PV pumped Hydronic Solar Hot Water

[sundug]

This Photovoltaic (PV) pumped hot water system has been working well, with no maintenance, for years on my house. I am now well past the point where the money I invested in the solar water heater equals the money I would have spent on electricity to heat water. Most of the year, we have more free hot water than we can use. Consider the fact that in the next five to eight years you are going to pay the cost of a solar water heater, whether you buy one or not. I kept costs down by doing all of the work myself, and buying a used collector panel, but still created a long lasting, efficient, high quality system.

I started by looking in the yellow pages under "Solar", and found a plumber in the nearest large city, with spare collector panels. I bought a 3`x13` aluminum collector with copper tubing and tempered glass cover for $100, guaranteed not to leak, but I tested it first, anyway. Assuming the collector needs to be freeze protected, a non-toxic antifreeze, usually propylene glycol, is pumped through the collector, to the heat exchanger tank.
https://www.builditsolar.com/Projects/WaterHeating/DougsSolarWater.htm

 

[SolarRich]

Wow! that's great!. You had the SS tank made by someone? That's a good solution. How did you insulate it?

 

[sundug]

Wow! that's great!. You had the SS tank made by someone? That's a good solution. How did you insulate it?

Yes, I had a local metal worker I know make the tank and I made the coil to go inside of it. I wrapped it in several layers of Reflectix insulation and then several layers of fiberglass insulation.

 

[Charleswgibbs]

I'm curious about the cold weather usability of these systems. I know you can circulate glycol to stop freezing at night, but then aren't you basically radiating away heat from the tank all night?

 

[sundug]

I'm curious about the cold weather usability of these systems. I know you can circulate glycol to stop freezing at night, but then aren't you basically radiating away heat from the tank all night?

No, there is a check valve to eliminate that

 

[Charleswgibbs]

But then aren't you at risk of freezing every night during winter if you aren't actively pumping heat into them?

 

[sundug]

But then aren't you at risk of freezing every night during winter if you aren't actively pumping heat into them?

No chance of freezing there's a propylene glycol and distilled water mix in the loop.The check valve just prevents thermal siphoning at night.

 

[Supervstech]

PG can handle some fairly cold weather, unless you live in Alaska or the northern Midwest, PG is freeze proof pretty much.

 

[sundug]

I

PG can handle some fairly cold weather, unless you live in Alaska or the northern Midwest, PG is freeze proof pretty much.

I'm in middle TN. 60/40 water /PG mix. Been in place since 1990.

 

[RV10flyer]

I’m planning on using 100 or 150 gal aluminum diesel fuel tanks. That’s a 2024 project.

 

[sundug]

I’m planning on using 100 or 150 gal aluminum diesel fuel tanks. That’s a 2024 project.

Be aware of galvanic corrosion- https://www.appmfg.com/blog/the-intro-guide-to-dissimilar-metals

 

[RV10flyer]

Be aware of galvanic corrosion- https://www.appmfg.com/blog/the-intro-guide-to-dissimilar-metals

We braze alum to copper on our HVAC coils. I had planned on having a drain back system. Non-pressurized. A copper coil lying in the tank horizontal with a lid on hinges that opens. This would preheat the water before it goes into my 80 gallon standard resistance heat water heater. So I’m not really planning on attaching any copper to aluminum. No PG needed either for a drain beck system in Kentucky.

 

[Supervstech]

We braze alum to copper on our HVAC coils.

Who does? I’ve NEVER seen aluminum brazed to copper…

 

[RV10flyer]

I have many repaired aluminum coils in the field. I sell Am Std. I repair Micro channels too. Many of my leaks are at or near the factory copper to aluminum joints. Sure beats a $2500 coil changeout.

 

[RV10flyer]

Another option.

 

[Charleswgibbs]

No chance of freezing there's a propylene glycol and distilled water mix in the loop.The check valve just prevents thermal siphoning at night.

I feel stupid! I was thinking the actual usable water got pumped up into the collectors to be heated, now I realize it stays in your tank and only the PG/water mix gets pumped up to gather heat.

I appreciate the explanation!

 

[Rain]

I

I'm in middle TN. 60/40 water /PG mix. Been in place since 1990.

Please clarify the 60/40 water/PG mix. I bought CryoTek 100 to refill our hydronic system. The product is 55% PG. Did you add water to a commercial PG mix, or mix pure PG with water to 60/40? I am considering diluting the CryoTek because our system requires 14 gallons and the Cost of the Cryotek is $40 a gallon. We live in the Arkansas Ozarks with generally mild winters. However, the system just failed after a few days in December with temps down to zero Fahrenheit. The community building is used intermittently so no one witnessed what happened. The system components are from 2001, we've been limping along since 2014 when the installer died taking all the information with him. A new internal heat exchanger water tank was added in 2018, but the panels and Elsid pumps are all from 2001. My guess is a vapor lock formed outside near the panels and when the sun started shining the panels boiled. The pressure relief valve on the panels blew out. The glycol left in the system is brown and full of sediment, oily looking but not smelling bad. Any assistance is very much appreciated.

 

[sundug]

Yes, it sounds like your glycol got overheated. It needs to be drained, the system cleaned and flushed and new glycol added. You can order a propylene glycol antifreeze tester online and that will tell you what it will stay liquid down to. Dilute with distilled water according to the manufacturer's recommendations for your climate.

 

[Rain]

Thanks for your reply. This is a twenty year old DIY system, what manufacturer would recommend the dilution ratio? The panel manufacturer or the pump manufacturer?

 

[sundug]

Thanks for your reply. This is a twenty year old DIY system, what manufacturer would recommend the dilution ratio? The panel manufacturer or the pump manufacturer?

The propylene glycol manufacturer