Adding a In floor heat run to a furnace exchanger seteup

[Arctiva]

So last year I installed a outdoor wood boiler and a water to air exchanger to the furnace. Quick and cheap all DYI, I'm redoing a porch and making it a foyer with a new concrete slab and am going to put tubing in for heat. 

I'm wondering how I'd control the heat in the foyer? I'm assuming I cant just circulate 180 degree water 24-7 like I do to the exchanger?

The foyer will be 11x15. So 300 feet or so of 1/2 tubing with 8" spacing and another 30 feet across crawl space to get there. 

Could i do a manifold on the supply and return side and use a separate thermostat to control a zone valve to only allow water to circulate when heat it called for in that in floor loop? But allow the water to circulate 24-7 to the furnace exchanger? Would I need a zone valve on the return side also then? 

Then I wonder if I'd need another pump? Maybe a small 1 for the infloor loop or another on the return side to push back to boiler. I'm 125' 1 way from boiler. 

[Southside]

Ummm - no.  You can't push 180 degree water through your slab, you will need a mixing valve and want to keep it in the 95 degree range.  So you will need a separate zone for that.  You could have a manifold that feeds the zone valve bank - one to the water to air, and the other to the mixing valve, when the foyer calls for heat the valve opens and it feeds the slab.  I had a similar set up and had the main pump loop from the boiler to the manifold, then smaller pumps for the zones.  No need for a zone on the return side, just use a check valve.  

[E Yoder]

After flow goes through the hot air coil put two close tees for a supply and return. Use another small pump (I like Grundfos 15-58) pulling through a mixing valve turned down to about 95 (as was mentioned). A thermostat in that room starts and stops that pump.

[DDW_OR]

Following

i will be doing something like this for my greenhouse
using a Central boiler 750
dig a 4 foot deep pit, install cement blocks, line it with insulation, add a Pex loop, then fill with dirt.
then put greenhouse on top of the cement blocks
yellow = insulation
red = Pex


 

[Arctiva]

Is 95 degree the right water temp then for Infloor heat setup?

[Arctiva]

Would you put the pump before or after the mixing valve? 
I assume after, mixing valve opens pump pushes water, valve turns off pump stops, check valve keeps water in the zone. 

That setup sounds the easiest for a crawl space setup like I have.

My thought was to run a 2" PVC with a long sweep 90 across my crawl space stubbed out to the slab and run my 1/2" supply and return through it foam the end where the concrete will be. Then I dont have exposed lines in a cool space and dont have to have exposed pipes in the foyer.

[doc henderson]

our slab temp water is 110 °F

[doc henderson]

is this indoors insulated room, or outdoor slab?  the circulate 24/7 makes me wonder,  great idea if energy is free.  but lots of losses.  24/7 is usually so the lines do not freeze.

[hedgerow]

I have my floor heat set up on a heat exchanger that runs off my Garn on the floor side its closed system with a pump, antifreeze and bladder tank and a thermostat to turn that pump on and off. You could came out of your water to air heat exchanger to a water to water exchanger and then back to the OWB and it sounds like you leave that pump going all the time. I wouldn't run the OWB water threw the pex in your floor. 

[Arctiva]

It will be a foyer so insulated and "inside". 

I think after researching and some comments here I have a good understanding of how to get it done. 

Still a little unsure of the mixing valve setup, all most seems like youd want the mixing valve tied into the pump/thermostat. You wouldn't wanna mix the water when the pump isnt running

[Arctiva]

I dont run antifreeze, I run the main pump 24-7. I want a nice warm floor and the heat to help radiate out to the 2 other rooms that will be connected to the foyer. I considered a wall radiator, or running a duct through the concrete of the existing system but a nice warm floor it the way to go. 

I did a electric heated tile floor in my last house and OMG the nice toasty floor and warmer rooms around it were a nice upgrade. But why do electric when I have a boiler and free wood