Dear all,
I’m enjoying my custom setup of a Samsung AE050CXYBEK.
My only remaining concern is that the volume of DHW is a bit small for us. only 120L for 5 people. Sometimes, the HP has to reheat it during our evening shower moment.
Also, the system is coupled with a solar heat panel so during summer, we only get to heat with the heatpump after 2/3 cloudy days. And the water can rise up to 85C (limited to avoid melting the plumbing)
The DHW request is 46C for the heatpump, which is pretty much ok for both shower and for energy required to heat the water volume.
After giving it a few thoughts, I want to have external review of my conclusions.
I have 3 options to cope with the insufficient amount of DHW :
1/ leave it like that, it will only reheat upon needs, but the whole point of that topic would go to waste.
2/ augment the DHW volume, and possibly lower the DHW temperature, I imagine to go with 200L or 300L max.
3/ raise the heatpump generated DHW temperature to 52/55C, this was my previous setup, but the electric consumption tradeoff is unbalanced according to me (going hotter means lower CoP).
4/ The unexpected option: a man-in-the-middle protocol optimization between the outdoor unit and the controller to lower the requested target tempeature (to 50C instead of 67C), to heat the DHW slowly and hence more efficiently CoP-wise.
May you be kind enough to share your thoughts on this?
Cheers
We have 3 ensuites, one with bath (we never use the bath).
It was built like that 10 years ago by developer (bespoke build).
It was a 300L tank with the gas boiler.
Octopus replaced it with a 300L tank suitable for ASHP.
With a 48C target temp (usually shows 49C on the MMI / app), it gives enough HW for us with guests and just one daily run at 1pm.
We don’t use the DHW during the heat up time.
Calculation over 15/20 years lifespan should give favour to a new big cylinder I would have thought.
Your lowest cost, greenest, solution (though the one least likely to appeal to you and your family) may be to make better use of your existing setup. Ask yourself:
Do all 5 of us have to shower every day? (E.g. would alternate days, with 3 showering on odd dates and 2 showering on even dates, be acceptable from a hygiene perspective?)
If we must all shower every day, can I spread the demand? (E.g. 2 in the morning, 3 in the evening, to give the HP more time to re-warm the water.)
Can the shower water requirement be reduced? (E.g. lower flow rate, shorter showers, pausing the flow whilst soaping down or shampooing.)
Can I use less tank water by heating it a few degC warmer, then blending with cold water at the shower mixer? The cost of this extra energy – even at a lower CoP – is likely to be peanuts compared with the cost and disruption of installing a larger tank.
Can I heat the tank to the required temperature at a lower LWT by heating it more slowly? This depends on your HP controller, but in many, LWT is not constrained during DHW heating (unlike space heating where weather compensation limits it). You can see very high LWTs – 70degC or more, at a lousy CoP – especially if the tank coil is undersized. You may be able to limit this with tricks like using Quiet mode if available, or heating your tank in 2 or more short bursts, rather than letting rip (see Daikon Altherma 3, sub 2 DHW COP - #10 by SarahH for further discussion).
Dear @SarahH
Your points are all very interesting.
Concerning the use of shower everyday, I hadn’t thought of alterning. Usually I’m the adjusting variable, and skip shower when heated water volume is low.
It’s only when 2 or 3 are washing their hair that the problem arises.
The tank I’ve reused has a 0.8m² coil so definitely not ideal for the heatpump, hence, optimizing the DHW flow target temperature is probably a good option.
Rising the temperature of the tank would be efficient, and ecologically wise.
I’ll see if I can make a quick MITM to overload the water flow temperature during DHW cycles. But really in the end, I’m almost thinking of completely redoing a MIM controller board
Cheers
Really? After half a dozen buckets-full? Maybe only half your tank is properly heated. Or the hair washing point is hundreds of meters from your tank. Something very odd here …
Addressing this point, I use Quiet Mode on my Samsung heat pump (Gen 6) for exactly this purpose, as it limits the power output thus allowing the DHW run to occur ‘slower and lower’. The net affect for me is less power consumption overall, with a lower power consumption for longer.
The benefits me because (a) a longer run at lower power allows more of the consumption to come from solar, and (b) the final LWT is significantly lower as is the delta between the final LWT and DHW tank set point as the longer run gives more time for the heat generated to be transferred into the DHW tank. So it’s more efficient (better COP) and cheaper.
Otherwise, it’s always more efficient to reheat the tank from cold, so get as much out of the tank as possible before reheating. So two showers, a reheat and two more showers should always be better than reheating between each shower. One would assume that increasing the tank size sufficiently to allow for a single reheat to 46C each day would be optimal but obviously comes at significant expense.
Very interesting, I didn’t know the quiet mode could impact the flow target temperature!
I’ll have a thorough reading of the manual, maybe I missed something…
Cheers
There isn’t a flow temperature target as such. The DHW tank has a set point, 46C for example. When the DHW cycle begins (assuming the heating wasn’t previously on), the heat pump starts to heat the flowing water and the temperature rises. You can crudely monitor the dT between flow and return in the controller (reported to 1degC), and I also note the difference between the LWT and DHW tank temp. Heating my tank to around 46C, the difference between DHW tank temp and LWT will be around 9-10C in summer at the end of the run (so when the DHW tank reaches 46C, the LWT will be ~55-56C). This is with my 12kW ASHP. The power draw will start low, less than 2kW and steadily rise as LWT rises, peaking at around 4.7kW. If I enable Quiet Mode, the power draw is limited to ~3.3kW (around 70%) and the difference between LWT and DHW tank temp is lower at completion, at around 6-7C (so for a DHW tank temp of 46C, the LWT may only rise to around 52-53C) as the cycling water (LWT) has a lower peak energy input and more time to dissipate the energy into the DHW tank.
With respect to Quiet Mode, the final LWT being lower is a side effect of reduced/lower input power (quieter), not a feature of it.
After few tracing and testing, I’m quite disappointed that the quiet mode doesn’t seem to be actionnable from the wired controller. Anyone confirms?
Cheers
It should not matter if the hot water comes on. It will only be for a short time.
If the hot water is running out make sure the cylinder sensor is at the bottom of the cylinder. If it is 1/3 up the cylinder you will loose 33% of the capacity due to stratification.
If you have a bigger cylinder the hot water cycle will last longer.
I’m not quite sure what you mean by this. Is your remote controller the MWR-WW10N? If so, you should be able to go into Service Menu and enable (or disable) Quiet Mode Automatic Time (QMAT). If you select enable it will ask you to set the Quiet times.
There is also a Quiet OFF/ON function under the Settings button, and the Schedule function should allow you to toggle the timers between DHW and Quiet. The note on p9 of the User Manual seems to suggest that QMAT overrides anything you do under Settings (one of the many manual translation problems). [I can’t confirm this prioritisation as I’ve never tried Quiet mode under rigorous test conditions.]
@Sarah, it took me a while to process and answer you reply. I’ve been willing to trace a bit what the wired controller was doing.
Firstly, thanks for the head up, I’ve checked out the “silence mode” on the wired controller. It’s playing with both 0x4046 and 0x4129 NASA messages. It sets both at 1. other values are prohibited by the MIM-E03 controller.
Setting only the 0x4046 to 1 is accepted. But setting 0x4129 when 0x4046 == 0 is not accepted. Their meaning will be much more understandable once I test the effect of the 2 settings.
I still have open questions regarding that Silence mode:
1/ what is the difference with the Quiet mode (level 0 to 3) described which can set on the outdoor unit using 7digit and K-buttons?
2/ how come there does not seem to be a configurable level of silence from the wired controller other than ON or OFF?
As far as I can make out, the 4 levels successively constrain the compressor speed (i.e. by limiting the maximum inverter frequency). They may also similarly constrain the speed of the evaporator fan, which is also inverter driven, at least on my HP, as fan noise also contributes. (I could check this using SNET by enabling Quiet mode mid-run but haven’t done so yet.)
You’d have to ask Samsung. Actually I’m slightly surprised that there are two intermediate Quiet levels in any case (the default ON level being maximum effect) - most of the time the compressor is trundling along at low speed anyway, and enabling Quiet Mode - at any level - would have minimal effect. So IMO Quiet Mode isn’t a very useful knob to twiddle except maybe during DHW heating, when it would still heat the water to the required temperature but at a lower LWT (though take longer to do it).
BTW I note that 0x4129 doesn’t appear in the published list of NASA codes - any idea what it is? And on the subject of code interpretation, do you know what (for example) “packetInformation = ((int)data[index] & 128) >> 7 == 1” means? (E.g. Does “==” have a different meaning to “=” ? I see that you used it in your post above.)
Thanks @SarahH, your explanation of the quiet mode suits what I understood so far. My only problem is that I cannot manage to engage the various levels whenever I want from home assistant. But I’ll work on that.
I plan to engage the quiet mode as an alternative to modify the requested water temperature during DHW runs by adding a card between the MIM board and the outdoor module. But if I have no choice, I’ll do that.
About the 0x4129, definitely it’s not described anywhere, hence my attempt at reverse engineering it. I saw it in the wired controller to outdoor communication. As a reaction to the silence mode activation.
About my syntax, ==, mean “is equals ?”, it’s an abuse of C langage syntax. I should have made it more readable.
I’ll give a try to SNET software connected to the F1/F2 link. My previous attempts were total feilures but who knows
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