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[idahohay]

I'm getting closer to the point of installing my Heatmor owb for a new shop with apartment.  The main floor has 6-275' circuits in slab with a design heat load of 23,000 btu/hr., the second floor apartment has 5 -275' circuits under a wood sub floor stapled up with plates and a heat load of 5,500 btu./hr.  (all 1/2" pex)

I've attached a photo of a very simplified schematic of what I am planning to do and would like some opinions on the pumping arrangement. The pump at the owb would run 24/7 and the other two pumps would be controlled by remote sensor thermostats. I show two-3way mixing valves for the two different temperature zones required. 

Any help would be greatly appreciated.

[Scott7m]

Just had a second to look but you'll need zone valves where you have the mixing valves and a primary pump to circulate on that loop, you could do it like that but i donno,  I was just thinking that it could always circulate with 1 pump on the inside loop through the air exchanger and only through the zone valves as it
Needed....   I'll look some more, just trying to get a break from this baby shower

RSI is a good one on layouts like these!!!

[idahohay]

If I use one pump and two zone valves, how do I get lets say 85 deg. water for the slab, and 120 degree for the second floor staple up?

[Scott7m]

You could do 120 through both, I think bondo has his radiant slab heat on like 160, never seen anyone use it that high but have heard of many in the 120 range.

[Scott7m]

You could use a strap on aquastat with a small pump to circulate the loop and keep it at 120, for example it would only flow through the plate exchanger when it dropped below 115 and once it got back to 125 it could shut off, a small pump could still be used for each zone or valve

[willieG]

i have ceramic tile on top of poured concrete i run 110 in teh slab but i think for different floor coverings (like staple up say  under wood they recomend much lower. I think htey say maybe 75 to 85...there are charts on the net that can be found.  depending on how many btu you require  they say to put more loops in and keep the water a little cooler. i have seen homes with 2 runs of pipe between 16" floor joists and some slabs set at 9 inche centers. i ran my slab at 12 inch centers because i knew i could run the water a little hotter to get my required btu output

[idahohay]

The pex is 8" o.c. under the second floor subfloor in aluminum plates, 12" o.c. in the main floor slab. There shouldn't be any problems there, I am just concerned about the pump arrangement. 

[willieG]

becasue of your desired heat loads i feel you will need a pump on each load (as it seems you may require a much higher gpm rate in each of the 2 zones. i wonder if without zone valves the higher demand loop may force water through the lesser demand loop?

there are other things you can do, i am thinking on it

[Scott7m]

Those are my concerns as well with how it is

[idahohay]

How about a check valve before each pump?

[willieG]

How about a check valve before each pump

i have been thinking...i think a check valve  right after your hot line for each zone leaves the header pipe and before it gets to the pump or mixing valve

[gtownky]

you may want to check out this site. It has some good info on radiant heat. http://www.radiantcompany.com/manual/index.shtml

[idahohay]

Thanks gtownky, I had at some time been on that site but this time found a heat exchanger system diagram that is pretty close.