ᐅ Heat pump for 148 sqm KfW55 house

Created on: 13 Nov 2022 11:27
J
junijulibaut
Dear heat pump experts and experienced home builders,

I would like to better understand what heat pump capacity we actually need.

Our project:
2 full floors
No basement
148 sqm (1,593 sq ft)
KFW55 standard

In our energy demand calculation, a 6 kW air-to-water heat pump is recommended.
However, the heating load calculation in the plan specifies an 8 kW air-to-air heat pump.
Both calculations seem to follow a standard procedure, as this is a developer project.
Which figures in both documents should I focus on?

To me, 8 kW seems quite high, but this is just a feeling formed by reading here in the forum.

The underfloor heating is already installed, also standard, and the screed has been curing for 4 weeks, waiting for the system to be heated up.
But there is no heat pump installed yet.
The builder would credit us €15,000 if we handle the purchase and installation of the heat pump ourselves.

All these questions are overwhelming us.
Is this even possible? Can we choose a different model or manufacturer?
Is it worthwhile, is €15,000 a reasonable amount?
Is 6 kW enough? ...
We need solid information to stand our ground with the builder.

Help!
Thanks!
wp.seeker12 Dec 2022 16:25
Alessandro schrieb:

A ventilation system is not mandatory for KfW55. You can quote whatever you want 😉
My brother-in-law is currently building a KfW55 single-family house without an automatic ventilation system...

We are also building without a ventilation system.
However, the calculations still include trickle vents in the window frames, which somehow got lost during the construction and selection process 😉
wp.seeker14 Dec 2022 17:51
Answer from Daikin customer service:

The Daikin outdoor unit ERLA11DAW1 planned for our project with 11 kW modulates down to 30% of its capacity, which is 3.3 kW.

Most of the time, this is probably still above the power we actually need.
face2614 Dec 2022 19:18
Wärmepumpe.seeker schrieb:

Response from Daikin customer service:

The planned Daikin outdoor unit ERLA11DAW1 with 11 kW (37,400 BTU/h) modulates down to 30% of the capacity, so down to 3.3 kW (11,300 BTU/h).

This is likely still above the load demand we require most of the time.

At least that. But yes, it will probably require 80–90% less most of the time.

What does the setup look like otherwise?

Buffer tank? How large? Mixing valve? Bypass valve? Circulation? ERR?
wp.seeker14 Dec 2022 19:28
@face26
I can let you know once it’s installed. The companies are very uncommunicative, both BT and HB.

ERR yes
Circulation yes (referring to hot water, to get it quicker at the tap? At least something like that seems to be prepared)

After repeatedly asking BT to check whether 11 kW (12 hp) is plausible, I only got
“The program calculated it that way”
“He has been doing this for 10 years, he is an expert in his field.”
Promised answers haven’t come.
face2614 Dec 2022 20:12
There probably isn’t much you can do either. You can hope that it won’t be too bad and then optimize it yourself as best as possible.

If it’s not completely messed up, you can still achieve quite a lot by adjusting settings and so on. The last 10%, however, won’t be achievable anymore.
wp.seeker14 Dec 2022 20:39
face26 schrieb:

There probably isn’t much you can do either. You can hope it won’t be too bad and then optimize it yourself as best as possible afterward. If it’s not completely messed up, you can still improve quite a bit through adjustments, etc. The last 10% just won’t be possible.

That’s how it will be.
When our monster arrives, the optimization thread will start.