ᐅ Repair a heat pump for €5,000–7,500 or replace it with a new one?
Created on: 16 Feb 2024 16:32
J
jx7
Hello dear forum members,
we are facing the decision of "repair" or "new heat pump" and would appreciate your opinions.
Our 7.5-year-old heat pump has broken down after 68,000 starts in 7.5 years (25 starts per day).
Problem with the heat pump:
- The cause of the frequent cycling is unclear. (Most individual room valves are fully open.)
- The only available customer service is the German distributor (400 km (250 miles) away)
- The heat pump is oversized at 3-12 kW; 7-8 kW would be sufficient according to calculations
- The hot water tank is somewhat small at 165 liters (44 gallons) for 5 people
Possible repair appointment:
- Compressor replacement €5,000 (including installation)
- Fault diagnosis (dirt trap in the heating circuit/brine circuit?, temperature sensors?, bypass valve?)
- Possible control system optimization (improving speed regulation to enable lower speeds? possible speed limit? night setback? high hysteresis? possible blocking times?)
- Optional retrofit of a buffer tank (€2,000 plus installation, no combination buffer possible)
- Risk that the frequent cycling persists afterwards
Alternatively, we could install a new heat pump:
- Change to a larger manufacturer with a better service network
- Several weeks without hot water (the current electric heater only heats the water to 32°C (90°F)) until new installation
- New 5-year warranty
- Unknown costs, probably very expensive
(1) What do you think a new heat pump including installation would cost?
(2) How long do you think the installation would take?
(3) What are your thoughts on the repair vs. replace decision?
Additional data:
Location: Budenheim near Mainz
Current broken heat pump: Ecoforest geothermal heat pump (Model C3 3-12 kW HTR EH), modulating 3-12 kW, connected to underfloor heating and two 100-meter (330 feet) boreholes. Hot water tank 165 liters (44 gallons).
It was probably oversized at the time. The calculated optimal size is 7-8 kW.
The compressor failed after 68,000 starts in 7.5 years (25 starts per day). Two neighbors have the same heat pump in similar homes (same construction company) with 5 starts per day. Customer service at Ecoforest is poor.
The heat pump’s annual balance shows:
Heating 12,740 kWh
Cooling 1,850 kWh
Electricity 3,180 kWh
Annual performance factor (COP): 4.6
Additional data:
Energy standard: nearly KfW-55
Annual primary energy demand Qp according to energy-saving regulations: 34.5 kWh/(m²a)
Specific transmission heat loss H’T: 0.305 W/(m² K)
Heated building volume 920 m³ (32,480 ft³)
Living area: 220 m² (2,370 ft²)
Heated living area: 170 m² (1,830 ft²)
Household: 5 persons
Controlled mechanical ventilation installed
9.9 kW peak photovoltaic system installed
Desired heat pump:
- Modulating heat pump
- Capacity smaller than current (3-12 kW)
- Larger hot water tank than current (165 liters (44 gallons))
- Passive cooling function
- Electric backup heater for emergency operation
- Connection for 10,000-liter (2,600 gallons) basement pool (max 31°C (88°F)) possible (currently connected via low-temperature heat exchanger to heat pump)
we are facing the decision of "repair" or "new heat pump" and would appreciate your opinions.
Our 7.5-year-old heat pump has broken down after 68,000 starts in 7.5 years (25 starts per day).
Problem with the heat pump:
- The cause of the frequent cycling is unclear. (Most individual room valves are fully open.)
- The only available customer service is the German distributor (400 km (250 miles) away)
- The heat pump is oversized at 3-12 kW; 7-8 kW would be sufficient according to calculations
- The hot water tank is somewhat small at 165 liters (44 gallons) for 5 people
Possible repair appointment:
- Compressor replacement €5,000 (including installation)
- Fault diagnosis (dirt trap in the heating circuit/brine circuit?, temperature sensors?, bypass valve?)
- Possible control system optimization (improving speed regulation to enable lower speeds? possible speed limit? night setback? high hysteresis? possible blocking times?)
- Optional retrofit of a buffer tank (€2,000 plus installation, no combination buffer possible)
- Risk that the frequent cycling persists afterwards
Alternatively, we could install a new heat pump:
- Change to a larger manufacturer with a better service network
- Several weeks without hot water (the current electric heater only heats the water to 32°C (90°F)) until new installation
- New 5-year warranty
- Unknown costs, probably very expensive
(1) What do you think a new heat pump including installation would cost?
(2) How long do you think the installation would take?
(3) What are your thoughts on the repair vs. replace decision?
Additional data:
Location: Budenheim near Mainz
Current broken heat pump: Ecoforest geothermal heat pump (Model C3 3-12 kW HTR EH), modulating 3-12 kW, connected to underfloor heating and two 100-meter (330 feet) boreholes. Hot water tank 165 liters (44 gallons).
It was probably oversized at the time. The calculated optimal size is 7-8 kW.
The compressor failed after 68,000 starts in 7.5 years (25 starts per day). Two neighbors have the same heat pump in similar homes (same construction company) with 5 starts per day. Customer service at Ecoforest is poor.
The heat pump’s annual balance shows:
Heating 12,740 kWh
Cooling 1,850 kWh
Electricity 3,180 kWh
Annual performance factor (COP): 4.6
Additional data:
Energy standard: nearly KfW-55
Annual primary energy demand Qp according to energy-saving regulations: 34.5 kWh/(m²a)
Specific transmission heat loss H’T: 0.305 W/(m² K)
Heated building volume 920 m³ (32,480 ft³)
Living area: 220 m² (2,370 ft²)
Heated living area: 170 m² (1,830 ft²)
Household: 5 persons
Controlled mechanical ventilation installed
9.9 kW peak photovoltaic system installed
Desired heat pump:
- Modulating heat pump
- Capacity smaller than current (3-12 kW)
- Larger hot water tank than current (165 liters (44 gallons))
- Passive cooling function
- Electric backup heater for emergency operation
- Connection for 10,000-liter (2,600 gallons) basement pool (max 31°C (88°F)) possible (currently connected via low-temperature heat exchanger to heat pump)
W
WilderSueden18 Feb 2024 17:32nordanney schrieb:
I seriously wonder what is included for that price.I don’t know how it is with Viessmann, but with Nibe you need an additional heat exchanger and a few 3-way valves. However, in 2022 it was offered to me for 4,000 euros. According to the installer, a dew point sensor is not necessary.There is an update:
1) A neighbor with the same heating system and bypass valve has the same problem with too many short cycling events.
2) Another neighbor with the same heating system, but without a bypass valve and instead with a hydraulic separator, does not have the short cycling issue. However, they have the problem that their system produced 2.7 times more kW of heat per year.
This leads me to the following conclusions:
1) The installation company had no expertise and made mistakes in three households.
2) The problem with the two heating systems that have a bypass valve is probably that the bypass valve is opened too far.
The plan is as follows:
1) This coming Monday, the Germany sales team from Ecoforest will come and replace the compressor.
2) After that, they will check the bypass valve. In the best case, they will find that it was completely misadjusted. In any case, it should be turned almost fully closed. (If there are still overpressure issues, it can be opened a bit again.)
3) In the following weeks, I will do a hydraulic balancing of the house myself. A neighbor will show me how to adjust the flow valves. Then everything will be set so that the valves are as open as possible, but arranged in a way that every room reaches the same temperature of 22.5°C (72.5°F). In the future, all room thermostats can then stay fully open permanently.
4) If there are still many short cycling events, I have the following further optimization options in reserve:
a) reducing the output from 3-12 kW (3-12 kW) to 3-6 kW (3-6 kW) or 3-9 kW (3-9 kW) for heating and/or hot water
b) increasing the temperature difference (delta T) from 5°C (9°F) to 8°C (14°F) (or 10°C (18°F))
c) lowering the heating limit to up to 12°C (54°F)
d) raising the pool heating time from 15 minutes per hour to 30 minutes per hour
A buffer tank will not be installed in the house, unless none of these measures help.
What do you think?
1) A neighbor with the same heating system and bypass valve has the same problem with too many short cycling events.
2) Another neighbor with the same heating system, but without a bypass valve and instead with a hydraulic separator, does not have the short cycling issue. However, they have the problem that their system produced 2.7 times more kW of heat per year.
This leads me to the following conclusions:
1) The installation company had no expertise and made mistakes in three households.
2) The problem with the two heating systems that have a bypass valve is probably that the bypass valve is opened too far.
The plan is as follows:
1) This coming Monday, the Germany sales team from Ecoforest will come and replace the compressor.
2) After that, they will check the bypass valve. In the best case, they will find that it was completely misadjusted. In any case, it should be turned almost fully closed. (If there are still overpressure issues, it can be opened a bit again.)
3) In the following weeks, I will do a hydraulic balancing of the house myself. A neighbor will show me how to adjust the flow valves. Then everything will be set so that the valves are as open as possible, but arranged in a way that every room reaches the same temperature of 22.5°C (72.5°F). In the future, all room thermostats can then stay fully open permanently.
4) If there are still many short cycling events, I have the following further optimization options in reserve:
a) reducing the output from 3-12 kW (3-12 kW) to 3-6 kW (3-6 kW) or 3-9 kW (3-9 kW) for heating and/or hot water
b) increasing the temperature difference (delta T) from 5°C (9°F) to 8°C (14°F) (or 10°C (18°F))
c) lowering the heating limit to up to 12°C (54°F)
d) raising the pool heating time from 15 minutes per hour to 30 minutes per hour
A buffer tank will not be installed in the house, unless none of these measures help.
What do you think?
Oh no, it’s getting even more complicated:
Both neighbors have a hydraulic separator instead of an overflow valve like I do.
What puzzles me is how the exact same setup can lead to such different results:
Neighbor 1:
- few starts
- excessively high amount of heat produced (factor 2.7)
Neighbor 2:
- excessively high number of starts (factor 5)
- low amount of heat produced
Both neighbors have a hydraulic separator instead of an overflow valve like I do.
What puzzles me is how the exact same setup can lead to such different results:
Neighbor 1:
- few starts
- excessively high amount of heat produced (factor 2.7)
Neighbor 2:
- excessively high number of starts (factor 5)
- low amount of heat produced
R
RotorMotor27 Feb 2024 20:19There is nothing to say based on this alone. More information about the houses is needed to estimate whether the 2.7 times higher consumption is realistic.
We have now received a quote for a Daikin Geo 0.85-9.1 kW with a 180-liter (48-gallon) hot water tank and a 300-liter (79-gallon) buffer tank for €21,500. After a 35% subsidy, the cost would be €14,000.
Alternatively, replacing the compressor would cost €4,800.
I might also inquire whether it is possible to remove the buffer tank (with possible retrofitting) and switch to the Daikin Geo 0.85-7.5 kW model, which would reduce the price.
Alternatively, replacing the compressor would cost €4,800.
I might also inquire whether it is possible to remove the buffer tank (with possible retrofitting) and switch to the Daikin Geo 0.85-7.5 kW model, which would reduce the price.
N
nordanney28 Feb 2024 14:47jx7 schrieb:
We now have a quote for a Daikin Geo 0.85-9.1 kW heat pump with 180-liter (47-gallon) hot water tank and 300-liter (79-gallon) buffer tank for €21,500. With a 35% subsidy, the cost would be €14,000.
Alternatively, replacing the compressor would cost €4,800.
I might still ask if it’s possible to remove the buffer tank (possibly retrofitting later) and go for the Daikin Geo 0.85-7.5 kW instead, which would lower the price. I don’t think the offer is bad at all... The 180-liter (47-gallon) tank is probably integrated anyway. Regardless, I would also remove the buffer tank and choose the smaller option (even though both have the same modulation limit of 0.85 kW).
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