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scott 
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 Topic: Water Heater element question
Posted: 17 Aug 2022 at 9:27am |
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Will an electric water heater element work at a reduced rate (not get so hot) with a reduced rate of power applied to it or would it just not work at all? I am trying to heat water for my shop floor heat without a monthly bill. There is a wind power generator I was looking at that hooks to a pole or a building that puts out 300-450W. Seems a standard screw in WH element calls for 1,500 watts. Would the 300-450W warm the element, maybe not hot, but warm? If I could do this and warm the floor more than a couple degrees it might be worth a try. I am only out there a couple hours a day if I'm lucky and the doors are kept shut and the building AND cement floor are both well insulated.
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steve(ill)
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Posted: 17 Aug 2022 at 9:37am |
Normal heater might be 1500 watts... and run at 240 volts.... so the line pulls 1500 / 240 = 6 amps ............ (you get 2 elements in a lot of water heater units.)
It is just a resistance heater, so yes, it will get hot..... 240v / 6 amps = 40 ohms resistance.
If your solar panel puts out 120 volts, it might work... Some only put out 12 volts ???
450 watts / 120 volts = 4 amps .......... but at 120v and 40 ohms , you get about 3 amp draw...
What voltage and current is your solar panel rated for ?
Edited by steve(ill) - 17 Aug 2022 at 9:38am
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scott
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Posted: 17 Aug 2022 at 9:53am |
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Hey Steve, Thanks for the help... I have the floor with tubing but no heat source yet. I thought a small windmill would be easy to hook to the top of the wall and as for the numbers I wrote of they were from an Amazon ad when I Googled it (not a fan but a 'helix'). I didn't figure the small windmills would make the 'rated' power requirement of a WH element but didn't know if I was barking up the impossible tree. What I'm saying is I have a clean slate and could set it up as required.
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estout81
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Posted: 17 Aug 2022 at 11:47am |
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I built a parts cleaning tank years ago and used a water heater element hooked direct to 120 VAC and it kept the tank at about 170.
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scott
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Posted: 17 Aug 2022 at 2:38pm |
How many gallons does the parts washer hold?
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steve(ill)
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Posted: 17 Aug 2022 at 3:11pm |
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Scott.... your main problem is making sure the wind mill will put out 120 volts and not 12 or 36.. etc..... AND you probably need 3-4 amps, so 450 watts is OK, as long as you have the VOLTAGE.
Edited by steve(ill) - 17 Aug 2022 at 3:12pm
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jaybmiller
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Posted: 17 Aug 2022 at 3:13pm |
re: heating elements
Can be either 240 (big tanks) or 120 (small/under counter) IF the distance from windmill to heater is short, 120 is OK, but med-long distance 240 is better. Higher voltage = less power loss = more hotter water
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scott
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Posted: 17 Aug 2022 at 3:17pm |
It looks like 12V, 120, and 240 windmills are all available. The one I referenced in the OP was a 240V with 300-400W.
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steve(ill)
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Posted: 17 Aug 2022 at 3:19pm |
for example... this wind mill OUTPUT is 12 volts - 400 watts..... So it is basically a 32 amp generator that you would use on a small car.... You need 120 volts..
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mdm1
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Posted: 17 Aug 2022 at 3:30pm |
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I would do some serious thinking about the wind turbine. Most of the time you would not have enough wind speed to develop the max out of it. Don't mean to dampen your hopes, but really check it out. Good idea but may not work!
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Everything is impossible until someone does it! WD45-trip loader 1947 c w/woods belly mower, 1939 B, #3 sickle mower 1944 B, 2 1948 G's. Misc other equipment that my wife calls JUNK!
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steve(ill)
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Posted: 17 Aug 2022 at 3:43pm |
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get ya a cheap fan and set outside and watch how often the blades are SPINNING at a good speed... Most wind mills are less than 50% efficient..
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estout81
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Posted: 17 Aug 2022 at 3:47pm |
scott, I don't remember the tank gallonage but, was probably 40 or so gallons. It was a dip tank with caustic in it.
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jaybmiller
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Posted: 17 Aug 2022 at 5:18pm |
Will you have a pump to move the water around ? If not, you'll need good hot water to 'thermosiphon' (move the water) Being electric, you can super insulate the tank,to get the heat INTO the concrete not the air. How many feet of PEX and zones ? Need to price out the cost of windmill, wiring,boxes,switches, etc. While all this is a one time cost, it may be cheaper to just pay the hydro company. Pencil and paper time !
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plummerscarin
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Posted: 17 Aug 2022 at 5:47pm |
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The heat source is sized for the square footage to be heated and average outdoor temperatures could be factored in. On colder days will have trouble keeping warm. My system has an outdoor sensor to ramp up input to maintain on colder weather. How big a shop? How cold outside? Temperature you want to maintain inside? You can't raise and lower indoor temperatures as quickly as hot air heat. Essentially set it and forget it. BTU rating is based on optimum energy input. Lower the input and you may have trouble maintaining your desired room temperature. Also may burn out the element sooner? Don't know for sure on that but I do know lower power supply from generators is hard on power tools
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jaybmiller
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Posted: 17 Aug 2022 at 7:11pm |
Actually the element will last longer, a LOT longer, running at reduced voltage.
At one time I could buy 130V incandescent light bulbs. While they were slightly dimmer, never had to replace them from burning out. Only 3 of us 'on the pole' here so '120' is volts is usually 124-127.
These days there's lots of websites where you can 'size' a PEX system, also the layout of the tubing is kinda critical.
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LouSWPA
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Posted: 17 Aug 2022 at 10:17pm |
Well, yes it will work, however, as has been pointed out already, there are a lot of variables. No 1, that slab of concrete is a giant heatsink, and I question 1500 watts being sufficient. But, assuming 1500 watts is sufficient for your purposes, you are now suggesting to do the same job with less than 25% of 1500 watts. Think about it, some hair dryers are close to 300 watts. I don't want to discourage you from trying, but I just don't think it will ever heat your floor noticeably. JMHO
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scott
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Posted: 18 Aug 2022 at 10:28am |
Some of the questions you guys asked... The 32' x 40' floor has 1000 feet (4 rolls) of 7/8" pex that made 4 equal length zones. There is two feet of 2" closed cell foam ran vertically around the wall and more closed cell- blue- under the floor. The system has a manifold with restrictor valves in the inlet side so the zones can be adjusted for temperature. The walls and ceiling are insulated, even the doors have a brush seal. This building is attached to another, 'the original' pole barn by a 10' x 10' doorway that has a wood stove in it. All the new building has ever had for heat was what wafted thru the doorway and it does an amazing job of holding the heat. I want to get away from the woodstove. I'm running out of Ash and need to do something. The firewood has been essentially free but the chainsaws, gas, and oil, plus a firewood truck, the stove, chimney pipe etc are not free. I re-Googled and found a Made in the USA company Windspire that makes wind generators in the 1 to 5 kW range. That would run a water heater correctly. The ad says call for pricing... The responses above sound 'negative' on the effectiveness of "300W going into a 1500W element". Makes sense, and that why I asked. Thank You.
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tadams(OH)
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Posted: 18 Aug 2022 at 12:39pm |
I run radiant floor heating in my shop and I turn it on the 1st of October before the cement loses it's heat mine is 28' X 56' and I used to heat it with one 80 gallon hot water heater and it worked great but I had a pump and valves to because it wsa divided into 2 section, garage & work shop, so you will also need electric to run the pump.
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steve(ill)
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Posted: 18 Aug 2022 at 3:43pm |
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Tom... most of those pumps are pretty small.. Couple of gallons per minute.... normally not over 5 gpm ... Is that what you have ?
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jaybmiller
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Posted: 19 Aug 2022 at 6:52am |
scott..
I'm thinking you have roughly 23 yds of concrete in the floor so no way 300W will heat it up. 300W is 5 'old skool' 60 watt light bulbs. yes ,that's a lot of heat BUT you got a huge mass of concrete !
you really need to go to a 'radiant infloor heating' website, toss your numbers into their online 'calculator' and see what amount of 'heat' you need for your floor. Once you KNOW the BTUs needed easy to convert to Watts.
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scott
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Posted: 25 Aug 2022 at 9:20am |
Hey jaybmiller, The info I found says I need between 45,000 and 90,000 BTUs. How many watts does that compute to? Thank You!
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jaybmiller
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Posted: 25 Aug 2022 at 9:25am |
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45k BUTs/hr = 13,188 watts
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DaveKamp
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Posted: 27 Aug 2022 at 4:01am |
1000w = 3412 BTU.
A 400w windmill will yield 1364 BTU... if it's running at a constant speed, producing full output, it will heat 1364lbs of water one degree F per hour... that's 1364/8= 170 gallons.
If you have a perfectly insulated 40 gallon tank, and you're not moving the water at ALL, for one hour, you'll get 4.26 degree temperature rise within the tank.
The THEORY you have (windmill heating water) is sound, but the magnitude you need to reach before it becomes viable in practice, is significantly higher... and for several reasons, first being that it's just gonna take more power to get into the total energy equivalent required. Woodburning furnaces are hideously inefficient at recovering heat... but they're burning SO MUCH, that they yield a significant output.
The cute part, is that the harder the wind blows, the more energy your windmill will be generating, at least until it hits it's max limits (you'll either max out the electric generation, or hit the speed limit of the airfoil's efficiency), at which point, you'll be generating no increase in heating power... it'll be maxed out.
The BAD part, is that the faster the wind blows, the faster your building looses it's heat... and it is NOT going to be anything you can even THINK of keeping up with, when your input power is so low. If you were swinging three 18ft blades and kicking out 18kwhr, then your water heating capacity would be up around 61,000btu. That's what a typical smallish-house furnace will yield... and it'd be enough to raise your 40-gallon tank's water temp by 190 degrees in one hour. Under THAT circumstance, your economy-of-scale starts making the windmill a viable possibility.
Now, if you wanna increase your efficiency, do away with the electric concept, and instead, put up a windmill that has a 90 degree driveshaft coming down through the roof of your shop, extending down into a pit wherein lies a 200-gallon round tank standing on end. On the shaft, put several boat propellors of misc. pitch, and mebbie a few chewed-up blades too. Add a belt-driven pump to pull water out of the tank, through the floor, and back to the tank. The windmill's mechanical output will go into thrashing water around inside the tank, and the resulting friction will very efficiently raise the water temperature and provide mechanical output to MOVE the water out into the slab...
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Ten Amendments, Ten Commandments, and one Golden Rule solve most every problem. Citrus hand-cleaner with Pumice does the rest.
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jaybmiller
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Posted: 27 Aug 2022 at 9:43am |
Dave , your idea is good, and works( 70s idea....) BUT you have to SUPER INSULATE the tank to keep the heat of the warm water from heating the soil it's in....
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Never burn your bridges, unless you can walk on water
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