Hello everyone,
Our heating system consumed about 8,700 kWh of natural gas between 12/16 and 06/17, even though the house is still being renovated and unoccupied. All radiators were set to frost protection only, and no domestic hot water was used.
The system was installed in 12/15 by the previous owners and mainly consists of:
This summer, I noticed that the pipe from the solar collector (supply line) was only hot up to the pump, while the return line was almost cold. From this, I concluded that the pump was not running. At the same time, the controller showed 999°C (1,830°F) for the temperature sensor mounted at the top of the collector, which the technician said is the maximum display value indicating no plausible reading.
Testing the temperature sensor (a PT1000) was successful, so the technician concluded that the controller itself must be defective (he believed the pump was still operational).
So, a new controller was ordered, which I am still waiting for as of today, but that’s another story...
Now, with the cold season approaching, we have temporarily installed some radiators to heat the construction site a little and, most importantly, to ensure frost protection.
I was able to reduce the natural gas consumption by lowering the target temperature for domestic hot water to 10°C (50°F); however, I would say the consumption is still quite high (since Saturday, so in 4 days, about 30 m³ [1,059 ft³]... :O).
Is it possible that due to the defective controller, the 800-liter (210-gallon) water volume of the solar thermal system is being kept warm using natural gas, and usually the ESR 31, depending on whether heat is available from the roof or not, activates or deactivates a heat exchanger between the domestic hot water tank and the solar thermal water system, which in our case might currently always be open or something like that?
Maybe someone, even as a layperson, can explain how a combined stratified storage tank works or is constructed?
Many thanks in advance!
Best regards
PS: The heating technician is hard to reach; unfortunately, I have to work with him since this is obviously a warranty case. Once this issue is resolved, he definitely won’t touch our heating system again… -.-
Our heating system consumed about 8,700 kWh of natural gas between 12/16 and 06/17, even though the house is still being renovated and unoccupied. All radiators were set to frost protection only, and no domestic hot water was used.
The system was installed in 12/15 by the previous owners and mainly consists of:
- Viessmann Vitodens 200 gas condensing wall unit 19 kW
- Austria Email KWS 800 combined stratified storage tank
- Flat plate solar collectors 9.36 m² (100.8 ft²)
- ESR 31 solar controller
- Delphis solar station FV 70 (with Grundfos circulation pump on the supply side)
This summer, I noticed that the pipe from the solar collector (supply line) was only hot up to the pump, while the return line was almost cold. From this, I concluded that the pump was not running. At the same time, the controller showed 999°C (1,830°F) for the temperature sensor mounted at the top of the collector, which the technician said is the maximum display value indicating no plausible reading.
Testing the temperature sensor (a PT1000) was successful, so the technician concluded that the controller itself must be defective (he believed the pump was still operational).
So, a new controller was ordered, which I am still waiting for as of today, but that’s another story...
Now, with the cold season approaching, we have temporarily installed some radiators to heat the construction site a little and, most importantly, to ensure frost protection.
I was able to reduce the natural gas consumption by lowering the target temperature for domestic hot water to 10°C (50°F); however, I would say the consumption is still quite high (since Saturday, so in 4 days, about 30 m³ [1,059 ft³]... :O).
Is it possible that due to the defective controller, the 800-liter (210-gallon) water volume of the solar thermal system is being kept warm using natural gas, and usually the ESR 31, depending on whether heat is available from the roof or not, activates or deactivates a heat exchanger between the domestic hot water tank and the solar thermal water system, which in our case might currently always be open or something like that?
Maybe someone, even as a layperson, can explain how a combined stratified storage tank works or is constructed?
Many thanks in advance!
Best regards
PS: The heating technician is hard to reach; unfortunately, I have to work with him since this is obviously a warranty case. Once this issue is resolved, he definitely won’t touch our heating system again… -.-
markus270328 Mar 2018 13:49I'm not an expert, but I think it's about the pipes. They are usually made of plastic, and they probably wouldn't react well if water close to 100°C (212°F) or even boiling steam from the roof were running through them.
Hello,
The pipes are certainly not made of plastic.
The reason the pump does not turn on is that if the collector temperature is too high and there is water vapor in the collector, steam shocks can occur when the solar fluid flows in.
However, the question is why the collector pump is already turning off at this time of year?
I suspect the maximum storage temperature is set to only 60°C (140°F).
You can safely increase the maximum temperature to 85°C (185°F).
This requires a domestic hot water mixing valve to be installed. If not, it should definitely be retrofitted.
This way, you avoid stagnation, overheating, and damage to the solar fluid, while increasing the efficiency of the system.
This can be further improved by using hot water for the dishwasher and washing machine during midday and afternoon hours.
Olli
The pipes are certainly not made of plastic.
The reason the pump does not turn on is that if the collector temperature is too high and there is water vapor in the collector, steam shocks can occur when the solar fluid flows in.
However, the question is why the collector pump is already turning off at this time of year?
I suspect the maximum storage temperature is set to only 60°C (140°F).
You can safely increase the maximum temperature to 85°C (185°F).
This requires a domestic hot water mixing valve to be installed. If not, it should definitely be retrofitted.
This way, you avoid stagnation, overheating, and damage to the solar fluid, while increasing the efficiency of the system.
This can be further improved by using hot water for the dishwasher and washing machine during midday and afternoon hours.
Olli
First of all, thanks again for your detailed explanations, wrobel! Great!
Another possibility: The pump (I only replaced the controller; the actual pump is still the “old” one) may no longer achieve its maximum circulation, causing the water at the roof to get hotter than with stronger circulation, is that correct?
wrobel schrieb:Good tip! I’ll check that.
The question is why the collector pump is already switching off at this time of year? I suspect the maximum storage temperature is only set to 60°C (140°F).
wrobel schrieb:Is there a way for a layperson like me to tell if a domestic hot water mixing valve is installed?
You can easily set the max temperature to 85°C (185°F). Provided a domestic hot water mixing valve is installed. Otherwise, make sure to retrofit one.
Another possibility: The pump (I only replaced the controller; the actual pump is still the “old” one) may no longer achieve its maximum circulation, causing the water at the roof to get hotter than with stronger circulation, is that correct?
Premature celebration...
I suspect there are air bubbles in the system again, but it seems to work intermittently; sometimes the supply line at the pump station heats up, sometimes it does not (the pump is always correctly controlled and running!).
I fear there is a physical issue that hasn’t been addressed yet:
The builder routed both pipes through the second, unused flue of the chimney from the basement boiler room to the attic.
So far so good, then the pipes run up along a rafter to the ridge, and on the other side of the roof they go down about halfway and then outside to the collector.
Usually, the collector is supposed to be the highest point in a solar thermal system, but in our case, the highest point is within the pipes—the collector is about 2.5–3m (8–10 feet) lower!
I’m concerned that air might be getting trapped at this highest point. Do you have any experience with a similar setup? Should we consider rerouting the pipes?
I suspect there are air bubbles in the system again, but it seems to work intermittently; sometimes the supply line at the pump station heats up, sometimes it does not (the pump is always correctly controlled and running!).
I fear there is a physical issue that hasn’t been addressed yet:
The builder routed both pipes through the second, unused flue of the chimney from the basement boiler room to the attic.
So far so good, then the pipes run up along a rafter to the ridge, and on the other side of the roof they go down about halfway and then outside to the collector.
Usually, the collector is supposed to be the highest point in a solar thermal system, but in our case, the highest point is within the pipes—the collector is about 2.5–3m (8–10 feet) lower!
I’m concerned that air might be getting trapped at this highest point. Do you have any experience with a similar setup? Should we consider rerouting the pipes?
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