Sizing of air conditioning system, experiences?

Hello everyone,

we have renovated an old building into a KfW-55 house (on paper). In reality, it almost became a KfW-40.

In the attic, the tenant informed us today that he probably has around 31° room temperature. During the renovation, we had already made provisions (empty conduits, connections...) for an air conditioning system.

How large would you dimension an air conditioning system? Attached is a floor plan of the attic. Living room = 26m² (70m³), whereby the partition wall in the hallway does not go all the way up due to the sloping roof. Here, circulation to the hallway and kitchen would be possible.

[ATTACH alt="dimensionierung-klima-anlage-690559-1.png"]91999[/ATTACH]

I have noted the following performance differences in Bosch air conditioners:

Climate 3000 26WE
Design cooling load 2.8 kW
SCOP moderate climate 4.1
Nominal air flow (indoor) 520 Nm³/h

Climate 3000 35WE
Design cooling load 3.6 kW
SCOP moderate climate 4.2
Nominal air flow (indoor) 530 Nm³/h

Climate 3000 53WE
Design cooling load 5.3 kW
SCOP moderate climate 4.0
Nominal air flow (indoor) 800 Nm³/h

Climate 8000 35WE
Design cooling load 3.5 kW
SCOP moderate climate 5.1
Nominal air flow (indoor) 851 Nm³/h

Addition, in the TAB of our distribution network operator I found the following:

The following are considered controllable consumption devices (SteuVE):

[*]Private charging points for electric vehicles (LE) without publicly accessible charging points according to § 2 No. 5 of the Charging Station Ordinance (LSV)
[*]Heat pump heating systems including additional or emergency heating devices (e.g. heating rods)
[*]Air-conditioning systems (ARK / air conditioning units) according to the type of system as defined by BNetzA BK6-22-300
[*]Systems for storing electrical energy (power storage)

with a connection capacity of more than 4.2 kW.

Heat pump heating systems and air conditioning units behind one network connection which, for multiple devices of the same type, together exceed 4.2 kW, are treated as one controllable consumption device.
Example: In a multi-family house with 3 owners, each owns a 2.5 kW air conditioner; thus, together they are 7.5 kW and are considered as 1 SteuVE according to §14a.
Consumption devices of 4.2 kW or less must still be reported via the Netze ODR and are not allowed to participate in the regulation according to § 14a EnWG.

We already have a heat pump (7 kW) for the entire house (3-family house) with preparation for a controllable consumption device. This means every additional air conditioner would have to be registered and equipped/prepared to be switchable. (Whether this could be easily implemented, I would have to discuss with my electrician. Most likely, a cable (for switching on and off) would have to be installed from the apartment (sub-distributor) to the basement (technical room/main distribution board).

I have two air conditioning units in the house (150m²). One in the living-dining area on the ground floor (2.5kW) and one in the hallway on the upper floor (3.5kW). I switch them on relatively early and let them run all day on a very low setting. At night, I turn them off. From experience, the smallest one should be sufficient. The problem will more likely be the air distribution, which probably needs to be assisted with fans. I always have a fan running upstairs that pushes the cold air from the hallway into the rooms.

Keep in mind that the power rating refers to the cooling capacity. The electrical power that your utility provider is interested in is significantly lower.

Problems will more likely be caused by the air distribution

How is this nominal airflow to be interpreted?

Keep in mind with the performance specification that it refers to the cooling capacity. The electrical power, which interests your supplier, is significantly lower.

The datasheet states:

Specified power in cooling mode at room air temperature 27(19) °C and outdoor air temperature 35 °C = 3.5 kW

How is this nominal air flow to be interpreted?

I don’t know exactly. My guess is the air flow that passes through the indoor unit per hour. What I meant is the air distribution in the building/apartment. For the lower bedroom, there will probably have to be a fan in the door to generate the same temperature as in the living area. It will also get colder without it, just not as cold as directly at the air conditioner.

The data sheet says:

Don’t take the brochure, but the installation manual distinguishes between nominal cooling capacity, nominal heating capacity, and maximum power consumption. Your utility provider is interested in the maximum power consumption.

Together with the heat pump, you will exceed 4.2 kW. The heat pump will have an electric heating element and will exceed this limit on paper by itself.

You don’t take the brochure, but the installation manual distinguishes between nominal cooling capacity, nominal heating capacity, and max. power consumption. The max. power consumption is what concerns your supplier.

How is the power consumption of the 8000 model (3.5kW) to be understood?

Power consumption at nominal capacity (3.5kW) = 780W
Power (min-max) 0.9-4.2 kW (even more than 3.5kW)
Max power consumption = 2000W (i.e., when it probably operates above nominal capacity)

That would mean that such an air conditioner could even be protected with 3x1.5 and 10A.