Sizing of hot water storage tanks

Hello everyone,

our house, which we will build next spring, will be equipped with an air-to-water heat pump, a controlled central ventilation system with heat recovery, and underfloor heating.

Living area (ground floor/upper floor & office in the basement) is about 180 sqm.

At the moment, I am somewhat puzzled about the size of the hot water tank – according to the construction company, a tank with a volume of 200 liters is included.

Currently, there are two of us, but we wish to have two children as well, so eventually there will be four of us.

Is a 200-liter hot water tank sufficient for four people?

The offered system is a Tecalor 403 SOL (we do not plan to have a solar module on the roof, however the lines for it will definitely be laid as a pre-installation up to the roof).

Regards,

Dirk

Hello,

.....Currently I am somewhat puzzling over the size of the hot water storage tank - according to the construction company, a tank with a volume of 200 liters is included......The offered system is a Tecalor 403 SOL

How high is the heating load according to DIN EN 12831?

.....(we have not planned a solar module on the roof, but the lines for it will definitely be laid as a preparatory measure all the way up to under the roof)..

Economically, that will not be viable!

best regards

What is the heating load according to DIN EN 12831?

Thank you for the quick reply!

I do not yet have an exact heating load calculation - we have not signed a contract yet.

Why do you think that the system without a solar module for domestic hot water heating is not economical?

What I forgot to mention earlier: From the beginning, we are installing a photovoltaic system with 8 SolarWorld SW255 heat pump poly modules (1.96 kWp) on the roof.

Since we largely generate our own electricity for running the heat pump, I did not necessarily consider an additional solar module for domestic hot water heating to be necessary.

Regards,

Dirk

...I do not yet have an exact heat load calculation - we have not signed a contract yet.

Without a heat load calculation as well as the demand for hot water, it is basically impossible to select a heat generator.

...Why do you think the system without a solar module for domestic hot water heating is not economical?

I meant it is uneconomical with a solar thermal system. In addition, "preparations" for this require a buffer storage tank. Usually an efficiency killer.
Well-designed systems (without solar thermal systems) do not need a buffer!

...What I forgot to mention before: From the start we are installing a photovoltaic system with 8 SolarWorld SW255 poly heat pump modules (1.96 kWp) on the roof.

Fundamentally a good approach. However, I would align the system sizing with the actual energy demand for heating and hot water.
Another positive side effect: Elevated photovoltaic modules reduce the cooling load during the summer heat period.

..., I did not necessarily consider an additional solar module for domestic hot water heating to be necessary.

Correct. Therefore, no SOL air heat pump is needed.

regards

Thanks again for the quick response!

Without heating load calculation as well as the demand for hot water, it is basically impossible to select a heat generator.

I can understand that. Our house will be a prefabricated house, but individually planned. The manufacturer offers two systems in the air-to-water heat pump sector, one for a living area of up to about 140 sqm, the other for a living area of up to about 210 sqm. However, once we have the exact heating load calculation, I will compare the data again more specifically. Thanks for the tip!

I meant that a solar thermal system is uneconomical. Moreover, "preparations" for this require a buffer storage tank. Usually an efficiency killer. Well-planned systems (without solar thermal system) do not need a buffer!

OK, then I wasn't so wrong with my opinion after all. I will reconsider whether these preparations even make sense.

Basically a good approach. However, I would align the system dimensioning with the actual energy demand for heating and hot water. Another positive side effect: Elevated photovoltaic modules reduce the cooling load during the summer heat period. Correct. Therefore, you do not need a SOL air heat pump

OK, then I will also take a closer look at this when I have exact documents. Such a photovoltaic system can certainly be easily expanded or reduced.

Best regards,

Dirk

OK, then I will take another critical look at it once I have precise documents. Such a photovoltaic system can certainly be easily expanded or reduced.

During the planning phase, the photovoltaic system can still be modified. Once it is installed on the roof, changes are no longer so easy (or inexpensive) to implement (change inverter, plan strings, number of trackers, etc.).