Primary secondary

Snowmelt

I know I best this subject to death but I finally did the job. I have a cast iron boiler 75,000 btu in. I divided the home into 3 zones, 1 back dinning room and tv room & small bedroom 2. Living room and master bedroom. 3 radiant floor in small bathroom and kitchen. The hard part was making sure the boiler doesn’t condense. I’m not worried to much about short cycling but I know I should. So I did I primary secondary looping.
Here are some pics

Ironman

Good.

hot_rod

nice pipe fitting! Why so many up and downs?
You might need a small vent up by those close tees, you could trap a bubble there.
I assume there is a pump on the boiler loop, hard to see in the shadow.

Snowmelt

Ups and downs, there was a 1-1/4 x 24 inch pipe on the supply, all I did was added a tee then a close nipple then a tee. I has 12 straight pipe on the supply & 8 inch on the return of the loop. The reason I came down a little bit on the supply and return is because it was too high, I would have to get a step ladder just to bleed the system out or to change the pump. I do like the black pipe instead of copper. Original boiler didn’t even have a back flow. Just a pressure reducer.

rick in Alaska

With your primary loop going up like that, and then down before it ever gets to the air vent, you are going to have a problem keeping air out of the top of the loop. You would have been a lot better off putting the air vent on the highest point there.
Rick

Snowmelt

I understand , on a good note I had the radiant floor heat on only and my return temp was 155.