I would still put a calibrated (put it in boiling water on the stove) thermometer inside the return line just before the boiler.
Nothing so heartwarming as seeing your theoretical analysis in action and knowing you got it right.
Whew...... This is going along.........
Ok, I have a thermometer on the boiler return, this is how I know the numbers as stated, never going below 155F.
EWD is correct, the indirect is not a buffer tank, it is a zone all by itself.
Also EWD, I like your idea of cutting the load (powering down the ZV controller in this case) w/o turning off the primary loop to let the boiler recover. I'm a fan of the simpler the better, the more reliable the better, but sometimes the more difficult to come up with.
The slab mixing station (which is fed from the closely spaced tees in the pic, also it's a Taco radiant mixing block pictured in my avatar) is set to 114F fixed injection temp. This pulls about 60,000 - 80,000 btu out of the loop (keeping the return temp above 165 as we did the math, and as I've seen on the thermometer.
I didn't want to get into all of this but hopefully it helps someone with their install.
EWD, the 0010 would push A LOT of water through the primary loop, but I wanted to eleiminate as many circulators from the system as I could, saving wattage, the 0010 is 126 watts, 007s are 81 watts. So I went the unconventional way, and modified some things. This may be confusing to some but here it goes.
I took apart a regular Taco 1 1/4" cast iron weighted flow check and removed the brass weight (pictured) and machined a new one out of solid brass round stock (don't have a pic) which is twice as heavy. This creates a 4psi pressure drop on the loop which brings the 0010s flow down to around 14 GPM. The reason I did this is now I can use zone valves (low power draw) on a primary/secondary setup. The only closely spaced tees are the ones pictured which feed the injection loop for the slab (the main draw), and the dump zone (unit heater in garage, never used). You can see in the second and third pics the top of the indirect and it's 1" zone valve (Caleffi Z-One). The unused ball valves are for future input/output. This is not conventional, and was an expierement, which has proven to work well, allowing my preferred zone valve setup without sacrificing the benifits of primary/ secondary pipeing. I have some small panel radiators on the second floor in the bedrooms and didn't want a dedicated (read: watt hungry) circulator for each one, now I use less that 150 watts to run the whole thing which is less than two 007s. I hope this helps quell all of the unclear words and puts a picture to some of it.
This forum has helped me to think out of the box and hopefully I can inspire someone else to do the same.
Taylor
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