I built this system 30 yrs ago in my garage it worked great no failures No issues saved me about 40$ a month im in Florida average water temp on a sunny day 143* f it's a great system
Very good explanation, thank you. I do have the quibble a bit with the fact that you said a heat exchanger is not needed and then later on added back a heat exchanger
Hi papa you are right everything overheat,and then u have a shock when the water reach the pannel even the glass pop in a drain back system. I tried them all thet all have a catch...Good luck
Great video. I have a system like this with a 2’ by 2’ by 4’ tall fiberglass drain back tank that needs to be replaced (30 years old both bulging and several slow seeps). I can not find anything to replace it with, any ideas?
Hi Dr. Ben, if I wanted to use a water only system for radiant floor heat of a 2000 square foot shop, 16foot ceiling, well insulated with cellulose, how large a system would I need to handle most of my heat needs? I live in southern Illinois. Or, are there some charts that a person can reference for such questions?
Hey Crew, I have a question about the collector panel, has anyone built a panel using a single tube 24" wide,48" long 1/2" thick, something similar to a baking pan with a copper facing soldered to it having a copper inlet on the bottom and an outlet tube on top, drain back system. this would eliminate all the tubing and allow 100% of the sun's energy to be directly transferred to a single collector plate to the water passing along the surface.
Very clear and easy to understand, thank you. Just one question, can evacuated tube panels be used on the roof in a drain back system like this? If the water drains out of the manifold on the roof and the suns still shining couldn't the manifold over heat and cause heat damage?
Yes one of many ways to heat water with solar power. I have an at point 13 gallon 120volt ac water heater which has power and temperature controls being run by my 700 watts worth of solar panels,60amp MPPT and one 100amp hr.12v battle born battery. I set the temperature to max and power setting to low which is 200 watts. By the time I get home from work on a sunny day the water temperature is 145 degrees which is enough hot water for two showers.
A few ten years later...Today, I see no issue with glycol in the same "drain-back" system. Either requires a temp shutdown...too high and/or too low, depending on your location. Just need a tank of appropriate size and proper set level and temperature control. In addition, flow can be controlled with a variable speed circulation pump, combined with a full shutdown valve. This process flow diagram only hints that direction, but very workable. It also does not cover the extra maintenance for cleaning and/or pre-filtering the water, if no glycol is used. Time for an update!
Apparently water is more efficient that glycol så you get more out of it on days that are less ideal. I have also thought about the water, you probably think of algae and such, my bet is that it will probably get killed by the high temperatures the panels will get up too on occasions.
Why not raise the hot water tank to just below the panels and have gravity fed hot water (and a float valve to refill) instead of the heat exchange, and a secondary boiler always involved? Some sort of temperature detecting diverter could route 160F water straight to the load?
This was the solar water heater used in military barracks in Florida in the ’40s. Trouble is, it is not scalable and can serve only one purpose, domestic hot water. Imagine a 2000 gallon tank (~17000 lbs) in the air feeding DHW, pool, and three heating zones.
If you don't use hot water during the day, the hot water tank still has to re-heat the stored water using conventional methods, even though your exchanger has plenty of stored heat. I'm not sure how many times the water in the tank would have to be reheated while we are gone typically 10hrs a day. I love the simplicity of this design. Maybe you can figure that out, unless you think the energy consumption for re-heating is negligible over 10 hrs?
You don't even need a separate tank for hot water. You just need a long enough stainless steel coiled tube inside, which starts at the bottom of the tank and winds it's way up to the top. This is called a "hot water buffer" rather than a conventional "water boiler". It also has the advantage that the tank does not need to be 60 C (whatever that is in F) all the time, and the hot water is always fresh. All you gotta do is make sure the top is always hot enough - depending on sizing, around 40 C (105 F) can be enough at the top. As for heating systems, whether it is underfloor, radiators or a combination, they can be extracted from various levels of this tank - directly. No heat exchanger needed, just use the same water for the heating system as there is in this tank (make sure there is enough air at the top). I would say it would be wise to make a vent at the top of the tank, leading into a non-pressurised air tank. This could be as simple as a good quality plastic bag (properly sealed). This ensures the air doesn't get aerated, which could cause (long term) corrosion issues in the system.
Simple explanation of what the difference between water heating system and water preheating system. Of course if you take something like 5000 gal tank the supply liquid temperature will be always lower so more of the solar energy gets absorbed, but then you need a gas or electric heater to do the rest of the job and while calculating the efficiency, i bed people doing the calculation, leave that out.
I would have the solar feed an exchanger in the storage tank. then feed water from the storage tank to the waterheater(or tankless). That way you get direct use of that big tank of "free" 160° water and not just a single pass through, plus your solar is still on a closed loop. The controller will have the same logic as your design, but you would need to add a reserve tank that when the pump kicks off, the panels will empty completely into.
I built this system 30 yrs ago in my garage it worked great no failures
No issues saved me about 40$ a month im in Florida average water temp on a sunny day 143* f it's a great system
This is a very good video, thank you for taking the time to explain so clearly how drain-back solar thermal systems work.
Brilliant! Thank you Dr, Ben, I have wondered about how to do this many times.
THANK YOU DR BEN, WATCHED SO MANY VIDEOS ON THE SUBJECT, I GOT MORE CONFUSED. ALHAMDULILLAH YOUR EXPLANATION IS CLEAR AND SIMPLE TO UNDERSTAND.
Great video! It answered a lot of my questions. You are an excellent teacher. Thank you for the lesson.
Great video, highly informative thanks for sharing
Thanks Ben, that flew by and I learned a lot.
Thank you for the video, you've been very helpful!
Thank you Dr. Ben for a nice explanation.
You are a great teacher.
Thanks.
Wow! That was extremely helpful. Thank you.
Very good explanation, thank you. I do have the quibble a bit with the fact that you said a heat exchanger is not needed and then later on added back a heat exchanger
thank you for sharing this, I would never know if I have not watch this video... now I can enjoy hot water more...
Excellent!
thanks for simple explanation of the drain back system.
Interesting and well explained.
excellent presentation .. Two other things that could be removed would be the fill and purge valves that are part of a closed loop system
How do you create the space in the tank to allow for drain back? Great post cheers
Hi papa you are right everything overheat,and then u have a shock when the water reach the pannel even the glass pop in a drain back system.
I tried them all thet all have a catch...Good luck
Thank you for that information...
Thank you so much..
Could we use drainback with U-tube collectors
Great video. I have a system like this with a 2’ by 2’ by 4’ tall fiberglass drain back tank that needs to be replaced (30 years old both bulging and several slow seeps). I can not find anything to replace it with, any ideas?
Hi Dr. Ben, if I wanted to use a water only system for radiant floor heat of a 2000 square foot shop, 16foot ceiling, well insulated with cellulose, how large a system would I need to handle most of my heat needs? I live in southern Illinois. Or, are there some charts that a person can reference for such questions?
Hey Crew,
I have a question about the collector panel, has anyone built a panel using a single tube 24" wide,48" long 1/2" thick, something similar to a baking pan with a copper facing soldered to it having a copper inlet on the bottom and an outlet tube on top, drain back system. this would eliminate all the tubing and allow 100% of the sun's energy to be directly transferred to a single collector plate to the water passing along the surface.
What type of panels do I use for an 80 gallon tank
Also where would I buy whole shabang
great content thanks
is ok to put another coil in my home water tank to get continue heat transfer from solar self drain tank
Very clear and easy to understand, thank you. Just one question, can evacuated tube panels be used on the roof in a drain back system like this? If the water drains out of the manifold on the roof and the suns still shining couldn't the manifold over heat and cause heat damage?
Anyone knows the answear?
@@killyblam3 the copper panels in the roof will bake in the Sun. They'll be extra hot and they won't last as long. How much less time? No one knows!
What type of pump will pump from basement to the roof and still drain back?
Yes one of many ways to heat water with solar power. I have an at point 13 gallon 120volt ac water heater which has power and temperature controls being run by my 700 watts worth of solar panels,60amp MPPT and one 100amp hr.12v battle born battery. I set the temperature to max and power setting to low which is 200 watts. By the time I get home from work on a sunny day the water temperature is 145 degrees which is enough hot water for two showers.
Absolutely legend
Got it thanks
Thank you , I have made small system and I have free hot water .😃
A few ten years later...Today, I see no issue with glycol in the same "drain-back" system. Either requires a temp shutdown...too high and/or too low, depending on your location. Just need a tank of appropriate size and proper set level and temperature control. In addition, flow can be controlled with a variable speed circulation pump, combined with a full shutdown valve. This process flow diagram only hints that direction, but very workable. It also does not cover the extra maintenance for cleaning and/or pre-filtering the water, if no glycol is used. Time for an update!
Apparently water is more efficient that glycol så you get more out of it on days that are less ideal. I have also thought about the water, you probably think of algae and such, my bet is that it will probably get killed by the high temperatures the panels will get up too on occasions.
How would this stop the panels or tunbes over heating and damaging them selves? It seems to me they would get super hot and cause problems.
When the water in the tank is over heat the circulation pump turns off.
It doesn't. The panels on the roof will get hotter than the other style system.
what about on winter(Frozen pipes)
No water in pipes, no cracks due to freezing
how do you stop pipes freezing when not in use
It's a pumped system, once the pump stops it drains down to empty.
Why not raise the hot water tank to just below the panels and have gravity fed hot water (and a float valve to refill) instead of the heat exchange, and a secondary boiler always involved? Some sort of temperature detecting diverter could route 160F water straight to the load?
Bump. I have the same question...
Probably because you wouldn't want to potentially consume water that went through such a system.
This was the solar water heater used in military barracks in Florida in the ’40s. Trouble is, it is not scalable and can serve only one purpose, domestic hot water. Imagine a 2000 gallon tank (~17000 lbs) in the air feeding DHW, pool, and three heating zones.
Nice....but what if the tempreture outside drops below 0° .....your panels will freeze
The water drains down via the temperature control to the pump well before it reaches zero so everything outside is empty and dry.
Where would an interceptor exist?
...all great so long as the tank is physically at a lower height than the panels.
If you don't use hot water during the day, the hot water tank still has to re-heat the stored water using conventional methods, even though your exchanger has plenty of stored heat. I'm not sure how many times the water in the tank would have to be reheated while we are gone typically 10hrs a day. I love the simplicity of this design. Maybe you can figure that out, unless you think the energy consumption for re-heating is negligible over 10 hrs?
You don't even need a separate tank for hot water. You just need a long enough stainless steel coiled tube inside, which starts at the bottom of the tank and winds it's way up to the top. This is called a "hot water buffer" rather than a conventional "water boiler". It also has the advantage that the tank does not need to be 60 C (whatever that is in F) all the time, and the hot water is always fresh. All you gotta do is make sure the top is always hot enough - depending on sizing, around 40 C (105 F) can be enough at the top.
As for heating systems, whether it is underfloor, radiators or a combination, they can be extracted from various levels of this tank - directly. No heat exchanger needed, just use the same water for the heating system as there is in this tank (make sure there is enough air at the top).
I would say it would be wise to make a vent at the top of the tank, leading into a non-pressurised air tank. This could be as simple as a good quality plastic bag (properly sealed). This ensures the air doesn't get aerated, which could cause (long term) corrosion issues in the system.
Simple explanation of what the difference between water heating system and water preheating system. Of course if you take something like 5000 gal tank the supply liquid temperature will be always lower so more of the solar energy gets absorbed, but then you need a gas or electric heater to do the rest of the job and while calculating the efficiency, i bed people doing the calculation, leave that out.
So when the pump turns off, water flows through the pump backwards? Is that a special type of pump to allow that, or is that normal pump behavior?
Most of the pumps allow backflow...
@@henryrollins9177 Thanks, good to know!
@@erictorbet8104 Your welcomed, sir.
Until it freezes in the winter
I would have the solar feed an exchanger in the storage tank. then feed water from the storage tank to the waterheater(or tankless). That way you get direct use of that big tank of "free" 160° water and not just a single pass through, plus your solar is still on a closed loop. The controller will have the same logic as your design, but you would need to add a reserve tank that when the pump kicks off, the panels will empty completely into.
Start watching at 2 minutes