If you are considering installing a Samsung ASHP (Outdoor Unit), I offer a few observations/realisations which may help your decision:
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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.
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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.
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Installation in May 2023 came with the controller User Guide (https://downloadcenter.samsung.com/content/UM/202312/20231215134435460/DB68-08470A-15_IB_EHS_Wired_Remote-Control_Kit1_EU_Book_EN_231117-D01.pdf) and Installers Guide (https://downloadcenter.samsung.com/content/UM/202307/20230724171125643/EHS_R-32_MONO_OUTDOOR_IM_EU_DB68-11904A-03_EN.pdf). Other useful documents if you need further info are the EHS Mono Technical Data Book (https://midsummerwholesale.co.uk/pdfs/-tdb--ehs-mono-ht-quiet-for-europe--r32--50hz--hp--ver.2.1-221005.pdf) and the EHS Installer Reference Guide (https://midsummerwholesale.co.uk/pdfs/ehs-install-guide-samsung.pdf). 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.)
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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.
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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.
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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.
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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.
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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).
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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.
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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…
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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.
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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)!
Sarah