Convert a solar DHW tank (or fuel oil) into a thermodynamic water heater with a small swimming pool heat pump

[Christophe]

difficult to conclude since I did not draw exactly the same amount of water ... necessarily!

A meter on the hot water circuit would have been needed for a valid measurement.

Yes yes izy, then you have to pay me a DHW calorimeter!

It costs an arm but seeing how you piss us off, I think I deserve it right?

Does this increase the cycle time and does the cycle always stop when the outlet temperature reaches 44,4 °?

It no longer rises to 44,4 ° C since I set the setpoint at 39 (must be followed) ... it stops between 40 and 41 ° C ...

Since the change of the delta the cycles are much longer ... but I have not measured! It's between 5 and 10 min vs between 2 and 5 min before ...

The goal would be for the heat pump to stop only when the temperature of the water in the tank reaches this temperature and not before ...

This is already the case ... and fortunately!

The setpoint will perhaps be at 35 °, but as the destination of the heat pump is deviated, this would be normal, since the volume of the water circuit is much smaller.

35 ° C heat pump set point that will be too little ... on the contrary I think to go back to 40 ° C and further increase the delta (6, 7 or 8 ° C ...) to see next week ...

The current settings for this week are:

a) High speed circulator 22W
b) High heat pump setpoint 39 ° C
c) Delta PAC 5 = low PAC set point of 34 ° C (set this morning)
d) No touching of the tank thermostats ("around 40 ° C")

Amazing thing there is little difference between the heat pump I / O temperature rise when I go from 7 to 22W circulator ... which would mean that at 7W we are already at a "max" speed ?? Weird ... If anyone has an idea ??

Also I find that the inertia of the heat exchanger of the heat pump is very important! In light standby mode, I always have 2 ° C differences when the heat pump restarts after a light standby, i.e. pump ON compressor OFF ...

To compare: I have a difference of about 5 ° C at the end of the heating cycle, i.e. circulator ON compressor ON ...

To be continued...

[sicetaitsimple]

Amazing thing there is little difference between the heat pump I / O temperature rise when I go from 7 to 22W circulator ... which would mean that at 7W we are already at a "max" speed ?? Weird ... If anyone has an idea ??

In my opinion (but I could be wrong ...), your cycles are too short (in both cases) for you to arrive at an established diet. At the start of the cycle, for perhaps 2 to 3 minutes, you push the "plug" formed by the contents of the coil into the heat pump, which is established at a temperature depending on the geometry of your balloon and the stratification in it. - here during the stop phase which precedes. It goes up all the same on the "hot" side of the heat pump, but it doesn't really have time to go around .... and it stops before having reached an equilibrium regime.

PS: it is a pity that you do not include the temperature readings at the start / end of the cycle identical to those you provided for the minimum circulator speed.

[Christophe]

I don't think so, the air temperature at the outlet of the heat pump drops quickly and stabilizes (around 10 ° C, i.e. -5 or-6 ° C cooling) between 1 and 2 minutes after the compressor has started ... (I haven't measured but it's very fast, probably closer to 1 minute than 2 ...)

So from 2 minutes of operation, the heat pump is in "cruising" mode ...

PS: it is a pity that you do not include the temperature readings at the start / end of the cycle identical to those you provided for the minimum circulator speed.

Uh if you are talking about the internal performance of the heat pump like that of the Biral circulator, I don't have them ... You would have to ask Poolex!

Otherwise tell me tell me what you want!

[sicetaitsimple]

Otherwise tell me tell me what you want!

I was just talking about the inlet / outlet temperature readings at the start and at the end of the cycle like the ones you attached on page 12, but this time with the maximum circulator flow rate.

[Christophe]

Ok I will do them ... from what I saw I have no more than 4 ° C delta at high speed ... against 7 at low speed ...

It should be understood that high speed is not necessarily advantageous because we will have the same phenomenon in the balloon heat exchanger (which is "not good") ...

[Christophe]

Intermediate morning readings after almost 48 hours in delta 5 ° C:

Duration: 46,5 hour
Consumption: 2,6 kWh
Average power: 56 W

The power therefore tends to go up, inevitably the cycles are longer ...

I'm not touching anything for the moment to redo a measurement over 6 or 7 days.

[Macro]

Ok I will do them ... from what I saw I have no more than 4 ° C delta at high speed ... against 7 at low speed ...

It should be understood that high speed is not necessarily advantageous because we will have the same phenomenon in the balloon heat exchanger (which is "not good") ...

I have a similar phenomenon with my DHW tank which is on my fuel boiler ... I had the idea of ​​improving the heating of the tank by integrating a circulator in the circuit which supplies the tank exchanger (a l 'origin it was in thermosyphon) and well ... contrary to what I thought the heating was less efficient the DHW was less hot than in thermosyphon ... I ironed that in free circulation ...

[Christophe]

So here is the low speed option which leaves time for the exchange to take place on the balloon side is undoubtedly the best ... (we rarely mount a circulator just for 1 balloon in individual housing ... your macro counter example is good !)

Especially since I can now increase the PAC cycle time with the larger delta ...

Last reading since yesterday (a heating cycle was in progress)

Duration: 25,7 hour
Consumption: 1,17 kWh
Average power: 45,5 W

We find the consumption of the previous setting, measurement time too short!

If I do it from high speed, I have:

Duration: 72,2 hour
Consumption: 3,77 kWh
Average power: 52,2 W

Also I noticed that with the high speed setting I had trouble reaching 37 ° C in the shower on the 2nd floor ... so the tank heats less well a priori ... The overall COP is therefore less good !

Considering all of this, I wonder if the best performance / lifespan setting isn't:

a) low speed circulator
b) Heat pump at 40 ° C (the COP is reduced a little but the tank heats up more and therefore there are fewer heat pump cycles therefore less consumption and therefore less wear)
c) Delta greater than 3 ° C to be determined (currently 5)

Why wait to test? So that will be the current setting and I zap the end of the high speed test which was done at 50% ...

[Christophe]

Otherwise tell me tell me what you want!

I was just talking about the inlet / outlet temperature readings at the start and at the end of the cycle like the ones you attached on page 12, but this time with the maximum circulator flow rate.

I measured 40,4 ° C and 35,9 ° C

Heat pump over 39 ° C max ...

[sicetaitsimple]

Otherwise tell me tell me what you want!

I was just talking about the inlet / outlet temperature readings at the start and at the end of the cycle like the ones you attached on page 12, but this time with the maximum circulator flow rate.

I measured 40,4 ° C and 35,9 ° C

Heat pump over 39 ° C max ...

That is to say? Heat pump outlet / inlet at the end of the cycle?