Solar water heating system

[Iuval Clejan]

I'd like to pump water from my cistern 12 ft up to the roof, where it will go through a black garden hose and be heated by the sun for about 100 or more feet. Then it will be let into an insulated (even from the sun) holding tank on the roof (gravity fed from there to a shower in the house), where a sensor, comparator and relay will turn the pump on if the water (or maybe air if it's too expensive to get a water probe) temp is higher than about 85C, and turn it off if it's lower than about 83C. For now I don't need a float valve to turn the pump off once tank fills up, I can do it manually once I see it leaking off the roof (and back into cistern through gutter and downspout). I am asking for recommendations on thermocouple (or should I get a thermistor?), pump (DC or AC? Lowest cost, sufficient lift, lowest power needed), relay (DC input from comparator, DC output from batteries, or AC output from inverter?), and comparator (and associated pots for empirical setting of on/off temps).

 

[Delta Prime]

So you desire a relay to turn on a water pump when the temperature of the water in you're holding tank is 85 degrees Celsius or 185 degrees Fahrenheit . (My mistake gravity fed to the shower.)
Get yourself a meat thermometer!
Have you ever seen 3rd degree burns?
At 55.5 degrees Celsius or 150 degree Fahrenheit water takes 2 seconds for the skin to acquire a third degree burn.
You must hate your family members....

I'd like to pump water from my cistern 12 ft up to the roof, where it will go through a black garden hose and be heated by the sun for about 100 or more feet

I would help you but I only work with red garden hoses.... Because the ID or inside diameter will magically conform to the amount of pressure needed for the job.

Solar pump for off grid home. Dedicated battery system?

Building off grid. Is there a solar pump kit with its own battery back up? 3 bed 3 bath home if that helps.

diysolarforum.com

 

[Bluejets]

The way everyday systems work is, there is a holding tank usually around 250 litres on the ground.
Tank has a sensor to tell water temp within.
Roof collector has a sensor to tell when temp up there exceeds that of the ground reserve tank.
When it does, a diaphragm type pump cuts in controlled via the differential temp circuit board and transfers the lower temp water to the collector above and hence the higher temp water down below.
Reserve tank can have it's own heating element for grid whenever rainy days if so required.
Naturally there is an automatic mixing valve on the lower tank feeding the outlet to the house to limit tank out temp (normally around 55 degrees C I believe)
Reserve tank must have pressure/temp relief valves fitted as well.
Normally all the above is a certified piece of gear installed by a licenced plumber.

 

[Delta Prime]

Circulator pump...
It's open loop system

 

[Bluejets]

The system you show is a "heat exchanger" type.
I referred to a storage unit, reason being the guts gets corroded out of "copper" heat exchangers here in most parts of Aus. in very short time.(maybe 3 months)
Never-the-less, what you show is obviously a "closed loop" on the solar heating.......no idea where you get the open loop idea from.

 

[Iuval Clejan]

So you desire a relay to turn on a water pump when the temperature of the water in you're holding tank is 85 degrees Celsius or 185 degrees Fahrenheit . (My mistake gravity fed to the shower.)
Get yourself a meat thermometer!
Have you ever seen 3rd degree burns?
At 55.5 degrees Celsius or 150 degree Fahrenheit water takes 2 seconds for the skin to acquire a third degree burn.
You must hate your family members....

I would help you but I only work with red garden hoses.... Because the ID or inside diameter will magically conform to the amount of pressure needed for the job.

Solar pump for off grid home. Dedicated battery system?

Building off grid. Is there a solar pump kit with its own battery back up? 3 bed 3 bath home if that helps.

diysolarforum.com

OK, that was a bad estimate. I'll get it as warm as I can without burning, and then mix in cold water if it's still too hot for a shower.

 

[Iuval Clejan]

The way everyday systems work is, there is a holding tank usually around 250 litres on the ground.
Tank has a sensor to tell water temp within.
Roof collector has a sensor to tell when temp up there exceeds that of the ground reserve tank.
When it does, a diaphragm type pump cuts in controlled via the differential temp circuit board and transfers the lower temp water to the collector above and hence the higher temp water down below.
Reserve tank can have it's own heating element for grid whenever rainy days if so required.
Naturally there is an automatic mixing valve on the lower tank feeding the outlet to the house to limit tank out temp (normally around 55 degrees C I believe)
Reserve tank must have pressure/temp relief valves fitted as well.
Normally all the above is a certified piece of gear installed by a licenced plumber.

I don't need 250 liters, and I want to try out the design I mentioned, which should be cheap, no need for high pressure gizmos. The tank on the roof is not pressurized. As Delta Prime said, my temperature estimate was too high, I'll bring it down, but I don't care about the exact temp, it will be whatever feels warm enough. I just need advice on the electronics and the pump. Can I get a ready made circuit that will turn on a relay at whatever I set the temp to, with some hystersesis? Otherwise I could just build it out of the parts I mentioned, but I was hoping for some more specific advice. Apparently thermocouples need a constant reference temp, which I don't have.

 

[Delta Prime]

To the thread starter!
There are many solar water heating systems.
Heat exchanger terminology is used by the Layman or Laywoman or anything between for generalities.
The previously posted diagram was taken at random from Google. But it's distinctive to me as a (DCS).
A (DCS) Direct Circulating System It circulates water from the water storage tank through one or more collectors and back into the tank. The solar collector is the main component of the solar system. A metal box with insulation and a black absorber plate that collects solar radiation and heats the water. The circulating pump is regulated by either an electronic controller, a common appliance timer, or a photovoltaic (PV) panel.

 

[Delta Prime]

I know you want it to be as inexpensive as possible but I need to know the diameter of yours garden hose
And your photovoltaic system.

 

[Iuval Clejan]

I know you want it to be as inexpensive as possible but I need to know the diameter of yours garden hose
And your photovoltaic system.

I was going to use a 1/2 or 5/8 inch diameter hose and my system is a 12V system with 3 200 W panels and I have a 740AH battery bank. But I need info about how to hook up the electronics, and what pump to get. Apparently thermocouples are more complicated than I thought, needing a reference junction and if that's not at a constant temp, they need circuitry to compensate for it. And thermistors don't have a probe I can put in water.

 

[Delta Prime]

Excellent! thank you for the information the data. If you can think of anything else pre-existing that is a part of your solar system it'd be most helpful.I'll be back..