Lowering the temp on a water heater

behaviorkeltonDecember 12, 2007

I'm splurging on new appliances: and I appreciate the past input on this stuff!... so about the water heater...

I just came home with a new water heater to replace my 17 yr old water heater. I paid a bit more because this one comes with more insulation and it has some interesting little electronics that can be adjusted for maximum economy.

If I set the temperature very low...does this really save energy? I mean, if the water isn't nice and hot, I will be forced to adjust my shower so that I am pumping *more* of the hot water into the mix just to bring the temp up to a tolerable level.

So, even though I have the water heater set to a low temp, I will be using more of that "hot" water during the shower (and less cold water). Therefore, the heater is going to have replace that huge loss of hot water by re-heating a new batch of cold.

Does it truly make a difference in energy usage to set it real low? Is 115 degrees F. the optimum temp? or is lower *always* the best choice?

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fsq4cw

I invite you to read this link.

SR

Here is a link that might be useful: Hydro-Quebec - Water Heaters

    Bookmark   December 12, 2007 at 8:40PM
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greif

yes this is correct, set to 115-120 this will save you money

Here is a link that might be useful: water heater temp

    Bookmark   December 12, 2007 at 8:46PM
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davidandkasie

mine is set so that we do not even turn the cold on when showering. even though you are heating more replacement water, the temperature differential is less so you use less energy to heat it.

    Bookmark   December 13, 2007 at 10:29AM
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peterbog

Ditto what davidandkasie said. Set mine in the winter so cold isn't turned on. In the summer I found I could turn it off completely and the "cool" showers weren't that bad. Course I live in an area where the water lines are buried 12 inches down to get below the frost and in the summer actually found the cold water coming in directly from the outside lines was warmer than the non-heated hot water that was evidently "cooling" in my hotwater tank.

    Bookmark   December 13, 2007 at 1:51PM
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meldy_nva

Well, that's interesting.

Quebec recommends to NOT turn down to 49C (aaprox. 120F) and to NOT turn off for periods of time due to possible bacterial contamination. OTOH, USAgov says 120F is plenty hot enough, and to turn off for extended periods. Who should be believed?

I've just started reading on this, but so far it seems that A) Legionaire's is a valid concern and found in many HW tanks, and B) Contaminated hot water systems can be disinfected by raising the temperature of the water heater to 70 degrees C (158F) and running each distal tap until a temperature of 65 degrees C (149) is obtained for 5 minutes or more.

I wonder if we could have the best of both worlds if --by heating the water to 70C at optimum time (sun for solar or midnight for electric) and then turning it off until the next optimum period?

    Bookmark   January 31, 2008 at 12:46PM
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fsq4cw

Re: meldy nva

This is just a suggestion, for family health & welfare reasons keep the water temperature high. For energy efficiency reasons wrap the tank in a blanket.

Also, keep in mind that electric heat is 100% efficient. So during heating season any heat loss from the tank is still a net gain for your house  youÂre heating anyways. ItÂs becomes a real net loss only when youÂre not heating and particularly while youÂre air-conditioning.

SR

    Bookmark   February 2, 2008 at 12:35AM
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meldy_nva

I suspect not enough mention is made of just how good those HWH insulation blankets can be. When we replaced an older [blanketed] model for a new "high efficiency" model, the electric bill went UP until we wrapped a new insulation blanket around the new heater.

fsq4 ~ present setting is 130°F, not nearly the recommended temperature for disinfecting Legionaire's. OTOH, I doubt that a higher setting is needed unless there is reason for concern that there is contamination or a diagnosis of bacterial infection is present.

I admit that I do continue to wonder if there is any energy benefit/savings to heating the water only once each day? If so, what is the optimum temperature to set? That would obviously be dependent on the insulative efficiency in combination with actual water use. But, if 6 days a week one turned on the heat only until the temp reached a predetermined figure, and then did not turn on the heat again until the following day, it does seem to me that there should be a savings in energy not used to *maintain* the water temperature.

    Bookmark   February 4, 2008 at 1:58PM
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fsq4cw

Re: meldy nva

As previously stated I believe there are health reasons to maintain the DHW water temperature at a constant high temperature. Once reached, a modern, well-insulated DHW tank does an excellent job of retaining that heat. The cost of temperature maintenance is minimal.

We keep our tank at a minimum of 175ºF, as this is the manufacturerÂs minimum temperature guideline. It is an OSO brand stainless steel tank that mixes cold water with the hot, internally, when there is a demand for hot water. This internal cold-water mixing reduces the water output temperature to 120ºF at the hot water tap. This method also increases the available hot water from a 62-gallon tank at 175ºF to 90 gallons (at the tap) at 120ºF. Also, being stainless steel, the tank should last as long as the building; no more tanks in landfills.

SR

    Bookmark   February 4, 2008 at 9:46PM
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