Solar Hot Water

[Night Sailor]

Is anyone using a solar hot water panel on their roof?

I've read the 4 sq feet is about right for a 6 gal water heater.

So years back I read about a young man who used an old radiating element from an under counter fridge as his solar collector.

Solar hot water seems like a great way to pre-heat water and save on both electricity and propane.

[sparky1]

check out this site I bought a panel & pump but there is NO control system & the pump runs to fast (my 2 Cents) so it doesn't collect well. water would cool off at night do to thermal action.

Heliatos Solar

[Night Sailor]

I saw those for sale on Amazon. They have the marine version available. I measured my roof and there is a spot it would fit that is about 2'x 2'.

[Night Sailor]

Oops. Wrong side photo. The area is 24"x26".

[Night Sailor]

The proper way to do solar hot water is with a second tank that is circulated to the roof. This pre-heated water goes into the water heater which ow only has to raise the temperature slightly versus a lot. It give you more hot water as you tank(s) capacity is greater.

Some water tanks have a heat exchanger on the back. It is designed to circulate engine coolant, though a single U turn on the outside of the back of the tank, so I am not sure how effective it would be with a solar hot water panel on the roof. It might prove to be of limited benefit unless temperatures get to automotive values--190 degrees.
That is possible but a larger size with automotive coolant, along with sensors and a pump to make it work.

[blodn1]

Not solar, but a big water and energy saver: Girard Tankless LP Propane RV Water Heater - $471.98

[Night Sailor]

I considered tankless heaters. It is interesting to me because I tend to be attracted to cutting edge technology.

I've read they tend to be wasteful of water while warming up and then you need to be careful of your flow. I've also read about people having lots of problems with these, and that they do not hold up well. Reliability is important to me.

I would expect they would be more vulnerable to freeze damage.

A traditional tank also allows you to carry a bit more water and I'd like to be able to carry more water. An extra 6 gallons is a big percentage increase. My capacity is 32 gallons and I'm not sure if that includes the 6 in the water heater. So, if it doesn't that represents a 19% increase in water.

[blodn1]

I've had tankless heaters in 4 houses and a commercial bakery for the last 20 years, and I love them. They warm quickly, and hot water is only limited to the amount of water you have. Flow is the key - in colder climates, a lower flow lets the water move over the coils more slowly, giving it more time to heat.

There is no freeze issue, because there is no tank. Water in the small traditional tank needs more power to heat - turn it on, and use in 15 minutes, so 15 minutes of propane or electricity. Trade off on the water use or the energy use, I suppose.

I believe you're correct about the extra 6 gallons in the heater tank - but that would cause the winterizing issue.

[Bob Miller]

Originally Posted by blodn1

Not solar, but a big water and energy saver: Girard Tankless LP Propane RV Water Heater - $471.98

The dark side of the RV style tankless water heaters is that they are noisy gas hogs when running and, in many cases, the existing LP lines and regulators will not provide sufficient flow to operate, resulting in yet another expense. (Per my local RV dealers service dept. who doesn't like o install them for those very reasons.)

We install 4 gallon Suburban water heaters in our FGRV's (I've done 4). To use we either press the start button or go out and light them. As soon as they cycle off (usually in 8-10 minutes) they are turned OFF. That leaves more than enough hot/warm water for most uses until the next day.

You don't have to leave it on to heat water hotter than needed, or to keep water you are not going to use hot.

[Bob Miller]

BTW: Except in dire emergencies you can't count the water in the water heater because in order to get it out you have to put more water in, unless you attempt to drain it somehow.

[blodn1]

Bob, I get what you said about having the warm-hot water holding all day - good point. However, the small amount of energy used to heat water as needed is worth it to me, since I don't really use it except for showering and maybe a small amount for dish washing. But it's there IF I need it.

the existing LP lines and regulators will not provide sufficient flow to operate

Fortunately, it's a new build, and I can correctly size the lines/fittings from the start.

I've found that a lot of (house) water heater installers don't recommend them because they don't need servicing, and can't leak, unless the fitting is leaking. I have the same on-demand water heater I installed in my condo in 2003, and it's heating as well as on the first day. The big bonus in a house - and probably in an RV - is that it doesn't leak. I live on the third floor, and I'm sure my downstairs neighbors appreciate this.

Didn't understand what you said about the dire emergencies.

[RogerDat]

I saw an awarding winning design for a solar heater. Essentially dark hose coiled in a shallow wood frame box, under glass. One end of the hose went to the water source the other became inlet for the water heater.

Whole thing just acted as a pre-heater for the conventional water heater. Only good at above freezing temps but not expensive to build.

Installed in a house it used a bypass similar to what one would use for a water softener and small drain petcock to shut it down in the winter. Don't think you would need all that in a camper.

Still think the best idea for a solar water heater for camping is 2 liter bottle with small holes drilled in the cap for taking showers. Leave in sun till the bottle gets hot.

[blodn1]

Had a solar heater in "sunny" Barbados. Hated those cold showers on not-so-sunny days. But maybe as a pre-heater, it would be OK.

[Carol H]

Originally Posted by Night Sailor

I considered tankless heaters. It is interesting to me because I tend to be attracted to cutting edge technology.

.

Not a lot of cutting edge about the tankless heaters. Been in use for many many years in Europe as well as here in NA. My girlfriends home had one here in NA 30 years ago.

[Night Sailor]

Originally Posted by Carol H

Not a lot of cutting edge about the tankless heaters. Been in use for many many years in Europe as well as here in NA. My girlfriends home had one here in NA 30 years ago.

I suppose I think of them as cutting edge, because everything I've read seems to indicate they have not be perfected yet. I frequently read about people complaining of failures, and hot water is something that we don't want to be without...

[Bob Miller]

About the only complaints I have heard of is with RV tankless heaters and that is a fairly new market with only 1 or 2 suppliers.

BTW: the more common name for them for about 100 years was "Flash Boiler" but the term "Boiler" was to scary for consumers. Same thing happened to steam powered automobiles....

[blodn1]

And if you have any trouble with it, here's all you need to fix it.

[Night Sailor]

I think I will put solar hot water on the roof of the house first. The electric bill is killing me.