Why would they choose to run at an inefficient condition instead of running at best efficiency point?
Do you think they’ve adapted (bodged) air to air controls to an air to water unit perhaps? Where they’re concerned about discomfort due to cycling on air based units so instead choose to run at an inefficient operating point once demand is met?
The old fixie ground source unit I have just runs degree-minutes away from setpoint in order to decide when to start. I think the Vaillant air to water units have similar settings.
What are Samsung thinking that we’re missing? (or not thinking that we’re seeing)
I will give it a shot regarding timed start/stop - but currently at these outside temperatures I have difficulties get it to hit the high flow rate - curently at 16-18 l/min - have only seen good performance at 23-26 l/min, which also is the recommended flow rate. I will configure the timed settings in the christmas days.
Thanks Arne, and Happy Christmas to you and yours.
I’ve reduced my water flows (primary and secondary loops) and will study the effects in the New Year. I’ll keep you posted…
Sarah
And Happy New Year
Tried the scheduled settings and this will not work. After 1 hour, the temp. began to drop inside and if we really packed us in, in some warm stuff, the ASHP started after 2 hours of off time, then it ran around 15 minutes and went back into cycling. During normal operation, the cycles are around 7 minutes and 40 sec. - Turned off in 15-20 seconds, then a new cycle starts.
A cycle on 8 minutes, starts with waterpump, then powerconsumption up to 1,7 kwh and short after its down to 1,1 kwh - dropping further to 0,8 kwh and the it turns off the power and shortly after that waterpump shuts down, and so on… DeltaT in that period varies from -0,4 to 3,0 so actually only half the time I have a “Positive” Delta T - rest of the time it is less than zero (minus something…)
Outside temp is 5-6 degC and flow is between 30 and 35 degC during operation.
This means I have approximately 180 starts per 24 hour - This is insane…
are you sure about this? I’ve put a lot of effort into tuning my 16kw system. I see the compressor speed vary from about 60hz (startup) down to 17hz when running at a steady state low power level, maintaining the WC target LWT in mild conditions. So that’s a compressor turn down to less than 33%. At this power level (e.g for my system right now, and for the last 2hrs completely stable) it can be efficient (emoncms reporting 50% of carnot) and low power (800w input, 3900w output, 35C flow).
Hi Ian.
This is what Samsung Tech Support emailed me in response to several questions (my emphasis):
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.
Best regards
Nick Kirwan
I guess I took his word for the 50% turndown (my ASHP is 8kW), and I don’t have any fancy monitoring equipment to verify inverter frequencies, but I believe him because I’ve never seen sustained thermal duty (as calculated from Q = m * Cp * deltaT on the circulating fluid) below about 4kW, or compressor power consumption below about 50% of the figures in the Samsung capacity tables (EHS Technical Data Book).
The one thing I would retract is my comment that at turndown the compressor has a poorer effieciency. This was based on early observations (I don’t have performance curves for the DS2BB5033FVA), but data from several subsequent test runs suggest that there is little change in efficiency across the speed range (no more than a few %).
I think 50% is the standard that customer services will always quote so they aren’t held to anything better.
there are two 8kw samsung systems on heatpumpmonitor, one HTQ (Cambridge, #22), one gen6 (Market Drayton, #71 - which is the one matt linked to). #22 appears to be setup to run in “short bursts” , has a COP over the last month of 3.5. #71 appears to be setup for longer runs and has a 30 day COP of 4.2. however both show that a steady state of 500-600w input, 2500w-3000w output is achievable.
I wonder if we are cross-purposes here, and trying to compare instantaneous compressor operation with operation over a 1-hour or 1-day period (or longer)?
If you have 15 minutes to spare, please have a look at my data from a recent test run: OEM2.xlsx (14.9 KB)
I can only get data from my ASHP controller display, and noted readings every few minutes once the LWT (column C) had more or less reached the weather compensator setpoint (column I). The lounge roomstat was set at 21.5degC which was only reached at the end of the test, so throughout the test the ASHP was just supplying room environmental loss and sensible heat.
I compared my instantaneous readings/calcs with the published Samsung data (columns K-M) to estimate compressor speed (columns O and P). Within experimental error (e.g. I only have ASHP inlet temp to the nearest degree), these did not drop below about 50%. The averages also tell a pretty consistent story (yes, I know - you can’t take averages when the time periods are different, but the principle still applies).
From this data, I think my conclusion - that the compressor really doesn’t want to go below about 50% - still stands.
Any comments? (Apart from my high weather comp setting - I’m still working the economics on that…)
yes we may be about cross purposes - I mean long periods of steady state. yes I’ve got more than 15 mins (I am out of contract and looking for next one - looking at this is far more interesting than talking to recruiters and walking the job boards and Linkedin…)
I don’t understand some parts of your spreadsheet I’m afraid , in particular K-M and O-P. you may need to spell those out for me, how are you inferring a compressor speed ?
I can see though that E is the calculated heat output based on DT and flow rate. Based on that having an average of 4.85kw (E26), your system is working at more than 50% of its rated 8kw capacity over this period. So not surprising the compressor would be working at 50% or more during this period.
also your room temp increased by 3C so the HP was putting more heat into the house than the house was losing. My point is about a long time period (hours) when the system is maintaining the room temp at a steady level - are you able to achieve that ? you mentioned about your high LWT setting, maintaining that high LWT will be why your machine is working quite hard (column F is the electrical load ?).
Columns K-M come from the capacity table in the Samsung EHS Technical Data Book. (Duty is constant for LWT up to ~50degC at any given ambient temp, but power increases with increased LWT and I simply curve fitted these latter numbers.)
To estimate compressor speed I divided my measured power and calculated thermal duties by interpolation of the Samsung published numbers at full speed. I assumed that both capacity and power varied linearly with speed. (The only scroll compressor datasheet I have - a Daikin - indicates that this is a good approximation.)
Yes column F is the controller display of ASHP power (i.e. excluding power to pumps and controller).
I take your point about the room still warming up, but the ASHP doesn’t care where the heat is going, whether warming a room or the environment. I deliberately chose a time period for the test when the roomstat didn’t stop demand, which would have upset what was otherwise a reasonably steady state.
Finally, I have my weather compensator set high because I am not yet convinced that “low and slow” would save much money in my case - I’m still doing the calcs .
Oh and good luck with the job hunting, though we do need you to keep up with your contributions here…
According to their marketing material, Samsung use BLDC twin rotary compressors in the gen 6 series, not scroll compressors. Apparently rotary compressors are cheaper and noisier than scroll compressors, which matches my heat pump!
My system is the Market Drayton one. The highest heat output that it has provided was just over 9kW and the lowest just over 2, but it won’t maintain that and cycles up and down with a mean of about 3kW. The electrical input does drop quite noticeably down to just over 400W with a peak of nearly 4.5kW , although normal peaks are about 2.5kW.
Roughly speaking the output modulates just over 2:1 but the input modulates 6:1.
ok, I think I get your method now. It seems probably reasonable as a rough-order-of-magnitude, and common sense says the numbers you’re getting are about right.
your power consumption numbers are what jump out as high to me. which will be down to the high LWT.
In steady state, my system sits at LWT of 36 (at the same ambients as your test) , power output around 4000W (no too dissimilar to yours), power input around 900W (significantly better than yours). system 71 does better than that and with even lower LWT . ah I see @billt the owner has contributed - thanks Bill!
My expectation would be that if you can run at a lower LWT, you can maintain the same output for a significantly lower power input: because we know (based on 2 other systems experimental evidence) that its possible for the compressor to work less hard than what yours is, for the same output. So doing the maths for what you need to do to your emitters to be able to run lower LWT, appears to be the key!
Thanks for the data, Bill.
Just for your info, this thread has been subject to “chinese whispers” and moved on from Gen 6 to EHS Mono Quiet, which do have scroll compressors.
When you say output and input modulation, I assume you are referring to heat generated and power consumed respectively?
Hi guys, I’m new here and glad I’ve found this forum. Just recently I’ve got AE080BXYDGG/EU installed and I would have some questions for some of the experts here. First just a backround about the system. I have house with 2 floors, standard radiators type 21 (10x) and 2x ladder radiators in bathroom. Heat losses are around 4.5KW at 0C outside with indoor temperature 22C.
So here they’ve installed and pump - it’s a direct installation connected to the circuit where an electric heating was. No extra stuff. Only a water pump installed at output. Grundfos Alpha 1 25-60.
So now the first problem was that often I was getting flow error because flow was lower than 7 lpm. This happened because thermostatic valves at 1st floor was mostly closed and some on basement as well so the flow was low. The heatpump was cycling every 15 minutes sometimes and was really bad. So I’ve removed TRVs and fully open radiators with lockshield valve. This helped much but still sometimes every few hours the heatpump stop for 5 minutes. I’ve found it is because installers forgot to connect PWM cable from the water pump. Would you believe that ? So the heatpump requested to lower the flow and nothing happened so after some time it stopped because temperature difference was very minimal.
So here my questions:
Is the PWM regulated water pump crucial for this heatpump. What are consequences of using a fixed RMP water pump, a.k.a. PWM cable not connected.
Until they connect PWM cable I’m running the pump at max. and with all radiators fully open it shows max. 16 lpm flow. Do you think this flow is sufficient for this heatpump ? HT Quiet has minimal flow of 7 lpm but I guess old generation required minimum 22 lpm which seems pretty much to me therefore I wonder if 16 lpm is sufficient or if I should use maybe more powerful water pump ?
Do you know what is the minimal power input this heatpump (8KW) can run on before it switch off the compressor ? I’ve seen 1.0KW in wired controller but can it get lower ?
For now I’ve measured COP 2.75 for roughly 45/40 temp difference with -1C outside which is roughly 0.5 less than in the sheet. I think those COPs on paper are little bit overrated and one should expect always a lower effectivity.
1… with the pwm cable, it’ll slow the pump down to try to preserve the target DT, which can make the operation more stable . although its not guaranteed, the issue could be something else, perhaps simply cycling because heat is going out of the emitters slower than heat going in from the heat pump
2. The min flow rate will be on the manufacturer spec website. can’t remember if its 7 or 12 for the smaller units. 16 is definitely enough
3. I think people have been able to get the 8’s to run at around 2.5-3kw of output . Not sure what the input drops to but I can run my 16kw at 800w input, so better than that should be do-able. have a look on heatpumpmonitor.org there are a couple of 8’s.
COP in -1C will always likely be affected by defrost. If you setup monitoring of your system like many on this forum, you will be able to see the difference between “running COP” and “overall COP including defrost”
No, it’s not crucial, you just need to disable it in the settings (set FSV 4051 to off) to avoid the errors. I ran my Samsung 5kW HP with a fixed speed pump for over 12 months and got a SCOP of 4.3 eg. Emoncms - app view dashboard.
My HP had older Samsung firmware which did not support PWM pump, in the past few months I’ve updated my firmware and got the PWM to work. The Pump now uses a few 10’s of Watts less, I’ve not noticed any significant difference in the COP. But if you can get the PWM to work it’s preferable. Does your pump have a PWM input? Do you have the cable for it?
You need 23 L/min to get 8kW at DT5 assuming no glycol, you need more flow if you have glycol since glycol reduces the specific heat capacity. 16L/min will only give you 5.6kW. If you’re only getting 16 L/min with the system fully open, you either need to upgrade pipework to reduce pressure loss or install a larger pump to be able to get the full output of the heat pump. However, there’s a good chance that your heat loss is lower than calculated and 5.6kW will be enough
The minimum power will depend on the outside temperature, looking at other 8kW Samsung HPs on https://heatpumpmonitor.org/ it should go down to about 450W. The minimum heat output seems to be about about 3kW. If your house requires less than 3kW, which will be the case when it’s mild outside the HP will cycle, this is nothing to worry about. Samsung doest seem to lose much COP while cycling.
How have you measured the COP? I’ve found the Samsung onboard monitoring to be very inaccurate, mine underreports heat by 20% and over-reports electricity by 5% compared to OpenEnergyMonitoring using MID approved meters.
FWIW I’ve been pleased with the performance of my Gen 6 8kW (apart from the poor CoP at low temperatures).
We recently had a period with the outside air temperature was about -7C. The peak power was about 9.3kW and the Cop 2.4. The spec says 7.35kW and 2.43. Generally I’ve found that the output power exceeds the spec and the CoP matches the spec quite well.
Flow rate for the Gen6 8kW is given as 7-48 l/min.
Thanks for reply. I will try with PWM but I only wonder why the system is shutting down when “water law” is selected. I thought it’s because the flow it’s either too low or just to high without PWM modulation. I wonder how the heatpump knows when to stop heating ? If I control by temperature on thermostat it’s clear but with water law I’m not sure. It is supposed to heat all the time ?
Yes, it’s 7 lpm but problem was that with some TRV closed it felt under this limit and error was thrown. Good to know 16 is enough but this is with all TRVs fully open which is not very desired since I would like to control temperature at least a bit.
Wow 800W is great, but to be honest I haven’t see this dropped below 1000W on this Samsung yet so I wonder if this is the lowest input it can’t handle. It’s scroll compressor. Problem is that they will use 3.7KW compressor in the whole range from 8KW - 14KW so probably the low limit is same with even 14KW units which is a little unfortunate.
It has been around 0C here past days but frankly it hasn’t defrost once! I was pretty surprised but fins were dry without any ice if there was 0C or -5C. It must have been really a dry air here.
What setup everyone is running to have such nice graphs? I have Shelly EM3 to monitor my whole house but I l like this one.
better to keep your TRV’s open (or removed) and control temperature with lockshields and getting the circulating water temperature right. you need all emitters that you can open with a heatpump.
your system could just be shutting down because its got warm enough. No it won’t heat all the time - if the WT’s get high, it will shut down for a bit. there’s a good description of the cycle behaviour from sarahh on here somewhere. its not necessarily a bad thing: its how the system works when its mild. If its doing it when its cold, then something could be wrong.
flow rate - glyn’s point is important, if 16 lpm is all you can get due to your pipework, you won’t get the rated output from the system. my reply was relating to min flow level to avoid an error, I thought that was what you were asking.
defrost - thats good. quite a lot of us are uk based who are constantly getting defrosts when its cold due to our damp uk climate
compressor - I don’t know.
monitoring - you can either install an inline heatmeter and electric meter, look at the openenergymonitor bundle with raspberryPI. Can’t help you more on that because its not what I use but most on here do. Or, you can use what I do, install the samsung modbus module to pull the flow rate +temp data from the unit itself into a suitable compute platform (I use home assistant). plus an electric meter dedicated to the HP. These monitoring systems REALLY help with troubleshooting and tweaking to improving performance.
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