Large drainback solar hot water project

[ESharp]

One issue I’m working through at the moment is getting reliable readings from the temperature sensors. As soon as I plug in a fourth sensor, I stop getting readings from all of them. I’ve done a bit of googling and I apparently chose the least recommended configuration for longer wire runs with multiple One Wire sensors, the star, or hub. This is when each sensor is on it’s own wire and they all connect back to the one spot next to the arduino. For larger networks of sensors a daisy-chain configuration is recommended.

Guidelines for Reliable Long Line 1-Wire Networks - Tutorial - Maxim

[osolemio]

ESharp, how is it going with your project, all these years later? Is it still working?

I am researching the drainback principle. Where I have built a few systems, most of every system is a closed system, with anti-freeze (glycol). They do normally NOT drain back.

I am working on combining various technologies, to take solar thermal to a new level of both efficiency, simplicity as well as reliability (and less maintenance)

[solarhotairpanels]

Stag temps can go over 180... keep an eye on it.
You may have to run 3/4 copper for a few feet coming off the collector then back to Pex

[solarhotairpanels]

How's everything in Hong Kong? Hope you and your family are staying healthy.

Did you build a solar hot water drainback system? If so how'd you make out with it?

[osolemio]

Originally Posted by solarhotairpanels

Stag temps can go over 180... keep an eye on it.
You may have to run 3/4 copper for a few feet coming off the collector then back to Pex

I didn't get to it yet. Well, I have started sourcing parts, but an ongoing pandemic has slowed things down a bit, to put it mildly. Also, starting a company in HK is a longwinded process. Just getting a business account (not even with a credit, just a savings account), takes months.

About the temperature, I am not using PEX or any other plastics in the primary circuit. I would only use PEX for underfloor heating and some heat storages, where I can control the temperature. All primary circuits are copper or brass mainly. Trying to stay away from iron and steel.

The drainback will be a closed system, understood as in - the air in the system will normally not vent. If it's an open system (the air can enter and exit), then the air (and then water) will have oxygen added to it. This is not good in the long run, with regard to corrosion and such. So it will all stay in tanks, some of them with partly air in them.

[solarhotairpanels]

Ok, sounds good and good luck with your new business.

Try to stick with 3/4 pipe because the water will drain back much faster with the larger diameter.

Haven't had any air issues corroding my pipes. System has been functioning now since 2010. System can be flushed with vinegar using a sump pump submerged in 5 gal bucket.

Similar to tankless water heaters your system should be flushed at least once per year to remove rusty water and contaminants. Red hot water passing thru copper creates rusty water.

When building your piping install flush kits. All a flush hit is is a water valve with a shut off allowing you to connect a garden hose to the flush valve. You want to install 2 flush valves total. One on the outbound pipe leading TO collector, one on the return pipe FROM collector.

How to flush solar hot water drainback collector system:
Drain system
Dump 3 gallons of vinegar into 5 gallon bucket
Put sump pump into bucket
Connect a garden type hose from sump pump to pipe (flush valve) that goes out to collector
Connect another hose from collector (flush valve) return pipe back to 5 gal bucket
Turn on sump pump and pump vinegar thru system for 30 minutes
Dump bucket and replenish with fresh water
Run the pump again with the fresh water in bucket to flush out remaining rusty contaminated water

All done!

Take care and don't forget to post pictures back in here of your system especially whatever your plans are for the parabolic setup. Like to see that.

[osolemio]

Originally Posted by solarhotairpanels

Ok, sounds good and good luck with your new business.

Try to stick with 3/4 pipe because the water will drain back much faster with the larger diameter.

Haven't had any air issues corroding my pipes. System has been functioning now since 2010. System can be flushed with vinegar using a sump pump submerged in 5 gal bucket.

Similar to tankless water heaters your system should be flushed at least once per year to remove rusty water and contaminants. Red hot water passing thru copper creates rusty water.

When building your piping install flush kits. All a flush hit is is a water valve with a shut off allowing you to connect a garden hose to the flush valve. You want to install 2 flush valves total. One on the outbound pipe leading TO collector, one on the return pipe FROM collector.

How to flush solar hot water drainback collector system:
Drain system
Dump 3 gallons of vinegar into 5 gallon bucket
Put sump pump into bucket
Connect a garden type hose from sump pump to pipe (flush valve) that goes out to collector
Connect another hose from collector (flush valve) return pipe back to 5 gal bucket
Turn on sump pump and pump vinegar thru system for 30 minutes
Dump bucket and replenish with fresh water
Run the pump again with the fresh water in bucket to flush out remaining rusty contaminated water

All done!

Take care and don't forget to post pictures back in here of your system especially whatever your plans are for the parabolic setup. Like to see that.

3/4" is my favorite for most work, so I agree. The trick is some times valves, flow meters and such.

There won't be any "rusty water" here, and that is because my systems will be closed. With no oxygen added, no corrosion is going on. Having an open vent is easier, but I just don't want the air to be added. Your system has lasted 10 years so far, but then you flush it with vinegar, and replace the water I presume. I won't need to.

And yes, there will be plenty of valves. Not just a few, but I need a lot of valves and places to connect, mainly as I am experimenting. I need to be able to shut off parts of the system. I will also be using conical connections, so I can change the design as needed, without throwing out a lot of pipe and other parts. As much as I love press, it doesn't have an "edit" or "undo" function.

[osolemio]

Originally Posted by solarhotairpanels

Ok, sounds good and good luck with your new business.

Try to stick with 3/4 pipe because the water will drain back much faster with the larger diameter.

Haven't had any air issues corroding my pipes. System has been functioning now since 2010. System can be flushed with vinegar using a sump pump submerged in 5 gal bucket.

Similar to tankless water heaters your system should be flushed at least once per year to remove rusty water and contaminants. Red hot water passing thru copper creates rusty water.

When building your piping install flush kits. All a flush hit is is a water valve with a shut off allowing you to connect a garden hose to the flush valve. You want to install 2 flush valves total. One on the outbound pipe leading TO collector, one on the return pipe FROM collector.

How to flush solar hot water drainback collector system:
Drain system
Dump 3 gallons of vinegar into 5 gallon bucket
Put sump pump into bucket
Connect a garden type hose from sump pump to pipe (flush valve) that goes out to collector
Connect another hose from collector (flush valve) return pipe back to 5 gal bucket
Turn on sump pump and pump vinegar thru system for 30 minutes
Dump bucket and replenish with fresh water
Run the pump again with the fresh water in bucket to flush out remaining rusty contaminated water

All done!

Take care and don't forget to post pictures back in here of your system especially whatever your plans are for the parabolic setup. Like to see that.

Update here is that I am still working on it. Not many pictures to show just yet.

Right now, part of the focus is on installing ducting in the house, and the pipes for hot water. Since there are 3 floors and rooftop, and all hot water comes from local electric instant water heaters, we need to route the pipes also (for hot water).

The A/C ducting will be built by isolation board (like styrofoam), with wooden on top of it (I think 3/8 inch). I won't even paint the wood, it will be a visible feature of the house. Which is not a bad thing, as the house will be some kind of proof of concept anyway.

Sourcing parts is not easy. We buy from various places, either local shops or online. For several challenges, there are so many ways to do it, and so many products, that the decision becomes hard by simply having to pick parts/methods! Here is an example:

The ducting will have variable control to dampen the flow to rooms where conditioned air is not needed. Also, bathrooms and the kitchen fan will have fans replaced by valves. Sensors of temperature, humidity, CO2 level and more will modulate inlet or outflow valves.

Initially, we were looking at which motor controlled valves we would use inside the ducting. Now we decided to combine louvre registers and valves. This means it will be much cheaper, and also simpler to build and maintain. Those louvres with servo modulation costs around 25-30 USD including register, motor and all. And they are silent (the ducting valves were surprisingly noisy, probably from the gear box).

CO2 sensors will help detect occupancy, and thus guide air where it's needed the most. Humidity will be used especially in bathrooms and the kitchen. And we are working on a solution where one or more sensors will detect foul air, to ensure bathrooms are vented as needed, also when it's not from humid shower air (!!!).

It will all be automatic, comfort, clean air and hot water year round.

And there is much more. Dishwasher will be installed, and it will use hot (solar) water. The same for laundry, it will be switched to dual cold/hot. It will all save lots of energy. And to ensure minimal water waste, a return pump will run in certain cases to ensure hot water is available throughout without having to let the water run for a while to become hot.