Long time reader, first time poster. Sorry in advance for the long post.
I bought a house a couple of years ago with a Pennco 1606 boiler. When I first got it, it was a sight, with a soldered copper "header" about 30° from vertical. The old owners didn't say there were any problems with it when asked, but then again all the radiators were pitched wrong, every other valve leaked at the stem, and the thermostat was set to 64 °F, so I'm pretty sure they weren't paying too close attention to much but their gas bill. Anyway, I've taken care of all that by replumbing the thing with a (sort of ridiculous-looking) drop header, adding some main venting, putting TRVs and new air vents on the rads, adding a vaporstat, fixing the leaks, insulating pipes, etc.. Dan's books and the help you all offer to the other posters has been invaluable to me; the thing hums pretty well now.
Last fall, we had our basement floor broken up, dug down a couple of inches and repoured (the boiler didn't move; so it sits on a little platform now), and in the process, we changed the main sewer drain, and insulated the slab and ran three radiant loops in it. The total load is ~21,000 BTU. This summer's project is to hook up the radiant to a heat source.
The boiler was a bit oversized to begin with, so I figure it can't hurt too much to steal the heat from there. I was planning on an Everhot RH-8 heating a conventional-looking (with the exception of the beefy pump I'm going to be forced to use because I could've done better designing the circuits) loop . My question is which tapping I should use on the steam boiler.
For available tappings, I have:
- a 1-1/2" tee I can reuse that's now the water supply feed on the return line (on the boiler side of the hartford loop).
- an unused 2-1/2" return tapping on the other side of the boiler.
- a 1/2" tapping about 3-1/2" above what's now the lower 1/2" tapping for the sight glass, also on the other side from the 1-1/2" tee.
I've read this: https://heatinghelp.com/systems-help-center/how-to-run-a-hot-water-zone-off-a-steam-boiler/
I can see a couple of options:
1. I can run across the mud leg, pumping from what's now the fresh water supply, through the heat exchanger and back into the boiler (I was also going to put a bypass on just to be on the safe side), but I understand that won't get me enough heat. Can I get away with it for 20,000 BTU out of the 153,000 the boiler can make? Getting the plug out notwithstanding, this seems easiest and cleanest, but if it won't work... I was planning on using a bronze B&G 100 for durability, so without having done the calculation, I suspect I'd be pushing a heck of a lot more flow than is needed through the Everhot to get the BTUs I need for the radiant with 180 °F boiler water.
2. I can still take from the water supply tee, but return by moving the lower sight glass fitting up to the 1/2" tapping 3.5" higher, buy a shorter sight glass, and return into the lowest 1/2" tapping. (The water level would be about halfway on the new shorter sight glass, which seems fine to me. Now, the bronze B&G 100 as recommended in the page above would generate a lot of flow to push through this 1/2" pipe. Is that going to cause problems? Noise? Also, I know from the link above that it will mess with the sight glass level if I tee right in, but does it make it ok by just going directly downward as little as 3.5"?
3. I can do the injection-through-a-bushing thing as described in the link above through the unused 2-1/2" tapping. I'm not enthusiastic about this option, as space on that side of the boiler starts to become an issue (that's where my electrical panel is).
4. I can do the injection-through-a-bushing thing from the other side, but this would have me undoing some unions on the Hartford loop and rejigging stuff. I'm also not so enthusiastic about this, but it wouldn't be THAT bad.
The Pennco's not the greatest boiler in the world, but it works, and since it's oversized for the steam radiation, taking the heat from it seems to make sense. As another option, I've also got a gas water heater that makes 38,000 BTU, which I guess I can crank up, put a mixing valve on, and run the radiant loop off a braised plate heat exchanger. Then I start to get worried about hot water in the dead of winter...
If I can pull this off without another heat source with another gas line, another vent, etc., I'd be a happy camper.