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Old 09-10-2008, 09:47 PM   #61 (permalink)
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For locations that don't freeze very often (or seasonal); I highly recommend it.

The primary improvement i would like to make is to add a recirculating pump on the solar portion only. That way I would have instant solar hot water, and the Bosch wouldn't get a cold charge every time I switch on a faucet. I'm guessing it would be about a wash on energy use due to less heating requirements, but would have enhanced creature comfort.

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Old 09-11-2008, 11:13 AM   #62 (permalink)
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It gets really cold here in nebraska...But it gets super hot in the summer so I think that if I had a drain valve that I could set up and clear it out for the winter and possibly disconnect it and bring it into the house in the winter it would still be worth doing.
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Old 04-09-2009, 08:40 PM   #63 (permalink)
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Still works GREAT!
I did have a pipe freeze on the roof this winter during a night that the weather man claimed would only get to 40f, but I woke up to no water on the hot side and a 29f thermometer, it was no problem I just turned on my solar bypass did my thing. The pipes all thawed out with no leaks.

I aimed the solar heater at its summer position today, I'm expecting that the tankless hot water heater will not have to work at all this summer.

As a waco note I've got a buddy who hates it when people say "hot water heater" because the water they are heating is cold, however I'm now officially allowed to say "hot water heater" around him because my tankless heats water that is already "hot" lol.
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Old 04-16-2009, 11:08 PM   #64 (permalink)
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drem'd how exactly does your system work? I tried to find a note about it in the thread but its kind of long.

Are you pumping the water to the roof heating it and bringing it down? Whats a much better setup us filling the pipes with anti-freeze and running that pipe outside the water as it comes in.

So a wide pipe that runs anti-freeze and then your water pipe flows through that.

Technique 2 is easier, but requires a rather large tank. Run the anti-freeze pipes into something akin to the coil on the back of your fridge and pump water into the tank.

The anti-freeze has a higher heat capacity than water, a lower freezing point, and more capable of energy transfer.

Also another thing the more coolant(anti-freeze) you have in the lines the more energy is stored. If you can get a separate insulated tank for the anti-freeze(a very small tank only a few gallons) you can store that extra heat overnight. With this system the best approach is to have the pump cut off overnight and have a pressure valve that doesn't open unless the pump is going(to keep from circulating the hot anti-freeze up to your roof and convecting it away).
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Old 04-17-2009, 02:54 PM   #65 (permalink)
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Quote:
Originally Posted by theunchosen View Post
drem'd how exactly does your system work? I tried to find a note about it in the thread but its kind of long.
The thread has gotten pretty darn long.

Fairly simple setup; Cold Water source(well) ->Batch heater(44 gallon tank in reflective box with doubble pane glass on top) -> tankless (heats the water from the solar heater up to desired thermostat temperature whenever the soar heater is unable to supply sufficient water temperature)-> House

Ideally I'd add a 4 way mixing valve so nobody burns themselves during the summer when the solar heater gets up in the 150+ range; but I just warn all of my house guest to be careful and it hasn't been an issue *yet*.

Currently my only "complication" is a valve I use to bypass the solar heater when it's freezing out.

Quote:
Originally Posted by theunchosen View Post
Are you pumping the water to the roof heating it and bringing it down?
No; everything operates in-line with my domestic water pressure being the only pump. KISS
Well; in a way I guess my well pumps the water up to the roof . . .

Quote:
Originally Posted by theunchosen View Post
Whats a much better setup us filling the pipes with anti-freeze and running that pipe outside the water as it comes in. So a wide pipe that runs anti-freeze and then your water pipe flows through that.
That would require a lot more parts and I wanted it as simple as possable. This way I have no thermostats, pumps, heat exchagers, toxic fluids, etc to cause issues.

If I would do a new/ different setup I'd go with a drain back pretty much exactly like this one The $1000 Soalr Water Heating System
What I actually want to do (eventually) is build a much larger version of that drain back system and use it as house heat + hot water . . ..


Quote:
Originally Posted by theunchosen View Post
Technique 2 is easier, but requires a rather large tank. Run the anti-freeze pipes into something akin to the coil on the back of your fridge and pump water into the tank.
I only see 1 tequnique above; I guess I'm just not following you.

Quote:
Originally Posted by theunchosen View Post
The anti-freeze has a higher heat capacity than water
False. I thought it was true until I got real technical with cooling on a road race Supra; most antifreezes reduce heat capacity/ mass by 10~20% per degree rise.

Quote:
Originally Posted by theunchosen View Post
, a lower freezing point,
True; but only an issue 5~7 nights a year at my location. If I lived someplace colder my setup would not be ideal . . . .

Quote:
Originally Posted by theunchosen View Post
and more capable of energy transfer.
False; Antifreeze reduces heat transfer. The only time that antifreeze will transfer more energy than pure water is when the hot surface being cooled by the water is exceeds the boiling point of water at the current pressure. (Basically water conducts heat VERY poorly as a gas; but VERY good as a liquid)


Quote:
Originally Posted by theunchosen View Post
Also another thing the more coolant(anti-freeze) you have in the lines the more energy is stored.
My batch heater holds 44 gallons (I *think* +-4 gallons). Bigger tank would be better, but this is typically sufficient. My big issue is that I have far to many feet of pipe from the 1 sunny spot on my roof back to my original hot water location.
Ideally that tank/ thermal mass would be in 1 lump with as few lines as posable (Pipes are difficult to insulate effectively and therefore loose more heat than anything).


Quote:
Originally Posted by theunchosen View Post
If you can get a separate insulated tank for the anti-freeze(a very small tank only a few gallons) you can store that extra heat overnight.
I can promise that you need more than just a few gallons to be useful for domestic hot water unless stored at very high temperature. Then there are a few drawbacks
1) more exotic materials for containment (must resist higher temps)
2) potentially more exotic storage medium Antifreeze is only good so high.
3) more insulation required to counter the higher delta between storage medium and ambient
4) naturally smaller solar window due to the higher temperature required which can be partially countered by solar trackers, but that adds cost and complexity.

Quote:
Originally Posted by theunchosen View Post
With this system the best approach is to have the pump cut off overnight
The best approach for a system like you are describing is a differential thermostat such as
SunEarth Differential Temp Control - Differential Temperature Controllers @ AltE


Quote:
Originally Posted by theunchosen View Post
and have a pressure valve that doesn't open unless the pump is going(to keep from circulating the hot anti-freeze up to your roof and convecting it away).
Why not shut off the pump? that eliminates the extra parts, and saves energy in not running the pump.


WOW that took almost an hour for a reply.

More questions are certainly welcome.
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Old 04-17-2009, 03:46 PM   #66 (permalink)
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. . .:madface:

Since you shot down my anti-freeze you should use a refrigerant. . .lol just kidding.

I really did not know that about anti-freeze. I'll have to go dig through some compressed liquid tables and find a better heat transistor.

Oh, method one was to have the anti-freeze pipes travel around the incoming water pipes to heat as it enters(before the tank) technique 2 is to put the coils in the tank. One of the only times you see type one over type 2 is when there is no convenient place for a tank to do the exchanging(or not tank at all). Thats the only time I've seen it done as a flow-thru pipe.

I was not sure if you had an additional pump to make sure the water made it to the roof or not. If you did the spring could just be gauged against the pressure of the incoming water and the pump and then just shut it off at night. Since you use one pump/diaphram whatever its just as easy to install a valve on the hotside of the solar unit(as it comes into the water heater).

I think the reason most systems use anti-freeze is for the dual purpose of avoiding freezing(I live in TN and it would freeze most nights from late october to now) and also if you had a much bigger array(more sun it sounds like in your case) you might want to go with anti-freeze to avoid it getting hot enough to increase the pressure on your lines. Anti-freeze won't get near its saturated point as soon and therefore it won't get close to the point where temperature heavily influences pressure.

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Old 04-17-2009, 04:07 PM   #67 (permalink)
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Quote:
Originally Posted by theunchosen View Post
. . .:madface:

Since you shot down my anti-freeze you should use a refrigerant. . .lol just kidding.

I really did not know that about anti-freeze. I'll have to go dig through some compressed liquid tables and find a better heat transistor.
Maybe heat pipes? I totally don't know. . . .

Quote:
Originally Posted by theunchosen View Post
Oh, method one was to have the anti-freeze pipes travel around the incoming water pipes to heat as it enters(before the tank)
Ah HA I've got it! But then you need sunshine when you have water demand; or is there another storage?

Quote:
Originally Posted by theunchosen View Post
technique 2 is to put the coils in the tank. One of the only times you see type one over type 2 is when there is no convenient place for a tank to do the exchanging(or not tank at all).
That's how I initially thought to do my system. Only reason I switched was the inherent efficiency of electric tankless heaters. (I know not 100% but bear with me) when used in my varying demand situation (Much of the time no one is home, much of the time it's just 2 people, and much of the time I have lots of house guest).

Quote:
Originally Posted by theunchosen View Post
I was not sure if you had an additional pump to make sure the water made it to the roof or not.
My house is all about KISS.
My car's on the other hand . . . .

Quote:
Originally Posted by theunchosen View Post
If you did the spring could just be gauged against the pressure of the incoming water and the pump and then just shut it off at night. Since you use one pump/diaphram whatever its just as easy to install a valve on the hotside of the solar unit(as it comes into the water heater).
I'm not following you; sorry maybe a flow diagram?

Quote:
Originally Posted by theunchosen View Post
I think the reason most systems use anti-freeze is for the dual purpose of avoiding freezing(I live in TN and it would freeze most nights from late october to now)
I totally hear you on the freezing; I've had a run in with it already and don't like it.

Quote:
Originally Posted by theunchosen View Post
and also if you had a much bigger array(more sun it sounds like in your case) you might want to go with anti-freeze to avoid it getting hot enough to increase the pressure on your lines.
Mine just relies on the collector tank being large enough to absorb the 16 hours of heat and loose enough at night so that it does not boil the following day less than ideal.

Quote:
Originally Posted by theunchosen View Post
Anti-freeze won't get near its saturated point as soon and therefore it won't get close to the point where temperature heavily influences pressure.
That's also a benefit to the drain back systems; they operate at virtually no pressure so no matter how hot the collector gets the pipes will not over pressurize.

Quote:
Originally Posted by theunchosen View Post
Kudos Dremd
Kudos 2 you as well for thinking out of the box.
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Old 04-17-2009, 04:11 PM   #68 (permalink)
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Technique 1. . .I'll get you a google sketchup image? Post back if you don't have it and I'll conver it to screenshots to get some views
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Old 04-17-2009, 04:14 PM   #69 (permalink)
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Quote:
Originally Posted by theunchosen View Post
Technique 1. . .I'll get you a google sketchup image? Post back if you don't have it and I'll conver it to screenshots to get some views
I *think* all I'm failing to understand is what the purpose of the spring/ valve is. Thermostat?
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Old 04-17-2009, 04:28 PM   #70 (permalink)
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Quote:
Originally Posted by dremd View Post
I *think* all I'm failing to understand is what the purpose of the spring/ valve is. Thermostat?
ooh, the spring-valve pressure valve or however you make that happen was for most cases that I have seen. Most systems usually have a second pump in the piping. For example the pump at my parent's house is not powerful enough to get the water up on top of the house in any timely manner so we would need a pump to get the water up there(of course then it comes back down and out the faucet with a little more pressure if the feed valve is closed(the native line to the water heater from your well)). In a system that requires an additional pump it is inconvenient to have to turn the pump off and then turn a valve to make sure it doesn't bleed out overnight. If the pressure valve only opens when the pressure is greater then just the weight of the water all you have to do to close the valve is cut off the pump with a timer everynight and it automatically seals off.

your system goes like this well->piping->pump->roof->solar collector->down->into water heater(holding tank)->through tankless heater(if hot enough no action->shower

My house would have to do this

well->piping->pump->second floor->secondary pump(to make it reach the roof)->solar collector->pressure valve(only opens if the pump is providing extra pressure)->same as your system from here.

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