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Master Of My Domain
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Discussion Starter · #1 ·
i love the concept of solar collectors heating water. i bet i spent two hours looking over your latest solar collector design, gary. hehe...i would love to build one someday soon. i priced march pumps. wow, they sure are pricey...and the controller units as well. i did glean some good info when shopping on ebay. some of those march pumps are made for transferring hot liquids and to be used as for homebrewing. i guess if i had a two week long period of cloudy weather, i could try cooking up a batch of homebrew, lol.

i wonder what the life would be on one of those pumps? i figure it would run probably 6 hours per day on average.

how effective do you think a thermosyphon design using an antifreeze would be? perhaps a dual coil system with potable water in one coil and antifreeze in another while still using a tank to exchange the heat.

how about insulating an old clawfoot bathtub? i have two of those i could use. i calculate the capacity at @ 80 gallons
 

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i love the concept of solar collectors heating water. i bet i spent two hours looking over your latest solar collector design, gary. hehe...i would love to build one someday soon. i priced march pumps. wow, they sure are pricey...and the controller units as well. i did glean some good info when shopping on ebay. some of those march pumps are made for transferring hot liquids and to be used as for homebrewing. i guess if i had a two week long period of cloudy weather, i could try cooking up a batch of homebrew, lol.

i wonder what the life would be on one of those pumps? i figure it would run probably 6 hours per day on average.

how effective do you think a thermosyphon design using an antifreeze would be? perhaps a dual coil system with potable water in one coil and antifreeze in another while still using a tank to exchange the heat.

how about insulating an old clawfoot bathtub? i have two of those i could use. i calculate the capacity at @ 80 gallons
Hi Meloc,
Did you see this page on my new pump?
http://www.builditsolar.com/Experimental/PEXColDHW/Pump.htm
It looks kind of rinky-dink, but the specs are very good, and its been doing well for all of a month now. If it actually met the 50K hour life they spec, it would last 23 years at 6 hours a day. At $50, even 10 years would be outstanding.

I think that some of the March pumps are good. I'd look for the brushless ones.
Some of the Grundfos or Taco pumps are pretty reasonable in price and available on ebay. Technically you would have to use a bronze or stainless case one since its an open system, but I've been running an iron Grundfos in another open system for 2 years now, and its doing OK.

I've thought about a thermosyphon design where the whole thing sits outside in a kind of lean-to against the south wall. I think this would work OK, and it would be simpler, but you do need to have the tank above the collector which gets a bit awkward to do.

Not sure about the tubs -- it might be better to sell them and make a tank with the proceeds -- I think they bring pretty good prices these days :) ??

My daughter in CA had their water tank go out a couple days ago. They thought they would get an estimate on going to solar water heating along with replacing the tank. The estimate came in at $8600!!

Gary
 

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Master Of My Domain
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Discussion Starter · #3 ·
i saw the info about the new pump after i made my post. lol, pretty awesome...and to think it is designed for computers!

i'm trying to do this on the super-cheap. :) i even thought of trying to make use of scavenged hydronic furnace controllers...somehow. i plan to talk my brother-in-law out of a sliding glass door he has. i figure that would get me started, even if i had to taylor the size of the collectors to fit the two windows i would salvage. i like the idea of copper, but my nephew has some surplus PEX. if the PEX is rated for hot water, i may try that. i have a roll or two of aluminum flashing and i have a good amount of aluminum siding type material salvaged from some type of wall panels. it is one piece about 4 feet wide and maybe 20 feet long. it would require lots of cutting, but oh well.

i am also thinking about how to design a system that could have both a heat exchange tank and a standard electric water heater tank working together. i fear not having adequate hot water during a cloudy spell of weather or during periods of heavy usage. there will eventually be that one early morning during a holiday where several folks need showers or there are lots of dishes to do as well as taking showers...or doing last minute laundry. i guess i am saying that eventually i would find myself in a spot where i couldn't wait for the sun.

i was thinking of a system where i had a temperature controlled valve that would switch between the solar tank and a hot water heater if the temp of the solar tank dropped too far and also a temperture controlled valve that would regulate a thermosyphon or seperately pumped loop to heat the hot water heater tank.
 

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That's a great looking pump Gary.

My kids have now had two homes with Pex tubing for the plumbing. I'm finding the down side to be that you cannot keep the hot water to a faucet hot without it continually running. As an example when doing dishes I wash a few then rinse in running water over my dish water to make it deeper for the larger items as I go. If there isn't continual rinsing the water in the line cools quickly and adds tepid water instead of hot upon the next items rinsed. A circulating pump would eliminate that but the lines would need insulated for certain so as not to loose heat.

BTW, their current home has Zurn brand of Pex and it gives an odor and taste to the water. At least something does and I blame the Pex for it. Their other home didn't use Zurn and didn't have the same problem.
 

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Gary, why 300 feet of pipe for the exchanger? Is it because it's not as efficient as copper or did you just want a big exchanger to hold more water?

That's a nice setup though. I can believe the price that your daughter was quoted. When I was doing all the research for my house solar heating system the quotes were outrages and couldn't compete even with the high price of propane. DIY is the way to go!
 

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Gary, why 300 feet of pipe for the exchanger? Is it because it's not as efficient as copper or did you just want a big exchanger to hold more water?

That's a nice setup though. I can believe the price that your daughter was quoted. When I was doing all the research for my house solar heating system the quotes were outrages and couldn't compete even with the high price of propane. DIY is the way to go!
Hi Kevin,
Its a lot because the plastic pipe is not as conductive as the copper. I think that less than 300 ft (maybe 200 ft) would be fine, but the stuff comes in 300 ft coils, so unless you have something you can use the extra 100 ft for it might as well go in the heat exchanger. One nice thing about 300 ft of 1 inch is that it holds about 12 gallons right in the pipe coil -- so most single hot water demands come right out of the water that has already been warmed up to tank temp in the coil -- a 100% efficient heat exchanger!

Hope your project is coming along OK.

Gary
 

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Unfortunetly I ran out of time to finish my outside work, busy fall with all the family commitments. I'm working on the inside stuff, tank, underfloor heat etc. etc. I'll have to finish the panels and trench in the spring once the ground thaws.
 

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Gary,

I've been considering building a system. I had a couple 50 gallon tanks to build a batch heater, but the problem problem I have is that shading from trees not on my property are making placement difficult. I can get full sun on the roof, but I'm thinking 800 lbs of water on the roof isn't a good idea.

This design looks like it could solve that problem. I am assuming a collector could be mounted on the roof without the weight issues. What I'm wondering is how does the efficiency compare to that of a batch heater?

Thanks,

Kendall
 

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Hi Kendall,
Yes, if you use the copper/aluminum version of the collector, it can go on the roof. I would not use the PEX/aluminum version on the roof, as the tilt angle won't be high enough to protect the PEX from overheating when the collector stagnates.

The system that I built is a drain back, which means that when the sun goes off the collector, and the pump is shut down, all the water in the collector drains back to the storage tank. This is how the freeze protection is provided. With this drain back arrangement, the pump must have enough startup head to pump from the water level in the tank to the level of the top of the collector -- for roof mounted systems this can be a ways, and it might be hard to find a suitable pump if the distance is large.

The copper/aluminum collector could also be operated as a closed loop system with antifreeze. With this kind of a system, the collector does not drain back, and there is no large startup head requirement for the pump. But, you would have to add a heat exchanger to transfer heat from the collector to the storage tank. This might be as simple as a coil of copper pipe immersed in the storage tank.

If this all seems like Greek, you might want to read the Home Power articles listed here in the Basics section:
http://www.builditsolar.com/Projects/WaterHeating/water_heating.htm
These articles are very good, and describe all the types of solar water heating systems in use -- they are very "hands-on" and build it oriented. Or, just ask more questions here.

Gary
 

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Gary,

How does this collectorsetup compare to a batch system? Which will provide more hot water? I may be able to set up a batch if I can find a spot away from the house, but this will require a lot of treching and insulating long lengths of pipe. Will this collector setup provide me with as much hot water going into my conventional heater? If not, can I get close with a longer coil in the tank?

Thanks,

Kendall
 

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Hi Kendall,
During the day when the sun is out, a batch setup and a collector setup with the same glazed area will be pretty close on how much they collect --they are both pretty efficient.

At night the batch heaters lose more heat because the storage tank loses heat out the glazing. This can be anything from not much of a problem at all for warm climates and in the summer, to quite a bit of drop for cooler climates.

Gary
 

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Gary, I'm building a system like yours with the collector and storage box ( but made the collector serpentine/copper). I'm trying to find a 140f snap switch so I can use a solar power source cutoff and skip theStecca diff. controller. 'Got any leads to where I can find one? Thanks!!!
 

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Gary, I'm building a system like yours with the collector and storage box ( but made the collector serpentine/copper). I'm trying to find a 140f snap switch so I can use a solar power source cutoff and skip theStecca diff. controller. 'Got any leads to where I can find one? Thanks!!!
Hi Frank,
I'd think about getting rid of the differential controller -- they do make the system more efficient. Because it senses both the collector temp and the tank temp, it can turn the pump on as soon as the collector gets above the tank temp. If the tank has gotten down to (say) 90F because of a couple cloudy days, than the controller will turn the pump on as soon as the collector gets above 90F -- this is more efficient than waiting until it gets up to some fixed temp like 140F.

But, if you want to give the snap switch a try, Grainger Supply ( www.grainger.com ) has them. I always have trouble finding them in their online catalog, but they are there for sure. Grainger technically only sells to businesses, but you can usually get your hardware to order for you.

Another possibility is that Home Depot sells a replacement snap switch style thermostat for their attic ventilation fans. These are adjustable from 80F up to 130F (or so) -- I think they are about $16.

You might take some pictures as you do the serpentine copper and post them or send them in. I agonized a long time over whether to do the riser/manifold thing or the serpentine thing -- it was kind of a coin flip for me. I'd like to hear how it works out. If you are doing a drain back system, be sure to slope the straight runs in the serpentine downward and level the bottom of the collector when you mount it.
My serpentine PEX/aluminum is draining back fine in our last few days of -20F nights. The high yesterday was -11F, and the collector still did well:
http://www.builditsolar.com/Experimental/PEXColDHW/Dec15Perf.htm

Gary
 

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Hey Gary, I found it! Grainger item number 2E365, model # 3l03-141. Page 3825. Open on rise 140f, close at 120f.
Now to see if I can get one...
Frank
 

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Gary, I'm building a system like yours with the collector and storage box ( but made the collector serpentine/copper). I'm trying to find a 140f snap switch so I can use a solar power source cutoff and skip theStecca diff. controller. 'Got any leads to where I can find one? Thanks!!!
Hi again,
I did not read your note the first time carefully enough.

If you can power the pump with PV and then use the snap switch to keep the storage tank from getting to hot, that should work fine. I think the differential controller does a little more efficient a job than the PV panel of controlling when the pump is on, but lots of people use the PV panel scheme and it works well.

If you are going to do the system as a drainback, then you would need enough PV panel and pump to get the pump to overcome the startup head requirement. Most of the PV driven systems use a closed loop setup that has no startup head requirement.

Gary
 

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Master Of My Domain
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Discussion Starter · #18 ·
how would someone fill a closed loop system and purge the air if they intend to use an antifreeze? i know my hydronic hot water heating system uses a check valve (i think it does) and you purge the air at the radiators. that is about all i know.
 

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how would someone fill a closed loop system and purge the air if they intend to use an antifreeze? i know my hydronic hot water heating system uses a check valve (i think it does) and you purge the air at the radiators. that is about all i know.
Hi Meloc,
I've never actually done this, but the way I understand it is that a bit downstream of the circulation pump you install either a check valve or a shutoff valve in the pump outlet pipe. Then you install a drain valve on either side of the check valve -- the drain valves should have garden hose style fittings.

With the shutoff valve closed and the two drain valves open, you use a separate fill pump to pump the antifreeze/water mix from a bucket into the most downstream the drain valve. A 2nd hose hooks up to the other drainvalve and goes to the bucket.

So, the fill pump pumps the antifreeze out of the bucket, through the system, and the antifreeze then drains back into the bucket at the other drain valve. You keep pumping until no air bubbles appear in the returning antifreeze.

The fill pump is supposed to have enough head to pressurize the system up to about 15 psi initial charge pressure.

This is one reason I like drain back systems -- less complicated with fewer parts :)

Gary
 

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I've been observing the sun on my roof here around the first day of winter. Here is my situation, I have basically 4 roof faces that receive some type of consistent sun.

a- the front roof of my house faces SW
b- the back roof face of my house faces NE
c- roof face on my carport, in back faces SE
d- roof face in front over living room faces SE

In the winter, c and d get sun at the same point in the morning, but d has advantage because it isn't shaded in the afternoon. C gets afternoon shade from the house being in front of it.

A (SW) is getting sun at the same time as d (SE), but I am unsure if the angle is good. It doesn't seem as direct in the morning, but once the sun swings more westerly in the afternoon, it could be at an advantage. Maybe placing a collector on a and d would help me get benefit from both times of day. What do you guys think?

Also, would using b (NE facing) give me any kind of advantage in the summer? The sun seems to spend a little more time there in the mornings during the summer if I recall correctly, and the SW face didn't seem to get much sun until the afternoon in the summer. Also, this morning, I see that this NE face gets sun from an angle kind of like what the SW face is getting. Would placing a collector on the NE face be worth it, or will the fact that daylight lasts longer in the summer compensate for morning shading on the SW face?


I hope my description of my roof isn't too drawn out and confusing. It kind of confuses me to think about it.

Thanks,

Kendall
 
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