Heating capacity calculation and heat pump selection

Hello,

Yes, but neither the house nor the heat pump need particularly much power. That’s what I mean. Then it is briefly defrosted and heating continues. During this time, no new building cools down noticeably - even not with defrosting every 30 minutes.

yes, presumably cooling down will usually not be an issue. However, energy is still lost during defrosting, and the coefficient of performance drops significantly.

Since it strongly depends on the surroundings, one probably cannot define a general direction as wrong or right.

Best regards

I would really appreciate some feedback.

I stand by it. Under no circumstances take the big machine. You will never need the performance and it is completely oversized.

It not only has the reserve to compensate for the withdrawn energy,

You don’t need this reserve because there is already sufficient reserve with the 55/6.

it will also have to defrost much less often and run more frequently in the low modulation range.

Let’s also put it the other way around. I see the 55/6 running in the low modulation range 99.9% of the time under normal operating conditions. The 75/6 will not be able to do that more often.

A disadvantage in the transition period may be that it already switches off on some days (lowest modulation level reached, but the heat doesn’t dissipate), compared to the smaller machine.

So about 60-70% of the heating period.

In this case the large machine 75/6 is in use and the described problem does not occur unlike with other users with the small machine 55/6.

Has the user ever had both devices connected to have a comparison? Maybe he also has a suitable house with appropriate design so that the 55/6 also runs well.

For me, the heat pump is not the weakest link in the chain to orientate on. For me, it is the design of the underfloor heating. If you have this planned properly, you relieve every heat pump enormously. So go ahead and reduce the pipe spacing so that you can also plan the flow well and let the heat pump run easily. In my case, 50% of the rooms were laid with less than 10 cm pipe spacing. The heat pump doesn’t even get into trouble having to work hard.

However, energy is still lost during defrosting, and the coefficient of performance drops significantly.

"Drops significantly" paints quite a grim picture. How exactly - in numbers - does the coefficient of performance drop? How much energy is lost exactly? Do you have any empirical data or calculations?

Yes, but neither the house nor the heat pump need particularly much power. That’s what I mean. Then it defrosts briefly and continues heating. During this time, no new building cools down noticeably – not even with defrosts every 30 minutes.

I also think there is no cooling down, especially since the 55/6, as mentioned, also delivers 7 kW at 0°C. Which is already more than what is needed at NAT.

Moreover, there would still be the electric heater, right?

Hello,

I only know the experience reports, in one example the daily performance dropped to 2.5-2.8 and the energy consumption tripled. Defrosting 1-2 times per hour.

Best regards

I will take another look at the theme as well.

Do the two models actually differ in the performance available for hot water generation?

Or are the same values to be applied as for the heating?