Vapor system conversion to hot water condensing boiler

Wet_Willy

I have an old VECO system that I am having spec'd for conversion to hot water w/ a high eff. condensing boiler. The original system looks just like the example in Dan's "History of Steam Heat". Are there any caveats on doing a conversion like this? The first and second floor rads are 2 pipe and have 3/4 " inlet and outlet piping with the fixed baffle trap as in the book. There are a few one pipe rads in a basement area, which are mounted on a wall above the water level of the boiler. These wilol be re-piped with an inlet and outlet, and the vents will be removed and plugged.



I would appreciate any comments or thoughts, the old system will be demo'd out later this week.

nicholas bonham-carter

conversion from steam to hot water

you are moving from a piping system used to ounces of pressure to a h/w system, perhaps with 30 PSI. what will be the result?

this system could more easily be restored to proper steam operation, than converted to h/w.

one way to tell, might be to pressurize the system, before you burn the bridges, to at least 20 PSI,  and see how much leaking there will be, and what size pans to put under the rads.--nbc

Jamie Hall

Why oh why?

The VECO system was -- and properly maintained, is -- one of the nicest and best ways to heat a space that's been built.  And maintenance for it is very minor -- you don't even have radiator traps to worry about!



Why not save a bundle of money and just get the system running the way it was supposed to?  If you are concerned about the difference in efficiency between a top end mod-con hot water system, with all the bells and whistles, and an equally top end new steam boiler (they cost, at worst, about the same -- and then the mod-con needs pumps and expansion tanks and all that on top), don't be.  A little quick arithmetic will show that the best you can do is save (using oil as the example) 6 to 8 gallons of oil per hundred gallons at the most.  Not putting too fine a point on it, you would be better off investing the money you would have put into the conversion into a CD somewhere- even if you don't have any problems.



Then, as Nicholas pointed out, you will probably (although not certainly) have problems.  The steam system and all its parts was built to run on somewhere around 10 to 12 ounces per square inch of pressure.  A hot water system must run on somewhere around 20 pounds per square inch, or more.  You may get really fortunate, and not have any leaks.  Then again...



Next, keep in mind that the pipe sizes and layout which are suitable for steam are a kludge at best (and unworkable, most of the time) for hot water.  To achieve anything like the efficiency noted above, never mind even heat, you would be well advised to completely re-pipe the system.  Don't even try to use the old steam pipes.



On the other hand, you could move to a nice new steam boiler, make sure that your VECO system is operating the way it is intended to operate (check things like venting, water levels in the new boiler, operating pressure, etc.), save a bunch of cash, and have one of the best heating systems ever made.



Your choice, I guess...

Wet_Willy

Not that simple

The boiler is original to the house, built in 1906, Obviously yhere have been some "upgrades" over the years, but it's also been poorly maintained by the previous owner of 30 some odd years. Bottom line it's time for the old gal to go.

I'm still not entirely sold on the conversion, we started out talking about a 83% efficient steam boiler. He's going to pressure test once the old boiler is cut out and we'll see.

In the meantime, please comment pro or con.

Jamie Hall

Oh clearly

the old boiler will have to go -- no question about that.  That's kind of a given. 

And it is possible that some of the "upgrades" will have to be un-upgraded too, unless they were done with the VECO system in mind (unlikely).  The poor maintenance will be mostly a problem with the boiler -- which is going anyway; the rest of the system doesn't need much in the way of maintenance anyway.  As a sort of general rule of thumb, the most likiely place for a problem is in the wet returns, which do corrode with time.  Otherwise there are plenty of steam systems out there working on their second century!



Be very careful with that pressure test.  It is very hard to pressure test a steam system, as the working pressures involved are so low -- never ever more than 3 psi at the boiler, which pretty well means air, and  sensitive gauges, nand temperature compensation.  Can't do it with water.  Anything over 3 psi and you will have to replace the vents, whether you want to or not (they can't take it) and you may well break loose things elsewhere which wuld be just fine for steam.



You should be able to get at least 83% efficiency from a steam boiler.  In fact, on a new install, properly adjusted, you may well see a good bit more than that.  Steam boiler makers tend to be conservative on their specs.



I'll still hold by my original comment: get a good new boiler, properly piped and installed (that means good near boiler piping, match the water line of the new boiler with the old one, even if you have to mount it on a pedestal or something, make sure the controls are correct (use a vaporstat, not a pressurestat) and set properly -- then set about bringing the rest of the system up to snuff.  In my opinion, you'll be much better off in the long run doing that than trying to convert to hot water.

Steamhead

Don't do it

I've seen where these conversions leaked all over the place. That's guaranteed to attract lawyers if you're the contractor who did the conversion.



Also the radiators might not be big enough to heat the building with hot-water. You get 240 BTU per square foot from a steam rad, 150 for a HW rad, and that's with the boiler at 180 degrees. And BTW, if you have to run those rads higher than 140 degrees, a condensing boiler won't condense. Bye-bye, super-high efficiency.



Are you burning oil or gas? If oil, the Burnham MegaSteam is far and away the best. If gas, the Slant/Fin Intrepid or Smith G-8 wet-base boilers can be equipped with powered gas burners, and would give roughly 6% better thermal efficiency than the usual atmospheric gas boiler.



Lastly, are any of those VECO pipes run in outside walls? If so, and you fill them with water, they may freeze. Then they'd leak when they thawed, damaging the building.



My company does not recommend or perform steam-to-water conversions, and will not work on a system someone else has converted.



Keep the VECO VECO.

Wet_Willy

Thanks for the replies

I should clarify that I am the home owner, and the contractor is a friend who does a lot of commercial boilers. He and his supplier were excited to do an old vapor system until they started looking over the old system and brainstorming.

I should clarify that my paperwork with the old boiler says veco, but the big open "tank" on the side of the boiler says Broomell by Vapor Heating Company , and the patent dates go as far as 1906. I guess the company became veco. Just as an aside, there are no vents in the mains and there doesn't seem to be a Hartford loop either.

Steamhead

They are essentially the same system

and as for main vents, they're pretty easy to add. The dry returns vent thru the receiver/regulator (open tank) then into the chimney thru a condensing radiator where the draft helps to pull air from the system.



The Hartford Loop came out a bit later, and became mandatory on Hartford-insured boilers in 1919.

Wet_Willy

Hmmmm??

What parts of the origional system could be/should be kept.? The Float inside of the reciever/regulator doesn't do anything anymore. should the condensing radiator and flue vent stay? Or should all of these go and the new (steam) boiler be piped in another way?

Henry

Steam to hot water

We have done several steam to hot water with condensing boilrs with great success. A few years ago we transformed the Montreal Rehab Institut to hot water. We cut energy costs by over 50% for both natural gas and electricity. We won for the best public health faciilty projext of the year. We are presently performing similar work at the Sorel hospital.

First. the old steam heating systems were sized to heat with the windows open. Therefore they are very much oversized! There is no problem using the exisiting cast iron rads except for modification to the connections and remouval of the steam traps and or vents.

Two, the condensing boilers will condense up to around 162F. It all depends on the return temperatures which we want to keep under 130. So, pump selection is critical. Also, the boilr will run at temperatures over 150F for at the most 300 hours of operation out of 1200. This is for the Montreal region. We install condensing boilers even if there is baseboard radiation.Our lowest energy saving has been 35% of the average 5 year natural gas volume. Some of our best includes: The Saint Sulpice Church (Notre Dame Cathedral) were we reduced the natural gas volume by 75.2%!



To do a cheap steam to hot water conversion, we keep the steam mains but install new returns. Ideally, it s best to repipe both supply and return as there is a lot crude to get rid of through bag filters.

Regards,

Henry

Steamhead

In order for your figures to mean anything

we have to know what condition the systems were in before you touched them. Every "case study" I've seen has compared a steam system on the verge of total failure to a new hot-water system. This is not, never was, and never will be a fair comparison. We've been down this road before.



And I can't believe you never had one that leaked. Many of the ones I've seen have leaked. We won't touch them, they're a liability lawyer's dream.



Care to elaborate on yours?

Jamie Hall

Apples and Oranges

This is a very old debate.  Steamhead, however, is correct in one major point: you simply cannot make a valid comparison of heating systems unless all the variables are controlled -- and, preferably, the same.



That is to say, if you are to compare fuel use in a building (or efficiency comparisons between heating systems -- same thing) you simply cannot come up with any valid comments unless all the systems are in the same state of repair (and I've seen some of the old steam systems in Montreal -- they're really bad) and, if you are working a before/after, all other changes, such as insulation, storm windoes, and what have you are accounted for.  If you do that, rather straightforward engineering analysis will show that the variations in efficiency lie in the boiler, and that if you can run a condensing hot water boiler so it condenses (which you can't, all the time), you will get slightly higher efficiency and thus slightly lower fuel use.  It amounts, from my research, to a maximum of about 8% for equally high quality units with one condensing and the other not.  The heat transfer medium -- steam, water, or (shudder) air -- makes no difference at all, provided each system is equally well designed and maintained.



Then the remaining questions have to do with the equally well designed part and the maintained part -- and in my opinion most of the older steam systems were very well designed indeed, much better than some of the newer hot water systems I've seen.  It is quite true that some of them were designed for greater heat loads than are now present in the building, but by no means all of them.  And in any event that simply means that the boiler won't have to fire as long to keep the temperature up.



The other biggy is the cost of conversion.  If one finds that one can use all or most of the old piping, and all the old radiators, then the conversion isn't all that expensive -- although you will never get it back on the energy savings.  On the other hand, if one finds that parts of the old steam system won't take 30 psi, and you have to rip the whole thing out...



To me it isn't a philosophical thing, it's pure dollars and cents.  Getting a good steam system, which hasn't been completely trashed by some gorilla, back up and running is cheaper than conversion.

BRIANJ

The Old Broomell

Where do you live? If you're going to tear out the old system I would love to get the olf receiver and condensing radiator.

I have a Broomell system and it provides wonderful heat to our house. I installed a Vaporstat to keep the pressure between 6 and 8 oz. and it just purrs like a kitten.

If you convert you will also have to change out all the radiator valves as they can't  hold 30 PSI and are made for steam not hot water.

Choose carefully and good luck!

ttekushan_3

Fuel savings.

Out of tune steam systems can use tremendous amounts of fuel. Unlike modern equipment which is just as likely to lock out and leave you with no heat, the old steam system will continue to operate in what may appear to be a proper manner while out of tune. Everything may appear normal. The excess fuel consumption is often the only symptom in evidence. Excess fuel consumption is more a symptom than it is a characteristic of steam heating, unless it is a self fulfilling prophecy created by decades-long habits. "Normal" becomes "Proper" in the mind. Its amazing how many times i've heard this from maintenance people and even steam service technicians, verbatim: "thats just the way steam is." B.S.I.M.O.



My last two church jobs involved minimal parts replacement but cleaning, balancing, control, load matching, venting rate manipulation and boiler timing/pressure control. One is a 1948 system with steel boiler, convectors, pneumatic control system. Major boiler cleaning & adjustments along with repair of the pneumatic system were all that was necessary. Reattached the wing to the steam heating system that was running with rooftop units for a decade. . . . The other church has an 1885 two-pipe with air vent system with a standard two pipe wing added along with two zone controls. The building was heavily insulated about 10 years ago. Together with oversized radiation, it was discovered that design temp for each wing could be maintained with a 50% duty cycle. So I downsized boiler, adjusted variable firing rates, restored two pipe air vent original building to original spec. Utilized two existing 4" zone valves to operate the zones sequentially with an "or" logic configuration so that auxiliary switches enable one of two different steam pressures depending on the zone in operation: either a firing rate controlling vaporstat for the original section (4 oz steam pressure) or a firing rate vaporstat @ 16 oz to allow slow pressure rise at low fire) for the newer piping. The usual 1.5 lb and upper limit pressuretrols remain as safeties. Isolation of returns is handled by a vented receiver. The 1885 section uses only float traps in the returns, venting being handled at the radiator vents.



The buildings' fuel consumption/DD dropped 50% and 55% respectively. If I were prone to using the term "Greenest Solution," now would be a good time to use it. Unless referring to the capital expenditure required of the churches involved. The payback period was less that one year in one case and about one year in the other. "Not a lot of Green," in these cases.



-Terry