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

[Christophe]

Yes I just ordered a new one ...

To follow friends!

[Christophe]

No readings today but a few photos of the inside of the Poolex heat pump and the wiring diagram ... from my experience it looks pretty well designed ... the capacitor looks good oversized ...

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[Christophe]

After a few leaky tests, here is the correct configuration of the condensate drain ...

Yes I know the use of a garden hose is not "orthodox" but it has the advantage of being flexible, fast and inexpensive compared to a rigid PVC pipe drain ...

3 photos of illustrations:

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[Christophe]

I received and tested the new differential thermometer ...

Heat output temperature measurements at 36 ° C:

7W circulator: delta 2.5 ° C
22W circulator: delta 1.9 ° C

It is more coherent but at the thermal power level it still does not stick because by going from 7W to 22W we have respective flows of the order of 2.1 m3 / h to 3.4 m3 / h with 1 m of cE ... therefore we should have the same ratio on the temperature delta for the same power ... which in both cases greatly exceeds 2kW ...



In short, I still do not understand what is happening ... except that I underestimate the pressure drops which are in reality much greater ...

Beginning of cycle:

Air inlet / outlet:

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Total hours:

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total kWh:

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Average power: 52W (8W 24/24 modem included)

Consumption per day: 1,246 kWh (tests and modem included ...) by removing the 8W modem I have 1,054 kWh per day ...

Too bad I don't have the resistive readings ... but it is clearly visible that the assembly is profitable with a COP of 2 to 3 ...

[Christophe]

ZE VE UNDERSTANDING!

Estimation of real pressure drops at fixed thermal 3kW.

a) Circulator curves (I use the last mode)



b) Estimate of the real flow at 3kW of heat exchange: P = q * 1,16 * deltaT

Q (m3 / h) = 3 / (1,16 * deltaT)

2.5 ° C delta: 1,03 m3 / h

1.9 ° C delta: 1,36 m3 / h

c) If we report these flows on the curves:

7W delta P = approximately 8 mcE

22W delta P = approximately 22 mcE

That the pressure drops increase with the flow I don't mind but that they almost triple by increasing the flow by 30% I don't believe it ... or else the thermal power is higher than 3kW at high speed (the power consumption is the same: around 650W ...) ...

In short, I still don't understand a thing!

Any other ideas? Help !

Merry Christmas !

[Christophe]

Some info on the assembly 2 months later... it still works well in terms of heating / regulation / consumption...

On the other hand, I noticed slight but regular drops in pressure...and the problem was at the level of the 1-inch plastic fittings of the heat pump: neither teflon nor oakum succeeded in sealing well. I didn't want to tighten them like crazy so as not to mess up the plastic nets...

So this weekend I glued the brass fittings on the plastic fittings with a mastic glue...there are Loctite hydraulic sealants (like Loctite 577) probably more suitable but I didn't have any on hand. ..and given the price of Loctite...

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For the moment, it's dry and the pressure has been holding for 24 hours...

ps: I had a power outage in January...the wattmeter was reset...so I wouldn't have the overall consumption for the DHW heating season...but we can estimate anyway since I still have the hourly consumption...

[Christophe]

This morning I turned off the heat pump of my homemade thermodynamic balloon: my solar heating is now hotter than 40°C...

Here is the energy balance of the assembly for the last 51 days

(power cut in January and no backup battery in the energy meter so we will have to be content with these figures...):

1223 hours or 51 days

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Permanent consumption of the modem

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Consumption: 65.7 kWh

I have a average daily consumption of: 65.7 / 51 = 1.3 kWh

I have a average power of: 65.7 / 1223 = 54 W - 11W of the modem = 43 W (heat pump + circulator)

Heat pump load factor if the average power consumed (heat pump + circulator) is 600W: 43/600 = 7.2% or 1h45 per day.

Estimated annual heat pump operating hours (if the heat pump was running all the time): 628 h

Power supplied to water if COPA (annualized cop) of 3: 1800W

Energy supplied to water per day: 3 kWh

As a reminder :

a) A shower is about 2 kWh...I live alone 50% of the time, it sticks...
b) I had estimated the thermal losses of this balloon at 37 W (see: water-pumping-filtration / transforming-a-solar-DHW-tank-into-thermodynamic-water-heater-with-a-small-swimming-pool-t17035-30.html) so the COP must be greater than 3...

37W that's 0.9 kWh in pure thermal losses if we assume 4 kWh supplied to the water, so I have an overall COP on the circuit of around 3.9!

To refine this calculation of the COP, it would be necessary to remove the consumption of the circulator but it is part of the installation so it must be taken into account in the overall energy calculation and it only represents approximately 10W or 10/600 = 1.7% of consumption when the heat pump is running...

[Christophe]

I haven't restarted the Nano heat pump yet this year but I finished the electricity at the end of August and put a connected wattmeter on the board:

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In addition to the heat pump, I have the heating (regulated, circulators), the solar pump and the modem on this wattmeter...

It gives this kind of data.

Per day :

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Per month :

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In this case, when only the solar pump is running, it allows me to follow...retroactively...the hours of real sunshine...it also gives the data per hour each day in real time.

We can see that October 2022 was sunnier than September 2022: about 110 hours of direct sunlight.

I recommend this kind of wattmeter to anyone who wants to precisely monitor and analyze their consumption or PV production! I have exactly the same on my solar production.

[Christophe]

The solar ECS is always sufficient for showering and it's a record since I live here, generally I had to complete the heating around All Saints' Day...

I think that the crawl space insulation work has something to do with it... in addition to the particularly mild month of October 2022...

The nano will wait a few more days before resuming service! I estimate the restart in the first half of December...to be continued...

[Christophe]

Last year I had restarted the heating of the PCs around October 20: chauffage-isolation/biral-mx12-1-bloque-remplace-par-circulateur-electronique-biral-ax-25-4-180-red-t17021.html

So I certainly had to restart the DHW heating supplement a few days later.

(when you have no memory, you have the internet! )