation in May 2023 came with the controller User Guide ( and Installers Guide ( Other useful documents if you need further info are the EHS Mono Technical Data Book ( and the EHS Installer Reference Guide ( Careful reading of these will help you understand and optimise your setup. (Your installer may enter conservative defaults on your controller settings – to guarantee a warm house even at high operating cost – but you can adjust these to reduce the latter considerably.)

  4. These manuals are very helpful to a beginner, but they don’t say much about the firmware or software behind in the ASHP control algorithms, probably because these are proprietary. In particular, little is said about compressor speed control, which is central to minimisation of operating cost and thus system efficiency, typically referred to as CoP (coefficient of performance) – the ratio of instantaneous generated energy to instantaneous absorbed energy, or SCoP (seasonal CoP – same as CoP, but averaged over a day or week or month). Strictly, energy absorbed should include running the compressor plus circulating pump(s) plus controller, but because the compressor is normally by far the dominating consumer, the others are usually ignored.

  5. The controller adjusts the compressor speed to satisfy 1) the weather compensated ASHP outlet temp if you have this option enabled (Samsung call this “Water Law” (WL)), or 2) your roomstat setpoint. See the User Manual for setting up Water Law (FSV 201* - 203*). You can set the controller to recognise an external (3rd party) roomstat (FSV 2091/2) or its own roomstat (FSV 2093, if your remote controller location is suitable) – your installer should set this up.

  6. You set your ASHP operation times and temperatures using your roomstat. Typically you will control your living room to ~21degC starting say an hour before you want it, with a “setback” (overnight temperature) a few degrees lower. When the ASHP starts each day, the compressor first spins up linearly with time to full speed. Mine takes ~7mins to do this. When I say “linearly” I am assuming that compressor speed varies linearly with energy generated (which I can monitor from the controller display). This assumption is pretty well true for scroll compressors (which the EHS series have). The compressor then operates at full speed (and energy consumed) until 1) the ASHP exit temperature reaches ~10degC below the WL setpoint, or 2) your roomstat temp is satisfied (depends on your roomstat), whichever occurs first. You can see the Samsung predicted compressor power requirements (and energy generated) from the tables in the Data Book referenced above.

  7. Assuming you have WL enabled (which is preferable for minimising operating costs), at an ASHP exit temp (LWT) of 10degC below WL setpoint, the controller directs the compressor to start slowing down. This slowdown is exponential – very little at 10degC deltaT but quite fast at 2degC deltaT – until at 0degC deltaT the speed (thus energy required) drops to ~50% of design (4kW). This is the Samsung declared turndown for the 8kW unit, but I don’t know whether this 4kW minimum is the same for the 12/14kW units.

  8. So, after about 40 mins (with my system) the circulating fluid (20% glycol in my case) has reached WL setpoint temp, with the compressor at ~50% speed (4kW generated energy). If the roomstat has not been satisfied (normally the case in winter) the compressor trundles along at 50% speed until it is, or else the LWT exceeds the WL setpoint (usually because the radiators are not discharging enough heat), then the compressor stops, and restarts when either the roomstat demand starts, or the LWT falls to about 2degC below WL setpoint (typically 30-40 minutes later in my case).

  9. 3rd party “smart” roomstats may send “nearly satisfied” signals to the ASHP controller at a frequency that is incompatible with the latter’s programming, and may need to be reprogrammed.

  10. Samsung offer a “Quiet Mode” which overrides the controller and forces the compressor to run at ~60% design speed, saving instantaneous energy (but extending the time needed for energy transfer). Useful to avoid annoying the neighbours at night and helping you sleep, but of limited value otherwise, I think…

  11. I can use this behaviour the estimate predicted compressor power consumption over time for a variety of ambient temps (i.e. house heat losses) and different setback temps. My optimum operating strategy (i.e. minimum operating cost) seems to be a large setback, tolerating a large initial power consumption on daily startup (up to 5kWh) but with zero running costs 10h/day during the night. My average winter total energy bill including ASHP/cooking/appliances is about £6/day.

  12. Unlike several contributors on this discussion group, I very much recommend the Samsung Mono Quiet series. Just find a knowledgeable installer (and a friendly Chemical Engineer if you can)!



Hi Sarah

Thank you for posting this. I’m in the process of purchasing a system and don’t wish to replace all of the existing radiators initially and one of the devices recommended is a Samsung EHS Mono Quiet AE140BXYDGG/EU. I’m curious about the size of your property and whether the 8kW unit is proving up to the job. I need to heat/cool about 300 m2 near Barcelona in Spain. Although not a direct comparison but it might give me some confidence!


Excellent write up! Lots of useful information :clap:

It’s probably useful to state that this post is about the Gen7 HTQ range i.e R32 high temperature. There is also an R32 Gen 6 range, a new R290 range, both the R290 and Gen 6 range also 5kW and 16kW models.

A useful thing to note is that apparently the HTQ range share the same compressor between the 8kW, 12kW and 14kW models, therefore the low-end modulation on the 8kW and 12kW models is possibly not as low as it could be.

I’ve also had a good experience with Samsung heat pumps and I would recommend them. However, the controller is not the easiest to understand compared to other brands, and they require quite a bit of tweaking to get running well. But then can give excellent performance. I’ve installed a couple of them (specifically 5kW Gen 6), which are both in the top 10 systems on

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Hi Alex, and welcome to the community.

My house is detached 2-storey and about 145m2 floor area (so only half yours), located southern England.

I’m very happy with the ASHP itself (I seem to achieve within 10% of the Samsung-predicted CoPs), though as Glyn says, the controller has a couple of shortcomings. For example, I don’t want DHW every day, but the programmer within the controller doesn’t support different daily settings (though Samsung tell me that I could do this by adding their Wi-fi kit MIM-H04EN - costs about £150 - and using the SmartThings App on a smartphone).

My other main gripe is that the controller cannot moderate LWT in DHW service, so if your tank coil is at all undersized the LWT can quickly hit 60°C or more (at a very low CoP) even if you only want 45°C hot water. [On CH, you have considerable control over maximum LWT, so can optimise your CoP.]

Finally, be aware that a number of Samsung Gen 7 owners have experienced rapid ASHP cycling (every 10 minutes or so), for reasons that are not yet fully understood. I suggest you read the “How to Reduce Cycling” thread fully, before committing yourself.


You can’t, the app is very basic, you can only manually switch DWH on/off, you can’t even set or adjust a schedule via the app! It’s mostly useful for switching off ‘Away’ mode before returning from holiday or boosting DHW remotely.

I’ve observed this in installations with a 3rd party e.g Honeywell thermostat which has TPI control which is designed for gas boilers and never should be used with an ASHP!

I’ve also observed cycling if the flow temp (WL) is set too low, with radiators usually if low temp is lower than 30C ASHP will cycle since the emitters cannot emit enough heat at such a low flow temp, this issue is compounded if the ASHP is oversized. UFH can usually handle much lower flow temp.

This sort of tweaking does not seem to be needed with other heat pumps e.g Vaillant have a much more advanced control algorithm which don’t require this sort of micromanagement, they do however cost a lot more! As the data shows on, an optimised Samsung can match or outperform many Vaillant systems.


Thanks, Sarah.

The size of property/power of ASHP ratio gives some reassurance even if simplistic.

I’m installing a separate ASHP Water Heater with tank so won’t suffer the water heating restrictions of the Samsung and that leaves all of it’s power for heating/cooling.

I’ve read most of the comments on that thread - probably more confused now! However, I get the gist and think we’ll be ok as it seems that the problems are due to having an over powered ASHP? I’m actually buying the Samsung instead of a more powerful ASHP so hope to avoid this issue. I guess that the choice of installer is very important in avoiding or resolving problems.

Thanks again


The design of the heating system as a whole is just as important as the choice of heat pump. Find an installer that is experienced in low temperature heating, and try to avoid choices like glycol and buffers.