The Tank › homemade hot water tank (solar/wood heated)
- November 22, 2012 at 1:05 pm #19211
Ok, this will be a little different, I will keep it short, no matter how long it takes,and I have multiple questions.
First part- I am using a stainless steel tank, it was a 12 inch stainless steel tube 1/8 inch wall that I split lengthwise then welded in two 1 foot wide stainless panels to form a tank oval shaped. I ofcourse welded on a stainless bottom.Welded on three 1 inch npt stainless fitings (top for a water level sight gauge, middle for a electric element,bottom for a drain)This tank sits next to a Blazeking fireplace (princess model), the tank is insulated except for the airea next to the fireplace. A dead air, super heated air space is created. this heats the water when ever the fire is going which is from end of Oct to end of April as I heat with wood. The tank is ofcourse unpressurized, and a insulated lid was made with a 20 foot long stick of stainless 1/2 inch line wraped in a coil to act as a condensing coil for steam vapor leaving the top. I found I had to add that part, as the tank usually sits at 125-150 most times but if a stretch of -35-40 cold sticks around that fireplace is going hard, and I can have that tank at 200+ .
The tank stands 5.5- feet or so, and holds roughly 48 canadian gallons or something near 60 or more US ones. Going from memory (this was 6 or more years back)I used 130 linial feet of 1/2 inch soft copper that I wraped into a oval coil and is set into the top 1/2 of the tank (way more than I needed) anyway, the tank is filled with rainwater as thats what I use year round. Cold water enters the coil at the bottom and exits the top of the coil fully heated.
Now to the first part of my question, I dont really understand if I need or should add a anode or if so what type. I had thought it not to be a concern but I did have a couple galvanized fittings threaded into the 1 inch stainless fittings and then a ball valve at the end. The galvanized fittings rusted threw at the threads in 3-4 years, so I suspect some type of electrolitic action that I did not anticipate is happening. Will this effect the Stainless? The copper? what Should I add for a anode? would grounding the tank help ?
Any ideas.I will try and add some pics.November 22, 2012 at 1:14 pm #19212
I forgot to add, code is not a concern, advice outside the box is welcome…November 23, 2012 at 9:30 pm #19217
Hello: I do know that aluminum anodes have been used to slow corrosion in stainless tanks. The galvanized fittings that rusted out…. perhaps they could be replaced with brass as they seem to go to copper piping. About grounding the tank: Is there any way stray currents could be flowing through the tank or piping? If so, than ground the tank.
Yours, LarryNovember 24, 2012 at 3:08 am #19221
Yes, the fittings have been replaced now with stainless. So everything is now copper or stainless. My concern is preventing any electrolitic action on either.
So if adding a rod will do that then I will. I didnt know what type with those metals. If aluminium is whats best, I will add it, I have lots of aluminium around. should I suspend the rod in the tank not touching either the stainless or copper,or can I just drop a piece in and let it rest on the bottom?
I have a 2 foot long piece of 1/2 inch thick 4 or 5 inch aluminium Ibeam that would be perfect. I have to make this last my lifetime, and more as the fireplace, and tank are being built mostly into the wall, and pulling the tank out for repairs would be a nightmare.
I thought it imposible (or less likely) to have stray currents as its heated by the fireplace 6-7 months of the year, and I thought the rain water should be more naturaly non conductive. When heated with the electric element I left the tank ungrounded(yes I know:shock:) thinking that would also prevent/reduce stray current paths, but clearly something went to work on those fittings.November 24, 2012 at 8:12 pm #19229
Hello: The galvanic scale is what I rely on to know how metals will behave with each other. Galvanized (zinc coated steel) is a long ways on the scale from copper or even stainless, so both of those metals will speed deterioration of the zinc and steel. It sounds like there is the slight possibility of stray currents, so I’d ground the tank. Best would be to ground it to the ground bar in your main breaker box. About the anode; you would want to suspend the aluminum in the tank so it’s basically equally far away from all surfaces. Then fasten a copper line from it to the tank itself. There needs to be a conductive path from the anode to the cathode, (aluminum bar to tank). Join the aluminum and wire using conductive grease, so the connection doesn’t fail. That connection might be tricky!
Yours, LarryNovember 25, 2012 at 8:08 pm #19239
Thanks, thats good info. The connection will be tricky, but I will figure something out.April 18, 2013 at 1:16 am #19777
Well I have let the fire go out until winter starts again so I decided now would be a good time to add the anode, and thats what I started to do when for the hell of it I decided to spin the element out of it. I no sooner put my wrench on it and the thing fell apart! the threads were completly disolved away. The element part was still in the tank but the base part just came off. I dug the element out and cleaned up the threads.
Im pissed, I used the best materials I could buy and am having problems. I suspect the element must be of a lower grade of stainless than the tank, or maybe its not stainless?
Its a 3000 watt element@ 240, and I think 2200 at 208. I have put in the aluminium anode, and a new element. I have decided to switch to dc to see if I can avoid future problems.I hooked 3 195 watt panels in series to give me a max power point voltage of 110 volts dc at 5.35 amps. This is now directly feeding the element (18 ohm) Today was the first day running it and it ran along at roughly 500 watts but I did hit ( when the sun was overhead) 5.3 amps at 99 volts or 524 watts out of a possible 585. I expect to hit that as summer comes. Starting temp of the tank was 100 f at 9 am, and over 130 f by 4 pm, but then clouds moved in, but not bad for a first day test….I think this will work.April 18, 2013 at 1:46 pm #19778
Hello: You’re doing some interesting work. 😎 Have you heard of http://www.usa-eds.com/web/ ? They make a direct PV to hot water system. As to the element base: I’ve used steel and brass, but never met stainless.
Yours, LarryApril 18, 2013 at 9:57 pm #19779
I am assuming it was a stainless element, I may be wrong, I long ago lost the package so I cant check, but will when I am next in the store. If it isnt stainless I may just have to make it part of preventative maintanance to replace it every 4 or 5 years. Though if its not stainless that explains why it failed so fast like those other fittings. It also explains something else that started happening last summer.
I had the tank on a timer that turned it on at roughly 3 am and off at about 7 dumping 2, 2.4 kw into the tank. I hit the shower one day early while the element was powered on, things were going well until I grabed the wash cloth hanging over the metal part of the knob, I got a shock, not a full 120, maybe half that or so it felt. It got my attention so in checking it out as I put my hand up closer to the shower head at about 2 inches I could just feel a slight tingle, at about half a inch from the shower head it was strong enough that I did not want to go further. I suspected it was voltage leaking from the element then but thought maybe I handled it roughly putting it in, now I know it must have been because it was dissolving.
With DC now powering the element it should be safer,as there is no way to make a ground loop.
Thanks for tip on that site, I did not know of any company doing that with solar panels, but in reading the info, I smell a little BS. They are talking about their patented process (turning dc to ac) to power the element, I suspect they have complicated it a bit unnecessaraly so you will think you need thier product,when in fact you can do the same thing powering the element with DC direct from your panels though If you are doing that with a typical pressurised electric water tank, I would have the element switched on from the thermistat with a DC rated relay (and hook the contact points in series) a hypertherm part number 003149 is a great one, from memory DC rated,over 40 amp contacts with mag blow out.April 19, 2013 at 12:39 am #19780
Hello: About that electric shower 😯 I would use #6 copper wire to bond hot and cold together above the heater, then take that line and run it to the ground bar in your electric panel. This should give electricity an easier path to take than through you to get back to ground. 😎
ps. I was thinking AC… For a DC powered heater, I agree it’s safer, but you’re still running a voltage that could do damage, so how about running that #6 wire to a good grounding rod?April 19, 2013 at 8:39 pm #19781
I put a magnet on what was left of the element and it stuck like glue, So its not stainless. Now I know. These three panels will be dedicated to driving the element, and not part of the house system in anyway so I am still thinking as to what I should do grounding wise. When I set up the system for off grid 13 or so years ago things were pretty relaxed code wise at the time, pretty much do what you want, I have heard there has been two major revisions to the code regarding RE systems since.
I Will get the latest code book and see whats recomended, Likely as you suggest grounding even when DC powered will be the requirement. I am thinking that now that the other galvanized fittings are out of the system this will leave only the element for any galvanic action to attack. This may cause even shorter life of the element….I quess it will take a few years before I know, and hopefully the anode helpsApril 20, 2013 at 1:43 am #19782
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