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

[Christophe]

An independent thermostat placed as close as possible to the coil used by the heat pump, if not at the top of the tank?

Um what I call the ECS thermostat (which triggered the ECS-PAC circulator, therefore the flow therefore the heat pump, which has a flow sensor) that's it, it is placed in a thermowell in the upper part of the balloon really not far from the interchange...

[izentrop]

Ok, I didn't remember.
If we believe your diagram, it would be placed above the coil, whereas it should be lower, so your Pac would stop too early
You can try raising the thermostat cut-off temperature to see.

Locate the adjustment position and try to raise this temperature to make your heat pump work longer.

[izentrop]

then

[Christophe]

It's a diagram, the coil is different in real life... on this diagram the heat pump doesn't even appear, it's 15 years old...

But there is the location of the thermostat (mechanical thermometer) and the hydraulic connectors (reserved if necessary)…

The thermostat I have access to of course it is variable but I do not have access to the 40 max of the heat pump…

[izentrop]

The disadvantage in this mode of operation is that the heat pump does many more short cycles whereas before I had 3 to 4 cycles of around 30 minutes per day...

The thermostat I have access to of course it is variable but I do not have access to the 40 max of the heat pump…

You should not touch the setting of the heat pump, but I think that raising the setting of the mechanical thermostat which controls the circulator a little would allow this duration to be increased by 30 minutes/day, to try to increase the water temperature like that that you currently have, without running the circulator constantly.

[izentrop]

Have you tried?

[Christophe]

Tried what?

Izy, if the ECS-PAC circulator runs 24 hours a day, it is because I have increased the setting of the ECS thermostat since it is this one which controls (controlled?) its triggering...basically now the ECS thermostat is no longer useful , it's just the circulator switch: it's on max all the time...

After analyzing the consumption and ambient temperature curves after a few days in this configuration I a start every 2 hours for approximately 10 minutes of compressor operation (= 12 * 0.167 = 2h / day)...VS 4 starts per day of 25 to 30 min for the first 2 seasons...( = around 2h / day too...How strange is that! )

But I consume a little more every day: gone from 1.2 to 1.3 kWh to 1.6 to 1.7 kWh...(+ 30%)

The circulator alone in minimum position (when the heat pump is not turning) is 0.01 * 22 = 0.22 kWh/day...before it consumed 0.03 * 2 = 0.06 kWh/day so the own consumption of the heat pump went from :

- Season 1 and 2: 1.25 - 0.06 = 1.2 kWh/day
- Season 3: 1.65 - 0.22 = 1.4 kWh/day

So the compressor runs a little more (+ 17% of the time) but for a slightly higher DHW temperature (improved comfort)...

On the other hand, if I put the DHW circulator at high speed in this configuration (which was the best setting for season 1 and 2), the daily consumption explodes to 2.5 kWh... (with 24 * 0.03 = 0.72 kWh of circulator consumption and 1.8 kWh consumption PAC)...

So the new configuration seems better to me but it creates more start-up cycles...Is this really annoying (= premature wear?) for a heat pump? A fridge must also start around ten times a day...

Well, still no one to do a similar montage?

[izentrop]

Thank you for the detailed feedback.
I thought that there could be an intermediate position between cutting off too early and continuous operation of the circulator... If you are satisfied with the 30% more, everything is fine

[Christophe]

The intermediate position is how seasons 1 and 2 work...

[jean_le_preux_]

Hello,

Bravo for this project and very interesting feedback on the influence of flow.
I am planning a similar project and I was wondering about the corrosion aspect: unlike a heating circuit with a DHW tank, the swimming pool heat pump and its pipes are not protected by an anti-oxygen barrier. Do you think this can accelerate the corrosion of the balloon or is it anecdotal?
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