ᐅ Optimization of the LWD 70A Heat Pump with Photovoltaic System

Hello everyone,
I’m a layperson and therefore looking for your advice.

I recently installed a 13.9 kWp photovoltaic system and now want to optimize my heat pump settings to work more efficiently with the solar system. It is an LWD 70A Alpha Innotec heat pump.

1) Adjust hot water settings with lockout times, suitable hysteresis and temperature/differential settings, and configure the electric heating element accordingly.
2) Reduce compressor pulses and optimize the heating system accordingly.

I would like to start with point 1, as I think this might be simpler. Do you have any recommendations?

Thank you very much for your help.

Heat Pump Commissioning: 09/03/2023 15:

System Status:
Heat Pump Type LD7
Software Version V2.88.3
Revision 9717
Control Panel 1003
Bivalence Stage 1
Operating Status ----

System Settings:
Utility Lockout without Backup Electric Heater (ZWE)
Room Controller No
Return Integration No
Mixing Circuit 1 No
Mixing Circuit 2 No
Mixing Circuit 3 No
Backup Electric Heater 1 Type: Electric Heating Element
Backup Electric Heater 1 Function: Heating and ...
Backup Electric Heater 1 Power: 6.0 kW
Backup Electric Heater 2 Type: None
Backup Electric Heater 2 Function: None
Backup Electric Heater 3 Type: None
Backup Electric Heater 3 Function: None
Fault without Backup Electric Heater
Domestic Hot Water Sensor 1
Domestic Hot Water Sensor 2 ZIP
Domestic Hot Water Sensor 3 with ZUP
Domestic Hot Water Sensor 4 Setpoint
Domestic Hot Water Sensor 5 with HUP
Domestic Hot Water + Heat Pump max 0.0 h
Pump Optimization Yes
Customer Access
Pressure Monitoring On
Heating Circuit Control Outside Temperature Dependent
Mixing Circuit 1 Control Outside Temperature Dependent
Mixing Circuit 2 Control Outside Temperature Dependent
Mixing Circuit 3 Control Outside Temperature Dependent
Heating with Mixing Circuit No
Electric Anode No
Heating Limit Yes
Parallel Operation No
Remote Maintenance No
Pump Optimization Time 180 min
Pump Efficiency Yes
Heat Quantity Cooling
Solar Control Temperature Differential
TDI Message Yes
Multi-Tank No
Backup Electric Heater Release 60 min
Hot Water Post-Heating No
Hot Water Post-Heating Max 5.0
Smart Grid No
Mixing Circuit 1 Control Fast
Mixing Circuit 2 Control Fast
Mixing Circuit 3 Control Fast

Temperatures:

Return Limitation 50.0°C (122°F)
Hysteresis HR 2.0 K
Max Compressor Boost 7.0
Backup Electric Heater Release -2.0°C (28°F)
Air Temperature Differential 7.0°C (45°F)
TDI Set Temperature 65.0°C (149°F)

Hot Water Hysteresis 2.0 K
Max Outdoor Temperature 40.0°C (104°F)
Min Outdoor Temperature -20.0°C (-4°F)
End Air Temperature Differential 6.0°C (43°F)

Setback down to -20.0°C (-4°F)
Max Flow Temperature 70.0°C (158°F)
Temperature Differential On 4.0 K
Temperature Differential Off 2.0 K
Max Storage Temperature Differential 70.0°C (158°F)
Heating Circuit Temperature Differential 2.0 K
Hot Water Temperature Differential 5.0 K
Min. Outside Temperature Flow Max.
Ground Floor Flow 62.0°C (144°F)
Max Hot Water Temperature 65.0°C (149°F)
Min Return Set Temperature 15.0°C (59°F)
Night Setback Heating Circuit 0.0°C (32°F)
Heating Limit:
Heating Limit 17.0°C (63°F)

Pump Efficiency:
Nominal Pump Efficiency 8.25 V
Minimum Pump Efficiency 8.25 V
Pump Efficiency Yes

Heat Quantity Cooling Priorities:
Domestic Hot Water 1
Heating 2

System Configuration:
Heating 1
Domestic Hot Water 1
Swimming Pool 0
Heating Curve Heating 34.0°C (93°F) 20.0°C (68°F)

Operating Hours Information:
Operating Hours Compressor 1: 5583 h
Compressor Pulses 1: 18619
Average Operating Time Compressor 1: 00:17
Backup Electric Heater 1 Operating Hours: 5 h
Heat Pump Operating Hours: 5583 h
Heating Operating Hours: 4738 h
Domestic Hot Water Operating Hours: 845 h

Temperature Information:
Flow 36.3°C (97°F)
Return 35.2°C (95°F)
Return Setpoint 15.0°C (59°F)
Hot Gas 40.9°C (105°F)
Outdoor Temperature 24.0°C (75°F)
Average Temperature 18.0°C (64°F)
Actual Domestic Hot Water Temperature 48.7°C (119°F)
Target Domestic Hot Water Temperature 48.0°C (118°F)
Heat Source Inlet 26.1°C (79°F)
Solar Collector 5.0°C (41°F)
Solar Storage 150.0°C (302°F)
External Energy Source 5.0°C (41°F)
Max Flow Temperature 70.0°C (158°F)
Compressor Suction 48.9°C (120°F)
Evaporator Suction 34.6°C (94°F)
Compressor Heating 60.5°C (141°F)
Superheating 28.9 K
Target Superheating 8.0 K

Yes = Yes

Shutdowns:
09/03/23 14:05 No Errors
09/03/23 08:21 No Errors
09/03/23 00:50 No Errors
09/02/23 18:35 No Errors
09/02/23 15:33 No Errors

Calibration:
NTC1 0.0
NTC2 0.0
NTC3 0.0
NTC4 0.0
NTC5 0.0
NTC6 0.0
NTC7 0.0
NTC8 0.0

You need to adjust this to your living situation and your shower/bath habits. The goal is to produce hot water when the photovoltaic system is generating electricity, so during the day. But how many people get up in the morning, when do they shower or bathe, how often and for how long? Are there any routines in the evening or on weekends?

This will lead you to the solution of when and how much hot water you need.

As an example, here are my own settings (300 l (79 gallons) storage tank for 4 people, 3 of whom work away from home):
Heating element completely deactivated
Hot water temperature set to 42°C (108°F)
Hysteresis 4 K
Higher hot water temperature activated as needed via a switch, and automatically during high photovoltaic surplus to avoid feed-in throttling, set to 55°C (131°F)
Hot water shutoff from 6 a.m. to 1 p.m.

This results in sufficient hot water for showers every morning, hot water being produced after 1 p.m. when solar irradiation is highest, and, in exceptional cases such as long bathing sessions, additional heating in the evening or at night if needed.

Thank you for the response.

I also wanted to disable the heating element, but I don’t even know how.

Reducing the amount of hot water stored is the most effective approach.

If the water isn’t there, it doesn’t need to be heated.

A 300-liter (80-gallon) hot water tank is too large. I have a 10-unit apartment building where I installed a 500-liter (130-gallon) hot water tank. It has never been completely emptied. Here, they want 300 liters (80 gallons) for 4 people. I don’t want to start a debate about whether showering daily is healthy; it certainly isn’t necessary.

My hot water heater runs between 10 a.m. and 3 p.m. using power from my photovoltaic system, if there is enough output. Usually, it only takes about an hour to heat the water to 70°C (158°F). From November to February, it switches to the electrical grid. The system serves 3 people with an 80-liter (21-gallon) tank and has worked reliably for many years.

The insulation on the tank is so good that the water stays hot from 3 p.m. until 10 a.m. the next day. It’s no longer 70°C (158°F) by then, but still hot.

My heating system...

By now, I’m quite experienced.

First, set the hot water hysteresis to 6–8°C (11–14°F).

Set the temperature to a maximum of 48°C (118°F).

Schedule a lockout period for hot water during the day, so the photovoltaic system can contribute more when the sun is shining.

Turn the circulation pump off or run it for a maximum of 15 minutes once a day.

Set the temperature spread between the supply and return pipes to 6°C (11°F) during a heating cycle, but you should only do this in winter.

And don’t listen to Buchsbaum—heating the water to 70°C (158°F) first and then cooling it down with cold water is obviously not efficient for a heat pump.

For me, the photovoltaic system often produces its highest output between 10 a.m. and 12 p.m. There is sun in the morning, but from midday onwards, cumulus clouds or overcast conditions are common. This was actually the case quite often this summer. So, what’s the point of blackout periods? Heat when the sun is shining!

Otherwise, I have a hot water boiler and not a heat pump, which I have also mentioned. I need about 1200 kWh of electricity per year, including the electricity for hot water production, for our fairly large property. This total electricity consumption also includes the oven, lighting for outbuildings, heating pump, chest freezers, and so on. I think that’s pretty efficient.