Anyone make dual-heating water tank?
I wasn’t sure that this has been asked before, let alone know how to search for it. Anyway, does anyone know if there is such a thing as a hot water tank with dual heating features that allows you to heat either with electric or natural gas?
Replies
Nuke,
Oddly enough I have exactly this set up in my basement - however it is not one unit. When the local utility finally ran gas lines into this subdivision, I signed on to convert to a natural gas hot water heater, stove, dryer.
I had a perfectly good electric hot water heater sitting in the basement and being frugal (read as cheap), I could not bring myself to throw it away.
So with a little pipe and a few valves I replumbed the old heater so that it can be brought back online simply by turning a few ball valves, closing the tank drain, and flipping a breaker in the main panel. The piping and valve configuration will also allow the electric heater or gas heater to be used as a "preheater" although I have never done this.
My normal configuration is water heating by natural gas; electric heater tank is drained with the valve left open, breaker is off and locked out at the main panel.
It is not hard to figure out the piping / valve configuration if you want to go with my solution - sketch a little and you will figure it out.
Jim
Never underestimate the value of a sharp pencil or good light.
You might try putting the unused heater in ahead of the one that's in use, but with the power off. That would make it a room temperature holding tank. It depends on the difference between incoming water temp and basement room temp, but that might save you a few BTU's.
I have two gas heaters in series, which works very well. The temperature doesn't go south during a shower.
-- J.S.
I thought about setting the electric heater as a room temp holding tank; decided against it because with my luck I would end up rusting out my "spare" electric heater.
Winter room temp in basement is about 55, late winter inlet water temp (coldest) is about 48, doesn't sound like much but with the projected astonomical price of natural gas this winter I may try it and see if there is a noticable difference in the gas use.
Jim
Never underestimate the value of a sharp pencil or good light.
Problem is, the electric heater is too well insulated to work well as a tempering tank. If you can get an old heater and strip the insulation off, that will work better. But a tempering tank is really only an advantage if the fuel is cheaper than the WH fuel.--------------
No electrons were harmed in the making of this post.
Like I said, the valves will let me do it, but I never tried it out. Of course, I'm not really sure how "well insulated" the electric heater is.
Jim
> But a tempering tank is really only an advantage if the fuel is cheaper than the WH fuel.
Here, there's generally a good delta between incoming water temp and room temp in the WH space, which is outside the building envelope. So for us, the first few degrees of water heating are free.
-- J.S.
Heck, if you can have the WH outside the building, why do you need heat?--------------
No electrons were harmed in the making of this post.
Wow, I had wondered if anyone had done exactly what you did. Guess that answers that. lol. The other suggestion for putting the unused unit in series with the used unit is also interesting. My only concern there is the following scenario:
Summer/Winter: Gas cheaper in Summer, Electric cheaper in Winter. If the water coming from the street hits the gas unit first and then the electric, then come Summer I'll want gas water heating. This means gas-heated water must pass through the electric-heated tank which is off, and certainly at a cooler temp than what is in the gas tank. The reverse scenario can also be said.
Put the electric heater last, and leave it turned on. If the gas unit is on the electric unit will just have to keep the water hot, using very little power. And losses from an electric unit, because it can be so well insulated, are very low.
--------------
No electrons were harmed in the making of this post.
Or make it so you can switch the direction of flow depending on which heating method is cheaper at the time.
Then you could have gas for "maintaining temp" & electric for intial heating of incoming water in the winter, then come summer, turn a couple of valves & it runs the other way .
With enough valves and pipe, you could rig it so you could swap the order of the units at the solstices.
-- J.S.
DIY there is.
Pix is fireplace part of loop that includes waterheater.
View Image
Edited 10/13/2005 4:30 pm ET by junkhound
Never seen a single unit, but using 2 in series is better (the way DanH said).
With parallel, you would need to be concerned about stagnant water in the unused tank.
Put another way, you want water flowing through both tanks all of the time.
You can then adjust the thermostat on each to set priority. Setup right, the 'low priority' tank would kick in as a booster if you were running low on DHW.
I understand the basic idea of two units in series, but as I stated unless one unit is always given priority over the other unit you might find yourself feeding heated water into an unheated volume of water and thus reducing the tap water temp.
BTW, why could not the unused tank be drained once per year?
But, as I said, a good electric tank has very low standby losses. Put it last, leave it on, and it will consume very little electricity while the gas unit is fired up. When the gas unit is off it will serve as a tempering tank for the electric unit.--------------
No electrons were harmed in the making of this post.
"BTW, why could not the unused tank be drained once per year?"
You could, though it is extra work.
Why are you interested in such a thing? In most parts of the country, natural gas is by far the most economical means of heating water. If you have natural gas service, it would be very unusual for your electric rates to ever get cheap enough to beat heating water by natural gas.
I would like to understand your interest.
Bill