[Acuario]

A while ago I was given an office acclimatisation combined cooling/heating unit. It was interesting as it had heating via a water circuit and cooling with a refrigeration circuit, the heat being supplied or removed in the water as necessary.

The unit had a tube-in-tube heat exchanger that I thought might come in useful.

Having installed a solar hot water system with a single panel, 160L tank etc. which provides hot water from roughly the end of February until the end of October, I decided to add a heat pump to create a hybrid system and therefore benefit from the best of both and (hopefully) have the most efficient hot water system possible. The heat exchanger, being flat and having the two required circuits was perfect.

A schematic of the system is shown in the photos below. The 3-way valve controls the circulation of the mixed antifreeze/water through either the solar panel or the heat pump heat exchanger.

In the photos you can see the solar panel, the non-pressurised fill valve and auto purge valve for any air in the system. When the system is filled (unpressurised) with antifreeze the valve is closed and the system is then pressurised via another valve connected to the pressurised cold water.

In the background you can see the heat pump (it's not the Panasonic one in the foreground).

I haven't any photos of the tube-in-tube heat exchanger without insulation so I've drawn on the relevant flows in blue for water and yellow for refrigerant. In the same photo you can see the 3-way valve.

In true eco tradition the solar panel was a ruptured unit recovered from a customer (cost 0 but it did cost me 150 euros for a new laminated glass panel), the heat pump (air conditioner) was recovered from another job where it was replaced with a larger unit (it was old but functional, again cost 0), the expansion vessel was given to me, the circulating pump was recovered from a scrapped boiler, the tube-in-tube heat exchanger was recovered from the office unit (cost 0), the rest I had to buy although the 160L tank was a necessary replacement as my old tank had failed.