ᐅ Is the operation of solar thermal systems with heating support correct?
Created on: 12 Sep 2019 18:27
S
ShawN46Hello everyone,
I am currently using the following system:
- Viessmann Vitodens 200 gas condensing wall-mounted boiler 19 kW
- Austria Email KWS 800 combined stratified storage tank
- Solar flat-plate collectors 9.36 m² (101 ft²)
- ESR 31 solar controller
- Delphis solar station FV 70 (with Grundfos circulation pump)
According to my heating technician, this system is set up for heating support (before we discuss whether this makes sense—the system was already installed when we bought the house, all installed at the end of 2015!)
In summer, I switched the Viessmann condensing boiler to domestic hot water only, which, as far as I can tell, worked well. (Gas consumption was below 1 m³ (35 ft³) natural gas from mid-June to early September.)
At the end of last week, the weather turned cooler, so I gave in to my family’s demands and switched back to heating plus hot water.;)
Now I am a bit puzzled about how it operates:
I set a target temperature of 22°C (72°F), and today the outside temperature was 21°C (70°F) (see image 1!).
The heating curve is set to 0.8 (see image 2!), which should produce a flow temperature of 45°C (113°F) at an outside temperature of about -5°C (23°F).
Under exactly these conditions, which were present today, the flow temperature at the pump station was indeed 45°C (113°F)! (see image 3!) 😳
Of course, no circulation was taking place (supply and return temperatures were nearly the same), and the pipes just above the pump station certainly never reached 45°C (max. about 30°C (86°F) by touch, in my estimate).
So why is the heating circuit temperature being pushed so high? Is this normal and correct operation?
At that time, the temperature coming from the roof was about 57°C (135°F), and the circulation pump for the solar system was running; the temperature in the lower part of the storage tank was just above 48°C (118°F). (In summer, with domestic hot water only and plenty of sun, the tank temperature sometimes exceeded 70°C (158°F), which lasted quite a while despite heavy and frequent use for paddling pools and the kids’ water slide in the garden...)
Before I forget to mention: During renovation, we switched to a dry underfloor heating (UFH) system from Roth (previously normal radiators). From my layman’s point of view, solar thermal heating support should make more sense with the lower flow temperatures of an underfloor heating system than with classic radiators and correspondingly higher flow temps, right?
Problem 1: The original installer of the system is very hard to reach, as they are now insolvent and difficult to understand...
Problem 2: My heating technician has to figure out a system he did not install, which apparently is unusual (the heating support is connected on the flow side but should actually be on the return or vice versa—something was definitely odd, he said... but apparently it works fine.)
I realize I will have to consult with my heating technician at some point, but I am hoping someone here can shed some light on my confusion...
Thanks in advance for your help!
Best regards
I am currently using the following system:
- Viessmann Vitodens 200 gas condensing wall-mounted boiler 19 kW
- Austria Email KWS 800 combined stratified storage tank
- Solar flat-plate collectors 9.36 m² (101 ft²)
- ESR 31 solar controller
- Delphis solar station FV 70 (with Grundfos circulation pump)
According to my heating technician, this system is set up for heating support (before we discuss whether this makes sense—the system was already installed when we bought the house, all installed at the end of 2015!)
In summer, I switched the Viessmann condensing boiler to domestic hot water only, which, as far as I can tell, worked well. (Gas consumption was below 1 m³ (35 ft³) natural gas from mid-June to early September.)
At the end of last week, the weather turned cooler, so I gave in to my family’s demands and switched back to heating plus hot water.;)
Now I am a bit puzzled about how it operates:
I set a target temperature of 22°C (72°F), and today the outside temperature was 21°C (70°F) (see image 1!).
The heating curve is set to 0.8 (see image 2!), which should produce a flow temperature of 45°C (113°F) at an outside temperature of about -5°C (23°F).
Under exactly these conditions, which were present today, the flow temperature at the pump station was indeed 45°C (113°F)! (see image 3!) 😳
Of course, no circulation was taking place (supply and return temperatures were nearly the same), and the pipes just above the pump station certainly never reached 45°C (max. about 30°C (86°F) by touch, in my estimate).
So why is the heating circuit temperature being pushed so high? Is this normal and correct operation?
At that time, the temperature coming from the roof was about 57°C (135°F), and the circulation pump for the solar system was running; the temperature in the lower part of the storage tank was just above 48°C (118°F). (In summer, with domestic hot water only and plenty of sun, the tank temperature sometimes exceeded 70°C (158°F), which lasted quite a while despite heavy and frequent use for paddling pools and the kids’ water slide in the garden...)
Before I forget to mention: During renovation, we switched to a dry underfloor heating (UFH) system from Roth (previously normal radiators). From my layman’s point of view, solar thermal heating support should make more sense with the lower flow temperatures of an underfloor heating system than with classic radiators and correspondingly higher flow temps, right?
Problem 1: The original installer of the system is very hard to reach, as they are now insolvent and difficult to understand...
Problem 2: My heating technician has to figure out a system he did not install, which apparently is unusual (the heating support is connected on the flow side but should actually be on the return or vice versa—something was definitely odd, he said... but apparently it works fine.)
I realize I will have to consult with my heating technician at some point, but I am hoping someone here can shed some light on my confusion...
Thanks in advance for your help!
Best regards
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