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Resource: Convert heater to high voltage DC
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Convert AC water heater to DC
using low voltage Resource: Convert heater to high voltage DC |
| Use only 600 volt wire. Lamp cord, extension cords are not rated 600 volt. Use copper wire only. Aluminum wire is fire risk and should be avoided or installed by professional. 30 amp breaker use 10 gauge / 120-240 volt 30 amp outlet can be installed on 30 amp breaker only/ use 10 gauge wire ... cannot be connected to 15-20-40 amp breaker.  Orange/ #10 gauge wire, with ground ... 30 amp capacity. Safe maximum: 30 x 80% = 24 amps. Buy: 10-2 gauge/ 30 amp 10-3/ 30 amp Southwire electric tools |
Yellow
12 gauge 20 amp 120 volt 20 amp outlet can be installed on 20 amp breaker, but not 15 amp breaker/ use 12 ga wire. ... cannot be connected to 30-40 amp breaker. 1  Yellow/ #12 gauge wire, with ground ... 20 amp capacity. Safe maximum 16 amps. Buy: 12-2 gauge/ 20 amp 12-3/ 20 amp NMB is house wiring UF is underground Rolls of stranded wire HOOK UP Wires |
| 50-60
amp breaker use 6 gauge / 240 volt 50 outlet can be installed on 50 amp breaker only  Buy: 6-2 wire Southwire electric tools NMB is house wiring UF is underground |
40-50
amp breaker use 8 gauge / 240 volt 40 amp outlet can be installed on 40 or 50 amp breaker only  Buy: 8-2 wire Southwire electric tools NMB is house wiring UF is underground |
 Multimeters Voltage is tested across two separate wires. Ohms or resistance is tested across both ends of same wire. Amperage is tested along one or two points on same wire. Buy: Analog multimeter Multimeters at Amazon Klein multimeter Electric testers at Amazon Clampmeter for testing amp flow on line |
 Electrical tools must be insulated. Always best to disconnect power, but insulation failure, lack of proper grounding, grounded neutral, lack of GFCI, out-of-code wiring, generator operating without transfer switch, and other problems still pose a risk to anyone working on electric power ... even when breaker is off. Buy: Electrician tools kits KLEIN TOOLS Tools kits IRWIN tools KNIPEX Telephone cable knife Low Voltage Mounting Bracket for Telephone |
 Protect wiring from damage Use nipper instead of pliers or screwdriver for removing staples (and nails). Do not damage cable or wires inside cable. -Code says: Cable SHALL BE secured without damage to the outer covering. NEC sec. 336-15 Buy End cutting nippers at Amazon |
 Electrically insulated tools When removing insulation from wire, do NOT score or put cuts on surface of copper wire. Doing so increases resistance and heat on wire and creates possible weak point. Buy tools: KLEIN TOOLS Wire strippers at Amazon Electric Wire Stripping Machine Linesman pliers Utility knife at Amazon |
 GFCI circuit breaker A GFCI circuit breaker will protect all boxes on circuit. Circuit must be grounded. Ground wire must be continuous and connected to each piece of equipment. White wire on circuit breaker must be connected to Neutral busbar inside the breaker panel. Buy GFCI circuit breakers |
Push down
 1" and 2" wide Push down breaker Buy single-pole: Choose from 15 to 60 amp Eaton CL series Siemens 15-60 amp Tandem breakers Buy double-pole: Choose from 15 to 125 amp Choose from 15 amp to 200 amp Eaton CL series circuit breaker Siemens circuit breaker Double pole GFCI |
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Question
from Jerry: I want to heat water with a solar panel kit from Amazon that shows 400 watt and 12 volt DC. Will it work if I connect it to the hot water element? Buy: 12 volt 400 watt kit |
| Answer: Yes ... but how much hot water will you get with 400 watts and 12 volts? Let's calculate !! 1) Calculate using Basic formula for number of gallons of water heated Per Hour (for Electric heater) = (KW x 3413) divided by (temperature rise x 8.25 lbs per gallon of water) 2) If incoming water temperature is 65°F and you want to heat tank to 105° (typical shower temperature), or 40° rise in temperature. 400 watt or .4Kw x
3413 = 1365
40 degree temperature rise x 8.25 per lb of water = 330 So 1365 divided by 330 = 4.13 gallons per hour If you get 6 hours of good sun = 24 gallons of 105° water 3) If incoming water temperature is 50 degrees, and thermostat set to 110° = 60 degree rise in temperature 400 watt or .4Kw x
3413 = 1365
60 degree temperature rise x 8.25 = 495 So 1365 divided by 495 = 2.75 gallons per hour. If you get 6 hours of good solar = 16.5 gallons off 110° hot (indicating that a 12-20 gallon water heater is about correct) Conclusion: Calculations indicate that the solar panels will heat water for a shower and misc use. Typical shower
consumes 9 gallons 100°F hot, so a good day's solar harvest
would probably give a couple quick showers if taken early in evening
before tank cooled. For cooking etc you would have plenty of hot water.
Water is cooling as soon as it gets heated, so add insulation to
the tank, and locate tank near the hot water usage points, then don't
use any hot when you just need cold or new cold water is added inside
tank, having a cooling affect on whole tank.
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| What
is needed: A 12-20 gallon water heater tank is probably best given the amount of hot water produced each day. If the tank is too large, say 30-40 gallon, then it will be full of unheated water that will quickly cool the water that is heated. Buy: 12 volt 400 watt kit Rheem point of use Dernord 12 volt element |
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 Reliance 120 volt/ 1600 watt 6-10 gallon Side connections/ 6 year warranty Buy: Reliance water heaters 12 ga extension cords 12-2 Southwire cable Resources Reliance manual State manual |
 American 120V/ 1500 watt 6-12 gal Top connections/ 6 year warranty Buy: American 12 gallon 12-2 Southwire cable Resource: American manual |
 Rheem 2-6-10-20 gallon Side connections/ 6 year warranty Buy: Rheem point of use 12-2 Southwire cable Resource: Rheem manual |
 What
is needed:You would have to convert elements on tank to same volts (12 volts in this example), and then match the wattage as close as possible. This means you need tank with screw-in elements as shown above. Tank with bolt in elements or proprietary elements as found with Bosch will not work. Buy short element to fit tank diameter. Single U is probably easiest to work with. If voltage from solar panels exceeds volt rating on element, then element will likely burn out. Buy: Dernord 12 volt element DC elements Single U 24 volt 600 watt element Double U element |
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 Question
from GregI have 3 PV solar panels, and distance between Water Heater and Panels is 200 feet. Setup I have two 50 gallon water heaters in series. Incoming cold water goes into first heater. Then the hot water pipe from first heater feeds second heater ... and second heater feeds my house. The first water heater was installed so I could take advantage of my 3 solar panels left over from my solar system on the roof. Currently the first water heater is turned off. Its wired for AC but not heating. I'm letting the 2nd water heater do all of the heating for now. What I want to do is use the 3 Panels to heat as much as possible in the first water heater, and let the second water heater finish the heating of the water. Not sure the best way to utilize the panels. My thought was to replace the bottom element on the first water heater with a DC element and let it go but not sure that's best and exactly how to do that and still meet safety, etc.  Alterations
void product warranty |
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| Response to Greg's question It is unknown what your output will be for the solar panels. Is it low voltage or higher voltage? It depends on output of each panel ... plus if panels are wired in series or parallel. So measurement is needed, and some planning. Connect your panels at night so you don't get shocked ... solar panels don't have on-off switch. I am going to refer you to my solar-safety webpage for more detail on safety. Resources Solar safety Safe electric wiring  Wire the panels and Test voltsWire your panels in series one night, then wire them in parallel next night ... check voltage output for each configuration. Series means each panel end to end with positive from one panel to negative of next panel. Just like batteries wired in series, amperage is equal to amp rating of any 1 of the 3 panels, and volts is three times the value of any single panel. Parallel means all positives connected together and all negatives connected together. Just like batteries wired in parallel, volts will be equal to the volt rating of any 1 of the 3 panels, and amperage is three times the value of any single panel. After connecting panels, you test for voltage across two different wires, the positive and the negative wires that will travel to the water heater. This test will tell you where to start with element voltage. Remember, the voltage rating of element must be equal to or greater than voltage from solar panels. Why? So the element does not burn out. If element is rated 120 volt, and you are feeding 100 volt DC solar into it, then that's good because element is rated for more volts than the solar. You need ordinary multimeter for the voltage test. Buy: Analog multimeter Multimeters at Amazon Klein multimeter Electric testers at Amazon Maybe use series configuration with higher voltage since the distance is 200 feet. Longer distances cause voltage drop, so a larger wire is needed to help prevent power loss due to distance. Except 3 panels in series @ 31 volts each would be about 93 volt at maximum solar harvest. In that case, the installation would not be 'low' voltage, and would likely burn out (melt) the thermostat pretty quick. Another option: You could put two panels in series, and then into parallel with the 3rd panel. Buy: 1500 watt 120 volt element  Test ampsElectricity has two dynamics: Volt and amps .... and standard formula is volts x amps = watts (power) Measuring amperage is different than measuring voltage. Amperage is the flow of electrons along one wire. Amperage only flows when the circuit is completed to the element. If the wire is just sitting there and not connected to element, then there is voltage potential across the two wires coming from solar panels, but no amperage is flowing. You need a clampmeter to test amperage. Buy Clampmeter for testing amp flow on line Size of wire Here's the problem. The amperage must be known before selecting correct wire size for the 200' distance ... Why? Each wire is rated by the amount of amperage it can carry. ... but amperage can only be checked on your solar panels installation when power is flowing through the water heater element. This means you need to install the wire before you know what size wire ... or make a best guess ... I am going to recommend a #10 wire for 200' distance and 3 solar panels (6 solar panels and 200' might use #8 wire). It's true, the smaller #12 wire might do fine for 3 solar panels and 200', but #10 will cause less power loss over long distance. Note that having a wire that is a bit oversized is not an issue, and tends to run cooler with less heat loss, thus allowing longer distance without voltage drop and power loss. Type of wire Use UF-B for direct burial underground without conduit. I recommend using conduit for best long term result (ordinary NM-B wire can be used inside 3/4" conduit and is easier to strip than UF-B underfoot cable). Ground wire is required for ALL installations. Do not make splices underground. Use 1 continuous piece of wire. Use solid copper wire. Code requires use of standard 600 volt wire. It is against code to use extension cord for any type of permanent electric wiring.  Buy:10-2 gauge/ 30 amp 10-3/ 30 amp Southwire electric tools How to connect to heater  Typically
this kind of solar connection would be made at lower thermostat and
element.Open lower compartment on water heater. Disconnect the two wires from top of heater ... cap them off and push completely out of the way. Connect the two wires coming from solar panels to the thermostat and element. You can keep upper part of tank connected to 240 volt AC without a problem. Thermostat and element nust be covered with insulation. Buy: 1500 watt 120 volt element Will the thermostat work with DC power? It will work fine for low voltage installation because it doesn't have a lot of force (voltage) pushing the electrons (amperage). If your amperage flowing from solar panels is getting pushed by a lot of volts, it will burn out the thermostat pretty quick. Why? Because DC has a problem with 'arc extinction' that AC does not have. DC current causes more spark (arc and heat) when it's switched off ... making DC problematic for AC-rated thermostats (and other AC rated electrical equipment). Resource: Arc extinction Thermostats are mechanical bi-metal switches ... nothing complicated about them ... and they work with any voltage (up to 480 VAC) ... and they replace easy. Note: This design works but I cannot guarantee how much hot water it heats. Why? Nobody has sent data on this project. I have not done this project myself ... and there are no product manuals ... so I do not have real world information that tracks specific outcomes for series vs parallel, cold vs hot weather, high ambient temperatures vs cold, cloudy vs sunny regions, higher voltage vs lower, etc. So the whole thing becomes an experiment requiring inventions and innovations by the installer. HOWEVER ... I know this is a common installation for low voltage because people have emailed about having such an installation. So I know it works, but I do NOT know how much hot will be supplied on a daily basis or if there is a payback. |
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Install ECO protection?  Replace
lower thermostat with upper thermostat... The ECO, or thermal reset
button will cut power from solar panels if tank exceeds 170°F.Yes this is good idea. Why? The 240 volt on upper part of tank is controlled by upper thermostat with ECO, and it will cut power to 240 volt if top of tank reaches 170°, but will not cut power from solar panels, so panels are still adding heat to tank. The tank has a TP valve that releases hot water if temperatures within top 6" of tank exceed 210°. The TP valve is designed to prevent steam explosion .... You
don't want
water to get 170-210°F, especially if tank is older and might be
weakened from rust etc. These temperatures can kill folks, causing
severe burns plus destroy home, belonging etc.Will your solar heated water cause tank to reach 170-210°? Without data from experimentation, I cannot say. But best judgment is that 3 solar panels cannot give that much heat (or even close) but it might be possible if more panels were added to the array. Buy: Therm-o-disc terminal protector Camco 90-150 F thermostats |
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By-pass lower thermostat on
2-element tank? This is one of the experiments I would try Do not recommend by-passing thermostat with 1-element tank Do not recommend by-passing thermostat with more than 3 solar panels Since thermostats burn out with DC power, and that adds expense nobody needs, then a by-pass might be tried ... and it might work well. |
 Larger imageUse a temperature controller and DC relay to bypass thermostat This plan is best if thermostats burn out frequently, and better than bypassing thermostat as shown above. The PID or temperature controller is more accurate than mechanical thermostat, but heating water is dynamic, and the probe is reading temps off the steel tank ... and the probe and thermostat and element covered with insulation same as any electric water heater. Inkbird PID temperature controller .pdf While the illustration shows thermostat probe at lower thermostat, it can be installed at top of tank on the upper thermostat if one chooses, and still control the solar power at lower element. The Omron DC relay is made for switching high-amp DC and will function over 10,000s of operations, and reliably cut off solar power if temps exceed setting. Omron relay spec sheet The disadvantage of the temperature controller and relay are the cost of purchasing the relay and other parts as shown .... need for low voltage power supply (12-24 volt LED driver) ... needing enclosure for safe install of the power supply, relay and controller ... and lack of simplicity. Buy: Omron DC power relay PID Temperature controllers Digital temperature controller 12-24 volt DC IP67 LED driver Bud industries hinged enclosure 6x8x4 |
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 Control high or low voltage DC using
timer-ST01 timer is battery-operated and rated for 120-240-277 volt AC or 12-24 volt AC or DC -Omron DC relays have a AC or DC coil depending on model selected, with a maximum rating 200 amp DC depending on model selected. -LED drivers produce 12-24 volt DC voltage, ordinary doorbell transformers produces 12-24 volt AC Buy from my affiliate links: Omron DC power relay Intermatic ST01c timer/ 1 year warranty Ei600/ 5-year warranty timer CR2 replacement battery Waterproof LED driver Resources: Omrom power relay spec sheet ST01C manual Sell sheet with model numbers |
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Recommendations for lower element
DC
install Larger image Local code requires direct bond (ground wire) from solar panel frames and metal conduit to nearby ground rod using #6 copper wire. Ground rod must meet local specifications. Solar panels should be bonded to nearby ground rod, and bonded to water heater tank, and water heater ground wire connected back to main breaker panel that is connected to proper outdoor ground rod. Connecting ground wires to metal water pipes is no guarantee of ground, and can cause deteriorated water pipe. In addition to information above, solar PV power is DC, with a positive leg and negative leg. The negative leg of solar power should also be grounded, and this is not covered here. |
| Tapered
drill bit
for any size hole in metal Drill 3/4" Hole into water heater for 1/2" conduit connection from solar Buy tapered drill/ step drill bit for any size hole Step drill bits at Amazon Neiko tapered drill bit 1/4"-1-3/8 holes |
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  3 pole non-fused safety switch wiring |
120-240 Volt 3-pole safety switch House power and solar power must have safety shut off to protect anyone working on water heater. Use fusable or non-fused. Clearly label, and locate safety switch next to heater. Local codes vary, and generally require another cut off for solar located outside near the solar panels Connect all household & solar ground wires together Buy: 3 pole 60 amp non-fused safety switch 3 pole 100 amp non-fused safety switch 30 amp AC cartridge fuse 20 amp AC cartridge fuse 30 amp DPDT shut off switch Resource: How-to-wire-safety-switch.html |
 Wiring diagram for element and thermostat |
You can use ordinary AC element for solar DC. Use new element/ lower part of tank 1500 watt 120 volt element: Buy: 1500 watt 120 volt element Resource: Read about / choose water heater element + how to clean out tank and replace element |
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DC safety switch Heavy Duty 250 V Dc Voltage; 30-60 Ampere Use 10 gauge wire with 30 amp fuse Use 6 gauge wire with 60 amp fuse Buy: Square D 30 amp DC/ outdoor/ fusable/ HU361RB Square D 60 amp DC/ outdoor/ fusable H222AWK 100 amp non-fusable/ outdoor/ at Amazon 100 amp 3-pole non-fused safety switch Resource: DC safety switches How to wire safety switch Convert AC water heater to DC water heater DC relays for solar power |
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Surface mount ANL
fuseholder Buy: e2 fuseholder with platinum plating ANL fuses |
 Fuseholder Fuse |
Photovoltaic fuseholder/ DC fuseholder/ 1000 volts DC/ DC fuse/ photovoltaic fuse: use 20-25 amp fast-acting for designs on this page Not waterproof... mount inside Nema 3R enclosure Mount on din rail/ change fuse with flick of finger Install 25-30 amp fuses Use 10 x 38 DC fuses Buy: Photovoltaic fuseholder / DC fuseholder/ ultrasafe/ at Amazon Ultrasafe fuseholders at Amazon 600 volt DC fuses at Amazon Mersen 600 volt DC fuse |
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Waterproof Solar
fuseholder/ 1000 VDC/ 2 amp to 30 amp Buy Solar fuseholder at Amazon Fuse holder plus 20 amp DC fuse Fuse holder plus 30 amp DC fuse |
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DC circuit breakers for
Solar/ use 20-25 amp for designs on this page Buy from my affiliate links: DC circuit breakers High voltage DC circuit breakers at Amazon Combiner boxes at Amazon Resource: How to set up solar array |
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1) Make sure thermostats
are covered with insulation, protector, and
cover. See image Without insulation, Thermostat exposed to room temperature will misread temperature and cause overheating. 2) Make sure thermostat sits flat against tank wall. Wiggle thermostat. Check that bracket is not rusted and loose. Buy: Upper element terminal protector Lower element terminal protector Resource Troubleshoot electric water heater |
| Misc notes and such that generally apply to higher volt installations: | |
 Back view Front view Example Renogy mono-crystalline panel |
Using PV solar
voltaic solar panels: Parallel means both negative wires are connected together and both positive wires are connected together. Series means negative wire on first solar panel is connected to positive wire of next panel... etc. If panels are wired in series, the volts are higher, amperage is lower, and resistance is higher. Resource with calculation. This is good for harvesting maximum power in low solar conditions. Series = good for low solar conditions (after 3 pm on sunny day or overcast day). If panels are wired in parallel, the volts are lower, amperage is higher, resistance is lower. This is good for harvesting maximum power in high solar conditions. Parallel = good for high solar conditions (mid-day sunny conditions) How to optimize solar panel array Buy from my affiliate links: One 100 watt solar panel $149 One 250 watt panel $350 Two 150 watt panels $300 Buy solar panels Mounting brackets |
Solar panels are like flashlight batteries. Total wattage or power stays the same no matter series or parallel. If panels are wired in series, the amperages stays same and voltage increases. If panels are wired in parallel, the amperage increases, and voltage stays same. So 2 Renogy 250 watt panels wired in series will produce 60.2 volts and 500 watts. 2 Renology 250 watt panels wired in parallel will produce 30.1 volts 16.4 amps and 500 watts On water heater, change lower element to 900-1200 watt DC, and disconnect wiring from top of heater. Leave upper element in place and connected to 240 volt. Upper element works in ordinary fashion when water heater is ON. Lower element is ON when solar panels produce electricity. Drawback of low voltage: long time to heat. Other option: use same plan using smaller 20 gallon heater/ read: Under counter water heaters Reliance/ 6-10 gallon/ Side connections/ 6 year warranty Buy Reliance water heaters 12-3 extension cords 12-3 Southwire cable> Resources Reliance manual State manual Example: If your panels produce 91 volts x 16 amps = 1456 watts (the 91 volts 16 amps will probably burn up the thermostat when direct connected to water heater so use high voltage plan). If your 91 volts drops to 60 volts in the afternoon, then the wattage drops and element produces less heat If you connect 1456 watt output to an element rated for 120 volt 900 watts, then element will probably burn up. If you connect 1456 watt output to an element rated for 120 volt 2500 watts, then element will still produce 1456 watts heat. If you connect 1456 watt output to an element rated for 24 volt 600 watts, then element will burn up. If your solar panels generate 145 volts x 15 amp = ? 240 volt x 15 amps = ? What happens when you connect 240 volt 15 amp electricity to 120 1500 watt element? The element burns up. Choose element rated for your output: Ordinary elements work fine for AC or DC, but are not often available in low volt and watt ratings, so you need DC element. Single U and double U DC elements, 24 volt 500-900 watts. The single U has ordinary element style with 2 screws for connecting the wires. So your solar panels are connected directly to the element. The double U element has 4 screws for 4 wires and can accommodate two separate connections.... meaning you can have two separate sets of solar panels, and each set of solar panels can supply power to one of the U 3U elements are usually made for 3-phase boiler installations, have larger thread, and will not fit a residential tank. Buy: DC elements Single U 24 volt 600 watt element Double U element  Resources Solar PV safety How to set up array How to replace water heater elements Figure volts amps watts All solar links Convert AC water heater to DC water heater/ high voltage What size water heater? Typically in residential water heating, small water heaters (20 gallon) use 1000-1500 watt elements. Ordinary shower uses 10 gallons hot, ordinary bath uses 20 gallons hot. You can set thermostat to higher temperature to get more miles out of a tank of hot. http://waterheatertimer.org/Increase-amount-of-hot-water.html Larger water heaters use elements with more wattage in order to heat the water.... A 500 watt element would struggle to heat a 40 gallon tank 5.866689 Kwh to raise 40 gallons of water 60°F (starting at 60- and ending at120°F) Typical shower might be 104°F 1000 watts for 1 hour is 1 Kwh Your 500 watt element produces 1 Kwh for each 2 hours operation So you would need 5.867 x 2 hours or 11.73 hours to heat a tank ... and that is with ideal conditions, no consumption of hot during those hours, full sunshine, no cooling of tank etc etc ... except the tank would cool, and sun is not dependable each day. .. or if you satisfied with less-than-thermostat-setting hot water, say 80°? http://waterheatertimer.org/Kwh-temp.html |
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Din rail fuseholder Install in-line fuseholder so circuit can be turned on. Multiple fuses and breakers on same circuit are fine. Buy: Din rail fuseholder 10 x 38 mm fuse Mersen DC fuseholder Mersen DC fuseholders Photovoltaic fuse 20 amp DC fuse 14 x 51mm fuseholder and fuse Din rails DC circuit breaker for solar panels |
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Buy
from my affiliate links every time/ thanks: Amazon ''As an Amazon Associate I earn from qualifying purchases'' Enter Amazon from any link on my site, fill cart with any item ... purchases pay small commission E-mail: geno03245w@gmail.com My response might end up in spam folder, check email folders Waterheatertimer on Twitter Message thru facebook |
