Hot water loop off of W-M SGO steam boiler

JeffM

Can anyone comment on where they would connect a small hot water heating loop to a Weil-McLain SGO steam boiler? My SGO-3 happily heats the house with steam all winter and provides plenty of hot water year round via the tankless coil. However, the tile kitchen floor is chilly and neither the wife nor the dog like that so I'm planning to put radiant in that area from below this fall (with plates). My initial thought was to use a small electric boiler for the independent radiant system, but I've been wondering whether it might be better/cheaper to tap into the main boiler for this small load (it's just floor warming and we're keeping the kitchen steam radiator, so I think only 5000 Btuh). There's an unused tapping on the SGO near the bottom front that I could pull this loop from, but where would I pipe it back to?

JStar

There should be one or more unused/plugged tappings in the boiler. They might be accessible with the jacket off. If they are not in a good location, you can use the front and back return tappings.

Be sure to use a 3-piece bronze circulator and appropriate controls to ensure trouble-free operation.

JeffM

That's a good thought. There's an unused 1/2" tapping on front, but it's close to the tankless coil so I'm a bit hesitant to send the return back there. The boiler manual lists a 3/4" tapping on the back that I didn't know about, so maybe I will open the jacket to check for that. I recently replaced the sight glass valves with no issues, so I have some hope that the plugs may come free without too much difficulty.

JeffM

Looks like pulling the jacket is a lot of work (all three sides are one piece and two sides have piping), so accessing the hidden tappings may have to wait for a future season. I could pull out a 1/2" drain valve on the bottom of the wet return leg and put in a tee to send return water back there, or pull the 3/4" main drain valve on the boiler and add a tee to connect there pretty easily. Either of those ideas have issues I'm unaware of?

Bob Bona_4

Think I would favor a heat exchanger for doing the radiant-small tubes and mud equal bad things. But for that small a load is it worth it to fire the boiler? Electric mat perhaps?

JeffM

I am thinking about a tiny electric boiler, but since the steam boiler is always hot for the DHW tankless coil there wouldn't be much extra firing. It's a 15x15 area and already tiled, so I have to do plates from below.

JeffM

...and I would definitely use a heat exchanger on the steam boiler loop.