Need Source For Domestic Water Tank For Solar Hot Water Application.
Q: I built solar cabinets that get up to about 180 degree F in the heat of summer (110 degree F now). I am extracting the heat and blowing it into my basement supplementing my heat. It didn't work well in the middle of winter due to sun being blocked by trees and lots of cloudy weather. The last week they have really done well, blowing 110 degree hot air from 10 am to 4 pm. Here is what I need help with. I plan on placing water tanks in these cabinets (there are two) and running my cold water through the cabinets / tanks before going into the domestic hot water coil on the boiler. The tanks would have to withstand (guesswork here, 180 degree heat) and 60 psi, my well runs 30 psi on and 50 psi off. I have found an RV supplier catalog and am contacting the supplier of water tanks on the specifications above. They have a 10 gallon and 15 gallon tank that will fit my solar cabinets. I could also get more complex and run the water from these tanks at lower psi into another tank in the basement. That would require a pump / tank (heat exchanger) and run the cost up. The tanks I am looking at cost $ 60 USA for 10 gallon and $ 75 for 15 gallon made by Elkhart Plastics. Does anyone have any ideas or no where other tanks would be available ? The tanks from Elkhart are for domestic water and have 3/8 fitting installed. Take Care, Kevin
A: I think the tanks inside of a hot water heater would be too big (they are 40 gallons or larger).The solar cabinets don't have much room and could probably hold about 15 gallons (depending on tank dimensions).I thought about the domestic hot water coils inside of a boiler but they probably don't hold much water and are expensive. I am in the planning stage now. Any help welcome. There have been some good suggestions here (beer kegs, soda kegs and hot water heaters). The RV water tank supplier notified me their tanks can't withstand the pressure / heat of a pressured solar application. I went to Lowes / Home Depot and found what may work best for my situation. The cabinets could fit (3 to 5) 100 foot coils of polyehtelyen black water pipe (they come coiled !). They are rated 125 psi at 78 degree F. Does anyone know how much water (in gallons) a 1/2 polyetheleyne pipe 100 feet long will hold ? I wrote down the name of the pipe manufacturer and will contact them about capacity and pressure capabilities at higher temperaturesYou might look at 4" and 6" PVC pipe. Add some reducers on each end, done. 4" holds about 2/3 gallon per foot, 6" holds about 1-1/2 gallon per foot. Not sure the standard stuff will like 180 degrees, 140 is OK. Beware that there is some "foam filled" larger PVC out there. Keeps the weight and cost down, won't stand the pressure. Using pipe like this can really change your design. The pipe can be set into the heat exchanger side frame, just diasppears. You can also use it for a heat exchanger if you want to run glycol.Just run a piece of copper tube through the center. .
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