Hi Everyone,
I’m a new ASHP owner and currently just trying to understand what does what and why.
My system is a Samsung EHS mono r290 (AE080CXYDEKEU)
I only have radiators and the flow and return pipe work is all 28mm with 15mm drops
I have a 50l volumiser in the return path and have antifreeze values so no glycol.
So I’m hoping my system should be quite efficient although the outdoor unit is 10 meters away form the house which I know is not ideal but the raised garden level close to the house wouldn’t allow any better placement.
Hi Sarah,
That is very helpful thank you.
Yes I’m using weather compensation (Water law seems such an odd term) and I have my old roomstat set to manual on or off. I do really like the constant temp compared to a gas boiler and rooms heating up then cooling down everyday this is a quite the revelation!
looking at the chart I see it now the LWT keeps increasing till it shuts down at roughly the same point with the same outside temp if i look back to overnight with colder temps outside the LWT gets a little hotter before shutting down.
I’ve also just found the Flow check box for the chart and can see the flow rate keeps stepping down with the slowest flow rate about 15 l/m. (with max about 20 l/m)
Is this lower flow rate so the radiators have more time to emit the heat from the water before being replenished? (Is that the correct way to think of it?)
Or is this flow reduction just a consequence of the compressor slowing down?
Hi Ian,
The water circulation rate is normally controlled either through TRV action if the pump is fixed speed, or PWM (pulse width modulation) control if enabled. Conventionally, the latter is a controller algorithm that seeks to maintain a constant (LWT - RWT). However in your case TRVs don’t normally have a step action like that, and your (LWT - RWT) is almost constant, so it doesn’t look like conventional PWM control either. I can only assume that with the Gen 7 Samsung have introduced a form of PWM that takes its input from compressor speed, as you suggest (unless anyone else has alternative experience?).
Did Samsung (or your installer) supply an installation manual? There’s a good one for Gen 6 but I haven’t seen one for Gen 7 yet.
Sarah
Hello there,
In my latest experiments, it appeared that to reduce the cycling (and mostly avoid it), playing with FSV 2093 is a good way. on my AE050CXYBEK, 2093 was set to 4, and moving to 1 instead avoided cycling. But it implies only relying on ambient targets temperature to stop the heat pump, so you must make sure they are accurate or you’ll overheat
Cheers,
Hi Sarah,
I do know my pump is a PWM as my installer mentioned it and said its speed is controller by the Samsung controller but that was all he said about it.
I have a box of manuals and paper work I’m trying to get through, I must admit I don’t’ find the Samsung book very easy to understand I’ll have a scan through it for PWM operation or settings and see what I can find.
I have looked for an online PDF version but can’t find one its so much easier to search a PDF than physical book.
If anyone else has a copy of it i would be very grateful to be pointed in its direction.
I’ll let you know if i find anything relevant.
Thanks
Ian
Hi Topaz,
Thank you for that info, I’ll have a look and see what mine is set to when i get home tonight.
Although I don’t want to change any settings until I have at least a basic idea of what I’m doing.
Is there an accepted level of cycling at what point does it become a problem?
Most heatpumps are generally okay with 3 starts per hour, so yours does not look terrible and this won’t result in excessive wear on the compressor. The controller will be programmed to avoid frequent starts, so I wouldn’t worry too much.
Cycling is quite common in the shoulder months while the weather is quite mild, as the radiators cannot shed the generated heat quickly enough. As the weather gets colder and the target flow temperature (aka Water Law) increases then you should see fewer starts. I would leave it as it is for now and see how it does on colder days.
In the mean time, ensure that radiators are open as possible, and only set TRVs to limit overheating in rooms that need it.
Hi Tim,
Thanks, its reassuring that it is not a problem, but there is room for improvement.
I don’t have any TRVs and most radiators are fully open, I’ve only tweaked the flow down on a few where the rooms were a little too warm.
This has resulted in Max flow rate going from approx. 21.5 l/m to 20.5 l/m which I don’t think is a problem.
I don’t plan on changing anything until I’ve got a better grasp on everything and I’m now keen to see what happens when it gets colder.
@IRMartini
Samsung notifies in its documentation that the min cycle should be 12 minutes. To reduce the wearing 3 times / hour is clearly acceptable as @Timbones explicited.
I’m convinced you’re right on this, I know I’ll end up with a higher consumption.
But my experiments (data in thread Samsung R290 cycling seem to indicate the change is more profound than this. And that the water law sound respected (although it’s not cold enough to observe the higher temp versus colder outside), at least the pipes’ temperature is not exceeding the expected value.
If the water law temp is respected then, relying only on ambient sounds like a god solution for me, where the inertia of my underfloor is really huge. I don’t observe the same cycling when heating the wall mounted radiators (one Type 21 and five Type 22).
Anyway, I’m investigating those parameters with all my might, I’m sure we’ll end up with something
Hi Sarah, is that really the case? I would expect the LWT to continue to follow weather compensation and remain stable, except in the circumstance where the heat pump cannot modulate low enough to match the emitter heat output. In this circumstance, yes the LWT will rise and COP will suffer, but then a new equilibrium should be reached where the emitter heat output at the higher LWT matches the heat pump’s output. 60C seems unlikely if that is the case. In colder ambient conditions the LWT will be governed by the water law settings, so I think it is incorrect to say that weather compensation has been switched off.
It’s probably cycling because the emitters can’t emit 2.5kW-3kW of heat at 30C when room temp is 21C, this results in the return temperature increasing. You could experiment with the target DT setting FSV 4052. However, cycling is expected and unavoidable this time of year, as the weather gets colder you would expect the run time to increase. Unless the heat pump is oversized compared to the emitters, you would expect to be running steady state when temperature drops below 5C.
Hi Glyn,
Thanks for the shot of your system showing the flow rate step down, its nice to know my system is behaving normally.
Yes I agree it looks like I’m not giving up enough heat to the house to run in a steady state but hopefully when the weather cools down it will. I do not believe I have an oversized pump my installers did a full heat lose survey before deciding on the unit size.
I havn’t got to grips with all these FSV codes yet what does 4052 do?
I don’t think so I haven’t done anything other than have the kit installed, but I’m happy for it to be added so anyone can see the data.
Are there some instructions on how to do this?
FSV #4052 (at least on a Gen 6) sets (LWT - RWT) if you control your circulation using PWM (which you do).
For what it’s worth:
New PWM output (%) = Current PWM output (%) + (LWT - RWT - FSV #4052) * FSV #4053.
If you can understand that, please educate me .
Sarah
PS I infer from the above that Samsung controllers parse all their inputs over a given time period in order to calculate the new set of outputs (just like my Sinclair Spectrum did in the 1980s - remember them?) but I have no idea what the parse period is. I’d guess no more than a few seconds…
It changes the target pump speed, a lower pump speed could help maintain a DT to lengthen runtimes, but there’s probably not much you can do other than ensure all your emitters are open.
Increasing the flow temp will also increase run times, but this will also reduce the COP.
Can you submit this system to https://heatpumpmonitor.org/? There’s currently not much data available for Gen7 R290 Samsungs
Hi Sarah, I believe that changing 2093 to option 1 simply removes the ability of the LWT to turn off the compressor if it rises above target LWT. Weather compensation still controls target LWT. The same goes for 2091 and 2092 when using an external thermostat.
Assuming that the emitter heat output is greater than the minimum that the heat pump can modulate down to then LWT will remain stable at the target, determined by the weather compensation settings.
Edit: The following is not correct. #2093=1 does not disable weather compensation; it only disables the ability of weather compensation to switch the compressor on/off. See clarification in posts 36 & 37.
Hi Mike,
You are partly correct. With #2093 = 1, at steady state (i.e. when the room temperature is at or close to roomstat target), LWT will vary such that emitter output = room heat loss, with the roomstat controlling compressor speed to make this so. This value of LWT may be greater than or less than the Water Law target (which the controller ignores with #2093=1) at the given outside temperature. So it isn’t the weather compensation that’s doing this - it’s the roomstat.
The situation I was describing above applies to non-steady state situations (like at the end of night-time setback, when the roomstat target suddenly jumps by a few degrees). With #2093=1, the heat pump will run flat out for a couple of hours until the room approaches the new target, and that’s when you can get high LWTs.
With #2093=2-4, LWT will be constrained at the weather comp target. Consequently the room will warm more slowly, but at a better CoP.
The choice of enabling/disabling weather compensation is therefore quite subtle - a poor CoP for a couple of hours or a better CoP for longer. It all depends on how you want to run your heating, and what tariffs you are paying .
Sarah
okay so FSV 4052 will be a decimal value is there a max min value?
would it be 1 to 6 range like 1 = min flow rate, 6 = max flow rate
or is its value actual flow rate eg value 20 = 20 l/m?
Yes no problem, I’ve just asked my installers if they want their company name listed or not as soon as I hear back from them I’ll add my system to the list.
Dear Sarah,
I guess you’re quite right in your tradeoff description: better CoP for longer time, or worse CoP for shorter period.
But IMHO, I think the real foe here is the cycling of the compressor, hence, starting the compressor many times and be driven by LWT temperature would lead to shorter compressor life time.
Cheers
.
.