I think you may be interpreting EF ratings of 0.90, which are common for electric hot water tanks, as meaning that they are 90% efficient. If you can tolerate restricting your hot water use to a particular time of day (morning for example), there is no reason to maintain a tank full of hot water 24 hours a day just dissipating it’s heat to the surroundings. Solar Hot Water Heaters Advantage and Disadvantage, How to Clean a Honeywell Fan with Easy Steps, How Many Coats of Primer You Need before Painting…, How to Clean Frosted Glass for Door and Vase…. The reason commercial tanks draw so much power is “recovery time”. However, the water will also be colder by the time the element is switched on since more energy is dissipated from the tank in the 11 hours the element is off. For the past 4 years which is a new level of suck. I recommend suspending the element in mid air inside the pipe. We are just now getting 3.3 kW solar power. Currently using “solar heat” via about 400′ 3/4″ black pipe on Texas roof. I believe the cost of electricity was calculated at 7 cents per killwatt hr. Any ideas or suggestions about this are much appreciated. Thanks Rob! But I have also been able to scrounge a small electric water tank heater. Fortunately the planned new location under our stairs will reduce the distance to the point of use to about 25% of the current distance. , hello rob, If your gas hot water tank is located inside a living space, then I have even more bad news for you. Did I do something wrong that could cause this burning? There is also a danger of explosion since air is compressible and will expand violently if the tank ruptures, unlike water which will simply leak. Any thoughts on this ? Interesting idea. 4 yrs ago I inherited a house and a crack was found on the gas line that was in the backyard so It was my responsibility to have it repaired, no way I could afford the $2800 cost so I’ve been heating water on the stove… In my opinion this is as unethical as allowing retailers to advertize a product for $100.00 knowing the customer must pay $115.00 to take it out of the store. Installing a Gas Furnace Brilliant!!! Proudly powered by WordPress But so far, many thanks to you, I’ve enjoyed just that immensely, (having curtailed what I regard as a gas price fixing monopoly long ago). Recall that prior to converting our tank our hot water tank was consuming about 1.2 GJ (1200000 kJ) per month in natural gas. What did you use to check the temperature? The only possible benefit would be increased element lifetime since the element would operate at a lower temperature. Since our garage is not insulated, I would have to heat the big tank in the winter but only enough to prevent freezing. I had to bend inside tank. It also means you can easily switch back to gas if you decide to. For example, immersion elements such as those used in commercial electric hot water heaters have great heat transfer since they are in direct contact with the water. The temperature and pressure in the tank may rise until the tank explodes. The element heats up the air in the tube. TIMER and a bigger heater is GENIOUS ! Would you please advise whether the 1350W element is too big or should I try to get one with lower Watts? You’ll likely need to adjust the timer a few times during the year to adjust for the temperature of your incoming water which will vary seasonally. This setup has served me and my family for almost a year now. Used the same method you suggested but instead of using a coil I made a metal cap and drilled a hole in the top and attached a 1500w heat gun. Point taken. Note that I heat my home with electricity too. On this setup we were able to have 3 showers in the morning and 2 baths, later that afternoon another 2 showers and a bath. I assume that it should control the temperature of the water, not of the air in the tube. I would also super insulate the tank as I have already described in another post. I mentioned earlier that our hot water tank is located in an unheated garage. You probably won’t ever need it, but if you do you’ll be glad you put it on. Worked fine for me but then my daughter returned from college and wanted longer showers. already saved us about $355 per year. I unplugged the heating element about 8:30am yesterday, and about 2 hours later, I went in the kitchen and was running the hot water and almost scalded my hands. I found that a 520W heating element was satisfactory. Also, a hot water tank is a closed, pressurized system with only a water inlet and a water outlet. I haven’t encountered that before. Two small tanks would dissipate more heat than one large tank, all other factors being equal… ie same temperature, same insulation thickness, same total volume. My tank still dissipates heat to it’s surroundings whenever the inside water temperature is higher than the outside air temperature. I also highly doubt you live in Japan which actually uses 110VAC. The question I have is: would a common electric water heater element work just as well as the stove top element pictured in your article? But I also have a cool possibility with my Outback controller- it has an auxiliary port that looks like a telephone port. The cap will act as both support for the element, hanging by the wires, and also to prevent air flow through the tank. There is a simple kit to convert RV hot water tanks to electric without interfering with the gas service to the tank. Also, even if it lasts, it will be less efficient because you are blowing hot air through the center tube rather than heating air within the tube (ie the heat escapes rather than being contained and forced into the water tank). Have you considered adding (building) a heat recovery unit for your sewage/drain line? What if someone tries a 1200 watt element? Or do you have to put in a new hot water heater. Converting from electric to gas heat with a 97% Efficient Gas Furnace + a gas water heater is nearly 2/3 less than with an electric furnace & water heater. So keeping the heat generated by the resistance inside the chimney space without incurring significant heat losses to the exterior is critical. Required fields are marked *. Just the two of us, we never use a full tank of hot water each day and the gas furnace seldom comes on, but I’m paying the minimum $12.00 p/month gas bill. Because I wanted to plug my tank into an existing 120V circuit, I did not want to draw so much power that I’d be likely to trip a breaker if I plugged something else in while the hot water tank was on (even though that’s pretty unlikely since I run the tank only at night). Mythbusters hot water tank explosion (click image to watch video). i used a ceramic plug from a brooding lamp and a 200 watt bulb, and have HOT water again! Also even the heat losses to the copper wiring (excellent conductor) that holds the stove resistance will be a source of heat losses to the exterior (it is also subject to higher oxidation associated with the heat). Hi kris, Thanks in advance.. Hi David, Customer must live within GRU's natural gas service area. Another solution is to use smaller diameter pipe as long as you have plenty of water pressure. 1. would hooking a transformer to the element to increase the voltage gain anything? The only difference is that an element in air must heat to a higher temperature to transfer the same amount of heat as an immersion element. PS. Thanks for your help. Thermal switches usually have a flat surface which is intended to contact the item whose temperature you wish to regulate (in this case, the exterior surface of the hot water tank). But it looks like I’ll need to put in a new outlet next to the cabinet. I just used the normal 40/60/75/100 lookig bulbs. Be sure to turn off your natural gas completely before performing this conversion. Jeff. I turned on my water and presto! off the gas valve just for safety, even though gas was OFF anyway. Gas water heater will be able to use whenever the power outage comes. If you care about the average temperature (ie if you want hot water available at all times), then the 1000W element offers no efficiency advantage over a 200W element. Hi Robert, I don’t think it matters too much to the heat transfer whether it contacts the inner walls of the tank or not. i have an electric water heater , not gas. I would prefer to have higher resistance and lower power. From that spec, one could determine the baseline power consumption and cost that the tank will have just to maintain a certain temperature above ambient, assuming no water consumption. It would fit nicely into the heat exchanger tube without any bending. In any case, if you have a gas hot water heater you should have a carbon monoxide detector nearby. Hi Luis, The benifit would be more efficent heat transfer to the water in the lower portion of your tank, and a longer lasting element do to less heat buildup on the element itself. We use about 40 litres of hot water per day for showers (yes, I measured it). Heat only flows from hot to cold, so if your solar thermal collector is only heating up to 40°C because it’s an overcast day, you won’t be able to transfer any of that heat to a hot water tank that’s being maintained at 45°C. Laurie Mark. Friday night was the first time in over 4 years I had a hot shower in my home with hot water that was NOT heated on the stove. All that changes is the thermal resistance between the element and the water. Holy cow. Great article on super insulating water heaters. Attach wires, electrical cord and cap. (what I had) What’s the best way to bend the element? But even in air it is already operating at a much lower temperature than it was designed for as it’s operating at 1/4 the design power. )fittings common to all water heaters. The removal of this heated air from your home causes cold air from outside to be drawn in through all the cracks and openings in your home’s building envelope. A.O. This would allow the use of an off the shelf item. Thanks for your feedback. Lastly, you should post a warning or disconnect the gas lines completely. I was able to convert my existing tank including adding the extra insulation for much less than the cost of a new electric tank, let alone the cost of installing a new tank or wiring a new 240V circuit to provide the power. Brian D Nelson, Sorry Also make sure you don’t exceed the current rating. Dishwasher element was harder to bend, though. Consider that old gas ranges and stoves had a full time pilot light. You can do a lot with your own two hands. Much more useful would be if manufacturers specified the thermal conductance of a tank (in Watts per degree C). I WILL TRY, Have you quantified these losses? WARNING!!! Every day I have a nice hot shower with water that is being heated only by the pilot flame!! See the section “Why are electric water tanks more efficient than gas ones?” in the article above for more details. But they give me more flexibility in the actual "power source." About 2 to 3 hours for all 30 gallons. For a single family detached home in the Toronto area with 3 bedrooms, 2 bathrooms , and 1,500 – 1,999 square feet of living space, the savings came to $1,817 – every year. I turned My gas statements from last summer showed that we consumed about 1.2 GJ of gas per month in the summer and about 2 GJ per month in the winter. Natural gas appliances provide homeowners significant cost savings compared to other sources of energy. I’ve looked at heat exchangers like you described but I determined there was not a big enough payback to justify the effort/expense for me, given how little hot water I use. Prices have changed since I did this project (8 years ago) but where I live they still favour the electric conversion. Your idea of adding the When I have time I’ll write an article showing how to do everything I described above (so many projects, so little time). In fact, it may even absorb heat from the surroundings if the incoming water temperature is lower than the outside air temperature. The hot water in the tank warms up the air in the tube (recall the tube is designed for maximum heat transfer). | In other words, a typical hot water tank requires enough power that you can empty the entire tank every hour and still have hot water. (It cost about $5000.00 all together with tax, etc. be HIGH TEMPERATURE insulated, like those found on an old CLOTHES IRON. It is possible, however unlikely, that water could be sprayed onto the element which could cause an electrical hazard. Hi Jeff, Now you have solved my delima. Inserted it in almost to the bottom and stuffed some more fiberglass pulled from the oven to seal the top. Slide the coiled element into the tube. This is a common misconception. On electric hot water tanks, the wall is reinforced where the elements mount to it. The idea is interesting but I would like to make some comments please: The idea of using any flammable parts for the cap or the insulation really makes me cringe. Good luck. Then disconnect the chimney from above the tank. Hi Cliff, When thinking about hot water tank efficiency, just think about “time at temperature”. The high temperature wiring should only be needed in close proximity to the element. . Inside the thermostat there is a thermistor (a temperature sensitive resistor) used for measuring the air temperature. At first I was skeptical, because of the air-gap from flue to tank, use of stove/oven components, etc. However, that isn’t the worst of it. (series? Therefore you want a resistance R of 14 to 28 ohms. For example is efficiency. You can often pick up a used stove element from any appliance recycling or salvage yard for free, or you can buy one. Hi Robert, I suppose it is in the manufacturer’s best interest to assume greater usage than what is truly typical since it makes their products appear more efficient than they actually are. Perhaps a 140 watt induction coil would be just right for a WH, and use less electricity than an electric stove element. A great deal of the heat disposed of in the shower waste water could be recovered to pre-heat cold water entering the tank. Further how would you go about setting a thermostat? At first glance you might think that this is just a waste of water rather than a waste of energy – it’s only cold water after all – but what it really means is that after any hot water use, 1.75 litres of hot water remains in our pipes and simply dissipates heat to the surroundings. solar. They are usually around $100 and I have seen suitable ones for as low as $40. Set the timer to heat the element for roughly 6 hours, turning it off just before you generally use your hot water. Recall the element is about 3ft below the cap. This will vary significantly depending on daily water consumption. https://burnshomeconstruction.com/how-to-convert-gas-water-heater-to-electric In the case of a water trough, it’s no problem because it is not pressurized. Again, it doesn’t seem to be smoking after about 2 to 4 minutes, but the heater is indoors enclosed in a built enclosure by the landlord, in the kitchen. You claim backwards compatible with gas as an advantage. If I were building new, I would go with a new electric and run it on 220V. The primary bacterial concern is Legionella bacteria which can cause Legionnaire’s Disease. I noticed the coil I made was slightly bigger in diameter that it was touching the tube. The gas company can keep their ever increasing convenience charges. There simply isn’t enough power going into the tank to overheat it (unless your timer breaks, or someone inadvertently plugs it in without a timer as discussed in the safety concerns section above). Much thanks — jack. You’re very welcome. I also learned to insulate the refigerators and it is making a difference too. That would be 80% efficient… etc on up to 10kW or so where you essentially have a hot water on demand system. The additional thermal resistance of the air pocket simply means the element will heat up to a higher temperature than it would if it were immersed directly in the water. I may add it as a separate article in the future. If you have a power meter, plug it into an outlet and plug the cord into it so you can see how much power the element is drawing. So instead of a stove element I said I would use a light bulb, after all its merely an oversized easy bake oven right? I plan to attach the sensor to the outside of the inner tank. Worst case is you may have a leak, but the trough isn’t going to explode ;-). Shape the heating element to fit inside the tube through the water tank. I think that’s pretty good. They are about $40 and you have to replace the thermistor to get to the right temperature range for hot water. It has nowhere else to go. Inlet and outlet pipes are a source of heat loss regardless of what kind of tank you have, gas or electric. And I’m sure it would have done more/quicker. It should be easy to retain it, preset it to 120F to 160F and lock it in place so as to avoid fire hazard rather than putting in without that kind of governance, right? Unfortunately, converting a programmable thermostat for hot water tank use is beyond the scope of this article. Without one, the temperature of the water each morning will depend heavily on the amount of sunshine the previous day. This was a great read. Using a timer with no thermostat or thermal fuse is like having a “boil” setting on your hot water tank. For the sake of argument let’s compare our converted tank on a timer to a 100% efficient “ideal” water heater. So the bulb and heat rated ceramic receptacle drop about 3 feet or so down the flue and cannot go any further because the brick with the holes acts as a stop and the fireproof cap. 24 hours later hot not just warm water for everyone to have a controlled shower. Any energy released from any kind of element inside the tank has no where to go but into the tank. The smoke eventually dissipated so I believe it was just the buildup inside that space from the gas operation days. Have an electrician (assuming you won't be doing it yourself) bring the new power drop to the water heater ahead of time so you don't have to go without hot water for a long time. That’s 463 W. So our water heating efficiency prior to converting from gas to electric was 58/463 = 12.5%. Hopefully the element won’t run too hot. Hi Ron, Comparing natural gas vs electric heating, Build a heliostat for solar heating and lighting, Build a Solar Attic for Heating, Cooling, and Growing Plants, Turn off the pilot flame of your gas furnace in the summer, Convert from gas to electric space heating, How many seconds of idling is equivalent to starting your engine, Build an electric foundry for melting scrap aluminum, I could achieve a higher efficiency by installing a 1000W or 1500W heating element and reducing the heating time accordingly. Looking into some sort of combination of the two. I placed a 75watt lightbulb at the bottom of the water heater where the gasFlame is. Before soldering, pass the ends of the electrical cord through a drilled hole in a metal cap. Wouldn’t the heat gun finally burn out? Improving the heat transfer (ie reducing the thermal resistance) between the element and the water will not affect the efficiency. Thermistors are available from Digikey (www.digikey.com) for under $1. This might not be a big deal to some (not sure how to connect and insulate though). If you have a hot water tank with EF rating of 0.90 I suggest you take the measurements and do the math outlined in the article to determine your real efficiency. Hot water tanks are typically designed for a recovery time of 1 hour. Instead of placing the element down the flu, is it possible I can drill into the side of the tank and place the element in like a regular electric? Is that right? You are correct. Still testing with a timer, but so far a 200W bulb operating for, say, 15 hours per day seems satisfactory for my needs. I can see the benefits of this idea as a band-aid solution as a temporary arrangement. How long will the water stay warm? Actually, there are some reasons that attract people to do it. The wattage is a bit higher (around 750W) for slightly faster recovery time. EF ratings are really not that useful except as a basis for making relative comparisons between similar sized tanks. I recently did a conversion of my 240 volt/3000 watt 60 gallon water heater to 120 volt/750 watt. A lot of people are commenting on the air gap being an inefficient transfer medium. Hi Jack, i had been looking for a way to switch my gas heater to electric. Also would it be OK to use a heat gun replacement element instead of an oven element? My proof of concept is still working well 10 years later and I’m very happy with it. This myth, unfortunately, is entirely true. On my tank, this will expel water safely into a pipe that leads outside my home. Our gas consumption for one full year was about 20 GJ or 5500 kWh. I also did a cost analysis in the article comparing my measured gas usage before and my measured electrical consumption after. your wires and cause hardening and cracking and baking of your wire! However, the wood was a temporary improvisation and has been replaced with a sheet metal cap. Hello Rob. I’m thinking if using a round dishwasher element (have one) down below instead of the light bulbs. I just now noticed the name of the web-site, and read the story behind it. First, find a suitable stove element. I did this but haven’t posted the instructions yet… so many projects… so little time. Warning! Great article! Thank you for all your valuable information and responses. It’s 120/240VAC, not 110/220VAC. Given that gas hot water tanks tend to have EF ratings around 0.6 and electric hot water tanks tend to have EF ratings around 0.9, it’s pretty clear that our hot water usage of 40 litres per day must be MUCH less than the “typical” usage that EF values are based on. Insulate though ) the heating path and this is a moot point since there is a thermistor a. Will likely be too hot to touch by hand with a propane water tank efficiency, just think about.... 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