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Old 09-18-2013, 05:33 PM   #1
boyAND1
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Default Can I use an external tankless water heater safely inside for floor heat

Hi,
I built my shop about 2 years ago and want to finally get my floor heat going which has just had my 3 loops hanging out of the floor with duct tape on the ends. I live in ND and each loop is just under 300'. Shop is about 960 sq ft.

Question is I understand that the condensing boiler or more efficient boiler will save money in the long run but prices I have seen basically justify an investment that would take 20-30 years to payoff. Due to my location I would have to use LP or have off peak electric installed. I firmly believe the heat from LP is better so going that route.

Now back to the question, I have found an external or outdoor tankless water heater that claims 95% efficient for about $800. Question is, would it be safe to install this in my 960 sq ft shop inside where the loops come out. If it matters, the shop is 26W x 36D x 10H. The loops come out about 2/3 back on the left wall (about 24' back). I don't do any welding or anything like that. I am just not sure why I could not use this inside assuming that I vent the main gasses outside through the pvc exhaust.

Oh yeah, I did do a heat loss online and was very conservatively in the 50-55K range, but I doubt it will take that much. I only plan on heating to about 55 degrees and have a large wood burner inside (forced air) to heat up the rest when I will be out there all weekend. But the heat might be so great I just say screw it.

Any thoughts? By the way I love this forum!!
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Last edited by boyAND1; 09-18-2013 at 10:00 PM. Reason: Change title
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Old 09-18-2013, 10:08 PM   #2
Jackfre
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Default Re: Can I use an outdoor tankless water heater safely inside shop

NO! Google carbon monoxide and read for a while.
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Old 09-18-2013, 11:29 PM   #3
Fast LT1
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Default Re: Can I use an outdoor tankless water heater safely inside shop

^^^^ lol!!
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Old 09-19-2013, 07:36 AM   #4
boyAND1
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Default Re: Can I use an outdoor tankless water heater safely inside shop

I said i would vent it outside. Is there any real good reason i should not be able to do this? What is the biggest difference b/t indoor and outdoor boilers? --Other than it being outside.
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Old 09-19-2013, 08:16 AM   #5
Jackfre
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Default Re: Can I use an outdoor tankless water heater safely inside shop

Different manuf of tankless have different ways of dealing with indoor/outdoor units. Find out the model/make of the unit, go to their website and read the install manual. It should detail the manuf requirements.
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Old 09-19-2013, 08:54 AM   #6
anthony666
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Default Re: Can I use an outdoor tankless water heater safely inside shop

mount it outside, pass your heavily insulated feed and return lines through the wall .. done & dusted
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Old 09-19-2013, 09:23 AM   #7
sands35
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Default Re: Can I use an outdoor tankless water heater safely inside shop

Pay attention to the details of the combustion exhaust. Likely category 3 - which means stainless steel parts and sealed joints with specific spacing and wall vent designs.

If you are putting it into a wood or body shop with lots of suspended contaminants, you will need an external intake as well.

Jackfre is right, get the manual and read.
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Old 09-19-2013, 09:24 AM   #8
rsa
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Default Re: Can I use an outdoor tankless water heater safely inside shop

Quote:
Originally Posted by anthony666 View Post
mount it outside, pass your heavily insulated feed and return lines through the wall .. done & dusted
Bingo—or buy an indoor unit.

This two part video shows the differences between outdoor and indoor types:

http://www.youtube.com/watch?v=mqPY_Nn4nyQ
http://www.youtube.com/watch?v=F9SxGPxN_HQ
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Old 09-19-2013, 12:54 PM   #9
boyAND1
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Default Re: Can I use an outdoor tankless water heater safely inside shop

The manual does not even have an option to hook up a flue. It is all built into the front of the unit. so guess that will not work. I don't want to hook that up outside when it hits -30F here in the winter before the wind chill.

Thanks for the help.
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Old 09-19-2013, 08:57 PM   #10
Jackfre
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Default Re: Can I use an outdoor tankless water heater safely inside shop

Good decision. Low cost is a part of a system equation, but should not be the sole criteria for the decision. Forge onward!
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