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!
B
Bauenaberwie14 Nov 2022 19:34An oversized heating system simply consumes more electricity than necessary. You are building an energy-efficient house, and the heating system is inefficient. That doesn’t make sense. Can’t you talk to the general contractor so you can discuss it directly with the company doing the work? You handle the daily business with the site manager, but when it comes to details, the individual trades are addressed directly. This approach is working very well for us at the moment 🙂
A larger modulating heat pump does not run at 100% continuously but operates the compressor at a lower level as needed. When the supply temperature is exceeded, it cycles accordingly.
Our current coefficient of performance (COP) for heating is between 5.6 and 6.1 despite oversizing... you can definitely get it to work 🙂
Our current coefficient of performance (COP) for heating is between 5.6 and 6.1 despite oversizing... you can definitely get it to work 🙂
X
xMisterDx14 Nov 2022 23:23Bauenaberwie schrieb:
An oversized heating system simply uses more electricity than necessary. You are building an energy-efficient house, yet the heating system is inefficient. That doesn’t make sense. Can’t you ask the general contractor (GC) if you could speak directly with the installing company? You handle the daily business with the site manager, but for detailed issues, it’s best to address the specific trades directly. That approach is working very well for us right now 🙂Good idea! I’ve been doing that for months and personally get along better with the heating installer than with the site manager or GC representative. But what good does it do? He can’t get the heating system installed...
And since he has a partnership with the GC, of course he would supply the heating system faster and cheaper if I brought him many follow-up jobs... oh wait, no—my recommendation doesn’t help the installer at all, since he relies on the GC...
And where exactly does an oversized heating system use more electricity than needed???
Especially with an air-to-water heat pump, the recommendation is actually to size it a bit larger rather than too small.
X
xMisterDx14 Nov 2022 23:24Baranej schrieb:
Our current seasonal performance factor for heating is between 5.6 and 6.1 despite oversizing... you can definitely get it to work 🙂That would be geothermal heat in an exceptionally mild winter...
S
SaniererNRW12315 Nov 2022 07:31xMisterDx schrieb:
When it comes to air-to-water heat pumps, it is often recommended to choose a size slightly larger rather than one that is too small.Yep – that’s typical advice from a heating engineer who doesn’t really know the details.Anyone who truly understands the subject sizes the system appropriately (and calculates properly first) or even opts for a slightly smaller unit.
A
Alessandro17 Nov 2022 08:09Search for "Bosch planning tool heat pump" and enter your data.
In the end, you will get a performance curve.
If you look at the minimum output the heat pump can provide and compare it to the building curve, the heat pump is oversized wherever its curve is above the building curve and will cycle frequently.
A larger heat pump cannot modulate down as far as a smaller one. Therefore, it is always important to plan and select appropriately.
Regarding cycling:
It is not a problem if the heat pump starts 15 times during the transition period.
The only important factor is the minimum runtime to ensure proper oil return, lubrication, etc.
Even if it cycles 15 times per day throughout the entire heating season, its expected lifespan is over 50 years!
In the end, you will get a performance curve.
If you look at the minimum output the heat pump can provide and compare it to the building curve, the heat pump is oversized wherever its curve is above the building curve and will cycle frequently.
A larger heat pump cannot modulate down as far as a smaller one. Therefore, it is always important to plan and select appropriately.
Regarding cycling:
It is not a problem if the heat pump starts 15 times during the transition period.
The only important factor is the minimum runtime to ensure proper oil return, lubrication, etc.
Even if it cycles 15 times per day throughout the entire heating season, its expected lifespan is over 50 years!
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