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Daox 11-18-10 09:00 AM

Insulating the water heater
So, a couple weeks ago I said I picked up a bunch of insulation stuff. I then insulated my hot water pipes. Its about time to get started on the next step. I bought a water heater blanket but I was not sure I am was going to use it since the heater is so old (12 years). So, I took a quick trip downstairs to evaluate the situation.

I've felt around my water heater many times. It never really felt 'warm' but I knew it had to be warmer than the air down there. So, this morning I went downstairs with my IR thermometer and shot the wall adjacent to the heater and the heater tank itself. The wall temp (this is an interior wall) was 58F (14C) and the side of the tank was 70F (21C). So, I think its pretty apparent that there is some fairly decent heat loss going on.

gasstingy 11-19-10 03:34 PM

I'm wanting to see the pictures of this install after you've wrapped it up. I've been putting it off at home because I haven't decided how much to wrap up. {As in how close to gas exhaust opening at the top, and how close to the gas valves and pilot light door at the bottom.}

Daox 11-19-10 04:02 PM

I've also just turned the heat up a bit on the heater due to turning the hydronic floors on in the sunroom. That'll only worsen the situation.

strider3700 11-19-10 04:09 PM

after reading this I decided to do a quick test on mine.

the metal furnace duct beside the tank was 18.9 (roughly basement temp)

The top of the side of the tank was 23.6

The top of the tank was 25.6

The nipple of the cold inlet and the hot outlet was 36 degrees

the hot outlet 3 feet up where it goes into the roof was 24.1

The hot water pipe roughly 8 feet down the line was 19 so basically back to basement temps.

When I replace/relocate the tank I will definitely be adding heat traps, insulating the tank and insulating as much of the pipe as I can get to.

Daox 03-27-11 03:38 PM

Whilst doing my flue damper testing I remembered I never put the blanket I bought for my water heater quite a while ago. So, I took some time this afternoon and wrapped it up. The instructions specifically say not to cover the top of a gas water heater, but I think I'm going to get some of it covered, but leave a decent gap between the flue and insulation so it can still get air. What are your guys thoughts?

Anyway, the blanket is rated at R-11, so its decently thick and its got the radiant barrier on it was well which should help out. I think the blanket was around $20. I'm anxious to see what the combination of pipe insulation and water heater insulation does to my gas usage during summer which is almost entirely water heating.

Here is the before shot of the heater.

First, I did my IR thermometer test again to see what was going on. I got my reference temperature of the wall next to the water heater first.

Then, I got the temperature at the top of the tank.

Then the bottom.

Here is the after shot.

And you can see how I had to cut around certain things.

Angmaar 03-27-11 04:24 PM

Do you have to worry about the insulation being lit on fire by the hot exhaust? It seems a little close to the flue.

Daox 03-27-11 06:22 PM

Right now the insulation only comes to the top of the heater. There is no insulation on top of it.

Angmaar 03-27-11 06:34 PM


Originally Posted by Daox (Post 12674)
Right now the insulation only comes to the top of the heater. There is no insulation on top of it.

:o The top of the water heater looked like it was covered in insulation in that picture. Sorry.

RobertSmalls 03-27-11 06:48 PM

The only feature on top of the HWH that I think shouldn't be covered is the flue vent. Also be careful to leave room for combustion air to enter between the tank and the floor.

You'll need to attach something non-shiny (e.g. black paint, or paper) to the insulation in order to take its temperature.

Daox 03-27-11 08:46 PM

Good point. I did just that. I shot it with some spray paint, let it dry, and it looks to be ~55F at the top of the tank now (vs 60 before). So, I can estimate that the heat loss through the side of the tank has been reduced by ~40%.

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