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Old 04-23-2008, 05:14 PM   #1
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why no water heater insulation?


I've heard from a couple of sources that one really shouldn't insulate the tank of a water heater. This is interesting to me since one would ordinarily think that would be helpful.

Is this true? None of my water heaters have any insulation around them, I wonder if I should install some.
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Old 04-23-2008, 05:24 PM   #2
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why no water heater insulation?


Virtually all water heater tanks are factory insulated under the shell of heater, but it helps to add water heater insulation blankets made for the purpose. especially if the heater is located in an unheated space (garage, attic, porch, etc.)
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Old 04-23-2008, 08:54 PM   #3
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why no water heater insulation?


Hi Guys...

Mike's right...especially if located in an "UNHEATED SPACE".

According to BRADFORD WHITE WATER HEATERS corporation...it has been documented that water heaters are so completely insulated that heat loss via TANK is *negligible*!!

The greatest heat loss is via the 1st 10 feet out of the hot water outlet of heater.

According to engineers at Bradford white...you want to insulate the first 10 linear feet of hot water pipe OUT of water heater.

Further, some suggest that a HEAT TRAP can reduce water heating costs as well. Here, create a trap in hot water outlet piping such that piping creates a MICROCAPILLARY ACTION THAT REDUCES HEAT LOSS...

I am still not sure what that means...

Anyway...engineers have suggested that greatest heat loss is VIA hot water pipe..

Let us know what you think.

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Last edited by Boston Plumber; 04-23-2008 at 08:57 PM.
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Old 04-28-2008, 06:03 PM   #4
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why no water heater insulation?


Because you will never recover the twenty bucks you spend on the blanket in energy savings. Those tanks are extremely well insulated, you can't feel any heat when you touch it can you?
Your heat loss is through the hot water pipe as has been stated and through the relief valve (that will be warm to the touch). Do not try and insulate your relief valve though as you may hinder it's functionality.
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Old 04-28-2008, 06:22 PM   #5
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why no water heater insulation?


Quote:
Originally Posted by darsunt View Post
I've heard from a couple of sources that one really shouldn't insulate the tank of a water heater. This is interesting to me since one would ordinarily think that would be helpful.

Is this true? None of my water heaters have any insulation around them, I wonder if I should install some.
Uh, exactly how many water heaters do you have?
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Old 04-29-2008, 08:57 AM   #6
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why no water heater insulation?


There's two ways of tackling this I will only tell you 1 way. Todays tanks normally have 3" foam insulation which is R15 or R16 and some tanks have 4" which is R20. The formula to determine savings is % energy saved = 1 - (0.5 / R-Value). Next, let's say you're adding an R11 wrap which in real world WILL act more like R7. Using the above formula we can see that

R15 saves you 96.7% w/R7 wrap 97.7% instead (1% savings)
R16 saves you 96.9% w/R7 wrap 97.8% instead (0.9% savings)
R20 saves you 97.5% w/R7 wrap 98.1% instead (0.6% savings)

Rule of thumb is, if the investment will pay for itself in 5 years or less it's considered a wise investment. If you know how much you're paying for hot water, you can calculate if it's worth adding a wrap. With my R15 tank when I was paying $500/year for my hot water putting a wrap on it and saving 1% ($5/year) was not worth it payback was too long and $ better elsewhere. Now I'm paying $1,000/year the paypack ($10/year now) is within 5 years and now a wise investment. If my tank was R20, be better elsewhere.

I won't get into the other way, btu loss calculations. You'd need to know the surface area of the tank, inside temps, outside temps, do it on a per month basis, and then come up with an estimate. I think the other method will give you an idea of what to expect. In short, if your tank is R16 or less it's likely going to be a wise investment saving you around 1%/year, more if your tank is under R15. The only reason it is likely a wise investment today even on an R16 tank is energy costs skyrocketed so much recently. Saving 1% on yesteryears fuel cost was a joke on how little it saved making a wrap pretty pointless. Todays cost of fuel has increased so much recently, the tiny savings a wrap offers on an R16 tank will now pay for themselves making them a good investment. If your tank(s) is R20, even today your $ better spent elsewhere (for the time being).

Last edited by Piedmont; 04-29-2008 at 09:47 AM.
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Old 04-29-2008, 01:31 PM   #7
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why no water heater insulation?


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Further, some suggest that a HEAT TRAP can reduce water heating costs as well. Here, create a trap in hot water outlet piping such that piping creates a MICROCAPILLARY ACTION THAT REDUCES HEAT LOSS...

I am still not sure what that means...
A heat trap is simply nothing more than having your hot water have to travel DOWN before going to its final destination. If you've ever had to install a boiler or tank, the mixing valve instructions say to install it something like 18"+ BELOW the hot port of the tank/boiler which inadvertently is creating a heat trap (a good thing) the mixing valve states it's to help prevent debri and premature failure of the the mixer. A heat traps main purpose is in a heating system. I included 2 pictures, to help explain the phenomina. Without a heat trap in a heating system you always have hot water flowing up on one side of the loop and down on the other creating a natural current that saps heat away from your tank/boiler 24/7 and 365 days a year. It also causes your AC to run harder in summer. Without a heat trap this flow occurs even when there is no pump running. With a trap, the heat rises up to the bend and can't go further, it can't travel down as heavy cool water has settled in the dip preventing natural movement. It matters mostly for heating systems... but for potable the mixing valve needing be installed 18"+ below the hot out of your tank/boiler also creates a heat trap, and it is nothing more than having the hot pipe come out of the boiler and run down towards the ground before turning up and going to the rest of the house. It consists of no moving parts or equipment.
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Last edited by Piedmont; 04-29-2008 at 02:00 PM.
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Old 04-29-2008, 05:58 PM   #8
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why no water heater insulation?


Great explanations Piedmont. I mean that..very thorough!!

Actually, I knew what a heat trap was all about...and I am one of the few plumbers I know that actually pipe the mixing valve almost exactly as you said!! Just did not want to scare the poster with too much info...

I remember those equations you posted....UGH!! I try to forget that stuff most of the time...

Hey!! Like I said, nice explanations. Have good day.
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Old 07-09-2008, 07:11 PM   #9
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why no water heater insulation?


I am going to insulate the pipes to the water heaters, since I have lots of stuff to do around them anyways.

I've seen the insulation they have for straight pipes. What about the flexible copper connectors? Can you use fiberglass to insulate them? Where can one find this fiberglass? Or do I need to use something else?

I have a hot line that is flexible plastic, I think it is an earlier version of pex. What could I use to insulate that?
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Old 07-10-2008, 08:34 AM   #10
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why no water heater insulation?


Fiberglass is probably best. Some of the foam insulation has very little r value and is really only good for preventing condensation. To wrap the elbows just cut the insulation on a 45 degree angle and tape the joints with the tape you buy when you get the insulation. Go to a plumbing or HVAC supply to find the fiberglass insulation.

By the way, Piedmont, I agree with Boston. Great info, although it sort of makes my brain hurt. We don't do boilers much here in Georgia so I am always glad to learn from you guys from the northern latitudes.
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