can to much insulation hurt hot water heater?

Old 02-22-09, 01:26 PM
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can to much insulation hurt hot water heater?

We live in the bush and have our power off for extended time every year. When that happens we go to generator. We run it 4 hours a day only. Our water system is 500 gallons of pressure tanks off deep well and 1 standard 40 gal electric water heater for 2 people. This is in an unheated basement.
I have a standard insulating pillow around the tank. Can I increase the insulation to say 6" of fiberglass. I'm thinking this will hold the heat overnight or at least give us a longer run of hot water from when we shut the gen off. I just do not want to burn up anything and if I need a special type of tank I will get it. Most of the "good" tanks that i have seen have more powerful elements and I would like to stay away from extra loads for the gen. Thanks
Old 02-22-09, 02:54 PM
Join Date: Oct 2008
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Hi snowtime, I do not believe there is any limit on the amount of insulation you can wrap around the unit. In addition to insulation, you may want to increase the temperature setting and add a mixing valve. The mixing valve will prevent you from having 160 degree water at your tap, it will pre-mix cold water for a lower set temperature. Thus you will use less hot water and the water in the tank will remain above the lowest warm temp you need longer. i. e. many more gallons of usable hot water.

Your heater my already have them, but make sure you have a heat trap the hot and I believe the cold pipe pipe as well.

Insulate all pipes and enjoy.

Old 02-22-09, 08:40 PM
Join Date: Mar 2006
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Bud is correct about there not being a limit to the amount of insulation you can add and also about raising the temperature of the heater and using a mixing (or tempering) valve to limit the temperature at the faucets.

I will state however that there is a law of diminishing returns that comes into play. A single water heater blanket may help add some savings but any more than one will likely cost more than it will ever save. The location of the water heater is also important in that if it is located outside any heat lost is really lost but if it is located inside, even if it is just a utility closet, the heat lost will help to heat your house. There is also the fundamental law of thermodynamics that states the greater the temperature difference the faster it will lose heat. That means for any given water temperature and thickness of insulation the colder the ambient temperature of the tank surroundings the faster it will lose temperature from the enclosed water.

In my opinion your biggest problem is simply the limited amount of water you have in your tank. In my previous house I installed an 80 gallon electric water heater in the utility/laundry room. It was an A.O. Smith water heater with foam insulation and as such had a higher value of insulation than the units insulated with only fiberglass. During one three-plus day power outage I was able to pretty much maintain my lifestyle with only slight curtailment of hot water usage. Of course I didn't try to run the dishwasher or the laundry but I was able to take a comfortable shower everyday before going to work. I seriously doubt that I would have had the same experience if I had only had a 40 gallon water heater.

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