Water heater blanket

Old 06-15-08, 09:36 AM
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Water heater blanket

After reading much about water heater blankets, I was wondering if they are useful in SW Florida, where I live. Our water heater is in the garage where it stays very warm in the summer and in the 50 to 60 degree range in the winter. Would it be beneficial for us to have one?
Old 06-15-08, 12:32 PM
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No. If you feel the outside of your tank, it will probably not feel warm. That tells you that you are not losing a lot of heat. The top of the tank is more of a concern, and if it is a gas WH, you cannot blanket the top.
The best thing you can do for any type heater is to insulate the hot and cold lines well, and even wrap a "box" of rigid foam around the TP valve.
Old 06-30-08, 10:40 AM
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Yes. I don't see how a tank hot water heater could ever be too insulation. Yours is likely insulated somewhere between R-8 and R-24, (1-3" of foam). It may be 60'F where it's located, but heat loss will be a function of the temperature gradient between the hot water (120-150'F) and the outside temperature. If there's a difference, heat transfer will occur at a rate governed by the R-value of the insulation. Insulation is so cheap, wrapping the heater will have an almost immediate ROI (Return on Investment), so why not? Do note the earlier poster's mention of gas HW heater limitations-- you can usually wrap their sides safely, but not the top, or the area around the gas/air inlet.
Old 06-30-08, 11:37 AM
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I disagree with adding a water heater blanket.

Adding additional insulation quickly becomes a matter of diminishing returns. This is especially true with water heaters and in the case of a gas water heater is almost always a net loser. The primary losses from a gas water heater are the constantly burning pilot and the constant draft through the flue. There is nothing that a homeowner can do to reduce these losses. The amount of heat lost through the sides of a gas water heater is infinitesimal compared to these other losses. I seriously doubt that the cost of the blanket could be recovered during the expected ten-year life of the heater.

There are, of course, exceptions and if your water heater is outside (or in a locker that is essentially outside) AND you live in an area that has a significant number of days when the ambient temperature is really cold, say, under 30 degrees, then a blanket may make sense. If your water heater is in a portion of your house that is normally warmer than outside temperatures then the "loss" through the sidewall insulation is really minimal.
Old 06-30-08, 02:23 PM
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I hooked an analog electric clock to my electric water heater through a dropping resistor.

Assuming no water usage,
W/O homebrew insulating blanket, 5 min on each 5 hours. W/blanket, 5 min on each 7 hours.

New heaters may do 5 min on each 24 hours.

Last edited by WDIBAA; 06-30-08 at 02:24 PM. Reason: clarity

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