One pipe steam heating system design

franeli

Need help with a one pipe steam system design.  Any help would be appreciated.  It’s a residential gravity heat system that I want to convert to steam.

nicholas bonham-carter

Are you converting a hot water system to steam?
Most of what you will need to know will be in the books available on this site:
The Lost Art of Steam Heating, and We Got Steam Heating.—NBC

ChrisJ

What kind of help do you need?

franeli

I have a gravity heat system right now and want to open the walls and install a one pipe steam system.  I want to make sure I get the piping right by installing the main vents, branches to the radiators and the condensate return all right.  The books I have seen give me a general idea, and was hoping to get a more detail layout.  

ethicalpaul

Are you opening the walls anyway? If you aren't, I would consider running some or all of the 2nd floor pipes in the interior along the walls instead of inside them like they did in the old days. It will be way easier to route the pipes there rather than inside the walls.

Jamie Hall

Is there a reason you want to convert from gravity hot water to steam? Gravity hot water is an excellent, very reliable (no moving parts!) heating system. So, of course, is steam. But one pipe steam is a very different beast from gravity hot water, and the conversion is not going to be simple -- or cheap. Two pipe steam might be a little less hassle, but it's not going to be simple either. Conversion to pumped hot water will be the simplest.

So --why are you doing this, and what do you hope to accomplish?

DanHolohan

The gravity pipes are probably not pitched properly for condensate return.

ethicalpaul

I've never heard two-pipe steam paired with the phrase "less hassle" before

Lance

Gravity hot water is the Cadillac of heat systems. and if you have a millivolt gas valve its runs without any electricity. Of course you can upgrade and add circulator or not, or go to a outdoor reset control which saves money and you can't do that with steam.

ChrisJ

ethicalpaul said:

I've never heard two-pipe steam paired with the phrase "less hassle" before

You never have to bleed a steam system or deal with air in any way.  You never have to drain it to repair a radiator or anything above the boiler.
 
I feel a correctly maintained steam system is in many ways, less of a hassle than hot water.

But that's me.

ethicalpaul

Oh I agree less hassle than water!! I mean vs one pipe. Re-reading Jamie's post above I see of course he was talking about vs water.

EBEBRATT-Ed

It it's a water system , keep it water unless it is so bad it has to be removed/replaced.

Nothing is as simple as a gravity hot water

JUGHNE

The existing gravity pipes most likely slope up away from the boiler.
This might work as 2 pipe counter flow steam.
I have seen one in the field but never in the books anywhere.

There must have been a reason it never became popular, although the system I speak of works quite well.

The supply is counter flow and the return matches the slope.
This had the advantage of not having the return being a head banger.
Both pipes hugged the ceiling at the same height.

IIWM, I would go for orifices in the supply valve unions to keep steam out of the returns.
You would have to keep the steam pressure constant at 2 PSI or less and may have to experiment with orifice sizing. You would start small and can drill larger if needed. Minor tinkering for someone who wants to take on a project like this themselves.

Radiation sized for HW will be over sized for steam.
So 60-80% steam fill should heat well enough.

Supply should be piped for counter flow drip at the boiler with air venting at the high end of the steam supply. That drip of counter flow would only handle the steam main condensation returning.
The other return pipe would carry radiator condensation back.

If no steam enters the return line it could, in theory, be vented with an open pipe.
Although I would put an air vent on the return at the boiler...just in case.

The installation I seen had TRV's and traps on each radiator.
That is a fair expense and lot of work.

Your HW valves may not have 100% shutoff as there was usually a small port to insure some water flow to prevent freezing.


The "less hassle" with 2 pipe may refer to no rad air vents, all that is done in the basement.
And 2 pipe can be throttled at the rad valve unlike 1 pipe.

Also smaller run out piping for both supply and return is needed.

jumper

Perhaps those water pipes are done for? Then if I want to go steam I'd do overhead two pipe.
Manifold in the attic to run individual pipes to each radiator. Then you can use small pipes.Perhaps flexible and pre-insulated? Definitely two pipe with TRVs. Modern sealants and mechanical air evacuation. What can go wrong?

SteamingatMohawk

Every moving part. Every mechanical connection.

leonz

franeli said:

Need help with a one pipe steam system design.  Any help would be appreciated.  It’s a residential gravity heat system that I want to convert to steam.

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1. DO you know how to identify a load bearing wall?
2. Do you know where all the load bearing walls are in your home?
3. "One thing you have to understand is you may have load bearing intererior walls that cannot be removed so it may not be possible to even contemplate doing what you want to do".
4. do you know if your boiler has an H stamp certifying it for steam use??
5.
I have to ask if you have had any painting done in the home recently that required removing the radiators to paint behind them BOO, HIISS. if there is little to no heat coming from this radiator or radiators it is entirely possible the plumbers discarded the flow restrictors that control the speed of the hot water entering and existing the radiators-bad painters!!!!..; no paid lunches or treats for you.

A gravity hot water system like the one on your home is a heating system that was designed with simplicity in mind as it uses convection to move hot water at 170 degrees to the top floor and then using simple gravity to let the 170 degree hot water to exit the open to air expansion tank and fall back down to the radiators below to heat the home and basement.

The boiler was centered in the basement of the home for the simple reason that the hot water riser rises to the attic in the center of the home and the hot water exists the open to air expansion tank and is piped outwards to the radiators of the home on the top floor and the slightly cooler water exiting the bottom of the upper floor radiators drops to the top tapping of the radiator below it and then the cooler water exits that radiator and drops to the radiator below it and then into the basement to the radiator hung on the wall in the basement and then returns to the to the boiler sump header pipe.

If your boiler makes use of two hot water risers to heat the home it will heat faster as it has more hot water and it will have two sets of return pipes to two common sump header pipes.

You have not told us if it is a bottom fed or top fed gravity hot water system and we need to know that anyway as a matter of course.

Going from memory here;

1. is the open to air expansion tank set up with the hot water riser entering the bottom of the open to air expansion tank and making use of a side tapping in the open to air expansion tank to feed the drop pipe to the radiators and a radiator in the attic or was it plumbed with an upside down U pipe to simply let the hot water rise and fall without entering the open to air expansion tank to keep the tank hot and let the water flow more quickly.

a. do you have a hot water radiator next to the open to air expansion tank to keep the open to air expansion tank warm??

b. where exactly in the attic is the gravity hot water heating systems water filling valve?

c. was the top fed system set up with a center riser that enters the open to air expansion tank in the bottom of the tank to allow the hot water to enter it?

d. where exactly does the vent pipe exit the open to air expansion tank? Is it vented to the basement drain if a water feed pipe and shut off valve is not used in the attic??

The top of the hot water riser has either a tee and or cross to reach to opne ot air expansion tank and the outer walls of the attic to reach the hot water radiators that will let the cooler hot water drop to the lower floors and then back to the basement.

3. A top fed system does not require bleeding as the water in the system falls by gravity to every radiator form the header pipe(s) in the attic.
4.
a. a bottom fed system requires bleeding of air to remove slugs of air if the system is heating poorly.

4. Converting a hot water system to steam will be more difficult and as Dan so kindly said earlier as the pipes may not be pitched right to drain back to the steam boilers water line. This is simply because the returning cooler water is more dense than the hot water and simply drops to the basement and the boiler sump header and there was no need to slope the drain pipes to allow them to drain as the entire mass of water is rising and dropping at the same time around the clock in the heating season.

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Hiring a licensed mechanical engineer with heating experience to look at your home will be money that will not be wasted as he or she will have to provide you with the facts to look at your system with "open eyes" AND not the eyes of an interior designer/architect telling you that you can do this or that to make it look better and have more room.

Once you have the estimated cost of a gravity to steam conversion on paper it may consist of or be a "cost plus" scenario in its entire cost basis as mistakes like broken piping, new radiators and a damaged upper floor piping system that would result in the use of a cost plus contract in addition to an "errors and omissions clauseaa" that may very well double the cost of a mistake by the installer or hidden damage that may show up later that you may or may not be able to reclaim if you sue for damages.

I have to re-emphasize to you what EBEBRATT-Ed has said; there is nothing as simple as a gravity hot water system.

Converting this is going to be extremely costly if even possible as you may very well need a new boiler as well to meet your home insurance requirements as well AND "The Return On Your Investment" will be very low as you already have a heating system that has little operating cost as the fuel used and the burner are the only annual expense besides cleaning the boiler and the steel or cast iron piping used is not under more pressure than one atmosphere/passive.

What you have a is a perfect way to heat a home with slow even heat and the benefit of a huge amount of thermal mass that heats the entire home at a very low cost per year as it only requires fuel and electricity to control a thermostat to create hot water heat.

Thermal mass is your best friend when it comes to heating.

I offer my sincere apologies if I overlooked something in my writing and I have no objection to it being edited by a forum moderator.

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