Is it sensible to install a heat pump and booster?

  • Erstellt am 2018-06-19 23:17:16

StefanWinkler

2018-06-19 23:17:16
  • #1
Hello,

I need some advice. The discussion with the landlord is tedious and there is no interest from the heating manufacturer, installer, or the metering company to change anything. Unfortunately, I am not a heating expert, but at least I believe that we do not have a good heating setup in the heating cellar and the heating installer is incompetent because he is not familiar with heat pumps.

Info:
Multi-family house, 6 apartments (480 sqm usable area total), built around 2011. The house is basically of high quality construction. Solid construction, triple glazing, underfloor heating throughout (no radiators). In winter, little heating is needed because of many glass fronts facing south. No solar on the roof.

Installed were:

    [*]Air-water heat pump Novelan LA31
    [*]500L buffer storage tank (TPS500 Novelan/Alpha Innotec)
    [*]Buffer storage Jura 140L with Juratherm 10kW flange heater (No.90410 400V/10kW) (installed from the end of 2015)


In 2011, 2012, and 2013 there were problems with the heating because it ran into a fault that no one read or fixed. As a result, it went into emergency operation and primarily heated electrically. This was only noticed in 2013 when we disputed the service charge statement because of ridiculous kWh consumption. This was fixed, and 2014 and 2015 ran very well (see consumption overview below).
At the turn of the year 2015/16, a 140L tank with flange heater was additionally installed because the landlord wants to comply with the regulation regarding legionella protection. For him, this means that domestic hot water must always be 60°. However, the heat pump cannot achieve this because it only reaches a maximum of 50-55°. Hence the idea of a "booster" to heat the domestic hot water from 50° to 60°.

Annual consumption so far:
2013: 20616 kWh (due to emergency operation)
2014: 15900 kWh
2015: 15690 kWh
2016: 24044 kWh (from here, installation of a "booster")
2017: 26302 kWh

Problem: The service charge statements for 2016 and 2017 show an energy cost share for domestic hot water of 1.8%. The remaining 98.2% is for heating.
Furthermore, electricity consumption rose from 15690 kWh (2015) to 26302 kWh (2017). This seemed incorrect to me. So far, it has not been possible to determine the split between domestic hot water and heating. Therefore, the billing was calculated based on the heat meters of the apartments. Hence the objection.

Up to now, there was only one meter installed, to which everything in the heating room was connected, i.e. heat pump, flange heater, and other circulation pumps. Separation between the heat pump and booster was not previously possible. After my objection, a separate meter for the flange heater (booster) was installed.

I have now observed this for one month and my theory was confirmed. The heat pump idles and uses about (in summer, although it would perform well then) approximately 90 kWh/month (including circulation pumps), whereas the booster alone consumed 780 kWh/month (June). The next service charge statements will therefore show an energy cost share for domestic hot water of approx. 65%. 35% heating. Currently, the split is even 11% to 89%, since we do not need heating in summer.

The hydraulic integration is shown in the attachment.

As I see it, the booster heats constantly because the heat pump cannot deliver 60°. The hot water flows from the 150L tank back into the 500L buffer tank and also warms it up. So almost all the domestic hot water is heated electrically.
In my naive theory, I thought the heat pump would heat the domestic hot water to 50° and the booster would add the last 10°. But with the current setup, the 140L booster heats the 500L buffer tank and the heat pump only heats marginally because the water is already warm. Specifically, we are talking about an additional consumption of 10,000 kWh per year (~3000€ at current electricity prices).

Therefore, my specific question: What should the plan look like for it to run efficiently (under the condition of legionella protection)?
 

Deliverer

2018-06-20 10:21:14
  • #2
Phew. Exciting.

I really can’t help with that, but isn’t it enough for legionella protection to heat the domestic water once every few days and then just skip the booster in between? The water doesn’t have to be kept constantly at 60 degrees...
 

Sondelgeher12

2018-06-20 16:03:29
  • #3


That's how I see it too and that's how it is with us as well...
 

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