Solar Water Heater

[Dog Walker]

All the panels and mounts have to rated for Florida's hurricane winds and are especially safe against the winds if the are mounted flush against your slanted roof.

Unless things have changed, you cannot use a standard tankless water heater with a solar hot water panel.  You have to use a tankless heater that is designed for pre-heated water.  I think that regular tankless heaters turn on when they sense water flow, not water temperature and would overheat with hot water coming into them.

All this information is as of five years ago and technology moves on.  You might want to look at the web site of Rennai or one of the other tankless water heater mfgs. for a current, definitive answer.

[Sigma]

Good info.  I was thinking that the tankless might use a sensor to read incoming water temp and then "make-up" the difference in water temp from pre-heated solar water, thereby using less elec/gas. 

[Dog Walker]

Electric tankless heaters just are not practical unless they are single faucet units.  You just can't heat an electric element fast enough or hot enough to supply a couple of faucets, a shower and a dishwasher all at the same time.

The downside of using a gas tankless in conjunction with a solar system is that you will still have to pay TECO's ridiculous monthly minimum during the summer months even when the tankless never turns on.  I think TECO's minimum is about $17.00 per month now just for being hooked up.

During the months when our electric backup hot water heater is turned off and we don't need heat or A/C, my electric bills have been between $0 and $18.00.

[Timkin]

Impressive.  Nice set up DW.

[Dog Walker]

Glen, aluminum won't last very long in our water especially if there is hot water in it.  Plexiglas (polycarbonate) doesn't hold up very well in sunlight.  Neither is a good material for a solar water heater.

You can probably find plans for a DIY solar water heater online.  You might even try Popular Mechanics website.

There are basically two designs for open loop (passive) solar hot water heaters.  The most common is a thin, flat collector plate or a series of copper tubes in an insulated, glass covered box that sits below an insulated storage tank.  A pipe runs from the bottom of the tank to the top of the plate and another from the top of the plate to the top of the tank.  As the water heats it rises to the top of the tank and cooler water is pulled into the bottom of the plate from the tank.

The other design uses big, fat pipes inside an insulated box and the pipes both heat and store the water.  Cold water from the supply side comes into the box where it is heated and stored.  Hot water comes off the top of the fat pipes to an electric water heater tank inside the house.

Both types are manufactured by two companies right here in Jacksonville and shipped all over the islands of the Caribbean and Central America.