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Old 12-10-2019, 11:40 AM   #1
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tech insight on simple water pump, h20 heat, switching...

I did try to review existing posts to prevent redundancy....
I aim to do a water system that uses a Whale foot pump AND an 800 gph DC pump with a mini on-demand propane waterheater (yes, I matched the pump with the pressure needed to switch on heater, and made sure the Whale will trigger it also).* There's one deep cycle with a HF solar panel, FYI.
*Not interested in storing pressurized water or having more pressure than needed to activate on-demand (don't mind pulsing).* There will be one WARM supply (not a HOT + COLD.* If I want COLD for some strange reason, I'll override heater to not switch ON. * [[Drinking water will be separate 5gal bottles, FYI]].* To wash dishes in sink, I will work the foot pump.* To wash armpits or put 4 inches of warm water in mini tub for kiddo, I want option to use foot pump or electric.* I also like this redundancy in case one pump fails in boondockville. * Also have a thermostat-driven switch to power pump with manual override (manual override switched ON will start on-demand warm water if I don't want to work foot pump). * The thermostat aspect will be for freeze protection when the rig is unoccupied: *A well-flushed-out car radiator sits under my 30 gal supply tank (actually tank is a defunct elec water heater built-in to my sink cabinet from the 1960's, flushed out mucho to get sediment out; if interior temp gets to freezing, the thermostat->pump->ondemand will fill the radiator with warm water.* Thermostat located in cabinet with water tank. * Also FYI the main heat for the rig when occupied is a woodstove, so there's no propane furnace.* I'll either use valves (when unoccupied) to divert to the radiator, or I may scrap the radiator idea and just leave the tank as part of the loop so that the on-demand heats the water in the tank up to a freeze-safe temp. * I'm confident that the bath water won't smell like antifreeze, but I don't much like the idea of the stored water having been cycled through the heater a bunch of times... * Finally, a 12v ceiling vent currently is wired for manual on/off, but I don't know if it would be prudent to have it switch on in freeze-protection mode. * Yes, there is a CO and combustible gas detector with alarm.* I don't know much about wiring things that need to be switched manually as well as automatically, and of course I don't want to install more valves than necessary.* Any advice would be appreciated. * Please keep non-constructive criticism very brief.* Thanks!

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Old 12-10-2019, 12:26 PM   #2
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Welcome, and * Please keep non-constructive criticism very brief.* good luck with that among all us hooligans!

I like the idea of repurposing an old radiator to keep the water tank from freezing. I'd probably support the water tank rather than placing it directly on the radiator.

As to the on demand water heater recycling water from the tank it works just fine. Remember the little on demands simply "add" heat to whatever the temp of the inlet water is and can quickly heat the water enough to damage both pex and pvc lines. My recirculating system allowed the hot water temp to swell the pvc lines until a joint burst (about 140 degrees to do that). I now have a thermocouple measuring the water temp at the heater outlet that shuts down the heater at 107 degrees so no more worries.

I see nothing wrong with your overall plan as you've thought out what you want and need. It might not be what others would want but it's yours so knock yourself out!
Jack
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Old 12-10-2019, 01:23 PM   #3
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I won't pretend to say I followed all of that...

I will caution/recommend this: An old car radiator and similar implements are built with lead solder and even lead in the tin bits...

Water sitting in contact with lead for any length of time WILL absorb some of the lead -- then when your "kiddo" is sitting in the bath water your kiddo will absorb the lead from the water...

We can't control the air we breath --
We can't even control the soil we live on in a lot of places...

Control everything you can control to keep your child lead-free.
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Old 12-12-2019, 06:58 AM   #4
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Thank you Banman for the thoughts on lead. This is exactly the kind of input I was hoping for. This and Old Trunt's ideas are making me reconsider the radiator idea for the sake of just cycling the water between tank and heater to prevent freezing and reduce number of points that could fail (the K.I.S.S. theme prevails again!).
Trunt, will you please post the spec/identifier of the thermocoupler you added post-water-heater? I think my thermostat/switch has a timeout function also, and I know that I can also set the heater on the lowest setting to reduce risk of overheating (which I appreciate your mentioning). But I'll look into the thermocoupler...
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Old 12-12-2019, 09:20 AM   #5
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Lots of these available. I have 4 of them working for me right now and considering the quality of such products I carry a spare.
Jack

https://www.ebay.com/itm/STC-3008-12...r=522453463038
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Old 12-12-2019, 12:07 PM   #6
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In addition to lead, both old car heaters and old hot water tanks should be considered excellent sources of cadmium, which should also be avoided like the plague.
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Old 12-12-2019, 05:10 PM   #7
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If setting this system up from scratch why would one even consider an old lead soldered radiator when a modern one could be sourced to better fit the application with no issues of lead
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Old 12-12-2019, 05:36 PM   #8
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Exactly.......
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Old 12-14-2019, 08:42 AM   #9
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noted, and noted, and noted. Nixing the used radiator is unanimous, and replacing the 30 gal heater tank could happen easily. Thanks, and now any insights on other aspects?
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Old 12-14-2019, 10:57 AM   #10
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My advice would be to remember the KISS principle and also do your best to think through all the consequences of what you're thinking about doing.

A little story that's relevant here: About 1959 or 60 my best friend's dad made a salmon smoker from an old fridge. There was an electric frying pan to be filled with alder sawdust on the bottom and the salmon fillets were to be placed skin down directly on the old fridge racks. My friend and I were enthusiastically waiting for salmon season so we could pig out on smoked salmon. But shortly before salmon season my friend's dad put his salmon smoking plans on hold and hauled that old fridge off to the dump.

The reason the plans got put off was cadmium. After the smoker was built, but before it was used, there were reports in the news of people dying from eating salmon smoked on old fridge racks. Apparently the plating commonly used in those days on things like fridge racks contained lots of cadmium as an impurity. People did not commonly understand how toxic cadmium is, and cadmium is an effective electro-plating material, so the cadmium content was ignored until people started dying.

My friend's dad eventually got another, newer, fridge, and went on to produce some delicious smoked salmon, but I never ate very much of it after the initial enthusiasm faded.
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