To save some money and improve my energy performance, I would like to study the possibility of transforming my (very) old (and very strong and heavy) solar DHW water heater (with double exchanger) of 300L in a "homemade" thermodynamic water heater (or almost because the idea is not to design a cold unit eh but to adapt an existing one ...)
I would like to study the transformation of this one for a maximum budget of 500 € because a thermodynamic water heater of 300L is 2500 € without installation or delivery ...
It is an old solar water heater with double exchanger of the 80s (it is 40 years old it should still hold the same thing ... especially at 4 months a year ...).
Photo of the top exchanger which has not been used since it was installed more than 10 years ago (used at the time):
- Chauffe_eau.jpg (70.62 KiB) Viewed 4734 times
It is currently used 4-5 months as an electric balloon in re-rise of temperature when the temperature of my solar system is lower than 35 ° C. The water gets there at a minimum of 20 ° C so ...
I plugged in 50% of the 3000W resistor, so it consumes 1500W. I have to be around 2 to 3 kWh per day during the winter (250 to 350 kWh each year ...)
I found small 3 kW fully integrated swimming pool heat pumps for less than 400 € with COPs of 3 to 6 ... this would be perfectly suitable from an energy balance point of view ... like the Poolex Nano 3kW (exists even in reversible ...): https://www.poolex.fr/fr/produit/2020-p ... ano-action
- Poolex_nano.jpg (70.01 KiB) Viewed 4734 times
Except that there are the following points that hold me back:
a) Max temperature 43°C 40 ° C (but apparently it is the same on thermodynamic water heaters generally it is 45 ° C max in heat pump mode then relieved by an electrical resistance beyond ....) Solved after one season: it's enough if you don't take a shower at 50°C
at worst the complement can be electric (as in commercial thermo balloons)b) Requires a high flow rate (that of a swimming pool pump ...) Solved after one season: an electronic circulator set to 5W is enough to trigger the heat pump flow meter
c) Usually plastic connectors, not plumbing connectors Solved after one season: the waterproofing is ok with oakum and joint paste but should not be tightened too hard
d) Not made for a pressurized circuit: Solved after one season: do not exceed 1.3 bars in the balloon / heat pump loop
e) 1st prize swimming pool equipment, I have doubts about the reliability at 10 or 20 years...but from what I have seen, after a winter of use, Solved after one season: it seems quite good in terms of implementation (see photos below) and a pool heat pump is made to operate continuously for whole days during heating at the start of the season! With 3 kW it takes 39 hours to raise the temperature by 10°C in 10 m3 of water!
In addition, ideally I would have liked to work in a thermosiphon to do without a circulator. in addition ... but I fear that with delta of T ° as low (25 ° C max ...) that is not possible ... especially for the flow rates requested by the manual ...
So tell me if this project inspires you ... the pros?
Edit at the end of November 2021, yes it is, the work was done a few days later:
water-pumping-filtration / transforming-a-solar-DHW-tank-into-thermodynamic-water-heater-with-a-small-pool-t17035-100.html # p476477
