Posted By snoslidr74 on 02 Mar 2012 02:30 PM
Joe, I am curious, I imagine your peak tank temperatures are occurring near mid-day or shortly after? What are your tank temps running in the morning? This has been one of my questions regarding solar hot water as much of our needs for hot water are in the mornings for showers, etc. Thanks...

it all depends on wether or not both of my daughters (7 & 4) take baths the night before. If no one takes a shower/bath at night the tank holds it's temp. I would recommend getting the 120 gl tank kit. It was what I was going to get initially and I should have stuck with that. 80gl goes pretty quickly.  This is why I have it pre feeding my 50gl elec tank. Plus we are in our 3rd day of clouds and rain.

   The 80gl system would be fine, I think, for two adults. With no usage the tank itself will only lose a degree or 2 over night.

Just wanted to do a follow up. For the month of March we operated at almost 100% on the solar hot water. Today the storage tank reached 170*, Yesterday it was 162*. We are not using all the hot water in the solar tank day to day. Mixing valve is sending out water at 110*

Joe-

I think that my storage tank has a maximum recommended temperature of 160 F, so hopefully your tank is rated to take the 170 F. There should be a control to limit the temperature in the tank to whatever maximum temperature it or the other hardware will tolerate. In my case, I take the hot water out of the tank before the mixing value and send it to my humidifier that is limited to 160 F water temperature, so I reset the maximum tank temperature to 150 F to give it a little safety margin.

Congratulations on getting your system operating so well. Now you can have hot showers with absolutely no guilt, unless you have a water shortage!

Posted By Lee Dodge on 05 Apr 2012 11:03 PM
Joe-

I think that my storage tank has a maximum recommended temperature of 160 F, so hopefully your tank is rated to take the 170 F. There should be a control to limit the temperature in the tank to whatever maximum temperature it or the other hardware will tolerate. In my case, I take the hot water out of the tank before the mixing value and send it to my humidifier that is limited to 160 F water temperature, so I reset the maximum tank temperature to 150 F to give it a little safety margin.

Congratulations on getting your system operating so well. Now you can have hot showers with absolutely no guilt, unless you have a water shortage!

Hi,
 My controler has defaults which have the tank temp at 140*. I have changed it to 170* to get the most out of the 80 gl tank I can. Adjustable range is up to 203* F. The system also has a built in heat dissapator, much like a car radiator, which will operate automatically to cool things down. I currently have that set at 175*. Pump is good to 230*F.  I just don't see 170* as a problem for any of the parts. The mixing valve is sending out hot water at 115* prefeeding our elec ht wtr htr. I have had 1 full month (March) to compare my elec bill, and my elec ht wtr htr is drawing very little electric. I think we had 2 or 3 days where we needed it last month. Pretty happy about that.

Nice Info ! and nice at

http://www.buysolarsystems.com/thankyou.html

Generally in HW 7-deg dT's seemed fast enough. -Just keeping Cu piping under 12 fpSec (errosion), if used .

500 x gpm x dT = BtuH , helped pic off efficiencies of in comparisons.

in 1980 a sheetmetal co sold boxes for 1.1/2" cellotex(then), 3-layered window screens (already baked at 500deg) bracketing for 3/4" spacing , tfe layer and sundex (then) glass or FyLon (sp)... Systems of warm-hot air, in cloudyareas cycled because temps tripped the 110-80, sensors for the fan (air-filters were 4" thich )...
TWO 3x8ft collectors did pretty good in Dayton ~ ? 50-51 degree standing/angled. est about 2700 Btuh/ea,collector, IF I remember correctly.

closed-air loop , well insulated to a std box-fancoil HX 20x20 3-row, > 6 gpm, to tank, simple diff controller, AND SPACE HEATING when not hot water ! and a simple 3-way duct diverter. Tanks had to have tempering valve for hitting 155 deg. Slowest air flow hit over 300 deg leaving the collectors, so some safety-venting was implemented.
LITERALLY , a Dave W of Dayton Ohio baked potatoes at the end of the duct in his ceiling register boot.

2) Air Collector 5400 btuh (peak)/ dtAIR of 20-deg leaves about 250 cfm to loop in closed-insulated-duct, a peanut fan. Now ECM makes it perfect I would guess, varying air flows by Temp. But a slow 200 degree rise would then be~ 25 cfm to "bake a potato"... HAH ! 

Distributing all air vertically downward, high returns in cold hall/room...in 1980 with co, built 6 systems to 6-collectors (1/6 hp blower) that COOKED a 1700 sq ft first floor most of the winter.
Here in NEOH cloudy below lake 10- miles, so cloudy , I will have to build this again soon and report.

The Sweedish concensus then was the LOWER the HEAT CAPACITY to Store Heat at the collector , the better the annual BtuH transfer overall, especially in cloudy- snowy areas... Moving heat 30-min in a day at a system- "on" port, cycled at least some way, measured, was said better than missing the say 10-short "windows" of heat exchange-cycling, throughout a daily period.

A low heat-content in a collector ever with low heat capacity design , water or air , seemed interesting.

Is this still taught in different scenarios?



Solar Phish Stories
...

Anthony at www.BuySolarSystems.com

As a distributor, IS very interested in extending markets and is as helpful as Joe says !

he understands adjustments for cloudy areas and has sensible working suggestions.

Anthony was a great help to me. www.buysolarsystems.com

I've been installing solar since the late 80s and I used to buy from China (I won't any more). I have a few simple lessons for installers and one of them is.....NEVER oversize tube collectors above what you need for 90% of peak summer time use. So, don't add to the system. Vacuum tubes have a much higher failure rate vs flat collectors and this is simply due to the very high temps they can reach. This adds stress around the bend between inner and outer glass and prolonged time at stagnation can break the tube.

Next, assuming you are really looking to get the most from the system year round, 45deg is your optimal angle, assuming you don't mind the looks of it. You won't sacrifice real summer heat production but you will improve the winter production.

Have the glycol checked within 3 years and if it is acidic at all, change it. Vacuum tube can potentially acidify faster than flat collectors, assuming both are sized correctly for the load. 40% proplyene glycol/water is all you need in your area. do not use ethylene glycol.

Thanks for the reply. I was quickly talked out of adding another collector. The current setup is perfect for us and has worked without a problem since day 1. The 80 gl system almost covers us 100% as long as it is sunny out. I also like that I can change out a tube in a matter of minutes should one fail. As for it being made in China, I have no problem with that. The US markets for solar are simply over priced. More so the cost of installation.

Next, assuming you are really looking to get the most from the system year round, 45deg is your optimal angle,

If you increase the angle of the collectors toward the vertical, you can increase the winter output while decreasing the tendency to overproduce in the Summer. That allows system oversizing to get a larger percentage of your hot water needs filled in winter and the shoulder seasons while reducing the need for heat dumping in peak summer output.

Posted By ICFHybrid on 07 May 2012 08:58 AM

Next, assuming you are really looking to get the most from the system year round, 45deg is your optimal angle,

If you increase the angle of the collectors toward the vertical, you can increase the winter output while decreasing the tendency to overproduce in the Summer. That allows system oversizing to get a larger percentage of your hot water needs filled in winter and the shoulder seasons while reducing the need for heat dumping in peak summer output.      

Thanks,
 I can make some small brackets easy enough to raise the top up.

It takes more than just few degrees of additional tilt to achieve that shoulder season boost & summertime reduction.

Solar geometry is the first-order factor, but seasonal & diurnal haze, fog, and dew make substantial differences in anticipated performance, as does the presence or absence of snow cover for secondary reflection. For space heating applications even going fully vertical isn't a very big hit in overall performance at a NY latitude & climate. for water heating only there's a happy medium in there somewhere.

Posted By Dana1 on 08 May 2012 12:03 PM
It takes more than just few degrees of additional tilt to achieve that shoulder season boost & summertime reduction.

Solar geometry is the first-order factor, but seasonal & diurnal haze, fog, and dew make substantial differences in anticipated performance, as does the presence or absence of snow cover for secondary reflection. For space heating applications even going fully vertical isn't a very big hit in overall performance at a NY latitude & climate. for water heating only there's a happy medium in there somewhere.

I am at 30* right now. The recomended angle for my area is 41* from what I could find.  Adding 10 degrees of tilt won't be to hard to do. Even at 30* I was still getting pretty good results in February (when I 1st installed the system). The storage tank was hitting the 120's. Even if the storage tank only gets heated to 90 or 100 degreesin Dec and January I'll take it. Less work for the elctric water heater. If I plan on doing space heating I would get a whole seperate system. Right now I am staying put with what I have. Along with this and two pellet stoves I'm pretty happy.

A mere ten degree difference in tilt won't mean much- less than 10% annually, so it's probably not worth the trouble & damage-risk to modify it, even if it's isn't hard to do.

Yeah I plan on leaving it alone right now. Everything is working so well. No need to mess with it.