German forum about plant engineering for home: heating system, solar energy, etc ?

131 posts in this topic

Our 2nd house in England, when we bought it the gas boiler was 40yr old.

We wanted to change it, like "we must, because it's old".

The gas engineer convinced us that would have been a mistake, "never change a working gas boiler".

Now 10 yr later, that very same gas boiler turned 50 and still going strong.

Of course a new one would be greener. But also much more likely to break, because all the electronics in it.

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Turbines are really tricky in built up areas. The low maximum height means they are often sited in gusty locations, rather than somewhere with clean, consistent airflow. I think they generally need to be fixed to the building in built up areas and this brings challenges due to vibration of the structure. No turbine is going to stay perfectly balanced over time even if it was at installation. Out on a windswept open site I would say you'd almost be mad not to include some sort of turbine as it complements solar PV very nicely (in winter when the sun provides less energy, it tends to be windier) but in a typical suburban environment I suspect the benefits are small and a lot of hassle.

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1 hour ago, scook17 said:

It's been windy outside all day. Currently 42 km/h according to the hourly weather

Haha, the windspeed is just over 100km/h right now! I live up a (small) mountain in the Eifel, and have plenty of room around me. Whilst almost all of the houses near me have PV, none of them have a wind turbine. 

Rather than planning regulations, my concern is that whilst it's often windy here by non-coastal German standards, just over ten years ago I was advised against buying one when I lived right on the coast in the south of England (no buildings at all between my house and Cherbourg), as they weren't efficient enough. As I understand it, they benefit hugely from economies of scale, and really want empty, flat spaces in between. Accordingly, whilst I am at one of the highest points for miles around, the fact that the Eifel is anything but flat, might be one of the reasons they aren't more successful here (for private use). I like the idea because it's just such a simple concept, that could provide extra power on those days when its not sunny.

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3 hours ago, murphaph said:

Ah I missed that if he did. It's a new one on me if you can be forced to replace an existing, functioning installation in your own home, Bestandsschutz and all that stuff. I've never heard of it anyway, maybe some local ordnance?

 

 

4 hours ago, murphaph said:

So do I. Solar thermal produces little hot water in winter and way too much in summer. I wouldn't voluntarily add it anywhere. And it's not maintenance free either.

 

I would also really question the assumption that the heating system is on its last legs. Who said this? You should maybe get a second opinion. I am guessing as you concede to having no DIY skills, that a third party told you the system would not last much longer.

 

Oil burners can last a very, very long time.

It is not a local ordinance...and neither a whim of mine :D

 

It is a legal requirement according to the The Building Energy Act (the acronim in german is GeG).

 

Oil Heater older than 30 years needs to be replaced if you bought the house after 1st feb 2002. It will be my case in 2 years (if the seller doesn't backoff from the deal :P  ).

On top of this new oil condensing boilers can only be installed until the end of 2025 , and pure oil heating systems are prohibited from 2026.
From 2026, only oil hybrid heating systems can be installed, in which a heat generator based on renewable energies is installed in addition to the oil heating system.

 

Of course I am hearing here where i live of people not giving a sh*t about this regulation and just keeping the oil heater because no one will control (?).

 

 

 

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https://de.wiktionary.org/wiki/wo_kein_Kl%C3%A4ger,_da_kein_Richter

 

In a rental property you might act differently but honestly, who the hell is going to police this in a private dwelling? I wouldn't even dream of binning a functioning system for that reason.

 

I would wait and see what happens. The Schornsteinfeger isn't going to be keeping records of who bought what when and how long they've lived there, so I wouldn't worry about him reporting it and he'd likely warn you in advance and give you a chance to rectify it.

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39 minutes ago, Frantic said:

It is a legal requirement according to the The Building Energy Act (the acronim in german is GeG).

Oil Heater older than 30 years

So who's to say the old burner is the same one as when the property was built?

Whilst this might be a requirement, honestly I would never be able to remember 30 years ago if it was 30, 35 or 25 years it was installed.

I am guessing really someone will need to come, check, and then inform you the burner was not changed out.

 

But on the question of if you should swap it out. I have lived in two properties with oil heating systems. From a convenience perspective, a pipe that bring gas is hugely better. As they plan to first start subsidy for replacing oil, as it's the worst emitter, one might decide to just wait a few years until there is a good incentive. Getting a delivery of oil is a pain, and price is all over the place, even in normal times. You have a huge tank which may one day leak with all the environment clean up costs. It really would be my last choice.

 

In the village I am, most people burn wood. Had a wood burner to in one property I lived in. Was really nice if you don't mind the wood stacking and cleaning the fireplace. The fire is cosy to have burning in the long winter evenings. It's not very healthy for you though if you look at the studies of particles. Electrical heating, heat pump or not, means mostly mains powered in winter, which is currently very expensive. Gas will be soon too by the look at the prices, so maybe it looses that advantage over electricity.

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5 hours ago, scook17 said:

So who's to say the old burner is the same one as when the property was built?

Whilst this might be a requirement, honestly I would never be able to remember 30 years ago if it was 30, 35 or 25 years it was installed.

I am guessing really someone will need to come, check, and then inform you the burner was not changed out.

 

Shall not be a kind of plate with the construction year and other info ? I guess so.

 

5 hours ago, scook17 said:

 

But on the question of if you should swap it out. I have lived in two properties with oil heating systems. From a convenience perspective, a pipe that bring gas is hugely better. As they plan to first start subsidy for replacing oil, as it's the worst emitter, one might decide to just wait a few years until there is a good incentive. Getting a delivery of oil is a pain, and price is all over the place, even in normal times. You have a huge tank which may one day leak with all the environment clean up costs. It really would be my last choice.

 

I am not getting your post. Changing the oil heating with a gas hybrid (condense boiler + solar thermal) is my current intention, not keeping the oil heater :huh:

 

 

5 hours ago, scook17 said:

 

In the village I am, most people burn wood. Had a wood burner to in one property I lived in. Was really nice if you don't mind the wood stacking and cleaning the fireplace. The fire is cosy to have burning in the long winter evenings. It's not very healthy for you though if you look at the studies of particles. Electrical heating, heat pump or not, means mostly mains powered in winter, which is currently very expensive. Gas will be soon too by the look at the prices, so maybe it looses that advantage over electricity.

 

so what will remain ? :)

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8 hours ago, Frantic said:

I am not getting your post. Changing the oil heating with a gas hybrid (condense boiler + solar thermal) is my current intention, not keeping the oil heater :huh:

so what will remain ? :)

Sorry, rambling...

 

Just happened to check the rates today. Solar PV given to the grid, after tax is paid was 5.6c, where as I pay 7.7c (currently) for gas due to being a long standing customer. Last year that was just 3.9c. Price today for new customers is 14.7c. Maybe you find a better deal with another supplier. So gas is now 2.6x more expensive than my own generated solar PV, but less than half the grid price. For a new PV system what is paid for solar PV is much less today (8.16 c pre-tax in 2021). At 20612 KWh of gas that's 1760 Euros today, but 3148 euros at the 14.7c which I expect them to send the older customers to at some point later this year.

 

So I, am presumably many other people who primarily use gas, will now be paying much more for that type of heating than electricity generated from the roof.

Roof has only a certain space, and I'd always opt for solar PV over solar thermal. There are some special system which actually do both BTW.

Solar thermal is complicated, needs maintenance, and you can't do anything with 'spare' heat.

 

You have radiators, so need a high water temperature as the surface area is low. Heat pumps are not great for this, and usually heat pump installations mean changing out all the radiators to much larger one to keep the radiator temperature from needing to be too high. Thus gas or a pellet stove works out the best choice in terms of temperature. Never had a pellet stove, so I can't speak from experience. If replacing the radiators anyway, opting for the maximum size might not be a bad choice anyway.

 

Ignoring standing charge we get

Solar self PV cost Heating element = 1154

Grid Electricity Cost (30c) Heating Element = 6224

Grid Electricity Cost Heat Pump (COP = 2) = 3112

Gas Cost (projected) = 3029

Difference Gas vs Solar heating element = 1875 Euros

 

So there is a good incentive to move away from gas, especially if you can move to system where you generate the power/heat yourself.

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Also remember that as electricity gets more expensive, a 2 tariff meter may make sense to run the heat pump. We did not install one when we built as the standing charge for the second meter was not worth the benefit of cheaper unit price (and factoring in the inconvenience because the network operator can remotely shut off your heat pump at random times of high network demand for up to a couple of hours) because our house has a low heat requirement in the first place.

 

I may revisit that decision based on where electricity prices go!

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13 minutes ago, murphaph said:

the network operator can remotely shut off your heat pump at random times of high network demand for up to a couple of hours

I hadn't heard about that! Does that mean you would not be able to heat your own home during those periods either?

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13 minutes ago, dstanners said:

I hadn't heard about that! Does that mean you would not be able to heat your own home during those periods either?

 

You can read about it here

 

If you choose a tarif thats a little cheaper, this shut off may happen.

But it's only max of 2 hours up to 3 times a day.

The WP won't be supplying heat, you'll be heating using your hot water tank (Speicher).

Article suggests allowing for this by having a larger WP / Tank

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1 hour ago, scook17 said:

You have radiators, so need a high water temperature as the surface area is low. Heat pumps are not great for this, and usually heat pump installations mean changing out all the radiators to much larger one to keep the radiator temperature from needing to be too high.

We changed to heat pump + Gas Brennwert last year. We do not have underfloor heating and only changed two radiators in the roof as they were tiny and the room is very big. The energy consultant took the measurements of all radiators and did some calculations. In his view, a heat pump would have been enough, but the plumber agreed with me that that would be pushing it on very cold winter days.  

 

What I have yet to figure out is if we can configure optimize the heat pump - gas boiler interaction based on the price of both. 

We originally had two meters when we had the heat pump installed, but realized after a few months that is was not worth it and we had to have it taken out when we installed the PV on the roof a few months later. 

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1 hour ago, dstanners said:

I hadn't heard about that! Does that mean you would not be able to heat your own home during those periods either?

The heating part shouldn't be a problem for most use cases (traditional UFH) as the thermal mass of the concrete screed can easily bridge a 2 hour gap with barely anyone noticing. Using a so called Pufferspeicher tank is actually not of much benefit and it's easy to see why when you compare the thermal mass of the floor screed to the that of the water in the tank. The screed will typically have a thermal mass many times that of the tank of water, so the water has minimal impact on the equation. If you are using radiators then the tank can make a difference, as it has a thermal mass much closer to that of the radiators. 

 

The times of high demand are also likely to coincide with times when you are generating waste heat elsewhere yourself, especially from cooking for example. In a well insulated and airtight house all these heat sources add up. It's the hot water interruption that can really be annoying. I have heard so from neighbours with the separate heat pump meter. They have had unlucky timing (in fairness rarely) where they have used up all their hot water and then the power was shut off just as the heat pump was starting to heat up the tank again. It's manageable using a large enough tank I guess, but that means losses elsewhere as you are heating more water than you actually need. I have no idea how significant those losses are, maybe very small given how well insulated these tanks are. It's just something I didn't like the sound of and in 2015 the price of electricity vs the energy demand of our house meant it was loss making to install the second meter and pay the standing charge on it to avail of slightly cheaper units for the heat pump. It was also messy incorporating any PV installation into this to allow the PV to power the heat pump as your over production flows through the main meter in reverse essentially. In less energy efficient buildings with no PV option, you'd probably want that 2 tariff meter for your heat pump. Again, reducing the building's energy requirement provides flexibility in the choice of heat source.

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40 minutes ago, maxie said:

We changed to heat pump + Gas Brennwert last year. We do not have underfloor heating and only changed two radiators in the roof as they were tiny and the room is very big. The energy consultant took the measurements of all radiators and did some calculations. In his view, a heat pump would have been enough, but the plumber agreed with me that that would be pushing it on very cold winter days.  

Our architect and energy consultant wanted to rigidly follow the standards and install a heat pump that would be capable of entirely heating the house without using the immersion heater even on -16′C days. I was like, WTF? I think it got to -16 once or twice in the 15 years I've lived here. I had to literally argue with them, that because we planned a wood burning stove (I'm so glad we have it now with a well stocked wood shed, should the worst happen we can heat largely with that) that on those exceptionally cold days, I can just light.a.fire to supplement the heat pump. Eventually they relented and we installed the "smaller" heat pump.

 

Quote

What I have yet to figure out is if we can configure optimize the heat pump - gas boiler interaction based on the price of both. 

We originally had two meters when we had the heat pump installed, but realized after a few months that is was not worth it and we had to have it taken out when we installed the PV on the roof a few months later. 

That's going to be really difficult. You'll probably never be able to get it exact but on colder days the gas is preferable (I am assuming an air source heat pump, if ground source then ignore) because the HP needs more electricity to extract the energy from the air. Gas converts into roughly the same amount of heat energy regardless of what temperature it is outside. So my very simple rule of thumb would be, the colder it gets outside, the more gas would be used. Also the time of day the heat pump runs (if air source) makes a huge difference as the available energy in the air is significantly higher in late afternoon than at the crack of dawn.

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19 hours ago, dstanners said:

Haha, the windspeed is just over 100km/h right now! I live up a (small) mountain in the Eifel, and have plenty of room around me. Whilst almost all of the houses near me have PV, none of them have a wind turbine. 

Rather than planning regulations, my concern is that whilst it's often windy here by non-coastal German standards, just over ten years ago I was advised against buying one when I lived right on the coast in the south of England (no buildings at all between my house and Cherbourg), as they weren't efficient enough. As I understand it, they benefit hugely from economies of scale, and really want empty, flat spaces in between. Accordingly, whilst I am at one of the highest points for miles around, the fact that the Eifel is anything but flat, might be one of the reasons they aren't more successful here (for private use). I like the idea because it's just such a simple concept, that could provide extra power on those days when its not sunny.

There is a DWD weather station in Roth bei Prüm Rheinland-Pfalz which is the nearest I could find to the eifel and you can do a (future) wind energy estimation with the historical data.

https://www.dwd.de/DE/klimaumwelt/cdc/cdc_node.html;jsessionid=13EC83799C1BFE6F1822D167565E7D7C.live21074

You have to dig around to find a local site. You could also use the data for a very accurate solar prediction (solar measurements are also there).

Smaller turbines (<100kW) can be almost as aerodynamically efficient as the larger ones (>1MW) but economically not so much. Wind energy, even taking into account the intermittency (predictable) is one of the cheapest energy sources available.

http://openwinddata.com/meas_data/04279/dashboard_04279.html

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Does anyone in this thread have any experience with the installation costs of Fernwärme? We live in an apartment in Munich and want to make the case to the other owners of the benefits of Fernwärme. But it is kind of hard to get any installation cost information.

The rest of the house won't go for it but we are thinking over a longer time frame, and as they get hit with higher gas bills and have to replace systems (and the older more conservative ones shuffle off to the Altersheim) we might plant the seed this year.

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First step would be (unless you've already taken it) to find out if there are any Fernwärme pipes in your vicinity. I asked some years ago, but the nearest pipes to my building in Berlin were more than a kilometre away. If the pipes aren't already in your street, it isn't a simple question of just connecting your building/house.

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4 hours ago, scook17 said:

 

Ignoring standing charge we get

Solar self PV cost Heating element = 1154

Grid Electricity Cost (30c) Heating Element = 6224

Grid Electricity Cost Heat Pump (COP = 2) = 3112

Gas Cost (projected) = 3029

Difference Gas vs Solar heating element = 1875 Euros

 

So there is a good incentive to move away from gas, especially if you can move to system where you generate the power/heat yourself.

 

Ok but probably I am dumb but I am not getting what are you suggesting. Water heating based entirely on PV ? This means a the old dear electric boiler concept that we know has an energy conversion factor not at all high...but I guess you are saying "hey, thanks to your PV you have free-electricity, why bother ?". Did I get right ?

If this is the case, how I manage the nights and the seasons with less irradiation per day ? The nights are my main issue. WIth an a battery or electricity storage ?

I know Gambatte, what I wrote till here is totally against environment protection and sustainability. :)

 

What I read often, also in this forum, is to pair the PV with an Heat Pump. Better energy conversion factor and you take (and pay) electricity for the heat pump just in the nights or whene there is not enough irradiation. BUt gain...heat pump most probably is not an option that fit the current "setup" of the house. I am not neither sure that could be enough just increase the size of the heater and for doing this we have to destroy part of the wall or totally change the position of the heater because they are all in wall recesses.

 

My idea of pairing the gas heater with a solar thermal was for:

  • get the 40% subsidies
  • "help" the gas heater to consume less gass thanks to the solar thermal. And the more the gas will increase the price the faster will be also the repayment of the solar thermal. So the solar thermal is a kind of insurance for minimize the hit we will have due to the increase of gas price

 

I did not at all that the solar thermal requires more maintenace than the PV. I knew just that the solar thermal are less resistant of the PV against hails that'S why there some solar thermal panel with rolling shutter.

 

At this point maybe could be an option to pair a PV with the gas heater ? I guess I will need an intermediate boiler where I will exchange resistance heat (generated by electricity from PV) with a an High Thermal Capacit fluid and then this fluid will go into the Main water container (Puffer they call ?) where also the gas is doing his job.

So we PV "help" the gas heater during the day and in the seasons with more irradiation. Not still sure about the efficiency of energy conversion in this way and not that keen to go over the infamous 10KWHp size...I don'T want to pay xxx euro to a steuerberater JUST for that reason (of course I would pay if my tax situation would have been complex).

 

EDIT: I am not sure if pairing a PV instead of the Solar Thermal will grant me the 30% subsidies (10% are anyway there for getting rid of the oil heater)

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4 hours ago, mako1 said:

Does anyone in this thread have any experience with the installation costs of Fernwärme? We live in an apartment in Munich and want to make the case to the other owners of the benefits of Fernwärme. But it is kind of hard to get any installation cost information.

The rest of the house won't go for it but we are thinking over a longer time frame, and as they get hit with higher gas bills and have to replace systems (and the older more conservative ones shuffle off to the Altersheim) we might plant the seed this year.

This is always going to be tricky to sell in a building with several owners because at any given time there will be a number of them who have recently replaced their gas boilers (assuming Etagenheizung as you mentioned "replacing systems") and they won't have amortised their investments yet.

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