ᐅ Water-to-water heat pump alternative, or is it feasible after all?

Hello,

we have been planning to build a house for some time now and already own the plot of land. Over the winter, we want to finalize everything so that construction can start around March/April 2017.

So far, we were quite set on a water-to-water heat pump. Since there is already a groundwater well on our property (about 7 meters (23 feet) deep), we took a water sample. Today, we received a sobering call from the lab: Iron: 0.79 mg/l, Manganese 0.21 mg/l, pH value 7.2! There is also aggressive carbonic acid at 10 mg/l. According to various heat pump data sheets, these values significantly exceed the allowed limits. After inquiring with several installers, we got—as is often the case in home building—many different opinions.

Two installers advised us to forget about it entirely. Another said that operation would be absolutely no problem with an intermediate heat exchanger. A third suggested simply flushing with citric acid once or twice a year. All these gentlemen seem quite convincing and competent to me, so I’m now caught between three opinions.

I am familiar with this citric acid cleaning process. A friend of mine performs it on his heat pump about every five years. But I think his water quality is nowhere near as poor as ours (he lives about 2 km (1.2 miles) away).

We are now looking for alternatives for our home. We exclude fossil fuels, pellets, and wood. Regarding ground collectors, our plot is almost too small (heated area approximately 155 m² (1,668 sq ft) over two floors plus basement, on a 690 m² (7,427 sq ft) lot). How does the energy efficiency of a brine-to-water heat pump compare? A borehole for probes should be feasible.

Is it also possible to cool with this system? Possibly in combination with a mechanical ventilation system? (So, not only through underfloor heating.)

Originally, we planned to run the heat pump together with a 5 kW photovoltaic system. (The roof is ideally oriented south.)

Thanks and best regards

Is an air-to-water heat pump not an option?
Is it very cold where you live during winter?

Why should or must it be a domestic hot water heat pump? What do you think about a soil-water heat pump? This way, you avoid all issues related to the components of groundwater and essentially use the same energy.

In the initial post, I already mentioned the ground source heat pump. That would be a possible option for me, at least. My partner prefers an air-to-water heat pump. However, I’m not so fond of that choice due to the somewhat higher operating costs, the outdoor unit, and so on. Also, I like the idea of being able to cool a little bit with the ground source heat pump.

What are the typical costs for a deep drilling/ground source heat pump installation for a 150m² (1,615 sq ft) two-story house with a basement?

Active cooling is also possible with an air-to-water heat pump. A ground-source heat pump is significantly more expensive to purchase, and it can take a very long time to pay off. Are there any subsidies available in Austria?

Subsidies for heat pumps are no longer available. They were offered a few years ago.

According to a technician from Viessmann, they don’t care about the water quality because they install a bolted plate heat exchanger.

I’m telling you, I’m slowly losing it. No matter where you go, everyone tells you something different. When you finally make a decision, the rest treat you like an idiot (which I don’t really care about).

The well would apparently be relatively cheap to set up here (according to the well driller). However, the drilling for the geothermal loop would be quite expensive.