ᐅ Combining a heat pump with a hydronic fireplace

We chose a masonry heater without a water circuit because our stove installer told us that water circulation systems are often problematic to clean and that he regularly has to deal with quite a mess to keep the system running properly. We did not further investigate the cost-effectiveness. We will support the hot water tank with a photovoltaic-powered heating element controlled by a smart system—this is where the cost-efficiency can be questioned and precisely calculated if looking for the cheapest solution. Our main goal is to achieve the highest possible self-consumption and level of energy independence, so we are willing to accept the second most cost-effective option. Currently, I am also looking into wind turbines, which economically are still somewhat uncertain. Therefore, it always comes down to a balance between maintenance effort, cost-effectiveness, and one’s attitude towards renewable energy, as people may have different priorities on this topic.

halmi schrieb:

As a layperson, that initially makes sense, but I would recommend looking into the concept of a modulating heat pump.

I have, so please explain to me why it wouldn’t make sense to use that in combination with another heating system?!

hampshire schrieb:

We decided on a masonry heater without water circulation because our stove fitter told us that water circulation often causes problems with cleaning, and he regularly has to deal with quite a mess at customers’ homes to keep the system running properly. We didn’t further investigate the question of cost-effectiveness. We will support the hot water storage tank with a photovoltaic-powered heating element controlled by the solar system – here, cost-effectiveness can be questioned and calculated precisely when looking for the cheapest solution. Our main goal is to achieve the highest possible self-consumption and level of energy independence, so we are willing to accept the second most economical option. Currently, I am also exploring wind turbines, which are still somewhat questionable economically. Ultimately, it is always a matter of maintenance effort, cost-effectiveness, and the attitude toward renewable energy, where people can have different priorities.

We also want to heat as self-sufficiently as possible.

Mycraft schrieb:

You can do that independently of the rest of the heating system. It doesn’t matter what you install.

You can also do it without the water-carrying features. Those were justified mainly in older buildings. Since the introduction of the energy saving regulations and the way houses are built today, that kind of setup is no longer necessary.

Why does the water-carrying fireplace only make sense in older buildings?

As far as I know, you should supply the fireplace with preheated water (~60°C (140°F)) rather than cold water. This, however, is unfavorable for a heat pump, which typically operates with underfloor heating at supply temperatures of around 35-40°C (95-104°F).

A fireplace generates a lot of heat. Therefore, the water heated to support the heating system is actually too hot for the heat pump’s supply temperatures and is mixed with cold water. This works, but it is not very energy efficient. Additionally, the cozy effect created by radiant heat is somewhat diminished by this method since less radiant heat is emitted compared to a traditional fireplace.

It’s better to invest in a photovoltaic system. Combined with a heat pump, this makes much more sense.

The problem with modern houses and fireplaces is that they usually emit too much heat. You quickly turn your living room into a sauna. For example, when we have many guests (which I can hardly remember due to COVID), the temperature in the living room rises by a few degrees very quickly.

Michlhausbauaa schrieb:

Why does a water-bearing fireplace only make sense in older buildings?

Because this pre-war technology has little to no benefit in modern houses; it is energetically inefficient. The whole system is a control engineering nightmare and ultimately provides almost no advantage. No, not everything that was considered good in the past is still practical today.

For these reasons:
- It is hardly used at all (the house heats up far too quickly)
- The effect is only marginal (the water chambers must not be too large, and the water cannot get too hot)
- Investment and operating costs are high since a lot of additional hydraulics are required, which also consume electricity during operation.