Steam to hot water

Tim Davis

Looking for pros and cons of converting 2 pipe steam system to hot water. I have read you lose about 30% heat output by doing this,also on the steam traps do you remove the entire trap or just remove the internal parts.

Thanks

Boilerpro_3

I have done a few

You do not have to lose 30% output. A standard steam system operates at 215F. A standard residential hot water system is at 180F, however you can push this water temperature up much higher as long as the system is pressurized. There are many systems operating at 210 F and higher.

This said, it is rare to find a steam system where the radiators are not significantly oversized. One small system in particular that I converted only needed 140F water to heat the home on the coldest day of the year.

The chief concern when converting a steam system to hot water is whether the system can handle the higher pressure without leaks, as steam systems usually run at most 2 psi, where hot water system run up to about 27 psi.

Some advantages of the conversion are: usually much lower capacity boiler can be used, since it can be matched to the current heat load of the sturcture. Typcally, a steam boiler is matched to the radiation capacity and if it is greatly oversized for the load, the boiler is much bigger than necessary. A smaller boiler better matched to the load will yield higher efficiencies over the course of a heating season. You also open the possibility to using a condensing heat source, which are much more readily available with hot water. You can then have a boiler with potential efficiencies of 90% to 98%.

Next is that most of the season the system will run cooler, again helping boiler efficiency. This occurs because the cooler heat exchanger can absorb heat more readily than one that is hotter.
The system efficiency also can increase. Cooler piping in spaces not needing heat reduces waste. In addition, radiators produce a higher percntage of radiant heat at lower temps than at higher temps, meaning less air is heated directly by the radiator, reducing hot air stratification and increasing the radiant temperature of the space. Both of these improvements lead to higher comfort.

The traps can stay, with removal of the internal components. A typical radiator only needs an orifice about 1/4 inch in diameter to have adaquete water flow, but things like this should always be checked. Never assume!

Hope this helps. You will find a variety of opinions on this subject. Alot depends on the age and condition of the system, and how well matched it is for the structure it heats.

Boilerpro

Steamhead

More cons than pros

Here's a link to Dan's article on this subject:

http://www.heatinghelp.com/newsletter.cfm?Id=22

You're probably dealing with an old Vapor system. Vapor systems were the Cadillacs of heating in their day, and are still some of the most efficient out there.

Besides the heat-output loss (which is 970 BTUs per pound of latent heat, hot water typically gives you 20-30 BTUs per pound), you also have to worry about the old pipes and radiators leaking, and whether the returns are big enough to handle hot water (many aren't).

And a steam system won't freeze up during a power failure like a hot-water system will.

I have found it's much easier and cost-effective to repair an old steam or Vapor system rather than to convert it.

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