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!
D
Daniel-Sp2 Mar 2023 11:04Hello.
With integrated electricity meters, the question always arises about what exactly they measure and how they measure it. Some devices calculate (estimate) the compressor’s power consumption based only on available measurement data. This can also affect the coefficient of performance (COP) and may make it appear significantly better. The electric heating element should, if at all, only activate at extremely low temperatures.
Best regards
With integrated electricity meters, the question always arises about what exactly they measure and how they measure it. Some devices calculate (estimate) the compressor’s power consumption based only on available measurement data. This can also affect the coefficient of performance (COP) and may make it appear significantly better. The electric heating element should, if at all, only activate at extremely low temperatures.
Best regards
Daniel-Sp
The set bivalence point should be visible in the settings.
Split heat pumps cannot operate effectively at very low temperatures. The heat pump’s limit temperature should also be specified.
Both values are required for the calculation, even if the exact SCOP values from the heat pump manufacturer are not used.
These pairs of values are often only shown in diagrams and not explicitly stated, so many HVAC planners end up using less accurate standard values.
The set bivalence point should be visible in the settings.
Split heat pumps cannot operate effectively at very low temperatures. The heat pump’s limit temperature should also be specified.
Both values are required for the calculation, even if the exact SCOP values from the heat pump manufacturer are not used.
These pairs of values are often only shown in diagrams and not explicitly stated, so many HVAC planners end up using less accurate standard values.
parcus schrieb:
Usually, both the indoor and outdoor units are wired so that their power runs through the meter.
However, I have often seen that the heating element was not connected through the meter. This then improves the annual performance factor. And how can I find out how it might be set up in our case?
Daniel-Sp schrieb:
Hello.
With integrated electricity meters, the question always arises what exactly they measure and how. Some devices only calculate (estimate) the compressor’s electricity consumption from available data. This also affects the seasonal coefficient of performance (SCOP) and can noticeably improve it. The heating element should only activate in extremely low temperatures.
Regards The heating element should not have been running so far, except for testing during delivery. And it is said that the heat pump can operate down to -25°C (-13°F).
parcus schrieb:
Daniel-Sp
The set bivalence point should be visible in the settings.
Split heat pumps generally cannot operate effectively at very low temperatures. The minimum operating temperature of the heat pump should also be specified.
Both values are needed for calculations, even if the exact SCOP values from the heat pump manufacturer are not used.
These value pairs are often only shown in diagrams and not explicitly stated, so many HVAC planners use more conservative default values. See above.
As I said, no hot water has been produced yet. So far, we have a calculated COP of 5, which isn’t bad, right? It will likely decrease when producing hot water.
Our electricity meter shows 513 kWh consumption for the same period. Work lights, radio, saws used for cutting the flooring, cooking—all were running. The kitchen has been set up since February 8, and we also provided meals for the helpers on the weekend.
Whether about 110 kWh were used just for that might be possible.
The electrician should know exactly what they have wired.
-25°C (-13°F) is unrealistic. Even a single-stage air-to-water heat pump can only dream of that.
You should be able to see the bivalence point in the settings on the display.
In any case, the heating engineer must know what is configured.
The COP (Coefficient of Performance) is not very relevant and nowadays is comparable to the diesel emissions scandal, hence the focus on SCOP (Seasonal Coefficient of Performance).
For you, the annual performance factor is the important value. This actually improves with domestic hot water production, not worsens, because you also need hot water in summer when the heating is off. (Unless cooling is used, which without photovoltaics lowers the annual performance factor.)
Unless you have an instantaneous water heater system, possibly even connected to a brine storage.
-25°C (-13°F) is unrealistic. Even a single-stage air-to-water heat pump can only dream of that.
You should be able to see the bivalence point in the settings on the display.
In any case, the heating engineer must know what is configured.
The COP (Coefficient of Performance) is not very relevant and nowadays is comparable to the diesel emissions scandal, hence the focus on SCOP (Seasonal Coefficient of Performance).
For you, the annual performance factor is the important value. This actually improves with domestic hot water production, not worsens, because you also need hot water in summer when the heating is off. (Unless cooling is used, which without photovoltaics lowers the annual performance factor.)
Unless you have an instantaneous water heater system, possibly even connected to a brine storage.
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