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[Belknap]

I am currently running a empyre pro 400.  In my barn which is 5000 sq ft I have radiant infloor heat in the slab on the first floor and staple up under the sub floor on the second floor.  When I have more than one large zone call for heat the return temps drop significantly.  My temp can be at 180 and if I have 2 of the larger zones call at the same time the "optimizer" or thermostatic valve will kick in so the temp going back to the boiler won't drop below 140.  I know this is protecting the boiler which is fine but just wondering what I can do to try and prevent this.  I am currently running the boiler at 180 with a 5 degree differential.  I have 1" Logstor feeding the barn.  It is 130 foot run one way from the boiler to the 80 plate heat exchanger exchanger.  I have six zones of heat with the 2 larger zones have 8 loops of approx 280' of 1/2 pex.  I am running a Armstrong 9.2 pump.  The run from the boiler to the house has 1-90 and 6-45 degree bends.

Just wondering if I put a larger pump in would that help or should I just live with it.  It just seems to take a long time for the boiler to recover after this occurs.

Thanks for any help.

[mlappin]

What's the differential for the radiant heat? Maybe try a 1 degree so it doesn't take as long before it shuts that zone back off?

[Belknap]

I am using a uponor thermostat made for radiant heat and it has a 1 degree differential.

[slimjim]

Are you changing the temps of the radiant slab, if so leave them at one set point. If the stove manufacturer will allow it, turn the temp up on the stove, I run all my installs at 190 or above.

[ITO]

 Can you use a priority zone and have only one loop call at a time or maybe half the loops depending on setup? I use floor/air sensing averaging tstats for my floor zones, they switch often and keep the loops warm so there is less heating, cooling and more consistent temps, it works well for me, not sure if that would help you or not.
 http://tekmarcontrols.com/products.html

[slimjim]

Great option Ito, where's that like button

[Belknap]

I have tried to use the priority but when it is real cold by the time the priority zone is satisfied the other zones are calling.  I spoke to Empyre and they don't want me to run the temp above 180.

[Belknap]

I looked at the floor/air sensing thermostat.

 http://www.pexsupply.com/Wirsbo-Uponor-A3041501-SetPoint-501s-One-stage-SetPoint-Controller-with-floor-sensor-2068000-p

I think I will try one next year and see how it works.

Thanks

[Sprinter]

What do you have for mixing valves and is this just a one pump system?

[Sprinter]

What do you have for mixing valves and is this just a one pump system?

From the 9.2 pump specs its 40' head max and 38gpm max. Very steep curve. 260' of logstor 1" @ 7gpm is 30'head not including fittings or exchanger.  And above 35' that 9.2 is under 5-6 GPM.

[LittleJohn]

BELKAP, is garage 5000sf total or each level??? 
  Are you runing a mixing valve between the OWB and the inslab? or are you runnign 180f water thru slab?? 
    Only reason I ask is I thought my dealer told me never to run the water temps for inslab over 140f or 150f, potential for excessive cracking and degridation of concrete.

Lets do some math; say you are running at 5gpm and temperature drop of 40f (max drop with out thermostatic kicking in)
BTU= GPMxdTx500   ->  5x40x500 = 100k BTU/hr  -> divided by 5000sf = 20 BTU/sf which is typically what you would want for a typical radiant application

So since you can not increase the temperature drop before returning to OWB, and still need more heat for building; you may need to increase the GPM to get more heat out of OWB. 

NOTE: Most people on this forum (from experience and a bit of reading) typically run in thearea of 20f across loops.

[Sprinter]

Different radiation requires different delta T.  There are charts and design tabs that show many types.

Infloor is 10 degree for reverse return layout. The more even you want the room comfort or heated the smaller the DT. As long as you build in flexibility, you can dial in what works best for you.
A simple mixing manifold or manifold block will control temp and provide adequate flow. That size should have multiple manifolds, or you would need commercial size $$$$ circ to do 5k on one mani.