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Old 12-04-2010, 02:44 PM   #1
Join Date: Nov 2010
Location: Ontario
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radiant heat

I have 3-100' loops in the floor of my garage, I want to get some temp heat in there for the winter. I don't want to do a full setup, I have a lot of other work to do in the utility room before I do a complete setup for the radiant heat system. I want to connect it to my house hot water tank. I have a 3 way mixing vlave (70-120) and a recirc pump which I plan to connect to a line voltage stat to control the flow. Can someone give me a quick diagram or explanation on the water connections.


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Old 12-04-2010, 03:31 PM   #2
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radiant heat

By your hot water tank I presume you are referring to a potable water heater. Any radiant heat zone using that as a source should, at a minimum, have a heat exchanger to separate the potable water from the water circulating in the radiant zone.

Radiant heat is typically run at low pressure--15 psi or so. Potable water systems typically are at least 50 lbs and if your water source is municipal it could be much higher--perhaps higher than the pressure rating on the ratiant tubing.

Last edited by Bob999; 12-04-2010 at 03:33 PM. Reason: add information
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Old 12-04-2010, 04:56 PM   #3
Join Date: Nov 2010
Location: Ontario
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radiant heat

yes, i mean potable hot water tank, why do i need a heat exchanger? these are new pex lines in the concrete, I just want to circulate the hot water through the lines,I am not looking to completely heat the garage this way, just take the chill out. I know the temp of the water needs to be around 90-100 hence the need for the mixing valve. I realize this is not the most efficient or proper way. I plan on running a glycol closed loop system later, but this is just to get me through this winter. I am just not sure how to tie back into the feed to the HW tank

I have a 3 way valve. here are the connections
H- tie into supply from HW tank
mix-ties into feed lines to garage, this is where I will put the recirc pump
C- return from garage,

My thoughts are to put tee at the c connection a line to the HW tank (cold side)

does this make any sense and will it work
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Old 12-04-2010, 05:52 PM   #4
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radiant heat

Ayuh,... I think the point by Bob is that it's not a good idea, 'n is frowned upon by governmnet, 'n industry...
'n there's the pressure differentials...

"T" off the cold fill side of the tank for the return, 'n "T" off the Hot side for the pump, 'n feed...
I wouldn't worry about the mixin' valve....
Your Dhw is low enough now, compared to boiler fired systems...

If you insist on the mixin' valve,... Put it so the pump draws From it, not To it....
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Old 12-04-2010, 06:28 PM   #5
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Location: Ontario
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radiant heat

thanks, someone told me to use a mixing valve, but i checked my HW tank its only set to 105 anyway so I think i'm good as far as temp goes. i will fill the lines until water comes out of the return. then connect the return into the system to eliminate as much air as possible.
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Old 12-05-2010, 10:29 AM   #6
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radiant heat

Wait till you get the first electric or gas bill, it's gonna probably about triple. Water heaters make very very poor exchangers for radiant. If it's an electric tank it will most likely never shut off.

Always ask to see your contractors license!
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