Convertin two-pipe air vented steam system to hot water

Marko_3

Purchased a home that was built in 1935 in Mass. just outside of Boston.

Steam heat -- for context, since I think it will be important to the discussion, it is a two-pipe, air-vented steam system (has a supply and return line to each radiator, 1.5" supply, 1.25" return, hand control valves on both the supply and the return, air vents on each rad, number dials that allow you to control the heat of each radiator)

Boiler is very old and needs to be replaced. During the conversion, we are considering converting from the system to forced hot water.

Would appreciate advice on how practical / doable this conversion is. Also, if there is a professional member of the board in the Boston Area who has expertise with this type of conversion and is interested in a job I would be happy to speak with them directly about getting a quote.

Jamie Hall

Systems...

such as yours -- if it hasn't been knuckleheaded -- which are two pipe, but have air vents on the radiators -- are a little unusual in a house as young, relatively speaking, as yours is.  They do exist, though.



Generally speaking, most of us are not at all keen on converting steam systems to forced hot water.  While it can be done, and some have had some success with it, generally the headaches which come with the territory are pretty severe and, compared with the ease with which a steam system -- even a neglected one -- can be brought back to really good condition, just aren't worth the effort.



The first thing to check is the radiators themselves -- are they connected across the top?  Not all steam radiators are; if they aren't they can't be used for hot water.



Second, and most severe, is the probability of leaks.  Steam systems operate on very low pressures -- fractions of a pound per square inch up to a pound or two.  Hot water systems, by their nature, operate on pressures 15 to 20 times as high, if not more.  The radiators themselves may leak -- in fact are rather likely too -- as well as all the pipes and valves; in fact, usually one would be better off replacing all the piping.



Third, it is possible that the radiation may not be adequate for hot water, although if there has been extensive insulation added to the house this may not be a factor.  Steam radiators operate at about 215 Fahrenheit; hot water at much lower temperatures (140 to 180, typically) -- resulting in much less heat output for each radiator.



Compared with which, it is very probable that with relatively little effort a new steam boiler (you'll need a new boiler anyway) can be installed and then system can be adjusted to give nice even heat -- with perhaps a few minor changes in venting and the like.  A much easier task.



My own advice would be that unless there is some other compelling reason to convert, don't.  Find a good steam man -- there are several which work in your area -- and have them install a new boiler, properly piped, and spend a little time to bring your present system back to good operating condition.

Steamhead

Don't even think about it

If the system is old enough to be two-pipe air-vent, the radiators probably won't work with hot water at all. Post some pictures of the oldest ones to be sure, but yours are probably steam-only.



The house may actually be older than 1935 if it has this system. By that date, Vapor systems had made two-pipe air-vent obsolete.



Other problems with these conversions are the possibility of leaks, since you're increasing the system pressure drastically, and inadequate heating because radiators emit more heat with steam than with hot water.



Stick with steam. Also post pics of the boiler area and associated piping, and the ends of your steam mains. We should be able to make some energy-saving suggestions.

Charlie from wmass

Do you know you can get

86% combustion efficiency with oil and 84% with gas and keep the steam system? And not have to tear apart and stress the old system. The low pressure you will be running if you stay a vapour system will also mean you can keep those beautiful radiators for that much longer.

Marko_3

Pictures

Really appreciate the help/thoughtful comments.

Attached are a picture of the typical rad in the house (and the boiler)

Look like hot water rads -- connected at top, tubular (not columns), supply and output. 

Front shot gives you a good view of overal rad. You can see the vent that I mentioned on the side shot. Each of those vents has a dial attached to the bottom of it.

Understand on the concrns re: higher pressure. My origianl thought was to get a plumber to increase the pressure in the system (both rads and piping) to see if the integrity of the system has been compromised. If hodling pressure, and rads do not need to be replaced, thought it might be an opportunity to convert to hot water instead of steam when we get boiler replaced. If pressure test looks worrisome then stick with steam. Thoughts? If system can take pressure, will these radiators work with hot water?

The Steam Whisperer (Formerly Boilerpro)

Why are you wanting to convert?

The energy savings are probably negligible, when you consider both fuel and electrical usage. You can zone steam on a room by room basis.  Steam can respond more quickly than hot water and, with hot water you would then have a system subject to freezing.  High efficeincy hot water boilers are also more complicated, so they are more likely to need repairs, and probably will not last as long as most good steam boilers.

Marko_3

Conversion

Advice on this thread is very helpful in my decision process. I guess my logic is that if my house already has the piping, rads, and sufficent EDR that make a steam to hot water converstion plausible w/o a signficant construction project then, on the margin, it would make sense. More efficient (your caveats noted), and more even heat -- steam is either running really hot or it is off.

Also, based on all the threads on this forum, seems like steam systems are pretty finicky -- folks constantly having rads that don't work or heat evenly. 

Marko_3

Conversion

Advice on this thread is very helpful in my decision process. I guess my logic is that if my house already has the piping, rads, and sufficent EDR that make a steam to hot water converstion plausible w/o a signficant construction project then, on the margin, it would make sense. More efficient (your caveats noted), and more even heat -- steam is either running really hot or it is off.

Also, based on all the threads on this forum, seems like steam systems are pretty finicky -- folks constantly having rads that don't work or heat evenly. 

Steamhead

Well, those Aero radiators

certainly were being made in 1935. Maybe there was an installer in your area who just didn't like Vapor systems, so he stuck with air-vent. Or, it was originally one-pipe and someone added return lines.



A properly operating steam system will deliver the same comfort as hot-water. Most of the reason steam has a reputation for being finicky is because people work on it who shouldn't. A good steam man can straighten yours out without much trouble.



The boiler looks like it might be a Weil-McLain 68-series. These weren't great on steam. If you're staying with oil, the best residential steamer  is the Burnham MegaSteam. Unfortunately they don't offer it with a power-gas burner (yet?). For gas, the Smith G-8 and Slant/Fin Intrepid are the most efficient I've found yet- these are wet-base boilers usually sold with oil burners, but their manufacturers have approved them for use with gas too.

Marko_3

Aero radiators?

Thanks. Very helpful.

Is an Aero radiator a manufacturer?

Are these radiators capable of handling forced hot water?

Thanks again.

 

Steamhead

Your radiators

were made by National Radiator Corporation, Johnstown, PA (home of the Flood). They are "large-tube" radiators which came out in 1925 or so, and were discontinued just before World War 2, superseded by the "small-tube" type which is still being made. The Aero is one of the most popular radiators in the Baltimore area and elsewhere.



Tube radiators were pretty much all made so they could be used on steam or hot-water. I've seen very early steam-only American Corto rads but not Aeros, and the ones in the pics do have push-nipples on top. So that's not an issue.



But again, you have to watch out for that higher working pressure causing leaks, and the reduced heating capacity on hot-water. Also, if any steam or return piping is in an outside wall, it may freeze up in very cold weather if there is water in it all the time. That would not be a pretty sight. And, depending on how those return lines were sized, you may have to replace them to provide enough flow for hot water. Return lines in most 2-pipe systems were sized rather small, since steam expands 1700 times from its equivalent weight as water, and shrinks by the same amount when it condenses in the radiators.



Our company does not convert steam systems to hot-water. There is too much that can go wrong, and we don't need the liability. It's far more cost-effective to fix the steam.

Steamhead

if you're near Boston

try Ed Wallace. He knows his steam, but doesn't have a Find a Contractor ad yet. I keep telling him how well it works for us..............

The Steam Whisperer (Formerly Boilerpro)

Finicky steam, allon/all off,efficiency......

People tend to come to this site when they have problems, that is why you see so many here.  It's alot like going to a car repair shop and seeing all those broken down vehicles and saying I never want to own a car.  Steamhead also hit the nail on the head too...Imagine the problems those cars would have if none of the mechanics were properly trained to repair cars.  I have to admit, the number of properly trained steam techs is low, but appears to be growing. 



 Also, steam, just like hot water, does not need to be all on or all off.  The use of TRV's allows infinite modulation of heating of the radiators in two pipe systems as does the installation of supply valve orifices and a modulating steam boiler.

Efficiencies are much closer than most know largely because the testing standards do not compensate for electrical comsumpion.  Forced air is by far the worst because it appears that the heat generated by the blower is added to the output of the burner, increasing its rated efficiency by about 3% and the very costly electricity to run that blower is not included in its fuel costs.  Furnace blowers appear to add about $20 to $30 per month to operation costs. Also, add in the costs of induced draft fans, humidifiers, electricon air filters and the cost continue to rise. 

Hot water heat, fortunately uses only about 10 times the electricity of steam, assuming no draft fans( which all "high efficiency" boilers have), and only a single pump (most high efficiency boilers require a second pump).  Again the efficiencies of hot water do not take these parasitic losses into account.

Marko_3

Thanks -- sent ed an email

Thanks -- sent ed an email

Marko_3

Referral

Thanks for the referral. Sent Ed an email through this site / forum.

Layman question: When you say "perhaps the installer didn't like vapor systems" what do you mean? At the most basic level, would be great to to understand how I would classify my steam system -- is it correct to say "two-pipe, air-vented, system". Seems when I classified it as such in my original posting that started this thread, that wording was synonymous with a "vapor system".

Also, I believe each of my radiators has a TRV (thermostatic radiator valve) since the valve on the side view of the radiator has a dial -- not sure if this also means that it is air vented.

Thanks again.





 

Steamhead

It's called a 'two-pipe air-vent" system

The basic difference is in how the air is vented, and that the rad return connections are completely open unless the valve is closed.



Your system vents the air from the radiators at the radiators themselves. The return lines only handle condensate. In a Vapor system, the air goes into the rad return connections and is vented at a central point, usually near the boiler. Rad vents weren't as reliable then as now, so this refinement got rid of a lot of spitting vents. Both types of systems need fast venting on the steam mains.



Also, there is nothing to keep steam from entering the return lines except the air in them- so keep the pressure low by using a Vaporstat! If the returns are dry (running above the boiler's water level) they will bang if steam gets into them. Vapor systems always have dry returns, and use a variety of methods to keep steam out of them, such as thermostatic traps, water seals and inlet orifices.



The dials on your vents don't make them TRVs. They're Vent-Rite #1 vents and the dial adjusts only the air venting rate. This does give you some control over how fast the rads heat up though.