I don’t think the hot water theft incidents are connected. The bulletin only mentions cyclic pump operations as part of heating off due to the outdoor temperature being higher than the FSV for heating off, ie not related to anti freeze strategy.
I can’t find it now but I do remember reading something about the antifreeze strategy using whatever the last heating mode was (Heat / DHW) but I have never confirmed this.
Thanks @SarahH
Unfortunately I will not be able to email as I don’t have any monitoring, so no available evidence other than my own informal observations.
Having installed my manual switch, I was able to make further observations last night during a further cold spell.
Firstly, the AF cycle lasted 7 mins for me (not 5 mins as previously thought).
I have a Joule pre-plumbed tank, which has a 3-way valve for selecting space heating / DHW, combined with further 2-way (open/closed) valves for space heating zones. I also have a 50L volumiser plumbed in the primary return to the ASHP.
When I lock the 3-way valve in the space heating position to protect the DHW tank, the circulating water simply loops round the primaries through the 50L volumiser. The 2-way zone valves for the heating circuit do not open (as the call for heat is off) so I’m simply circulating the 50L of warm water in the volumiser combined with the volume of water in my 28mm primary pipes, some 25-30m of it for both flow and return, combined.
My flow temps for heating are typically ~32C, with a dT of around 3C, so when a heating run ends, I’m assuming the temperature in the volumiser is around 29C as it’s located on the primary return. After an hour, when the first AF cycle ran, the LWT sensor in the outdoor unit was registering 26.5C after a few minutes, which seems reasonable. I left the heating off all night, and nine hours later the LWT sensor was reporting closer to 20C after a night of AF cycles - still sufficiently warm not to present a risk of freezing (and I have glycol anyhow). However, if I had such a pre-plumbed arrangement without a volumiser fitted on the primary return (for example, installed within the emitter circuit, or no volumiser at all), then the AF cycle would have a very limited volume of water to work with using our hack. Thus I can maybe see why Samsung defaults to using the DHW circuit, as in these circumstances just the volume of water in the primary pipework with no additional source of heat may provide insufficient protection.
Still, it would be nice to have an installer configurable option giving the choice.
Anyway, I’m happy with my solution but it would be nice to see Samsung take this on board.
Great news Sarah! I’ll find some evidence from my own monitoring at send them on. Thank-you for getting the conversation started.
Hi Sarah, here some proofs for the guys. Can’t believe they are not aware of it…. You can easily see that when pump is running AF or AS cycles it opens always DHW circuit even if the pump is actually at CH circuit but not heating. You can see each AF run takes 2C from the tank. 5 cycles during the night steals 10C from hot water tank!
This was when I didn’t have DHW connected. You can see no problem for AF/AS cycles. It simply run the water in a circuit for 3 minutes or so and then finished. No issues, no freezing, no stealing.
Many thanks, @Michal_S, I’ve forwarded the more compelling data to Nick.
Sarah
I’ve emailed Nick directly with some evidence from my own system last night
Well done, @jakeymd1. Nick has just emailed to say thanks, he now has enough data.
Do you guys think there will be any outcome from this initiative? I can’t really believe they are not aware of this behavior. I’m not sure if R290 units do behave same like R32 HTQ units or older. I think there was some discussion with Nick about this topic few months ago and he said something like it’s normal it takes heat from DHW because there is a good chance there is some extra heat. So don’t know what to think. A very easy FSV could sort this out, for this you don’t need any analysis or anything. Just have switch - operate 3-way valve or not during AF/AS cycles. Let’s see but my hopes are low.
Btw, seems Samsung is not the only one doing this but probably on ecodan you can change this behavior in settings? Look here.
Hi everyone,
I just read the entire thread and found a lot of interesting information.
I seem to be the only person who doesn’t mind the AF mode drawing heat from the DHW. I have a parallel backup heating source (pellet boiler) and I don’t want the HP water pump to interfere with the backup boiler’s water pump when in use.
But I can confirm that the temperature drops on the 300L DHW tank are 1 to 2 degrees per AF cycle.
What I’d like to change is the default position of the 3-way valve. It’s set to UFH by default, and I’d like it to be set to DHW by default. I can’t change this either with the wiring or via the FSV.
The second thing I’d like to change is the hysteresis of the room thermostat. The hysteresis is one degree and can’t be changed to my desired 0,5 - 0,7. There are no settings for the FSV 106x on my HP (manufactured 2022 or 2023), but they probably wouldn’t help. I’m considering using an external thermostat.
Hi @szybkowar, welcome to the forum.
Can this not be changed by FSV #3071, default direction of 3-way valve (3071=0 [heating]; 3071=1 [DHW tank])?
I use an EPH C4 external wireless room stat which works really well for me. The hysteresis can be set in the range of 0.2-1.0C.
no, unfortunately if I change 3071 the valve position will change but then the pump thinks it is heating DHW but the water flows to UFH and vice versa.
Thanks for the thermo recommendation, I see that it is a simple dry contact, I will look for something similar on the Polish market or use a zigbee switch to control via HA.
