I know we were chatting about whether the “Force” mode for DHW on the Ecodan was making it less efficient. I can’t for the life of me find it amongst the threads this evening. There is so much wonderful conversation going on. So I’m giving up and posting a new thread, sorry.
Here is my system running yesterday where it forced the DHW on because I had DHW set to prohibited on the FTC5.
I’ve re-programmed my system today to allow hot water whenever the tank temp is 15 °C below the desired temp. Then I just push the desired temp to 10 °C so that the DHW doesn’t come on until I want it. At that point I push the DHW desired temp up to say 40 °C and it begins heating the water. So basically it’s still just an on/off switch for DHW but I’ve stopped using the force mode to achieve it. Here are the results from this evening:
I’m going to leave it using this new algorithm and see if there are scenarios where the outcome is interesting. I should probably fix that little on/off flip at 20:54 though.
I’ve not had chance to play with this myself, but one thought I had is that the FTC might override “Eco” mode if the heating system is calling for heat at the same time. Just a guessing.
Yep, that’s possible. We won’t find out in about 15 minutes because my “cheap overnight” hot water run isn’t going to kick in because the water is already hot. I’ll keep an eye out for it happening.
As you know already, in the controller it does talk about limiting a long-running DHW so I’m hoping that the team who decided to implement that option considered what you are talking about. Of course they might have decided “heating was on, get the DHW done ASAP” as you propose.
I have to report a user complaint. Mostly because they don’t happen very often.
Apparently the shower wasn’t hot enough this morning. That’s because I had stopped doing my “force it on during the night” run. The bottom of the tank had dropped to 31 °C by noon.
I was just pondering altering my scheduling logic to allow independent schedules for heating and water so it looks like I shall have to implement that!
For reference, we can see that when I was forcing it on during the cheap overnight electricity window the tank was still at 45 °C for a late-morning shower.
The max power was 3.5kW rather than 5kW when using the force.
The max flow temperature was 48 °C rather than 55 °C. The tank only got up to 38.5 °C rather than the target of 40 °C.
Note that (due to physics) we need the return to be at least the target temperature. Then there’s a 5 °C dt to add on top so the max flow temp needed to be something like 45 °C.
So, anecdotally it was more efficient, but only improved from a CoP of 2.5 to 2.8. I know every little helps, but this is pretty marginal.
I’ll keep running in not-force mode to see what happens.
