Oil 2 gas steam job w BB loop

worldclasshvac

Looked at an oil to gas conversion with an old Smith steam boiler. Piped horribly w copper but what stood out was the baseboard loop tapped in below waterline.  Never dealt with this situation before on steam it's usually a gas to gas swap and they have a standalone gas water heater.  What are the options/control possibilities for a DHW indirect AND a loop of BB that feeds fin tube.  Thanks

Jamie Hall

Oil to gas, gas to gas, oil to oil -- the fuel makes no difference in the control scheme.

That said, the baseboard loop most likely has a thermostat. There is very likely an aquastat on the boiler (as well as the steam controls) to hold its temperature for heating, or, if it is a cold start loop, to fire the boiler when the loop thermostat calls. That thermostat or the aquastat will control the circulator for the baseboard loop. The aquastat will also limit the maximum boiler temperature when the steam system isn't calling.

EdTheHeaterMan

I have done this in a foolproof way.

Ordered a steam boiler that has an optional tankless coil for DHW
Connected the hot water baseboard system to the tankless coil as if the coil was the boiler supply and return. Top of the coil is the supply. from that I piped to the air vent (scoop) and expansion tank set up of some type. I also placed a tee for a 30 PSI relief valve in there somewhere. After the expansion tank comes the circulator, then to the baseboard. Follow up with a purge station at the return and into the bottom of the coil.

Set the aquastat for the tankless coil at 170° for the high limit in series with the thermostat line that runs the burner. That way the boiler does not steam if only the baseboard zone calls for heat. You can also operate an indirect off of that tankless coil.

My job was a large Church with 3 zones of steam radiators. The Secretary and Pastor office was in the smallest zone that operated a small chapple that was rarely used. So whenever the pastor or the Secretary was in, they needed to heat the chapel that was not used very much.

I added the baseboard zone to heat the two offices and the 2 restrooms. This was a great savings for the church because they did not need to keep the Great Hall, the Large Sanctuary or the Small Chapel steaming just to get the office to warm up.



HOW BIG IS YOUR PROJECT?

worldclasshvac

Currently an older farmhouse style with a 250ish BTU steamer.  I gotta go measure the rads but it's oversized for sure.  I need an indirect and the BB loop to make it all happen.  I appreciate your insight Ed thank you. I was looking at a DHW coil boiler but couldn't rly find anything about the control settings for the limit.  I know a lot of modern boiler controls/aquastats have flexibility for dhw and provisions.  

EBEBRATT-Ed

Just be cautious using a tankless coil for a baseboard loop. It will work fine for a small loop. If the loop is large , you have seen tankless coils they have a lot of small tubing in them and are quite restrictive,

Also the hot water loop must not exceed the steam boilers pick up factor which could be an issue if you down size the new boiler. boiler

worldclasshvac

That's my issue as I need to feed an indirect and a loop of fin tube BB. Gotta look into a brand that has available below water line taps to see if I can set something up custom.  

Jamie Hall

worldclasshvac said:

That's my issue as I need to feed an indirect and a loop of fin tube BB. Gotta look into a brand that has available below water line taps to see if I can set something up custom.  

I have yet to hear of a boiler which doesn't have at least one below water line tap. I suppose they exist. The return can go into the wet return before the Hartford Loop.

Mad Dog_2

I have drilled and tapped quite a few boilers when there wasn't any available tapping.  Mad Dog 🐕