Changing steam radiators to hot water

Georg_2

I want to change from steam to hot water heating. And I would like to use my cast iron steam radiators in the new hot water system.

Will these radiators produce the same BTU when run with hot water or will I need more radiators?

Steamhead (in transit)

That is a bad idea

Not only might the radiators not produce enough heat, but since a hot-water system runs at over 10 times the pressure of steam, you will immediately notice any weak points in the radiators and piping when they leak. This can damage your building.

My company does not recommend or perform this type of conversion, and will not work on a system someone else has converted. We don't need the liability.

What's wrong with your steam system?

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Mike Reavis_2

With all due respect to the esteemed Steamhead,

I have converted two, and serviced two others. They all work well. We had to convert the two systems so that the owners could utilize the space in the basement--one for business, and one for the home. They worked great after much planning. They also worked because we were improving the building envelope, and the heat needs were reduced. The answer to your question is that when they operate at the same temperature, they produce the same heat. This is of course assuming that the steam radiator is full of steam, and not air. Hot water systems commonly operate between 140-180 degrees. Some as high as 200.

You really also need to be sure that your radiators are the type with connections at the top and the bottom by push-nipples. Water will not flow well through old column radiators that are not connected top and bottom.

Your best results will be on two-pipe steam systems with the piping connections at the bottom. Old vapor systems where you have one high and one low connection will work, but you might get a "waterfall" noise. High and low connections on the same side will tend to "waterfall".
You can convert single pipe radiators with lots of luck, and big breaker bars. There are contractors on this site that do it all the time. You will need to run a complete return system.

Being that the system will be pumped, you can usually remove or drill out the seat on the trap, and achieve sufficient flow through the radiator. Use sealer on the threads of the trap.

C.Y.A. concerning potential weaknesses in the radiators, and pipes. Install a y-strainer before the pump. These were my experiences with this type of conversion. Do not use copper fittings going to old steel piping--this could be a superstition of mine, but I offer it for what it is worth.

I applaud you for wanting to investigate the possibility of staying with radiator heat. In Washington, Baltimore and other large Eastern cities there are probably ten houses with radiator heat lost to each one that remains after a major rehab.
Mike

Mike Reavis_2

With all due respect to the esteemed Steamhead,

I have converted two, and serviced two others. They all work well. We had to convert the two systems so that the owners could utilize the space in the basement--one for business, and one for the home. They worked great after much planning. They also worked because we were improving the building envelope, and the heat needs were reduced. The answer to your question is that when they operate at the same temperature, they produce the same heat. This is of course assuming that the steam radiator is full of steam, and not air. Hot water systems commonly operate between 140-180 degrees. Some as high as 200.

You really also need to be sure that your radiators are the type with connections at the top and the bottom by push-nipples. Water will not flow well through old column radiators that are not connected top and bottom.

Your best results will be on two-pipe steam systems with the piping connections at the bottom. Old vapor systems where you have one high and one low connection will work, but you might get a "waterfall" noise. High and low connections on the same side will tend to "waterfall".
You can convert single pipe radiators with lots of luck, and big breaker bars. There are contractors on this site that do it all the time. You will need to run a complete return system.

Being that the system will be pumped, you can usually remove or drill out the seat on the trap, and achieve sufficient flow through the radiator. Use sealer on the threads of the trap.

C.Y.A. concerning potential weaknesses in the radiators, and pipes. Install a y-strainer before the pump. These were my experiences with this type of conversion. Do not use copper fittings going to old steel piping--this could be a superstition of mine, but I offer it for what it is worth.

I applaud you for wanting to investigate the possibility of staying with radiator heat. In Washington, Baltimore and other large Eastern cities there are probably ten houses with radiator heat lost to each one that remains after a major rehab.
Mike

Steamhead (in transit)

Mike, you got lucky

I've seen some converted systems that leaked badly. One was in an old church and the building suffered much damage. Not sure what happened after that, we told them we weren't interested in being "the last ones to work on it" and therefore liable. If I were the building owner or manager, I would have taken that contractor to court and cleaned them out.

We have found that we can achieve pretty much the same real-world savings by fixing steam systems rather than butchering them. Why ask for trouble?

Beware of inflated fuel-savings estimates that some salesmen who should be selling used cars will quote. I have never seen any case study that wasn't fatally flawed- in one infamous case, the steam system was in such bad shape that the boilers had to be started and stopped manually!

Oh, and it's possible to run a steam main tight to the basement ceiling without any pitch if you drip it properly. One of my Dead Men's Books tells how- I think Alfred King wrote it, have to look it up. Bye-bye, head-knocker.......

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Steamhead (in transit)

You know when you are

in the presence of a true philistine when someone can off-handedly mention killing a vapor system. These are works of art that work and work well with a little TLC

When I was a kid in Baltimore, they were tearing out the street cars and replacing them with modern omnibuses. Now, at great expense, they are putting street cars (aka light rail) back.

It will be the same with steam.

Georg_3

Changing top connection to bottom

Thanks for these valuable comments.

I want to change all the piping to pex, so leakage should not be a problem. The radiators are the only part that I would like to keep. This is a nice mission-style house and the cast-iron radiators really go with the style.

The steam system is two pipe and the connections are that the top and bottom of the radiator. But I could change the top piping connection to the bottom, I suppose. Would that be worth the effort?

Steamhead (in transit)

The radiators can leak too

if you jack up the pressure on them and there are any weak spots. Then you would have spent all that money on demolishing the old piping system and buying and installing all that PEX, and you'd still have leaks. If you try to get old plugs out of rads and aren't careful, you can crack the cast-iron (ask me how I learned that).

In the example I mentioned, they had leaks in both the piping and the radiators. That system had turned into a Swiss cheese.

A 2-pipe system with rads connected that way is a Vapor system. This was the Cadillac of heating in its day, incredibly quick and efficient. It's much more cost-effective to repair these systems than to tear them out.

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Steamhead (in transit)

Sir

Please post pictures of your radiators and their connections.
Also, any pictures of "odd" looking piping around your boiler would be helpful, too.

Dean_7

steam

I'm just a homeowner however I have a steam system. I bought Dan's books and listened to these folks and restored my system 4 years ago and dropped my fuel (natural gas) costs 60% ( I've got the bills to prove it.). The system has been tweaked a bit again with the advice of these same people and now runs on about 6 oz of pressure. It is quiet and comfortable and my neighbors who have "modern" heating systems and used to laugh at my "old fashioned" radiators aren't laughing anymore. Also It has been my experience that anything you fill with water will eventually leak and it will leak at the least convient time resulting in the most expense. I think you should really listen to these people.

Dean_7

steam

I'm just a homeowner however I have a steam system. I bought Dan's books and listened to these folks and restored my system 4 years ago and dropped my fuel (natural gas) costs 60% ( I've got the bills to prove it.). The system has been tweaked a bit again with the advice of these same people and now runs on about 6 oz of pressure. It is quiet and comfortable and my neighbors who have "modern" heating systems and used to laugh at my "old fashioned" radiators aren't laughing anymore. Also It has been my experience that anything you fill with water will eventually leak and it will leak at the least convient time resulting in the most expense. I think you should really listen to these people.

Mike Reavis_2

AArgghh!

If a steam system is not rotting from the inside out, what is all the black stuff that is purged from the returns? I love steam systems. They are a challenge, the physics, and the consequences of screwing with the physics is cool. I really do like steam. But don't tell me that a non-leaking hydronic system will corrode its pipes faster than a steam system will. I think I am making your point about not pressurizing steam systems with water--oh well aargghhh!

Timco

I just acquired a hot water rad that was one pipe steam it's whole life. It worked great as steam, and still would but I already have hot water. I pressurized it and it lost 25# of pressure in 5 minutes because all the top sections leaked. I had to hook it up to a water heater with boiler seal for a few days and I now HOPE it holds...If there is a way to rehab the steam, add TRV's and not roll the dice on rads leaking, do so. HW conversion should be you last choice.

Tim

Mike T., Swampeast MO

Georg:

Steamhead is very right that the rads can leak as well. The ONLY "salvage" rad I ever bought that leaked (weeping at numerous lower nipples at 20# or so of pressure) had come from a steam system.

When the steam in a rad often condenses in the presense of "air" that contains carbon dioxide, a small amount of carbonic acid is produced. Combined with the natural oxidation of the iron from the oxygen in air, steam rads tend to corrode faster than water rads. While it may take many more decades for a leak to occur with steam, the 12X or so higher pressure of hot water systems can cause leaks MUCH faster...

Proceed with caution. Particularly since you [appear] to have an original vapor system, I'd really suggest you do everything possible to find a good steam man to get your system in top-notch shape.

While residential steam can NEVER approach the efficiency of a mod-con properly installed into a well-suited system the very nature of steam has some efficiency advantages above "traditional" hot water systems.

If your boiler is an ancient thing converted from solid fuel (quite common) and oil is your fuel, then give highest consideration to the Burnham "Mega-Steam". Properly installed into a system in good order it will operate at nearly the physical efficiency limit for residential steam.

Jamie Hall

So Georg

I have one question which I haven't seen in this thread: why do you need to change to hot water? As someone pointed out, the theoretical efficiency of a really good new hot water system (mod-con) is better than good steam (particularly the Burnham someone mentioned) it isn't enough better to recover your investment in the change over -- even if the old rads don't leak. But they will... dang near guaranteed. I'd find a good steam pro (they're a little thin on the ground) and fix the Cadillac you've got, rather than buying a new Chevy.

john_27

I'm the owner of a vapor system....dropped bills 40 percent with a few weekends with steamhead.....the tough part is getting a qualified steam guy. Steam got a bad names when many of them were converted from coal to oil....the intermittent firing caused air to remain in the system....where air is, no steam.Also, vacuum vents(those things at the end of the mains)could actually get water to boil at 180 instead of 212....the industry still hasn't figured out a way to keep a system under vacuum with intermittent firing. So, steam runs hotter than water...but costs the same cause it gets there faster and has less gallons of water to heat up....john

Mike Reavis_2

970 btu's required to change state at atmospheric pressure.

That same amount of heat, can be added to the same pound of water circulating in a system that will allow the heat to gently jump off the radiators warming the rooms. This argument about the lesser amount of water in steam vs. hydronic boilers does not seem to be a good argument.

Steamhead (in transit)

Not just in the boiler

but in the entire system. Remember, when water changes to steam it expands 1700 times. This is why you don't need to pump steam to the radiators, which eliminates a parasitic load.

The greater delta-T between the steam and the room air tends to speed up heat transfer at that point too.

Also, 90+% boiler efficiency IS possible on steam. Too bad American boiler manufacturers are sadly neglecting the sizeable steam market, still selling pin-type oil and atmospheric gas units. Burnham is the only exception, with their 3-pass Mega-Steam.

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