I'm interested in installing a solar hot water system in my home. Unsure of what to do/what system to go with. I'd ideally like to go with something made here in the states. The most likely system I've found is by Solar Heat Exchange Manufacturing. Anyone know anything about the Simple Drainback System? I think a closed-loop drainback system might be the way to go... freeze protected, so as no worrying about a messy glycol system. Any ideas? Thanks, J

Jerome-

To get intelligent feedback, you should probably specifiy the approximate location for the house, since there are different solutions for south Florida versus Minnosota.

Drainback systems have at least two potential limitations: (1) if you are in a freezing climate, a one-time failure of the drainback system can lead to ruptured, worthless panels, and (2) problems with the system overheating during stagnation conditions could result if the system drained after the storage tank reached maximum temperatures.

I don't find glycol systems to be particularly messy in my cars or my solar thermal system. In fact, compared to replacing freeze plugs in a V-8 from using water instead of a glycol-water mix, I have become a firm believer in the chemical properties of a good antifreeze, anti-corrosion solution.

Lee

http://www.solarroofs.com/

I have not tried them, but people I know have with success.

If you have a system that requires "help" in draining back, or might fail in draining back, then it is not a drainback system. Copper pipe, water, and air can easily be made into a system that won't fail to drain back - it only takes a clear path and some slope. Duh.

I'll save the lecture on the requirements of glycol systems for later, especially the part about stagnation in sunny climates.

Jeff

... and temperature sensors that never fail at the wrong time.

I live in the Hudson Valley area of New York State (near West Point) and have a drainback system. I am using the Sunmaxx evacuated tubes. I have been through two winters (this is the third) and have not had a single problem with freezing. There is no anti-freeze in my system.

Tell us about your SunMaxx system. Do you run it all year and do you get anything from it when it is overcast and colder out?

Posted By Lee Dodge on 04 Jan 2011 01:16 PM
... and temperature sensors that never fail at the wrong time.

If the temperature sensor fails (no input), our system shuts down and the water drains. For the temperature sensor to fail AND adversely affect the system, it would suddenly have to read erroneously high AND it would need to be cold enough outside to freeze circulating water. Just my .02 BM

BM-

I am sure that drainback systems work fine almost all of the time. If considering a drainback system, which is Jerome's situation, then you need to consider the advantages, such a reduced cost due to no heat exchanger, no need to mess with glycol, etc. However, you should also consider the disadvantages, that include the possibility of freezing, even if that possibility is thought to be remote. A friend in San Antonio had a drainback system that froze due to some failure. Then he had an expensive piece of junk on his roof that he was trying to give away. Now San Antonio is not know for severe winters, but it does have very hard water that causes fairly rapid failures of many types of standard plumbing items, such as faucet seats, toilet valves, etc. I expect that the plumbing in solar hot water systems does not receive an exception when it comes to hard water problems messing up valves and piping in otherwise well-designed systems. In fact, I would think that drainback systems would build up hard water deposits even faster than if the water did not drain due to evaporation of water films on the inside of the plumbing leaving deposits behind. I was simply mentioning some things to consider in the selection of a solar hot water system, not condemning drainback systems. I gave thought to using a drainback system even though I was going to use antifreeze and a heat exchanger, just to reduce the possibility of freezing since I live in a cold climate now. The installer recommended against it.

Generally there is not a "correct" or "incorrect" choice, but rather one that appears better for a particular application.

Lee

Let me ask a couple of questions to be sure I'm on the same page here. I think of a drainback system as using water from a separate tank being pumped up and through collectors then down through a heat exchanger to transfer heat.  If that is true then wouldn't distilled water be used, and be  be free of minerals t that would buildup?
 If its a drain down system then it would be city water pumped through system with no heat exchanger.
 And doesn't both systems require a vacuum breaker to let the water drain properly? I had a draindown system in Colo, it worked great for a few years. Then one afternoon the vacuum breaker did not open. Not sure if it stuck from mineral buildup or froze just enough, bottom line, two very broken collectors.  So the system i'm using now? Proplene gylcol. Not as effecient, more murphy proof.

I have a 240 gallon drainback system with 5 panels that I use to heat my house (directly) and my hot water (indirectly) and my hot tub (indirectly). I've had it installed for a year. When the pump turns off, the water is in the tanks. When I turn the controller off, the water is in the tanks. When it's night, the water is in the tanks. Gravity is a great thing, and I don't have any valves or any vaccum breakers or any other machinery - just a pump. Barring a piping failure, or an earthquake that changes the topography of my house, I can't imagine what might cause my system to fail and my ppies to freeze.

Jeff

jbaron
   Are you are running an open system then? If so do you put anything in  to prevent the  water turning green?

I run my closed, heating system water through the panels, as my two storage tanks are plumbed as part of the heating system. When the storage tanks are hot enough, a separate differential controller runs water from the storage tanks through the lower coil of a solar DHW tank. Note that I run a closed heating system with air in it. (Hi Rob!)

Jeff

Posted By good58 on 05 Jan 2011 02:39 PM
I live in the Hudson Valley area of New York State (near West Point) and have a drainback system. I am using the Sunmaxx evacuated tubes. I have been through two winters (this is the third) and have not had a single problem with freezing. There is no anti-freeze in my system.

good58 - Have you had any problems with the Sunmaxx heat pipes sliding out of the manifold down into the tube? There does not appear to be anything retaining the heat pipe.

Hi,

I think you can install a split solar water heating system:

The split solar water heating is an active system, because it uses a pump with a controller to circulate the fluid between the heat pipe series solar collector and the storage tank, tank and solar collector are separate, while the collector is integrated in to the roof of the building, the tank and the pump station can installed anywhere of the building. The piping between the main components is made of brass and a special insulation with high temperature resistance for solar systems.

An Once Heat-exchange System is suit for climates where there is no risk of freezing. Recirculation freeze protection can be provided by the Recirculation feature in the controller. An Open Loop Water Heating System provides many advantages. It is the simplest and typically the least expensive active system to install. There is no heat exchanger, which allows efficient heat transfer directly to the water. The system operates at standard line pressure. It is simple to add capacity to the system if demand changes. The system integrates easily with existing systems.

The main components of Once heat-exchange split solar water heating:
1) Solar collector
2) Solar Workstation including:
Circulation pump,
Check valve,
intelligent solar controller with sensors
rass connector
3) Solar pressurized tank from 100L to 500L


Advantages of split solar water heating:
1) No disorder water tank on your roof
split solar water heating systems is using a high efficiency solar collector on your roof
and a high pressurized storage tank in the house. Integrated in to the roof of the building
perfectly.
2) The perfect solar collector for domestic hot water heating system can be combined with
existing energy source, such as your gas water heater, electric water heater, boiler, etc.
3) There have an auxiliary heating device--electric heater booster in the tank, so providing hot
water in case of cloudy or rainy days, you will no need to worry about it.
4) No water inside the tube, the system can still in service even with several tubes breakage.
5) Completely automatic.
6) Cut out your energy bills
Hot water heating (on average) accounts for 26% of your annual energy bill. With a solar water heater you could generate enough solar energy to heat 70% of your hot water,
FREE, year after year!

Having a solar hot water system has become more and more common in everyday households as home owners seek to find more sustainable living options and save money on expensive energy consumption.

With carbon tax set to be introduced, soaring fuel prices and rising electricity costs, many Australian families are looking for any means to save money and solar hot water is an obvious and beneficial move.

Since solar water heating has become more mainstream, it has also become more affordable. The constant innovation in technology has also made the systems more efficient, making now a great time to invest in a more sustainable future. Remember, every household can make a difference!

Solar Panels, BC Solar

http://www.greenbuildingtalk.com/Forums/tabid/53/afv/topicsview/aff/14/Default.aspx check out my thred in the general forum. I installed an 80gl system myself made by Sunpeak USA sold thru www.buysolarsystems.com

I am using the Sunmaxx evacuated tubes and it does what it says.

Can you be more specific?

Posted By Lee Dodge on 26 Jan 2011 07:31 PM
BM-

I am sure that drainback systems work fine almost all of the time. If considering a drainback system, which is Jerome's situation, then you need to consider the advantages, such a reduced cost due to no heat exchanger, no need to mess with glycol, etc. However, you should also consider the disadvantages, that include the possibility of freezing, even if that possibility is thought to be remote. A friend in San Antonio had a drainback system that froze due to some failure. Then he had an expensive piece of junk on his roof that he was trying to give away. Now San Antonio is not know for severe winters, but it does have very hard water that causes fairly rapid failures of many types of standard plumbing items, such as faucet seats, toilet valves, etc. I expect that the plumbing in solar hot water systems does not receive an exception when it comes to hard water problems messing up valves and piping in otherwise well-designed systems. In fact, I would think that drainback systems would build up hard water deposits even faster than if the water did not drain due to evaporation of water films on the inside of the plumbing leaving deposits behind. I was simply mentioning some things to consider in the selection of a solar hot water system, not condemning drainback systems. I gave thought to using a drainback system even though I was going to use antifreeze and a heat exchanger, just to reduce the possibility of freezing since I live in a cold climate now. The installer recommended against it.

Generally there is not a "correct" or "incorrect" choice, but rather one that appears better for a particular application.

Lee

Lee, I think you are confusing a "drainback" system with a "drain down system". A drainback system has a HX and is exactly the same as a pressurized system except for a small tank to take the volume of water needed to fill the panels and not starve the pump. A drainback system can have no air vents.

 A drain down system uses zone valves or solenoids, normally open, they will allow the potable water in the panels to drain down to a floor drain or somewhere else. When closed, potable water from the DHW tank goes up to the panels and is circulated directly to the tank. Very efficient but water is wasted (usually) and if the drain zone valve doesn't open freezing can occur. A draindown system should have an airvent on the roof to allow the mains water pressure to vent the air quickly.

Ha, didn't see the rest of the posts till after.

No Drainback system should get rid of the air at the top or have a vacuum breaker.