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

daboom · 2024-02-04T09:52:22.000Z

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

Alex

Timbones · 2024-02-04T10:31:08.145Z

daboom:

I guess that the choice of installer is very important in avoiding or resolving problems.

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.

CymroinSlovakia · 2024-05-27T13:15:42.757Z

Very useful introduction Sarah, especially as I am finding the manuals supplied with our new 14kW model difficult, even opaque!

You mention you use an external thermostat as the main control - can I ask how? There are a few inputs for thermostats and thermistors on the PCB, but only the dhw and the zone ones are referred to in the FSV section.

We have the HP delivering its output to a large (850l) thermal store, and it seems to me to be ideal if a temperature sensor in a relevant pocket in the store produced the information on which the HP switched on or off. But I am at a loss how to do so. A thermostat feeding one of the zone control inputs and make the HP think there is a zone demand? Using zone 2??

A thermistor would seem to me to be preferable, and there is an input shown at CNS043, but no mention of its use.

Any thoughts??

SarahH · 2024-05-27T14:05:04.239Z

Hello Andrew, and a warm welcome to the Community.

But I fear that I must disappoint you. I simply asked my installer to retain my old (wireless) roomstat for HP control, and he did the necessary wiring (I’m no electrician!).
He seems to have used the MIM B19/B20 for the roomstat receiver signal input, with nothing connected to B21-B26 (I assume you’ve had a look at p92 of the Installer’s Manual).

BTW I don’t have an indoor unit - my MIM is installed standalone in my garage with the remote display in my utility room (the roomstat TX is in my living room with the RX in the garage next to the MIM).

I can see a “CNS045” mentioned on p110 of the manual (associated with a zone mixing valve) but not a “CNS043”.

Did you self-install? If not, maybe you should consult your installer?

Good luck!

Sarah

CymroinSlovakia · 2024-05-27T14:25:40.466Z

Thanks for the quick response!
Ok… yes I saw that area as a possibility, but the manual says 19/20 is the power supply to the thermostat(s), the signal being on 21/22, 23/24. So maybe the thermostat is simply acting as a power breaker? Anyway, that’s a lead to follow. But do you know where in the FSV settings that thermostat is set to work in preference to the WL or remote sensors? Is it 2092-2??
I should mention that the huge heat store has a large solar array associated with it, so IF that worked properly (another story involving hail and snow damage) a thermal sensor/thermostat at the store would tell the HP not to start up for space heating.
But hey ho, I can’t even stop the thing cycling on and off when the outside temp is 23° and 4013 is set at 21°

SarahH · 2024-05-27T15:12:16.204Z

I summarised my (feeble) understanding of the relevant FSVs in Samsung EHS mono 5kw settings, post #61.
Actually, the whole thread may be useful if you haven’t already read it.
Sarah

CymroinSlovakia · 2024-05-27T17:27:50.196Z

Thanks Sarah. From what I have read, your understanding of any of this is considerably better than feeble!
Yes, I did read that thread, on Saturday I think, as I entered the rabbit hole that is the Samsung ashp control experience.

But back to that post 61 of yours, you mention that the MIM display does not show the outside temp. Maybe we have a different model, because ours says in the top left ‘outside temp 18.4’ and, on the heat page, ‘inside temp 17.1’?

SarahH · 2024-05-28T08:25:11.811Z

Oh good spot, Andrew - I’d never noticed Outdoor Temp on the display before. I rarely use the Home page, and normally just keep an eye on LWT on the Zone subpage.

Thanks for your kind words, but I’m still in learning mode - @glyn.hudson very kindly lent me his MIM-C02N which I’m using to figure out what makes the Outdoor Unit tick. I’ve made good progress, but I’m stuck on the economiser (intercooler) circuit - there just isn’t enough instrumentation to reverse engineer its controller algorithm (and Samsung UK Tech Helpline don’t know either, so I’m not alone). I’m probably the only one who is interested in this stuff, but I do hate a mystery…

Sarah

flatplate · 2024-06-30T11:21:06.234Z

Hi @SarahH thanks for this useful post. Just wondering how you managed to find the modulation/turndown ratio for your pump? I’m trying to find the same for the Gen 7 R290 units, and although it’s referenced in the installation manual it doesn’t appear to be actually quoted anywhere. Any ideas?

SarahH · 2024-06-30T16:14:21.393Z

Hello Rod .

You pose an interesting question.

In my particular case I asked Samsung UK Tech Helpline (Nick Kirwan) and he told me (sic) “The minimum turn down for your unit 4KW.” (I have an 8kW HTQ R32 so that would be 50% turndown.)
But that’s just heat delivered from the Outdoor Unit, of course, not compressor speed. Using a borrowed MIM-C02N (thanks again @glyn.hudson - I’m finding it really useful!), I can see that the compressor stops when the required motor inverter frequency drops below 20Hz (vs max speed of 50Hz, so min compressor speed would be 40% of max - more or less consistent with the above if one assumes that speed, power consumed, and enthalpy added are related linearly, as should be the case with a scroll compressor).
The puzzle for me is that the same compressor model is used in the 12kW and 16kW HTQ units, suggesting a turndown of 33% and 25% respectively. I find that a bit surprising given that compressor surge can occur at ~30% of nameplate. I can only assume that the Samsung controller algorithms prevent this using some opaque operations such as opening refrigerant liquid/vapour bypasses, or superheating the suction temperature electrically, or something .
I had a look through the Samsung R290 unit manuals. As you say, there are no clues there. I suggest you email the Helpline - you never know, they might be able to give you a helpful answer… .

Good luck, and please let us know how you get on!
Sarah

PS I should add that I see my ASHP compressor cutting out at about 3.7kW Outdoor Unit heat output (calc’d from Q=m.Cp.dt on circulating fluid), equivalent to about 45% nameplate duty, so fairly consistent with the above…

flatplate · 2024-07-01T21:10:55.820Z

Samsung replied pretty quickly! See below minimum capacity output for each model:

Hope this helps others! Hopefully someone can help with my next question:
If the capacity of my hot water tank is big enough that I don’t need a buffer tank to stop the compressor cycling on/off, can I just use a flat plate heat exchanger between the underfloor heating circuit and the heat pump? Are there any good reasons not to do this? Thanks.

SarahH · 2024-07-02T09:36:22.473Z

Good work with Samsung, Rod.

As for your question, you may be conflating two separate issues. Assuming your hot water tank is plumbed conventionally (water from heat pump flows either to your emitters or to the hot tank coil via a diverter valve), then the size of the hot tank is immaterial - DHW is only heated for a few minutes each day so has no effect on heat pump cycling, and in any case the coil volume is tiny (compared to that of a buffer/volumiser tank which are large enough to affect cycle times).

The main reason not to install a PHE on your UFH is that you are introducing a temperature loss - (search for “temperature approach” if the term is unfamiliar) - and will need to operate a higher than necessary LWT to compensate.

Or maybe I’ve just misunderstood your question…

flatplate · 2024-07-02T13:53:32.164Z

Thanks Sarah you are spot on I completely overlooked the actual capacity of the exchanger/coil inside the water tank. In that case it looks like I’ll need quite a decent sized buffer tank (circa 50l) if I’m running only the water tank on the main pump circuit. Thanks for your input!

SarahH · 2024-07-02T15:34:06.002Z

No problem, Rod, but before you rush to buy, have a good read up on buffers/volumisers. A badly tuned buffer tank (secondary flow substantially different to primary flow) brings similar temperature problems to fitting an intermediate exchanger (plus it needs a second pump).
I’d say 80% (or more) of contributors on this forum hate buffer tanks, and they’re pretty lukewarm about volumisers too. Personally, I’m firmly in the 20% - my 50l buffer doubles the effective volume of my circulation water, and thus its thermal inertia, and as a result I’ve never had problems with excessive cycling on weather compensation control (plus it’s a good source of heat for defrost, of course).

flatplate · 2024-07-03T11:54:58.887Z

Thanks Sarah. I don’t see why one would not want a buffer tank in order to control the hot and warm circuits independently and, as you say, reduce pump cycling.

One thing I don’t understand is how the heat exchange takes place inside the buffer tanks. Are they simply jacketed vessels?

flatplate · 2024-07-03T11:56:04.828Z

Just to add, these values also apply to the BEK series (with integrated pump).

SarahH · 2024-07-03T12:59:51.749Z

Yes, Rod, they are. Take a look at

HeatGeek

Low Loss Headers: The Complete Guide For Efficient Design

The complete guide to Low Loss Headers. What are low loss headers and why would you need one? All you need to know directly from the experts.

(A buffer tank is one type of low loss header, with a few pros and cons. They are not intended to be heat exchangers - they are for hydraulic separation, but if not balanced - as explained in the article - some heat exchange occurs as a result of any bypass flow.)

flatplate · 2024-07-03T19:05:06.907Z

Thanks Sarah. Looking at that diagram (and others online) I can’t see how the flows are actually separated, i.e. what (other than pressure) stops the flows from mixing?

glyn.hudson · 2024-07-04T00:29:50.823Z

Did Samsung specify what outdoor temperature these values are measured?

Since

heat output = compressor input + environmental yield

The minimum compressor input is fixed, but the minimum environmental yield will change depending on the outdoor temperature. Unfortunately, this results in the heat output modulation being the inverse to what’s desirable! When it’s warm outside, the heat pump minimum heat output will be higher than when it’s cold outside in winter.

Looking some real world data from an 8kW Gen 7 R290 (AE080CXYDEK/EU) on heatpumpmonitor: https://heatpumpmonitor.org/system/view?id=266 the minimum heat output when it’s 13C outside is about 2.6kW with the minium compressor input about 500W. This is actually pretty decant.

My Gen 6 kW will go down to 2kW at similar outdoor temp with 350W compressor input.

If possible you want to design out the need for any buffer tanks or heat exchanges since these add inefficacy and require additional pump(s) which increase electricity usage. Ideally, you want to run the system ‘open-loop’ with just a single pump and no hydronic separation and no zone controls or at least as many zones/emitters and TRVS as open as possible. If you’re short on system volume, adding a volumiser is not a bad idea, but generally systems that are correctly sized with emitters and pipework sized for efficient heat pump operation e.g 40C flow temperature at -2C/-3C have sufficient volume to not require an additional volumiser.

You’ll want to ensure your pipework is correctly sized for open-loop, here’s a good video that shows how to do this:

SarahH · 2024-07-04T09:24:57.368Z

The primary and secondary flows do mix, Rod. Even if both flows are identical, there will inevitably be a bit of circulation/mixing in the buffer. That’s one (of many) reasons why @glyn.hudson doesn’t like them (per his subsequent reply above) .