Good questions, Frederico, though I don’t think that there’s a straightforward answer to them.
It sounds like you are thinking about heat pump cycling, and presumably minimising it. As I’m sure you know, cycle frequency is all down to hysteresis – both in the LWT controller, and in the roomstat (though the former depends upon the #209x setting).
Although I don’t think we know exactly how hysteresis is programmed into either algorithm (e.g. 2- or 3-term control), almost always LWT hysteresis will be faster than roomstat hysteresis, because the thermal inertia of the house (or more precisely the room where the roomstat is) is normally much larger than that of the circulating fluid and its containment system (radiators, volumisers/buffer tanks, piping etc.).
So if you are worried about cycling, you should be looking for ways to reduce the effect of LWT hysteresis. One way is to simply increase it (if you have access to #1061 for example); another is to prevent the compressor from stopping even if the LWT setpoint is satisfied (by selecting #2093 = 1). And it is possible to reduce compressor speed (thus heat produced) through selecting Quiet Mode or other (much more advanced) techniques like Frequency Ratio Control). Reducing heat production lengthens the hysteresis time and thus decreases cycling frequency.
Don’t forget that there is a limit to how slow the compressor can run – a controller algorithm shuts it down before damage can occur due to loss of seal/lubrication oil or compressor surge or whatever. Equally there is a limit to maximum speed – the algorithm will constrain it to avoid excessive vibration and casing temperature for example. Not surprisingly, there’s nothing you can do about these limits.
With the #209x settings, Samsung have provided us with flexible options to prioritise roomstat control over LWT control or vice versa, depending upon our individual operating objectives and constraints. For example:
- Folk who don’t even have a roomstat (or have disconnected it) can control their heat pump simply on LWT, using #209x = 0.
- Those who choose to operate with a big night-time setback, but want their house to re-warm as fast as possible each day, irrespective of operating cost, might choose #209x = 1. This will allow LWT to keep rising as fast as possible, until the roomstat is satisfied, which would result in a minimised house warming time, but at the cost of a lower CoP due to high LWT.
- Folk who simply want to minimise their operating costs might choose one of #209x = 2, 3 or 4. This will constrain the LWT (per the WL settings) and thus minimise the operating cost, but would take longer to warm the house if a setback is operated.
The pros and cons of #2093 = 2 or 3 or 4 are more subtle. Keeping the circulating pump on (#2093 = 3) will reduce LWT faster (so reaching the hysteresis temperature quicker and thus increasing the cycling rate), and cost pump energy, but results in a more even heat flow into the house. Switching it off (#209x = 2) results in radiators – and thus the house – cooling more quickly (occupant comfort considerations), but saves pump energy. I’m guessing that this why Samsung provided the compromise (#209x = 4) where you sort of get the best of both worlds through on/off cycling of the pump.
Hopefully none of the above conflicts with Jake’s excellent response above.