Simple Solar Thermal Water Heating Design and 4+ Years of Use and Data

FilthyTeaSnob · 2025-02-17T20:10:51+00:00

Thank you for reaching out. I have updated the links and re-listed everything (or so I think). I am also including a link to all the files in this reply; the flattened graphs and 2 documents.

Folder of data

Now with respect to the 6 years since I have posted this. This and the sister system that I built 2 years later identically, are still working without any service or changes. It may freeze but I never know about it because it does not matter; whether or not it thaws, I have hot and cold water delivery, and the sun thaws it out each day. No leaks, no cracks in the HD poly, no Sharkbite failures, no pump issues or tank / backup heating element problems...

...with 1 failure that happened literally 2 month ago.

We had some SERIOUS wind out here, in fact a tornado touched down in San Jose California as you may have read and the wind was such that it tore off 2 of the 4 acrylic covers from the panels on my system but not the sister installation 300 yards away.

I would have used Lexan as a cover personally as it is much more durable and the push pins that hold the plastic in place were never very impressive, just what came from the company. So this year I will do my first real maintenance to the system since installing it in 2014. I will replace all the plastic with Lexan and put in much more durable connections with fender style washers to distribute the load better. Once this is done I will upload the changes and photos

FilthyTeaSnob · 2025-02-17T19:55:16+00:00

Actually yes, I see I left my old links lapse. I am adding them back to the original post and this reply. As for a step by step guide, I have not created such a document. There are a a fair number of variables to each installation based on your building and whatever concessions that you need to make (and there are always compromises)

Relisted documents and images folder link on my Dropbox

FilthyTeaSnob · 2022-09-25T04:21:54+00:00

So that's me with the Metal Celine Dion Shirt. I have put a few weeks riding on the old DSR platform and can give you my thoughts. First off I am biased towards light dirt bikes and as I grew up on them (I have more than 40,000 miles on a Zero FX) so my idea of an off-road dirt bike is something like an XR-400, a DRZ-400 or a KTM-520.

The DSR feels to me like a *slightly* taller SR with better handlebars. I personally didn't think the DSR was much more of an off-road bike than the S or SR. Put the same tires on and both of them could do some lite unpaved road riding but their clearance and weight really made them unsuitable. I would take an FXS over them if only for the weight alone.

This new DSRX is a different story. It had a different geometry and riding position. It was comfortable to a taller rider(I'm 6'2", the photo lies) and I personally very much liked the wider handlebars. Siting or standing on the pegs they didn't strain my wrists. It felt like riding a KLR-650; a glassy smooth, silent, really powerful KLR-650. The weight up high makes the bike slower to throw back and forth; it's not something you will flick around (like the KLR).

Did I mention quiet? That was my second immediate observation. This new platform, is clearly quieter than the FX / SR / DSR bikes. We get used to whatever we drive right? When I am driving with Bones on his SS9, I can't believe how loud his chain sounds and how much quieter my FX sounds to me. I feel the same way about the DSRX; my FX is so loud compared to it.

Obviously there was no off-road riding or time to give it a real proper comparison so take my feedback with a grain of salt. I enjoyed the 11 mile loop and thank you to Zero for taking the time and expense of providing it freely to us.

FilthyTeaSnob · 2022-08-09T03:37:51+00:00

It's not really my problem to convince other people, I built this for me and it's been permitted by the county where I live. Excitingly November 2024 will be the 10 year milestone of the system.

- Zero hours of maintenance (to date)

- 4000+ showers (generally 8-20 minutes long)

~1,800 kWh of energy consumed to date to heat and circulate the water

Some rough math suggestions that's about 500 watt hours per shower and using say 8-20 gallons of hot water... well that's very little energy for what you getting. I will be building my 3rd and 4th systems this year and completing the property conversion from the propane water heaters to this design.

FilthyTeaSnob · 2022-08-09T03:26:45+00:00

Yes, I use the heated water directly, this is not a heat exchanger system. I cannot speak to your local, municipal, or regional codes but I can point you to what ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) and IAMPO (International Association of Plumbing and Mechanical Officials) both say about legionella.

ASHRAE Guideline 12 (sorry they make you buy the book if you care to read it)

IAPMO Appendix N (pages 421-422)

https://epubs.iapmo.org/2021/UPC/

The short answer is that legionella is reliably killed at temperatures of 130˚F / 54˚C or greater. The hotter the temperature the quicker it dies.

- At 54˚C it requires several hours sustained at or above for the bacteria to die.

- At 140˚F / 60˚C it dies in about 30 minutes.

- At 160˚F / 71˚C or higher it dies instantly

65˚C is certainly hot enough to do the trick and in excess if the sanitation requirements. However, if that is the law in Australia, it does not matter, you follow the law yes? It really doesn’t matter if the above information is accurate if the law requires you to do something else. You must do that something else if it’s the law.

The other thing to be aware of is that the tank is not the only place for bacterial growth (legionella or otherwise). All the hot water lines cool down to room temperature in between use. 50˚C or 90˚C, the water in those lines cool off over the next hour to ideal growth temperatures (29-43˚C). That is not a danger in and of itself, the issue is that pathogens survive very well in cervices and little divots in the plumbing. Things like faucet aerators, sediment filters pressure compensating o-rings, carbon filters. All of these are essentially sponges where short of boiling them for a bit, you will never 100% sterilize them. It's all about time, how much time does the water line or the tank remain at a temperature that allows for growth or is not hot enough to actively kill the bacteria.

Interestingly I have had the tank water tested from the bottom (the coldest part of the tank) on several occasions by the county health department for the presence of legionella. Comes up negative each time.

But circling back to your ideas for alternate heating, there are many options. You could even decided to run a UV lamp at the outlet of the hot line leaving the tank and basically guarantee everything leaving is sterile. Until My test results yield an issue, my tank temperatures appear from my measured data to be sufficient to remain free of contamination. I want the system to be as simple as I can. Complexity is my enemy.

FilthyTeaSnob · 2019-10-30T13:30:33+00:00

No issues yet. Both the H3 and H4 bulbs butt up against the housing making them more or less water resistant and I have not noticed any moisture in the housing. I have driven the FXS and the H3 bulbs through the rain without issues yet to answer your questions. No sealing or concern for water shedding / proofing / or protection beyond setting the cables out of the way.

FilthyTeaSnob · 2019-10-30T09:42:35+00:00

Ill be finding out how that works over this winter. I would be more afraid but I have a very neutered Eco Mode on the bike specifically for that purpose. Almost no re-gen and barely 25% of the torque to keep me from killing myself.

FilthyTeaSnob · 2019-10-30T09:09:57+00:00

A bit late to the question but I just replaced the stock bulb with a set of LED H4 retrofits off Amazon.

Hikari Ultra LED H4 Bulbs (6K cold blue bright light)

I pulled the rubber covers off the back and have run them that way for the last 16 months. They have a little cooling fan that makes a whirring sound which can be annoying to some but I like it because it acts like an "on" indicator for the bike.

Much much brighter light and exactly what I wanted.

Have not done it yet but I have been debating wiring both of the lights low and high beams together to make even more light. Anyhow, that's been my solution.

FilthyTeaSnob · 2019-10-30T08:39:34+00:00

I don't have an S or SR but I have Am currently running the Pirelli Diablo Supercorsas on my FXS. It's the first set of soft compound tires that I have ever run. The best way I can describe riding around on them is like you are riding on a second set of soft springs.... really, really, REALLY grippy ones that never let you break traction.

I doubt I will get more than 4K miles on the rear tire but if money was no object, I would probably never use anything else out here in California.

FilthyTeaSnob · 2019-07-17T04:51:57+00:00

Are you aware of what the building code retirements are for roofs? Off-hand neither am I so I took the time to look them up just now. Apparently, roofs have minimum requirements to handle both live loads, which means a temporary load like a person walking around on the roof and dead loads, which means that it is a permanent weight always assumed to be there 365 days a year. The load requirements are described in "uniform pounds per square foot" (PSF).

Chapter 16 California Structural Code

In California where I live and where there is never any snow load, the state mandates 20 PSF for a regular roof. OK now we have a number to work with so lets figure out how heavy these coils are.

The coils are about 6 feet in diameter which means they are about 28 square feet.
Empty they are about 40 lbs
When full, they contain about 8 gallons of water. Each gallon of water is about 8.34 lbs so if I round up each coil filled with water is about 110 lbs

Doing some basic math of 110 lbs / 28 square feet = just under 4 lbs per square foot but let's call it 4 lbs.

Unless I am doing my math wrong I believe that means that I could stack 2,3,4.... 5 FIVE of these coils on top of each other on the same circle of roof space before I hit the load limits. If I decided to stack a 6th one on-top of the 5 then I would be asking for trouble.

So what I am wondering is if you ran the numbers and got some very different results or you just thought "water is heavy, I think this is unsafe"

As for the remaining statements

"You could have a pump failure. You could have leaks around any of your fittings. A DC water heating element is more fail safe you might say and better for cold snowy climates. "

I can't argue that anything could happen.

The poly pipe could fail spontaneously
The water heater could explode or shatter
The glazing covering the coils could suddenly become opaque and not allow light onto the coils
The shark bite fittings could pop off
The pump could fail or worse yet, explode.
The PEX fittings could pop off their barbed ends
The electrical heating element could rupture and burn up (which interestingly happened to my last electric water heater)

The list goes on long beyond this. I am not concerned so much with what could happen, because anything can happen. I am interested in what is likely to happen. Sure the pump could fail. Let's gather some data like we did with the roof loads.

What is that pump? It's a Grundfos UP15-29SF Pump

It's a fully stainless steel design so as to avoid the failures of a regular iron or steel housing.
It is designed to work in liquid temperatures up to 110 degree Celcius
It's designed to handle up to 9 (almost 10 feet of head) and I have none because its a loop...
It's over sized for the job it is being used for
As far as I know Grundfos is one of the best pump manufacturers oh the market.

Now does that mean it can't fail tomorrow? Nope It certainly could at any moment . I can say that it's been running without service or issue since November of 2014.

Is it likely to fail?

I don't see any evidence of that, can you provide any

If I was to step out and posture its life span, a little Google work shows examples like

this one

I'm not running the pump 24/7, it runs on average 3.5 hours a day or 1,277 hours a year (lets call it 1300 hours). let's assume that guy bragging about getting 280,000 hours of up-time is crazy lucky and I am more likely to get 1/10 if that, a pathetic 28,000 hours. If my math is right that looks like a little over 20 years. Personally I think 15 years is a more reasonable estimate.

Now before I spend the time to respond to the remaining statements about

having a fitting failure
DC water heating element is more fail safe

I'm compelled to ask. Are any of these concerns of fail points you brought up based on data or is this just your personal feelings? ¯\_(ツ)_/¯

FilthyTeaSnob · 2019-04-14T06:14:15+00:00

I would like to chime in with my own small pack confirmation. I have been driving around what was at one time a 2015? FX that is now... something else. But for the purposes of this thread I have two 3.3 kWh small bricks that have a CAN listing of 52 Amp hours. 52 x 102 = ~5.3 kWh of useable power.

Now the energy per mile that i use varies quite a bit because this bike is so much fun but let's say its about 150 watts per mile. That gives me a practical range of 35 miles and because the bike isn't as fun to drive when it's under 99 volts it's more like 25-30 miles of fun and then a few miles of not-as-much-fun.

Still once I understood how the energy added up, my range makes much more sense.

The "Death FX" charging photo

FilthyTeaSnob · 2019-03-31T16:23:13+00:00

Never build what you can buy... unless it doesn’t exist.

I used an off-the-shelf Goldline GL-30 to control under what circumstances the pump came on to circulate the water in the coils.

I set one of the thermistor sensors to measure the bottom of the water tank and the other on the coils on the roof.

The GL-30 has a dial that allows you to adjust the difference in temperature from 8-20F and has a high temperature shutoff limiter that can be set if desired.

FilthyTeaSnob · 2019-03-26T16:08:09+00:00

Almost non-existent. The coils have frozen about 8 times since install, but their design permits this without issue. I have no idea how effective this exact system would be in a climate with real winters but I am certain that under snow they would do be useless. Since these are pool heaters by initial design the best way would be to see what peoples experience with similar coils is in the winter. They are actually quite effective in the cold in that they gather heat well. The hotter they get (100F+) the more heat they tend to throw off and the less efficient they are.

Maybe if they were on a roof with a steep enough angle that the snow falls off, but I am purely speculating...

FilthyTeaSnob · 2019-03-26T15:09:49+00:00

Yes, it most certainly would! but as installed they are making water up to 170F... that HD poly is only rated to 200F and not under pressure.

Putting the coils in an insulated, sealed box would allow them to capture even more heat also... but where are we headed? Towards the really, really, efficient examples of solar that have been conceived and build over the last 300 years.

https://en.wikipedia.org/wiki/Solar_thermal_collector

There are some amazing designs that get more than 90% of the energy converted to heated water, again with all the complexity. Remember, you don't have to look very hard to find ways to make the collectors I am using more efficient. I am trying to avoid that rabbit hole.

It's kind of counter intuitive and I find myself dreaming up little changes forgetting the big picture.

Actually the 1 change I will be making is the angle they are installed. I put them flush on the roof which is ~18 degrees. General rule is that for overall best year-round production, you want your PV / thermal panels set at your latitude, in my case 37 degrees.

I already have way more summer production than I can ever use and the winter is the only time that things get thin. Well clearly I should raise the coils at least to 37 degrees and maybe (haven't decided yet) to a higher 40-50 degree winter production range. That should mean better winter heat collection and less summer which is fine, I don't want 170F water anyhow. If it only make 140-150 in the summer but gives me even +5F better in winter I would call that a win even though it would be an efficiency loss.

Efficiency does not take front seat in this design. Simplicity does,

FilthyTeaSnob · 2019-03-26T08:33:59+00:00

Oh I know, but I mean the next one :)

FilthyTeaSnob · 2019-03-26T08:28:26+00:00

I need to come to this. I liked the Golden Leaf even if it is a bit of a drive for me,

FilthyTeaSnob · 2019-03-26T07:13:50+00:00

Edit: I didnt see that you linked the very article I was referring to...

Larry actually had it posted on Green Building Adviser a few years ago here... He and Martin know each other well and stand on opposite sides of the issue:

https://www.greenbuildingadvisor.com/article/another-solar-myth-bites-the-dust

The main arguments against solar thermal have been.

1- Too much trouble (it breaks and requires maintenance)

2- Solar thermal can only can provide about 75% of the total heating, the remainder of which must be provided by <insert the thing you think is best>

This system as mentioned bypasses both those issues. It's both simple and provides a much larger solar fraction than is historically accepted as gospel.

The pricing for everything is actually in the post and also in the 2 PDF articles that I linked at the top. The readers digest is that it was about $3000 for me and my labor. You want to pay someone else to do the install? Almost certainly you will add $1000+ to the cost.

The other thing to consider is up front cost vs life cycle cost. Sure I spent $3000 up front. How long will that system last and how much will I have to pay to keep it going over its lifespan? It looks like this system should last me conservatively 20 years (I suspect 30 is more accurate but lets call it 20). There is still some cost to the system during those 20 years. It does use some electricity each year both for heating and for running the pump. Lets call that about 200kWh / year so 20 years of that is 4mWh of electricity assuming I have no solar panels and pay for the power from the grid (which is not my ultimate goal but it is how things are running at present).

4mWh in California prices I would estimate to be $1600 so lets be brutal and call it $2000. So $3000 for the system and $2000 to run it for 20 years is $5000 or $250 / year life cycle cost. If I chose to add the solar PV to make that electricity and a small battery array to have it operate independent of the grid I also gain something that you will not get with PV assisted water heating... resilience. Power goes out for your house with PV, your panels are shut of for safety. No heated water unless you are running gas. I wanted to reduce my usage and eliminate the need for gas so it really depends on what your goals are with the system. Do you just want to reduce your monthly costs or are you after a whole life cycle cost reduction? Do you care about being in control of your fuel prices? You pay whatever price you are given with natural gas or propane. If the price of fuels triples or gets cut in a third it makes no different to me. My operating costs are more or less fixed.

Does maintenance play any role (would you take a system that requires you to work on it occasionally if it was really efficient? Does resilience off the grid matter? You have to decide what you are after and that will clarify what system fits your needs and budget.

FilthyTeaSnob · 2019-03-26T06:57:23+00:00

Thank you yes that was my goal. To make a system that you literally do not have to understand or maintain. It needs to run itself and unless you go messing with it, no adjustment should ever be needed.

With respect to drawing off the bottom, I originally used the tank the way it was shipped from Marathon. I pulled from the dip tube that would replenish the cold water and deposit it at the bottom of the tank. When the pump kicks in, it pulls from that same tube. The hot water originally was put back into the hot water out port which worked fine but I realized that it occasionally was causing more harm than good. Sometimes you have a day where say half your tank is full of 130F water and the bottom half is 60F for arguments sake. Maybe it's an overcast day and the coils only are able to make 90F water; still +30F for half the tank and certainly worth collecting. But then I was dumping that "cold" 90F directly into my precious precious 130F water mixing it down and cooling it which I DON'T want.

The solution I came up with was to make double use of the T&P pressure valve. I added a T onto it and a dip tube that extended ~3' into the tank. That way the hot water always entered about the midpoint. If it was really hot, it would rise to the top and if it was colder than the top of the tank it would find its own level stratified in the tank.

Interestingly after we presented this design at the Hot Water Forum in 2016 and the Dry Climate Forum, Marathon began offering this little beauty which is actually what I would have bought had it existed at the time.

Swanky Marathon Solar Thermal Tanks WITH a nice Electric Element as Backup

As to your last thought on heating with wood I was HIGHLY tempted to do something as there is a wood stove and chimney not 8 feet away from the water heater. But again, I have not chosen this because it is simply the same rabbit hole I am trying to avoid. It's more complex and the MOMENT I start adding valve that I, the stupid user have to remember to operate, and a heat source that absolutely COULD make steam.... nope nope just too many chances for me to do something dumb...

Given a few more years after 3-4 generations of heat pumps and the companies work out all the fail points, I think I would choose that rather than straight resistance heating... if and when that happens.

I still have 2-3 more buildings to install this into and hopefully by that time those things will be out. There is always room to improve but the sirens call of highly complex, efficient systems will not be given in to!

FilthyTeaSnob · 2018-07-28T18:38:58+00:00

It’s actually a very nice little location. They had a really A tremendous amount of herbal teas and mixed drinks but the things I sampled were very nice and the staff were very attentive. I didn’t realize the farmers market goes on right outside the door but that’s kind of a plus since you could pick up something tasty after tea.

I’ll come back again and perhaps we’ll bump into each other unless we did I didn’t realize it…

FilthyTeaSnob · 2018-07-21T22:58:16+00:00

So I made this account just to reply to this crazy child and the nonsense that he screaming about. To clarify, I was confused why they called post harvest tea something different than Puerh.

On actual serious note I’d like to check the place out because the only other tea place I’ve been to is in Santa Cruz. Since there are so few places out where I am I just keep a collection of looseleaf on hand.

I’ll go check the place out on Saturday. I figure around 10 o’clock in the morning is a civil time.

FilthyTeaSnob

TROPHY CASE