Saving money on gas water heat...


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Old 01-15-08, 12:10 PM
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Saving money on gas water heat...

I've often wondered whether I could reduce the amount of gas I use to run my water heater by manually turning it down when leaving the house and back up when returning. But I never had enough desire to know to give it a try. And, I've been told by people who I thought should know that it wouldn't be worth the time or effort. Now I read svenrgy's post about a programmable digital water heater controller for a gas heater, and I'm really confused. Any ideas? I'm going to give it a try, just to see, because it seems to make sense. What does anyone else think? Thanks in advance - Chris
 
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Old 01-15-08, 02:06 PM
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Did you notice that svenrgy (save energy?) is a new member with only one post? I kind of think it is a spambot.

I am the first to agree that the common tank-type gas-fired water heater could be significantly improved in regard to energy usage. The standing pilot, atmospheric burner and single open flue all scream energy hog.

Yet I am also quite leery of a device, sold on a website that does not show any pictures other than the fancy digital display unit, that is purported to be "easily installed" being able to have a significant saving. That $135. will purchase a lot of gas for a conventional water heater.
 
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Old 01-15-08, 02:19 PM
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I have played around with this concept, from what I have found with my electric heater if I turn it off during an 9 hour period it doesn't run much, half the time not at all. I couldn't justify the cost of a timer seeing as it wouldn't make much of a difference in my case. Now if we go away for 2 days or more I will turn off the breaker to my water heater and well pump. When we get back I turn it back on and the heater runs a while, however we still have warm water even after 3-4 days. I would invest in an insulating jacket for the water heater and only turn it down if you are gone for a day or more.
P.s. I have a 20+ year old electric heater,50 gal, with a really thick insulating blanket on it, When I put my hand in between the heater and the blanket its really warm. In my case I figure that the blanket makes a huge difference. If I were to get a gas water heater (LP here) I would get a direct vent ( because I don't have a flue and you have no gas usage when its off) or a on demand type.
 
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Old 01-15-08, 03:20 PM
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Well taken, furd. I still wonder about the potential savings of turning the 'stat down and up by hand. Would the long burn when you get home and raise the temperature offset any savings seen by dropping the temperature when you leave? I keep a fiberglas blanket on my water heater to help reduce heat loss and keep temperature stable. Yes, manually adjusting the 'stat 2 or more times a day would require a lot of discipline and committment, but if it saved me enough, it would be worth it. Anyone? Thanks again - Chris
 
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Old 01-15-08, 03:51 PM
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Thanks, Civicminded. You posted while I was typing my reply to furd, or I would have recognized you as well. My gas unit has a "vacation" setting on it - I think it keeps the water from freezing while you're away, more than anything else. if such a setting existed on an electric, it would eliminate having to turn off the breaker. However, since you're on a well, killing the pump and heater prevents coming home from a trip to a flooded house and a water heater that's been running non-stop trying to keep up! Point well made about the blanket - as I wrote to furd, I do have a blanket on mine. If recovery and standby behavior is similar between electric and gas, no hot water being used for 8-10 hours while everybody's gone may mean no burn during that time. I'll have to monitor while I'm the ONLY one home, not doing laundry or dishes, just watching SPEED channel and drinking coffee... Anyone else? Thanks again - Chris
 
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Old 01-15-08, 05:25 PM
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Saving money on gas water heat...

Another way to look at it is the big picture. -

If the water heater is in an insulated home during the winter, there is really no heat loss to the outside. You just lose the heat from the water heater in a random, uncontrolled manner, but is is really not lost, since it eventually heats the house. This can actually reduce the amount of time the furnace will run. Any way you look at it, it is not a big thing since the benfits (heating the home with the escaped water heater heat) offsets the need for the furnace to run.

Summer is a little different, but any good water heater is reasonably well insulated. - Maybe you should not insulate your basement in the summer so you can get the thermal benefits of the soil that reduces AC costs.

The biggest gain in turning down the water heat a few times daily would be the heat you expend running around doing it, but then you have to buy food to provide the energy.

I think caulking is a more benficial way yo worry about energy loss. - There are no simple short answers since the are always trade-offs.
 
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Old 01-15-08, 07:25 PM
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The primary loss with a gas water heater is the constant pilot and the constant airflow through the flue. The heat loss through the "jacket" to the surrounding space is minimal in comparison. Adding a blanket to the outside of a gas water heater, at least one built in the last few years, will effect minimal savings.

Setting the thermostat to a lower temperature while you are away will allow the tank temperature to drop to a lower setting before energizing the main burner. Heat loss (primarily to the air continually passing through the flue) is directly proportional to the temperature difference so as the water cools it will lose fewer heat units (BTUs) to the air passing through the flue.

Unfortunately all that heat loss will later be made up when you return home and turn the thermostat back to the desired water temperature. It is a fact of physics that it takes one BTU (heat unit) to raise the temperature of one pound of water one degree Fahrenheit. However, while raising that water temperature you are also releasing a great deal of heat up the stack and rather than heating the water it is only trying to raise the temperature of the great outdoors.

As an example I will cite some numbers on my own water heater. I have not used any hot water for several hours yet the temperature of the air leaving the flue on my heater is 100 degrees versus about 40 degrees entering the bottom of the heater. After I use enough hot water to energize the burner the exit temperature of the air will climb to over 400 degrees and If I have used a large amount of water (filling my whirlpool tub, for example) the exit temperature will peak at about 440 degrees until the thermostat is satisfied and the burner shuts off.

Tank-type water heaters could be made with a much higher energy efficiency if they had electric ignition rather than standing pilots and dampers that closed the flue whenever the burner was shut down. If this was done they would give tankless water heaters (which I dislike for several reasons) a darn good run for energy supremacy.
 
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Old 01-15-08, 07:55 PM
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CMil,

Now that I've been sitting home all day for several days in a row, working in my garage (where my gas WH is), I can tell you for a fact that lowering the thermostat setting in the morning and raising it back in the evening when you get home isn't gonna save you a dime on your gas bill. My WH is 10 years old, and, unless somebody goes in and runs hot water through a tap, that WH simply never comes on during the day.

If you were going to be gone for a week or more, then set the gas valve to the "Vacation" setting. That keeps the pilot light lit and doesn't allow the burner to fire.
 
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Old 01-15-08, 08:55 PM
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Wink

I think you will find that the pilot on the gas heaters warms the water a lot. We have a gas water in the shop. To wash is about all no showers. To this day we have never turned the burner on just pilot and have all the good warm water we need. The outside blanket on the heater helps a lot.
What no one here has said .Is if the water tank is in a basement and the cold water pipe gets warm going into it. Or the hot water pipe is warm and no one has used it for a while. You should put a U trap in it. Or the flow check valves that go on top of the tank. So hot water dont get out of it when its not used.
Then if you run the AC a lot where you live. Look into a hot water recovery on the AC this way you get free hot water and it kicks up the SEER of you AC. Down in FL. I had 8months of free hot water with 3 in the home. I could turn the heater off.
CMIL think you will get that snow ? Im north of you they say 1" here
 
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Old 01-15-08, 09:43 PM
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What setting do you have it set at?
 
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Old 01-15-08, 09:48 PM
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Wink

If you mean the gas water heater I spoke of in the shop. Just the pilot is on never have turned the heater all the way to on.
 
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Old 01-16-08, 09:49 AM
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Sorry, I meant Cmil. Some folks have it set way to high.
 
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Old 01-18-08, 07:22 AM
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WOW! Thanks for all the input! To answer in no particular order: I keep the heater on the high side of the WARM range, hot tap water shows 115-120 degrees. Heater is in a semi-berm house, in the garage, which is on the berm side, so I'm getting some thermal stability in the room there. House is single story, no basement. I always try to remember to switch to VACATION when we leave town for more than 2-3 days. This weekend I plan to try to monitor burn time, as there will be some time with only me in the house and PLENTY to do in the garage. I suspect I will find, as most of you have indicated, little burner activity if any. I just started thinking it would be nice if there were a way to recover heat from the flue to help heat garage and/or house (from the fireplace flue would be neat, too). I like the idea of a damper on the flue - is such a thing available? Ed - didn't get any of that snow Wednesday; how far north are you, did you get it? Thanks again to all; I'll post findings as I get them. 'Til then... - Chris
 
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Old 01-18-08, 08:24 AM
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Ok, your temp is within reason...Good luck, post later!
 
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Old 01-18-08, 10:43 AM
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I have to agree with most here. I had a Sears gas water heater, built around 86 I think. I had some issues (long story) and I wanted to 'be there' when it was burning.

After a shower and the tank heated back up I'd put it on pilot. When turning it back up the next day I'd say 99.9% of the time the burner wouldn't even come on.


Baldwin
 
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Old 01-18-08, 01:56 PM
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Im at Lake of The Ozarks.. You cant have a flue damper on a standing pilot light. On the fireplace use a heater insert. that way you can have the air blow in, heat it and back out to the room. not in the flue . Glass doors on a fireplace help Also a outside air intake for the fireplace right at the hearth. Help keep heat in the home
 
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Old 01-19-08, 11:22 AM
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Well, I caught the water heater on one time in about 8 hours yesterday (Friday), and the air temp in the garage was about 40 deg. F. I am inclined to agree that if it saved me anything to turn the thermostat down while the house is empty, it wouldn't be enough to justify the effort involved.

Ed - did you read my post in the fireplaces forum? As to outside air supply, www.woodheat.org cites a Canadian study (I was suspicious, at first) that found supplying air to the firebox from outside was prone to all kinds of problems, including backdrafting smoke into the house and the potential for a "cold hearth" condition. I think that if incorporated into new construction, such problems could be addressed while building the fireplace. The woodheat site is a valuable (advocacy) resource for burning firewood.
 
 

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