When water comes back from the collector hotter than the thermostat setting on the upper element, it will rise and keep the element off. If it comes back warm, it will leave hot water in the top of the tank undisturbed, waiting for use. When use occurs, then the solar preheated water moves to the top of the tank and is boosted to 130 degrees or so. On a good day the element may never go on. A cloudy day may see it on a ~ lot. • • • ~ All the above applies to electric systems which adapt very ~ well to solar. Gas systems are a little different. A gas HW heater has the heat source at the bottom; therefore it will ! heat the cntire tank regardless of any solar input (the thermo stat sticks through where the control box is). You will then be supplying hot water to the collector! To avoid this it is I recommend using rock wool, because it won't burn, and necessary to use a two-tank system if you want gas backup. disconnecting the gas entirely. If some(Jnc trics to light such If you just want to use the tank for 100 percent solar, you a tank, NOT knowing it's plugged full of insulation, it could can (see figures below). In a two-tank system, you usc a be dangerous. preheat tank which is sized for your entire demand (maybe a used tank). The backup tank should be the existing or new OTHER NOTES: small gas water heater_Such two-tank systems can be used 1. If you don't remove the lower electric heating clement, be with electric but arc not as easy or cOSt effective as thc other sure to turn it down all the way or disconnect It properly. methods. You might use it if you had a good small electric 2. Add extra insulation to the tank. Johns Manville makes tank and needed a much larger volume of storage. As you can a kit, or just wrap some insulation and tape or tie It to the sec, there are a lot of ways to do it. tank. If you have a gas tank and you want to go 100 percent 3. Set thermostat as low as you can (experiment). solar with no back-up, you can put some insulation down in 4. Insulate all HW lines, especially to and from the collector. the flue of the tank. If you don't, you will lose a lot of heat. 5. All lines to the collector should be lIZ " copper or larger. 6. Connect copper to steel pipe through diekctric couplings _~ or unions, or use brass nipples. ~., __ ,.•,....'" "'~I\OO" 7. eom pipc in,uh,ioo <xpo~'d to the sun. Use alumi!lUm : '; •... '.. 'lil~~_ foil, or speCial tapes made for that purpose. Pamt will help , -.- . .' .. ~..""...... $UI'fl!IIM6 C()Ww~R1b'f ' h h' I '\. _.,: !.....;. lla.SIIIEAr" " .6Iif...... , .'f~Nt.( ~ I you don t ave ~nyt mg e se. . " G£r,.~,.Ii I>&>foIToA. ...' F!:~~'Usc freeze protectIon, Hot water reCirculation m warm ~Ofo\ VL"!>IUUof"TO' I d' d . Id I "'z,"'TlIItuop. eoRe oc.4'- .: p aces, ram own m co p aces, 01'1 UIS'l4I to Ill." PIf1£ _ ~ '" ... 9. Us.: an air vent to let out air. Bt'll & Gossd No.7 or No. Goe.!. TlIItlA. N,WIII " pf JIUoIIII 0 " 1)oNIC.. .' 67 '11 k '1'ol'llo'l1b.lP. li'IT'O f~1(. "" _.' WI wor . ~-r~f.I,&l4~IF~Go'!!''£.~s t 10. Install check valve in r.:turn line to prevent reverse J,lr.' '" PliLEa'IeIC. COIIf'U" ~,......... . 'hSoIIN6 POoJ'T"SGIIII\oJU>MR ~Gr-..:Nft)OF,..,. ~ thermosyphonmg. ~1.1)oHI( -tIIc.OdQ'GIf,' -. ........ ,0/ . IF 'fOM CoIIH"I'.f'O/OIC)11; U. LDf' 11 . Don't think there is a nything magic about manu factured components. Do make surl' you und~rstand the prin<.:iplc: before you try to improvise. Hope you can svrt this all out. Sincerely, John Broberg 1399 Piney Rd. Ft. Myers, FL 33903 !().., August/September 1979 RAIN Page 17 ~Mf~ t?1~f,M. ~PAAftoI) window and other materials, their durability and cautions on their uses, cost information and manufacturers of the various products and equipment. Parti· cularly valuable coverage of hazards and improvements in foamed insulations and cellulose insulation. A resource that every weatherization project should have. -TB Windows for Energy Efficient Buildings, free from: Energy Efficient Windows Program c/o Stephen Selkowitz Bldg. 90, Room 3111 Lawrence Berkeley Laboratory 1 Cyclotron Bldg. Berkeley, CA 94720 A DOE-sponsored publication to nctwork research and development relating to window efficiency. Contains research reports, new products, research funding opportunities, patents, etc. Focus tends to be high-tech. Price information would add realism to exotic product information. -TB Nuclear Shut-Down Is Nuclear·Free America possible today? If so, how much will it cost? Numbers put together at Barry Commoner's Center for tht~ Biology of Natural Systems by Rich Carlson, David Freedman and Robert Scott show that 63 of the 71 currently licensed nuclear power plants can be.shut down immediately with no loss of ekctrical output or reliability. The remaining 8 plants can be phascu out in the next few years and all nuclear plants expected to come on line by 1987 can be cancelled, also with no shortage of needed power. All this is possible because your dforts at energy conservation have lowed growth of energy tkmand so much that substantial extra capacity exists in almost every bulk power n:gion in the country! The shutdown would increase oil consumption by 3.4 percent and coal by 8.9 percent. (Tha.t'S without additional improvement m use efficiency.) And the cost? A maximum of about $1 a month per family. Enough of those cries of doom voict'd by (he power IIldustry at prospects of nuclear shutdown. L<)ok for details in a fut ure Issue of Etlvirormumt. (Thanks to In These Times) - TB
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