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Author Topic: return line  (Read 2114 times)

cweeks

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return line
« on: February 17, 2014, 07:06:07 PM »
Hi, newbe here. I was wondering what the water temp would be coming out of my water to air exchanger on my forced air furnace? Would I be able to loop the return line uninsulated under a floor that's above a crawl space in my home to heat the floor before going back out to the owb? Sorry if this is a confusing question. Thanks for any info.
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lindnova

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Re: return line
« Reply #1 on: February 17, 2014, 07:33:10 PM »
Depends on how much demand.  I don't have thermometers on mine, but with the infrared gun it doesn't loose too much heat.  I would guess a few degrees underground, and a few more thru the hot water, furnace and flat plate for the garage depending if they are calling for heat.  The return water is still pretty warm.  I would recommend a small flat plate and separate pump to do what you want which is actually effectively heat the floor.  You aren't going to be able to control the heat the way you want.  If your crawl space is uninsulated you will lose a lot of heat unless you insulate under the pipe.
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juddspaintballs

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Re: return line
« Reply #2 on: February 17, 2014, 07:41:41 PM »
As lindnova said, it depends on the demand from the water/air heat exchanger as well as your incoming water temperature, pipe sizing, and flow speed.  Properly sized, you should have at least 160 degrees returning to the boiler if you're starting with 180 coming out of it.  The higher return temperature, the more efficient things will run since the temperature change will be not as drastic.  If you want to radiantly heat your floor above a crawlspace, use a side loop off of the main loop with it's own tiny circulator to control the flow with a thermostat and then insulate between the pipe and the cold side of the crawlspace.  Don't forget your vapor barrier either.  A metal heat transfer plate to hold the pipe up against the floor will help you maintain a more even heat since PEX doesn't like transferring heat very well. 
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cweeks

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Re: return line
« Reply #3 on: March 04, 2014, 05:09:20 PM »
Thanks for the help.   I am just trying to get my ducks in a row and figure out the best way to do my project before I get started. The more I have looked things over I'm thinking about just running my return line thru a unit heater placed in the crawl space. Like I said thanks for the replies, don't think you have heard the last of me as I am sure I will have a lot more questions. Thanks again 
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