ᐅ Replacing an Old Heating System with a Heat Pump or Gas Boiler Combined with a Domestic Hot Water Heat Pump
Created on: 5 May 2022 10:01
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GePrest
Hello, my gas heating system (roof heating central unit) is 22 years old, as is the solar thermal system. The solar thermal system is no longer functioning properly. The first builder recommends demolishing both the heating system and the solar thermal system and installing a Weishaupt heat pump. He has been installing only Weishaupt products for several years. A second builder recommends renewing the gas boiler and additionally installing a domestic hot water heat pump. A photovoltaic system has been commissioned with 9 Luxor ECO LINE HALF-CELLS M120/380W modules, which will be expanded by at least 3 modules when the solar thermal system is removed. The property is a mid-terrace house, fully equipped with radiators, with 106 m² (1,141 sq ft) of living space, housing 4 people, and approximately 10,000 kWh annual gas consumption. Postal code 76661, average annual temperature 11.1°C (52°F), standard outdoor temperature -10°C (14°F). According to the builder, the heat pump is to be installed on the roof. Regarding the hybrid system: can I install the heat pump for domestic hot water in the basement even though there is no existing hot water pipe? How extensive would the work be if additional piping needs to be installed? Installation in the attic is not possible.
D
Deliverer31 May 2022 21:33I’m not exactly sure where it is located. However, heat pumps are fairly independent of location, as long as the air can freely circulate. The temperature of the incoming air does not vary as much as the temperature of surfaces.
Deliverer schrieb:
I’m not exactly sure where it will be located. But heat pumps are relatively independent of the location, as long as the air can move freely. The temperature of the supply air doesn’t vary as much as the temperature of surfaces. When using surplus electricity from the photovoltaic system, I don’t need a second meter, right? The BAFA subsidy has been applied for, but now I’ve read that a separate meter is required to receive the subsidy. That would mean I’d have to install a second meter. The builder will dismantle the old PV system first, then the photovoltaic system will be installed. I don’t yet have an appointment for the heat pump installation. Does it matter which system is installed first? The photovoltaic system is planned for late July or early August. It’s unclear if the builder has availability before then. What is more sensible, installing the photovoltaic system first or the heat pump first? Who connects the heat pump to the photovoltaic system – the builder or the solar technician?
D
Deliverer3 Jun 2022 10:33Many questions. I'll give it a try:
You should learn to control your heat pump yourself. Otherwise, no one will do it because no one has the time. Here is how you do it: during the transitional period, heat from 9 a.m. to 5 p.m. That should get you through the night.
If that’s not enough, run heating 24 hours and raise the temperature by 2 degrees Celsius (3.6°F) between 10 a.m. and 4 p.m.
Heat the domestic hot water once a day, preferably around midday.
That’s the whole “coupling” of photovoltaic and heat pump.
GePrest schrieb:No. You only need a bidirectional meter, if you don’t already have one. But you don’t have to worry about this. Once your solar installer submits the request for your system and then reports the commissioning, the utility company will know they need to come out. Important: neither you nor the solar installer should order the meter change. This is the responsibility of the metering point operator and should cost you nothing. So be careful what you sign.
If I use excess electricity from the photovoltaic system, do I need a second meter?
GePrest schrieb:It doesn’t matter. When it comes to photovoltaics, keep an eye on the ongoing discussions about the future feed-in tariff. What matters is the commissioning (i.e., turning the system on), which you and the electrician carry out together. But this should be clarified in the next few weeks once the federal council and parliament reach an agreement.
What makes more sense to install first, photovoltaic or heat pump?
GePrest schrieb:Neither. The systems are independent of each other. There are control options, but they tend to cause more problems than benefits.
Who connects the heat pump to the photovoltaic system? The builder or the solar installer?
You should learn to control your heat pump yourself. Otherwise, no one will do it because no one has the time. Here is how you do it: during the transitional period, heat from 9 a.m. to 5 p.m. That should get you through the night.
If that’s not enough, run heating 24 hours and raise the temperature by 2 degrees Celsius (3.6°F) between 10 a.m. and 4 p.m.
Heat the domestic hot water once a day, preferably around midday.
That’s the whole “coupling” of photovoltaic and heat pump.
Deliverer schrieb:
Many questions. I’ll give it a try:
No. Only a two-way meter, if you don’t already have one. But you don’t have to worry about that. As soon as your solar installer submits the request for your system and then reports the commissioning (IBN), they will know they need to make the switch. Important: neither you nor the solar installer should order the meter exchange. This is the responsibility of the metering point operator and should cost you nothing. So be careful what you sign.
It doesn’t matter. With photovoltaic systems, you should keep an eye on the ongoing debate about future feed-in tariffs. What matters is the commissioning (IBN), meaning the system activation that you and the electrician carry out together. But this should be resolved in the coming weeks once the federal council and parliament reach an agreement.
None. The systems have nothing to do with each other. There are control options, but they do more harm than good.
You should learn how to operate your heat pump yourself. Otherwise, no one else will, as nobody has time for it. And here’s how you do it: during transitional periods, heat from 9 a.m. to 5 p.m. This should get you through the night.
If that’s not enough, run heating 24 hours and raise the temperature by 2 degrees Celsius (3.6°F) between 10 a.m. and 4 p.m.
Heat your domestic hot water ideally only once a day around midday.
That’s how you “couple” photovoltaic and heat pump. Thanks for the information. So, using a control signal such as the potential-free contact of the Fronius inverter to trigger a relay during surplus power generation is not efficient? Doesn’t that increase the self-consumption of the photovoltaic system? What speaks against it?
D
Deliverer3 Jun 2022 10:59If done properly and working well, this can be efficient. But according to Pareto’s principle, it involves a lot of effort for little additional benefit.
Why:
First, you need to define what should happen when there is "too much" photovoltaic power available. Should the heat pump only run when the sun is shining? Probably not. Should it just heat a bit more? That works with my suggestion. Should it produce hot water? That also works with my suggestion. Even better, because instead of heating up three times by five degrees, it heats once by 15 degrees. That is better for the heat pump.
During the core winter, there is almost always too little photovoltaic power available anyway. So, you get the most out of it by increasing the power slightly throughout the day and using some of it during the night. But caution is needed here too: efficiency suffers. The heat pump does not like to run “hotter than necessary” occasionally. For me, after “optimizing” for photovoltaic input, the coefficient of performance dropped by about 0.3 points. But electricity is cheaper then. You need to do the math.
The last reason why controlling it is hardly worth it: the heat pump simply isn’t a large consumer. Yes, it consumes a lot over time, but not much all at once. It has to be quite cold outside for a heat pump to draw over 1-2 kW. And if 10 kW is currently available, that does not change anything for the heat pump. A car battery can ramp up to, say, 11 kW. But the heat pump, which might be asked to increase temperature by about 2°C (3.6°F), only needs an additional 100 watts, which doesn’t make a big difference.
So keep it simple and get to know the systems.
And if you really enjoy home automation, feel free to tinker a bit in the background. It’s fun. But saving money is hardly possible.
Why:
First, you need to define what should happen when there is "too much" photovoltaic power available. Should the heat pump only run when the sun is shining? Probably not. Should it just heat a bit more? That works with my suggestion. Should it produce hot water? That also works with my suggestion. Even better, because instead of heating up three times by five degrees, it heats once by 15 degrees. That is better for the heat pump.
During the core winter, there is almost always too little photovoltaic power available anyway. So, you get the most out of it by increasing the power slightly throughout the day and using some of it during the night. But caution is needed here too: efficiency suffers. The heat pump does not like to run “hotter than necessary” occasionally. For me, after “optimizing” for photovoltaic input, the coefficient of performance dropped by about 0.3 points. But electricity is cheaper then. You need to do the math.
The last reason why controlling it is hardly worth it: the heat pump simply isn’t a large consumer. Yes, it consumes a lot over time, but not much all at once. It has to be quite cold outside for a heat pump to draw over 1-2 kW. And if 10 kW is currently available, that does not change anything for the heat pump. A car battery can ramp up to, say, 11 kW. But the heat pump, which might be asked to increase temperature by about 2°C (3.6°F), only needs an additional 100 watts, which doesn’t make a big difference.
So keep it simple and get to know the systems.
And if you really enjoy home automation, feel free to tinker a bit in the background. It’s fun. But saving money is hardly possible.
Deliverer schrieb:
If done correctly and it works well, it can be efficient. But following Pareto’s principle, it usually involves a lot of effort for little additional benefit.
Why:
First, you need to define what should actually happen when there is "too much" photovoltaic (solar) power available. Should the heat pump only run when the sun is shining? Probably not. Should it just heat a little more? That also works with my suggestion. Should it heat domestic hot water? That works too, and even better because instead of heating up three times by five degrees, it heats once by 15. This is better for the heat pump.
In the middle of winter, there is almost always too little photovoltaic power. So you get the most out of it by increasing the output a bit over the whole day and then using some of it during the night. But caution is needed here as well: efficiency suffers. The heat pump does not like to run “occasionally hotter than necessary.” After "optimizing" for photovoltaic input, my system’s coefficient of performance dropped by about 0.3 points. However, electricity is cheaper then, so you have to do the math.
The last point why controlling hardly pays off: the heat pump simply is not a large consumer. Yes, it uses a lot over time, but not a lot at once. It has to be quite cold outside for a heat pump to draw over 1–2 kW. And if there’s currently 10 kW available, that doesn’t affect the heat pump at all. A car battery system can ramp up to, for example, 11 kW. But the heat pump, which might only need to increase by 2°C (3.6°F), requires just about 100 watts extra, which doesn’t really make a noticeable difference.
So first, keep it simple and get to know the systems.
And if you really enjoy home automation, you can certainly experiment around with programming. It’s fun. Just don’t expect to save much.Thank you very much for the detailed information.Similar topics