Every heating guy loves a vapor system.

Tony Viz

But what if the house is chopped up into apartments and a hydronic system makes more sense.

The Job......

Single family residence that was converted into six apartments.

Original Veco system. Half of it has the right orifice valves at the top of the radiators. all of it still has the little p traps on the returns.

The boiler is history in more ways than one.

The $64,000 Question

Would it be possible to plug in a couple of condensing boilers using the 4" main supply and the 1-1/2 dry return?

I would use a thermostatic Danfoss valves on the supply of every radiator and have to work in a air vent somehow. The little p traps would have to go. Pumping would be handled by some kind of smart pump.

All the return piping leaving the radiators is 1/2" so that limits BTU to 15,000 per radiator.

Supply piping to each radiator is 3/4" so maybe i could eek out 20,000

Not sure what my 1-1/2' dry return will handle as far as BTU.

Am I nuts to attempt this?

Alan (California Radiant) Forbes

Conversion

I recently asked the same question myself on one of my jobs. But two things made me pause.



1) Properly sized steam radiators are typically undersized for hot water. I did the heat-loss calc's. and sized the radiators and they were typically 10-20 percent too small. The house still had single glazed windows and no insulation.



2) The old steam pipes may be strong enough for vapor steam, but not for 15 psi hot water. And probably very coroded.



But you may be able to get away with it with all the added insulation and if you are able to test and flush the piping.

Alan (California Radiant) Forbes

Conversion

I recently asked the same question myself on one of my jobs. But two things made me pause.



1) Properly sized steam radiators are typically undersized for hot water. I did the heat-loss calc's. and sized the radiators and they were typically 10-20 percent too small. The house still had single glazed windows and no insulation.



2) The old steam pipes may be strong enough for vapor steam, but not for 15 psi hot water. And probably very coroded.



But you may be able to get away with it with all the added insulation and if you are able to test and flush the piping.

JohnNY

I did it here:

http://www.heatinghelp.com/professional/66/Gateway-Plumbing-and-Heating



Actually, the system was converted from steam to hot water before I got there, but everything outside the boiler room looks like a steam system.



It works far better than I expected, and evidently, improvements in the building envelope far compensated for the radiators being sized for steam.

There's a techie guy in the building who monitors the system daily and records outdoor and system temperatures and in three heating seasons the system temp hasn't gone higher than 137° water temperature.



Ultimately, our scope of work was to convert the system from gravity flow to pumped circulation and the boilers from a oil-fired on/off to natural gas fired modulating condensing.

The pressure sits steady at 22 psi with a slightly oversized compression tank.



My opinion is based on what might be a uniquely-gratifying experience, but I'd say *Go for it!*

jumper

how about return for supply ?

Consider using the return for the new supply ? Also figure the height and use minimum pressure required. Try circulating water before you install new boiler.

Paul48

?

Pressure test it before you run water?