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Old 08-25-16, 01:17 PM   #1
oil pan 4
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Join Date: Nov 2012
Location: NM
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Default Hot tub insulation improvement

I got this little gallon hot tub for my wife.
It holds around 280 gallons of water and has a 1,000 watt heater and it sits outside.
I figure if it gets cold enough and the heater runs all the time that could increase the power bill by up to $75 a month. That is really bad.
Then I remembered I own a FlirI7 thermal camera this should be easy.

This picture is the cover to the hot tub. You see the one line of heat escaping, that is where the cover folds. As you can see about 99% of the rest of the covers surface area is doing a very good job.


This is not a very good image of the side. As you can see some heat is getting away. It was 64'F that night.


The most obvious place for improvement. The filter housing. Just wrapping some insulation around it should take care of it. The water in the hot tub is 99'F that housing is pretty close to 99'F.

The filtering assembly will likely get a foam box built around it.

Turning the hot tubs temperature way down then back up to save power really is not an option right now. I figure with the 1,000w heater it will only be able to raise the temperature 3'F every 2 hours assuming no losses, so I got an 240 volt powered industrial grade 500w fish tank heater to help. It looks dangerous and is not GFI protected so it wont be on while anyone is in the tub.
The fish tank heater and the built in heater could bring the temperature up 2'F every hour.
If it works well I may order another one or 2.
I think what I can do on her last night off turn the temperature down, so the heater maintains a much lower temperature the 3 nights she works then turn it back up the morning she starts her 3 days off.
With the outside temperature being between 65 and 70 at night the tub can lose up to 5'F per hour while the cover is off. Only opening half the cover cuts losses to between 1'F to 2'F per hour.

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