Hot Water Loop off Steam Boiler vs. Separate Boiler

[jgoodnow]

My question is strictly fossil fuel so it is slightly off topic. But I do burn wood for supplemental heat and I like this site, so here's my question.

My existing heating is gas-fired one-pipe steam. I'm doing some remodeling involving some changed and new radiation. I've settled on removing one steam rad and adding two new hot water rads. So I need a source of hot water. My heating contractor has given me two options for this. One, I can tie into my steam boiler below the water line and circulate the hot water through a heat exchanger, which would heat the water to be distributed to the new radiators, or two, I can add a new mod-con boiler to run the two new radiators. I have a desire to add one or two additional hot water zones at some point in the future and would also like to go with indirect hot water when I need to replace my water heater. The separate mod-con would be able to handle these loads but not my existing boiler. My view is that the separate mod-con boiler is the superior solution but it does come with a price premium that I was not quite prepared for given all the other remodeling costs.

My question is, what do the heating experts and homeowners here think of these two solutions?

 

[mikeyny]

well I am no expert in steam systems but , why wouldn't you just add 2 steam radiators? Steam systems work at much different temps and pressures, so they do not mesh well with hot water systems. The use of a heat exchanger is a good idea for domestic hot water, but there are always eff. losses with hx.

 

[jgoodnow]

why wouldn't you just add 2 steam radiators?

Good question. One of the two new radiators would be difficult to pipe due to its distance from the boiler. I did get an estimate for steam but ruled it out because the difficult-to-pipe radiator is in a high heat loss room where I really want heat. I also have a desire to create a zoned heating system so that I can heat a small portion of the house comfortably while keeping the thermostat a little lower on the steam side.

there are always eff. losses with hx

.

Good point, I had not thought of that.