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!
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!
xMisterDx schrieb:
And the project isn’t very realistic either. Because where do you think you can get a heat pump faster in the current situation than your main contractor or their installer? If you knew an installer well enough to get one for you, you’d be asking them these questions here 😉I agree. So why exactly is there no heat pump available right now? And why would you, as non-professionals, be able to obtain one faster than a well-connected expert?
J
junijulibaut14 Nov 2022 17:26We were able to estimate the installation spacing fairly well by looking at the boxes of the stapling mat. However, we have no idea what the original specification was.
Realistically, I don’t see us handling the heat pump ourselves. There are quite a few implications involved, such as warranty issues and so on. Our developer and their plumbing subcontractor are not exactly putting in much effort to procure a heat pump. They just throw their hands up and apologize—nothing more comes of it. Other suppliers are much more proactive, as we’ve seen on nearby construction sites. We’re exploring all options.
According to friends in Denmark, heat pumps are available there.
But back to an initial question: are the 8 kW oversized? Not that it really matters, since the 8 kW unit has already been ordered and will arrive eventually. Switching to a 6 kW now would only delay everything further. I just wanted to hear your opinions.
And can the Daikin Altherma 3 R F modulate?
Realistically, I don’t see us handling the heat pump ourselves. There are quite a few implications involved, such as warranty issues and so on. Our developer and their plumbing subcontractor are not exactly putting in much effort to procure a heat pump. They just throw their hands up and apologize—nothing more comes of it. Other suppliers are much more proactive, as we’ve seen on nearby construction sites. We’re exploring all options.
According to friends in Denmark, heat pumps are available there.
But back to an initial question: are the 8 kW oversized? Not that it really matters, since the 8 kW unit has already been ordered and will arrive eventually. Switching to a 6 kW now would only delay everything further. I just wanted to hear your opinions.
And can the Daikin Altherma 3 R F modulate?
S
SaniererNRW12314 Nov 2022 18:19junijulibaut schrieb:
But back to an initial question: is the 8kW oversized? For the house? Definitely. For the pipe spacing? I think so too. As a DIYer, I would install a 5kW Panasonic monoblock for the house size.
But since you are building with a developer (? – or is it a general contractor), they should handle it. If the heat pump doesn’t fit properly, they need to provide alternatives. They can’t simply avoid responsibility, especially when warranty issues are involved. What contract details do you have (construction period, handover, penalties, etc.)? That also plays a big role.
junijulibaut schrieb:
And can the Daikin Altherma 3 R F modulate? Yes.
P.S. Of course, it will also work with the larger heat pump. But normally, it’s better to choose something slightly smaller than way too large.
D
driver55a14 Nov 2022 18:50junijulibaut schrieb:
The spacing for installation is 15cm (6 inches), and in the bathrooms 5–10cm (2–4 inches). This is estimated based on photos. Please show one or two examples...
junijulibaut schrieb:
All together, the design heating load is 6233 W. And then why...
junijulibaut schrieb:
In the heating load calculation, however, an 8kW air-to-air heat pump is specified in the plan. B
Bauenaberwie14 Nov 2022 19:23So, we have a KFW55 house with 145 m² (1,561 ft²) of living space, two full floors, and no basement. The pitched roof is unheated, so similar conditions apply. We received a complete heating load calculation where every room, including ventilation, was considered. The result was 4,090 W. So, I would also say that 8 kW is much too large. A 5 kW system would be a reasonable recommendation. Don’t you have a calculation for your property?
Before accepting the hassle, I would simply choose the 8kW heat pump. Where do you see the risk? Too large = a bit more difficult to adjust and will especially cycle during transitional seasons => Not a big deal, because your general contractor/plumber probably won’t set the air-water heat pump efficiently anyway, so you will have to deal with this yourself regardless.
The purchase costs won’t really explode either considering the longer time until everything is finished, plus the stress with the general contractor, and then having to take care of the heat pump yourself.
I would stay with the heating scope of work handled by the general contractor, and something like that should have been considered with the general contractor before starting whether the package fits you or if more customization is desired.
PS. We received a 7kW heat pump from the general contractor for 167m2 (1800 sq ft) KfW 55 standard and are happy with both the efficiency and the cycling behavior, even though it took quite some time to fine-tune it. We could have also sized it smaller with better underfloor heating planning, but that’s the general contractor… they just don’t understand.
The purchase costs won’t really explode either considering the longer time until everything is finished, plus the stress with the general contractor, and then having to take care of the heat pump yourself.
I would stay with the heating scope of work handled by the general contractor, and something like that should have been considered with the general contractor before starting whether the package fits you or if more customization is desired.
PS. We received a 7kW heat pump from the general contractor for 167m2 (1800 sq ft) KfW 55 standard and are happy with both the efficiency and the cycling behavior, even though it took quite some time to fine-tune it. We could have also sized it smaller with better underfloor heating planning, but that’s the general contractor… they just don’t understand.
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