Hot water tank construction

[Simi 60]

Originally Posted by GILow

Which is kinda why you have to read the whole thread.

They are utterly and totally useless for the job.

But that's ok, because I went with your watching videos on a boat suggestion from another thread and it's a winner. So you are still ahead on points.

Strange
We have a 180 litre version of the same on board that's been going strong for 10 years.

It still has the 240v element which, thankfully we have enough solar and roof real estate to keep it and the battery bank charged up.

[Tricolor]

As to the life time of the integrated circulation pumps I remember this. I have used a Webasto DBW2020 this was a beast without an integrated pump, a Webasto 90 also with an external pump and several ~5 kW Webasto's I think these where Thermotops with internal integrated circulation pump. Only one with a internal pump failure, after replacing the pump and testing it before assembling again I made a short circuit and with this killing the heater forever. Overall for me these Webasto pumps gave an acceptable service time.

[GILow]

Originally Posted by Simi 60

Strange

We have a 180 litre version of the same on board that's been going strong for 10 years.



It still has the 240v element which, thankfully we have enough solar and roof real estate to keep it and the battery bank charged up.

Read the thread if you want to understand why they are useless to me.

Very happy for you and all your solar.

[GILow]

Originally Posted by Tricolor

As to the life time of the integrated circulation pumps I remember this. I have used a Webasto DBW2020 this was a beast without an integrated pump, a Webasto 90 also with an external pump and several ~5 kW Webasto's I think these where Thermotops with internal integrated circulation pump. Only one with a internal pump failure, after replacing the pump and testing it before assembling again I made a short circuit and with this killing the heater forever. Overall for me these Webasto pumps gave an acceptable service time.

That’s good to know.

The duty cycle of my system is a bit of an unknown at this point, in part because I will be travelling and I simply don’t know where I will end up. If it’s the South Pacific I guess the Webasto pump is in for an easy life, but if I settle down in Tassie then the pump will be in for a hard time.

Nothing, I hope, will match John’s heating demands in Canada though.

[Typhoon]

If I get a chance this weekend I will shoot a video of my system and all its components and put it up here and on my YouTube site .

Regards John

[GILow]

Originally Posted by Typhoon

If I get a chance this weekend I will shoot a video of my system and all its components and put it up here and on my YouTube site .

Regards John

That would be very interesting to see.

[Tricolor]

@GILow already producing parts? Then I love to see pics [emoji4]

[GILow]

Originally Posted by Tricolor

@GILow already producing parts? Then I love to see pics [emoji4]

I have boxes of bits (see photo). If I can get on top of my studies this weekend I promised myself that I’d do a test run of the boiler and tank and measure how long it takes to get up to temperature. Probably not the most interesting video, but it will help me to get my head around some of the performance figures.

I am going to share the code for my temperature system for critical analysis from the CF code geeks. Just waiting on a few bits in the post. I only had the larger 18M picaxe chips in my stock, so I’ve ordered half a dozen assorted chips, including a few 8M2’s for these sorts of jobs.

[Silverbullet]

NO! Period. I am a solar energy pioneer and inventor. I built my first thermal system in 1970. Years of experience, trial and error. Do not use pour foam of any type, you would never be able to get the tank out of it without a lot of headaches. A square foam box will leave a valuable insulating space in places around the tank and is easy to install and remove. You should be thinking small stainless steel tank. No more that thirty gallons. I would use one solar thermal panel (4 x 8 or 4 x 12) if you have room on the boat. Powered by a small solar pv panel with a small 12vdc pump. A second pump can be used to come on automatically to pump heated water into (my preference) hydronic baseboard units. And a third pump for heated water for showers, dishes, etc. Its hard to get all the comforts on home on a sail boat but this comes as close as you can get. Aluminum foil faced Styrofoam with the foil turned towards the water tank. No need to fill in the voids. Three inches thick minimum. Top bottom and sides. Also allow for a drain. This is what works best for me and the pumps are the greatest expense. Used stainless tanks are available for cheap. Hot water in a plastic tank is a no no. It will cause outgassing from the chemicals in the plastic and you will die of cancer or some other disease. With this set up, the circulation to the solar panel will only occur when the sun shines. This eliminates any complex control system. As always IF you run out of hot water surely you have a propane stove? Heat water on the stove to get by for a day or two. You will need a pop off valve in the tank just in case you should overheat. Capture the water/steam and reuse it. Any further questions let me know!

[GILow]

Originally Posted by Silverbullet

NO! Period. I am a solar energy pioneer and inventor. I built my first thermal system in 1970. Years of experience, trial and error. Do not use pour foam of any type, you would never be able to get the tank out of it without a lot of headaches. A square foam box will leave a valuable insulating space in places around the tank and is easy to install and remove. You should be thinking small stainless steel tank. No more that thirty gallons. I would use one solar thermal panel (4 x 8 or 4 x 12) if you have room on the boat. Powered by a small solar pv panel with a small 12vdc pump. A second pump can be used to come on automatically to pump heated water into (my preference) hydronic baseboard units. And a third pump for heated water for showers, dishes, etc. Its hard to get all the comforts on home on a sail boat but this comes as close as you can get. Aluminum foil faced Styrofoam with the foil turned towards the water tank. No need to fill in the voids. Three inches thick minimum. Top bottom and sides. Also allow for a drain. This is what works best for me and the pumps are the greatest expense. Used stainless tanks are available for cheap. Hot water in a plastic tank is a no no. It will cause outgassing from the chemicals in the plastic and you will die of cancer or some other disease. With this set up, the circulation to the solar panel will only occur when the sun shines. This eliminates any complex control system. As always IF you run out of hot water surely you have a propane stove? Heat water on the stove to get by for a day or two. You will need a pop off valve in the tank just in case you should overheat. Capture the water/steam and reuse it. Any further questions let me know!

Some interesting ideas...

Solar thermal hot water... I built such a system for my house here in South Australia, using 30 evacuated tubes. It was awesome, even heated the pool with it. It was also MASSIVE. Weighed around 300 kg when full, and that was just the tubes and collector manifold, there was still the heat exchanger and storage tank in the house roof..

Solar thermal heating, on a boat... in Tasmania... in winter... yeah, nah, not really gonna fly. For a start, the hills mean you maybe get a few hours of sunlight if you are lucky. Then there's the clouds. And the area needed for the collectors is already taken up with 760 watts of solar, and I am not giving up a single nano-watt of THAT resource.

Propane heating... been discussed, and dismissed, further up the thread. Don't wish to be launched into space without a space ship.

Getting the tank out, if I ever need to... solved. There's already an outer box, just wrap the tank in plastic before I pour the foam. The outer box is sacrificial anyway.

Outgassing of chemicals... ok, open for debate, but given the number of things already lining up to kill me, I'll tell the carcinogens to take a number.


"I would use one solar thermal panel (4 x 8 or 4 x 12)"

A unit of measure would help. 4 inches by 8 inches... yeah, I guess I could fit it on one of the rails, 4 feet by 8 feet, forget about it. cm/meters ditto. Really not very useful numbers without units. 4 gerbils by 8 gerbils? What size gerbil?

[Uncle Bob]

Originally Posted by GILow

Some interesting ideas...

Solar thermal hot water... I built such a system for my house here in South Australia, using 30 evacuated tubes. It was awesome, even heated the pool with it. It was also MASSIVE. Weighed around 300 kg when full, and that was just the tubes and collector manifold, there was still the heat exchanger and storage tank in the house roof..

Solar thermal heating, on a boat... in Tasmania... in winter... yeah, nah, not really gonna fly. For a start, the hills mean you maybe get a few hours of sunlight if you are lucky. Then there's the clouds. And the area needed for the collectors is already taken up with 760 watts of solar, and I am not giving up a single nano-watt of THAT resource.

Propane heating... been discussed, and dismissed, further up the thread. Don't wish to be launched into space without a space ship.

Getting the tank out, if I ever need to... solved. There's already an outer box, just wrap the tank in plastic before I pour the foam. The outer box is sacrificial anyway.

Outgassing of chemicals... ok, open for debate, but given the number of things already lining up to kill me, I'll tell the carcinogens to take a number.


"I would use one solar thermal panel (4 x 8 or 4 x 12)"

A unit of measure would help. 4 inches by 8 inches... yeah, I guess I could fit it on one of the rails, 4 feet by 8 feet, forget about it. cm/meters ditto. Really not very useful numbers without units. 4 gerbils by 8 gerbils? What size gerbil?

Mate, I just don't get it, is the concept really that difficult for others to understand?
Oh, and remember not to gargle the warm coolant.

[RaymondR]

Hi Uncle Bob. Did you buy evacuated tubes or DIY.

[GILow]

Originally Posted by RaymondR

Hi Uncle Bob. Did you buy evacuated tubes or DIY.

OK, either that was a typo, or one of the best bits of irony I've seen on C.F. in ages. I'm guessing it was the latter.

IF the question was directed at me, I used evacuated tubes after very nearly building my own collectors.

I found some great pointers on DIY collectors, mainly from my membership of the The Alternative Technology Association in Australia, and I was sorely tempted to get brazing. There was one system built by a NZ chap that was, frankly, brilliant, in much the same way Typhoon's re-imagining of hydronic heating is for boating.

But the same ATA membership got me a lead on some very cheap evacuated tubes that were simply too good to ignore, so I focussed my efforts instead on the plumbing side, with a neat little arrangement that heated the house water first then turned its attention to the swimming pool.

Unfortunately I sold the house, and I decided it was best to NOT sell my half baked technology solutions with the house in case it blew up and took someone with it. So all gone now.

But great fun to build.

[GILow]

Originally Posted by Uncle Bob

Mate, I just don't get it, is the concept really that difficult for others to understand?
Oh, and remember not to gargle the warm coolant.

The thread has certainly gone down an unexpected path, but I've got some great ideas from it, and I never have a problem with people telling me where I have got it wrong.

I dunno, I read Typhoon's original post, and I had to ask quite a few questions before I understood what he had done, but when I did it was a real Eureka moment. It all made so much sense... eventually.

Perhaps it helped that I had no "30 years of experience" or was not "the most experienced solar installer on the planet", I had no preconceptions of what was normal so was willing to adjust my thinking to his.

And you are right about the coolant. I gargled some the other day and it didn't even taste remotely of mint, which is should have, because it is green.

[Silverbullet]

Use two cola tanks! Most misunderstood is that the more water you have to heat the longer it takes to heat it back up. For example if you have a large tank that will last through 2 days of no sun, then it could take 2 days to heat it back up. With a smaller tank you are back on solar within a couple of hours.