Converting one-pipe steam to hot water

steve_6

I had my two pipe steam system with a 75 year old snowman style boiler converted to hotwater about 12 years ago. A number of heating contractors talked me into it, painting the picture that installing a higher efficiency boiler adding a couple zones and setback thermostats could save me 30-40% on my heating bill ( natural gas). They told me steam is inefficient. So I listened. I spent an additional $2500.00 to convert. And guess what? My gas bill went up 10 %and my electric bill went up 50%. Some savings Huh! Oh I also had 10 to12 no heat calls @ about $50.00 a pop, and my house was never as warm as it was. So guess what I did this spring ? I converted back to steam. And you know what? the system is as quiet as can be, heats very, very fast and basicly has no moving parts to break. Speaking from personal experience, I wouldn't convert!

Ben Kennedy

Converting one-pipe steam to hot water

I've heard about converting steam to hot water by running little PEX tubing through the old steam pipes (using them as conduits). Is it possible to do this with my one-pipe steam system? I guess I would need a replacement for the valve (a magic valve?) that would allow a PEX supply line into the radiotor and a return line back through the same pipe. I want to avoid wholesale destruction of my house with the return lines. All my pipes at the radiator are 1-1/4"

I crunched the numbers; I have enough excess radiator capacity to make the switch, My radiators are thin-tube "hot water" types, I need a new furnace, and I think multiple zones that hot water would give me would help me save some money.

Any help is greatly appreciated.

kframe

Anything is possible with enough money.

PEX is a good choice to do this with, as you can fish it through the walls to create the return loop.

I'm not sure I'd try to fish TWO PEX lines through a single steam pipe, though. In fact, I'm pretty sure that a 1 1/4" steam pipe simply wouldn't be large enough to get two PEX lines through it.

[Deleted User]

mind if i ask why you

want to do this....

Steamhead

Ditto

Are you having problems with the system as it is (besides needing a new boiler)? If so, they're a lot easier and cheaper to repair than to convert your system.

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kframe

Wow! Wonderful first hand experience, Steve.

I'd bet that the system wasn't as warm because the radiators were sized for steam. Because steam hits the system a lot hoter than a hot water system, the radiators don't need to be nearly as big.

Change over to hot water, and your BTU output per radiator drops, and your rooms are going to be colder, your gas bills higher, and you'll definitely spend a lot more circulating that water around with the electric pumps.

I grew up in a house with a one-pipe steam system, and rather liked it.

I know quite a few people who say that they would never buy a house with steam heat. I know I certainly would.

heatboy

It would seem..........

the only way to convert a steam system to hot water, would be to completely remove the steam system and start over. It would cost several hundred, if not substantially more, just to find out if the steam rads would hold water pressure. Then, if they do, drill and tap every one of them. Unless the homeowner is doing this himself, the money he would pay a contractor to do this would buy a couple of flat panel rads for the new hot water system.

As long as the distribution system is sound, leave it steam. Remember, this comes from someone who is, admittedly, steam stupid.

hb

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Boilerpro_3

Hot water rads can put same heat as steam

A radiator running at 225F supply and 205 return will put out the same amount of heat as a steam radiator at 215F. Don't get stuck on running water only at 180F supply.

A conversion I did a few years ago for a church yielded a fuel savings of about 60% over the 12 year old WM that was in there. Some of those savings came from disconnecting a snowmelt system and better equipiment sizing and controls, but they were real. Comfort and control improved dramatically. It sounds like whoever did the conversion didn't know what they were doing. Things like boiler short cycling when small zones were running (kills efficiency and electronic ignition components), no outdoor reset, etc. would all be things I'd look for.

Boilerpro

Boilerpro_3

Say Heatboy, tapping little 1/8 or 1/4 inch returns....

really isn't that hard. I just use the bosses for the manual air vents or the old steam air vent tapping for the return for 1/8 or tap the radiator end plugs for 1/4. Helps keep the system balanced too, no short circuiting.

Boilerpro

Guy_5

old steam system

I think that if you replace that old boiler with a properly sized unit, you will be more than impressed. I am also a believer in keeping the character of the home.There is something to be said about the old steam systems. You know, A hundred years from now.....

Ben Kennedy

Looks like I'm sticking with steam!

Sounds like converting to hot water won't be cheap or easy or neat, and I'm cheap. But I am a masochist, so perhaps steam is for me.

I do like the simplicity of my one-pipe steam system and when I added on to my house a couple of years ago I read Dan's book cover to cover and ran a new main to the new area. After two years of tweaking it's actually not too badly balanced. I even found some sweet radiators from someone who bought an old house and gutted it (What colossal gall to rip out a perfectly good steam heating system!).

SO I think I'll put in a modern boiler to replace the ancient gas (nee coal) behemoth, and be happy that I don't have to mortgage my future to pay for the hot-water conversion.

Or maybe I'll convert to forced air? NOT!

Bryan_5

Ben,
Glad to hear you are going to stick to the steam. I was given the exact same suggestion. Then I discovered the wall and through the excellent advice I have learned from the Pro's here my system is running darn near perfect.
Bryan

kframe

How many home systems run at those temperatures, though?

If you have water heated to the same temperature as steam, of course you're going to get the same heat out of the radiator.

But AFAIK most home systems run in the 180 range (my parents does), roughly a 35 degree difference.

kframe

Done a number of drill & tap jobs on radiators over the years.

The hardest part is getting the hole drilled straight.

steve_6

steam vs. hot water conversions

How long does it take to heat 100 gallons (system water content) to 215 degrees and how many btu's does it take to do it? You can get 212 degree steam to the furthest radiators in 10 to 15 minutes from a cold start up. and your only boiling 10 gallons ( system water content) or less on an average residential boiler.

Steve_35

I think the poster that said you're going to get the same heat out of a steam boiler with water at the same temp forgot about the latent heat available in steam. It's around 950 btu per pound of water. That will make a significant difference in the heat output of the radiator.

Unknown

Yes, per pound of water delivered.

But the radiator output doesn't care if you have 1 pound of condensate or 20 pounds of water inside it.

It only cares about the surface temperature, and the air temperature, all other things being equal.

Noel

kframe

But my question is, once again, how many home hot water heating systems run at 215 to 220 degrees F?

Those would have to be pressurized systems, wouldn't they? The only way to raise the temperature of water above the boiling point without converting it to steam is pressurize it, or conversely add an anti-freeze/anti-boil (glycol?) to the system.

If you do this, there's no way that PEX could be used for the conversion. I don't know of any PEX products that are rated for temperatures that high.

Boilerpro_3

Very Few, IMHO

The small one pipe steam system I converted a few years ago only needed 140F water at design temp. Needless to say the home was over radiated, especially since it had been throughly insulated. A couple of other converted two pipe systems I've worked on are only running about 185 to 190F supply at design... and one with a significant portion of the radiation removed. Have yet to find a steam system that really need to run at 215F. Most only need 180 to 190 at most. This if why conversion often makes sense, you can use a smaller better sized boiler that will have much longer firing cycling cycles. You also can reset the radiator output. Often times the thermal mass of a converted single zone system tends to reset itself.


Boilerpro