ᐅ Combining a heat pump with a hydronic fireplace

mete111 schrieb:

Hi everyone,

I came across this thread by chance, as we also planned a heat pump plus a hydronic fireplace. So far, we have only tendered for earthworks and the shell construction, but the building services will be coming soon.

Most people here are against this solution, and I’m almost convinced to give up the hydronic system and switch to a regular fireplace. My problem right now is that the fireplace (I think 6kW) was included in the energy balance for KfW55. Do you think it’s still possible to change that? I’d rather not have the energy consultant reassess everything unless absolutely necessary.

Tell me more about your design. Supply temperature, etc. :-)

Is it possible? Yes!
Is it sensible? Yes, all kinds of air-source heat pumps consume a lot of electricity at sub-zero temperatures. That’s usually when photovoltaic systems don’t help much either.
Is it technically feasible? Yes, but not every heating engineer knows how to handle it.
Is it cost-effective to implement? No!

berny schrieb:

Is it possible? Yes!
Does it make sense? Yes, small air fans of all kinds consume a lot of electricity at subzero temperatures. Usually, solar panels don’t help much then either.
Technically feasible? Yes, but not every heating technician knows how to handle it.
Affordable to implement? No!

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Absolute nonsense. It is not practical because it is not economical, technically very demanding, and prone to errors. What exactly is supposed to make this reasonable? Even if the air-to-water heat pump consumes a few extra kWh in the coldest winter, who cares? This year, at -18°C (0°F), it ran without the electric heating element and still had a COP of 3.0. This solution offers no advantages.

Install a chimney without water heating. It provides pleasant, cozy warmth and looks fantastic, too.

Why is that absolute nonsense? I also wrote: not inexpensive, and most installers can’t do it properly. By the way, I have the exact combination you described and am very satisfied with it. Less aggression, my friend... it’s better for your mental health.

OK, you’re right, I guess I got hung up on the "makes sense, yes" part. What makes you think it’s sensible, and in what way?

As described above... the purely technical weak point of the air-to-water heat pump is the deep winter, as I can see with my own system. From December to February, it consumes about 80% of its annual energy demand because the heat source simply contains less energy. I always use the fireplace for heating in below-freezing temperatures, which indirectly supports the heat pump (I would have preferred a ground source system, but I couldn’t find any company offering a reasonable solution for our soil type); fireplace heat is pleasant and also looks nice with the three-sided panoramic fireplace. However, this excludes the use of a water jacket. I would have liked it anyway, and if my wife hadn’t wanted the three glass panels... no matter. Financially, it’s all nonsense anyway—the cheapest heating option in my opinion is a gas boiler. Everything else tends to be expensive and far from a mature technology. From my previous work experience, pellet boilers with vacuum feeding systems for the fuel are, in my opinion, the most problematic when it comes to malfunctions.