ᐅ Is a multi-split air conditioning system suitable for heating?
Created on: 19 Mar 2022 22:46
L
lesmue79
Does anyone here use a multi-split system for heating, for example as an alternative in older buildings when insulation or renovation is no longer worthwhile?
I’m not familiar with the various split systems, but I’ve come across them often as an alternative to conventional heating when insulation and renovation hardly make sense anymore for the current residents.
I would have concerns about noise, drafts, and the resulting dust circulation since it is an air-to-air heat pump after all.
A photovoltaic system would at least be available for the transitional period from spring to autumn.
I’m not familiar with the various split systems, but I’ve come across them often as an alternative to conventional heating when insulation and renovation hardly make sense anymore for the current residents.
I would have concerns about noise, drafts, and the resulting dust circulation since it is an air-to-air heat pump after all.
A photovoltaic system would at least be available for the transitional period from spring to autumn.
R
RotorMotor20 Mar 2022 10:27kati1337 schrieb:
I can hardly imagine that.
When we moved in here in 2020, we had problems with the new heating system, which didn’t work for a week. We used our split air conditioning system to heat our KFW55(!) house just enough to get by. We only ran it a little when the rooms got too cold, and we only have three split units, so it was far from cheap or economical.
I really can’t see an economical scenario for an uninsulated old building. But I’ll follow along with interest. Can you explain where exactly you had problems?
On the other hand, I can’t imagine that a split air conditioning system wouldn’t heat a KFW55 house very well.
Split AC units are available in almost all power ranges and with good COP when heating.
They are completely independent from existing radiators and similar systems.
kati1337 schrieb:
I can’t really imagine an economic scenario for an uninsulated old building. But I’ll be following the discussion with interest.That certainly depends on the starting point, for example if the building is currently heated with storage heaters. Then it’s also about what can actually be installed without completely tearing the place apart. A ductless mini-split system is quite minimally invasive and is likely to be about three times more efficient in terms of energy consumption. In addition, air-to-air heat pumps qualify for a 35% grant from Bafa for existing buildings.
RotorMotor schrieb:
Explain where you had problems with it.
On the other hand, I can’t imagine that a split air conditioner wouldn’t be able to heat a KFW55 house very well. Sure, it would have been great for heating, but you might as well have sat in front of the electric meter with a bowl of popcorn.
It was simply really expensive. So, we only ran the system as long as necessary.
Our air conditioning is of course not designed to heat the house; I don’t know how much you could optimize that to make it more economical.
But it doesn’t make sense to me in an uninsulated older building. Warm air rises, so you’re basically blowing the expensive warmed air straight up into the roof space, right?
D
Deliverer20 Mar 2022 11:30@kati1337 If heating your house with an air-to-air heat pump is much more expensive than with an air-to-water heat pump, then something is not right.
My first suggestion would be that the units were not running 24/7. Just like with a heating heat pump, an air conditioner performs best when running continuously at a low level.
In theory, there are no efficiency differences – in practice, you just need to be more careful when ventilating, and it is even more important not to let the living space cool down too much, since it takes longer for the building structure to warm up. Often, air conditioners are much cheaper than heating heat pumps, which can sometimes be a downside in terms of efficiency.
Of course, an older building is not ideal for heat pumps. But that goes for other heating systems as well. And if grandma is going to stay in the house for another 10 years before it gets demolished and rebuilt, air conditioners are definitely an option. Also in a passive house, they can be useful as a backup. Heating with them is definitely better for the climate.
My first suggestion would be that the units were not running 24/7. Just like with a heating heat pump, an air conditioner performs best when running continuously at a low level.
In theory, there are no efficiency differences – in practice, you just need to be more careful when ventilating, and it is even more important not to let the living space cool down too much, since it takes longer for the building structure to warm up. Often, air conditioners are much cheaper than heating heat pumps, which can sometimes be a downside in terms of efficiency.
Of course, an older building is not ideal for heat pumps. But that goes for other heating systems as well. And if grandma is going to stay in the house for another 10 years before it gets demolished and rebuilt, air conditioners are definitely an option. Also in a passive house, they can be useful as a backup. Heating with them is definitely better for the climate.
My post was serious; the old building isn't a cave but more like a castle inhabited by a 65-year-old lady of the manor.
So, it’s a building whose insulation has been neglected accordingly. Windows from the ’80s. Masonry or basic structure from 1930 with 40–50 cm (16–20 inches) brickwork and plaster. The ceilings consist of laths and ash filler, or whatever the correct term is. Here and there, some DIY insulation done more or less poorly (attic), so I call this castle an uninsulated older building.
Currently, it’s heated with a 14 kW pellet boiler and radiators. About 4–5 tons of bagged fuel per year across 3 floors of around 60 m² (645 sq ft) each.
By climate split system, which is also a heat pump, I meant using it during transition periods and/or on warmer days to support the existing pellet heating and potentially reduce pellet consumption.
With a hybrid heating system using an air-water heat pump, there wouldn’t really be an alternative except that I’d have to either enlarge the radiators to lower the flow temperature or install underfloor heating to achieve 35–40°C (95–104°F) to integrate it into the existing structure—and I would need to check if the piping system can circulate enough water.
If I’m correctly informed, for example, a multi-split outdoor unit can supply up to five indoor units.
The affected ground floor includes an open-plan living-dining area with kitchen, hallway, bedroom, and bathroom. The refrigerant lines for the cooling split—and possibly necessary condensate pipes (though I think those are only needed when cooling)—could be routed below the basement ceiling. The other two floors only need to be kept at temperate, frost-free conditions since they are unoccupied.
Renting out isn’t an option without completely renovating the entire place, and I don’t want to put the lady of the manor through that anymore.
I found a 12.5 kW multi-split air conditioning system with five 2 kW indoor units online for about €6,500 (approx. $7,000), but going through a refrigeration company would probably cost around €15,000 (approx. $16,000) before subsidies.
If I go to a heating specialist, they’re quoting around €20,000 to €30,000 (approx. $22,000 to $33,000) for a 12 kW air-water heat pump with new radiators or underfloor heating and integration into the existing heating system. Considering the ceiling and floor structure, underfloor heating is probably out of the question; it would likely have to be wall heating instead.
The split system also has the added benefit of cooling. Hence the idea, but I’m probably really crazy.
So, it’s a building whose insulation has been neglected accordingly. Windows from the ’80s. Masonry or basic structure from 1930 with 40–50 cm (16–20 inches) brickwork and plaster. The ceilings consist of laths and ash filler, or whatever the correct term is. Here and there, some DIY insulation done more or less poorly (attic), so I call this castle an uninsulated older building.
Currently, it’s heated with a 14 kW pellet boiler and radiators. About 4–5 tons of bagged fuel per year across 3 floors of around 60 m² (645 sq ft) each.
By climate split system, which is also a heat pump, I meant using it during transition periods and/or on warmer days to support the existing pellet heating and potentially reduce pellet consumption.
With a hybrid heating system using an air-water heat pump, there wouldn’t really be an alternative except that I’d have to either enlarge the radiators to lower the flow temperature or install underfloor heating to achieve 35–40°C (95–104°F) to integrate it into the existing structure—and I would need to check if the piping system can circulate enough water.
If I’m correctly informed, for example, a multi-split outdoor unit can supply up to five indoor units.
The affected ground floor includes an open-plan living-dining area with kitchen, hallway, bedroom, and bathroom. The refrigerant lines for the cooling split—and possibly necessary condensate pipes (though I think those are only needed when cooling)—could be routed below the basement ceiling. The other two floors only need to be kept at temperate, frost-free conditions since they are unoccupied.
Renting out isn’t an option without completely renovating the entire place, and I don’t want to put the lady of the manor through that anymore.
I found a 12.5 kW multi-split air conditioning system with five 2 kW indoor units online for about €6,500 (approx. $7,000), but going through a refrigeration company would probably cost around €15,000 (approx. $16,000) before subsidies.
If I go to a heating specialist, they’re quoting around €20,000 to €30,000 (approx. $22,000 to $33,000) for a 12 kW air-water heat pump with new radiators or underfloor heating and integration into the existing heating system. Considering the ceiling and floor structure, underfloor heating is probably out of the question; it would likely have to be wall heating instead.
The split system also has the added benefit of cooling. Hence the idea, but I’m probably really crazy.
lesmue79 schrieb:
By “climate split,” which is after all also a heat pump, the idea was to use it during the transitional seasons and/or when daytime temperatures are warmer to support the existing pellet heating system, and possibly reduce pellet consumption. For the pellets saved, the electricity bill will go up. Have you compared that? What is the cost of producing 1 kWh of heat from pellets versus electricity (assuming a COP of 3.5)?
The biggest disadvantage, and perhaps the main reason why air-to-air heat pumps are not particularly favored even in new builds, is heat transfer through the air. It simply tends to be quite uncomfortable. To bring the necessary heat energy into an older building, a gentle breeze is not enough; you really need a higher airflow. The air mentioned is also quite dry.
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