steam radiator/EDR theory

thfurnitureguy_4

Steam being lighter than air, displaces the air out the bottom of the radiator section by section, and moves it out toward the vent. So no, the bottom is not a trap. Try this example: if you turned your radiator up side down and filled the valve side with water. The water would fill the first section and after full it would move on to the next section and so on. Each time the air is displaced by the water and moving toward and out the vent. It is the same with a gas like steam only it works up side up!.

T. Riley

steam radiator/EDR theory

If on the coldest day of the year, oversized steam radiators heat the rooms to 73 degrees, and are cold toward the bottom of the radiator, can I say that effectively the bottom half of the radiator is a trap? If you buy that thinking, then does it not follow that the real EDR is a lot less than what is usually figured by the tables/charts? And would I not want to size the fire to that "new" EDR?

Bob W._3

Tom, you raise an interesting point. While I would agree that the unheated sections are not a trap, one could make a case that they are not necessary to the sizing of the replacement boiler. The concern about undersizing is that the boiler will not be able to heat ALL the piping and ALL the rads and will therefore run constantly, wasting fuel. That may be true. I have noted, however, that rads that are shut off will stop the steam from going up that particular riser. One could theorize that the cold metal somewhere above that air plug should be taken out of the equation. There was a fascinating exchange on this some years ago, with Boilerpro as the proponent, and Steamhead and Noel (as I recall) arguing the traditional method of sizing the boiler. Don't know if there was ever a consensus.

T. Riley

Ignore radiator construction. If steam never reaches the trap, then it's always open and effectively is not there. Then all that metal mass that doesn't heat becomes nothing more than part of the return line. You don't figure return line mass into EDR calculations. What say you?

T. Riley

Any idea how to hear from Boilerpro?

Bob W._3

He checks in from time to time. You could start a post with his name in it. Calling Boilerpro!

gerry gill

your pretty much correct Tom..

but the ''homework'' on the boiler sizing would definitly need to be done..some old vapor systems were done that way, in that there is more iron than the boiler can make steam for, but the key to this would be radiator balancing..cause the boiler doesn't know or care how much iron there is..so it has to distribute the steam evenly..so yes, if you ran the heat loss calculations and would today have 1/2 the radiator iron size (due to better windows etc) then you could use a boiler that supplies only that amount of net edr..but the balancing of the radiators would need to be nuts on..and if you do that, always leave yourself a steam tap just in case a reservoir tank is needed for added water capacity, you'll be set up to equalize the tank that way..did that make any sense?

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Boilerpro_3

It's already being done

I was in touch with T.P. Tunstall and he forwarded me an article about a company out east that has been retrofitting existing 2 pipe system with oricfice plates in the valves to meter steam to the current heating load and installing TRV's. I believe the number of systems done successfully in the past 5 to 10 years is in the hundreds.
In fact, I believe they even pulled out the Pick up factor for the systems, since the orifices restrict flow to the rads until pressure could build a little in the main after the mains finally filled. What this all means, is that we may finally be able to size steam boilers to heat loss on two pipe steam instead of radiation. On a typical install, you will probably be looking at a boiler that is half the size. Imagine the improvement in seasonal efficiency when a steam boiler is finaly loaded on the typical day to 50% load or greater, rather than cycling on and off at 25% load. This change in operating characteristics alone is probably worth about 20% reduction in fuel usage. It's been awhile since I read the article, but payback on the upgrade was in the range of 3 to 5 years, I beleive.

The concept is nothing new, like Gerry said, and was put into practice all over the country quite successfully. This is one of the reasons I love the old Moline systems. They metered the steam with orifices, limited the pressure supplied, and eliminated all the traps on the system. You end up with a system that is low maintainance and very efficient. The Moline system I worked on extensively a few years back heats very evenly, even with an "undersized" boiler, and required a small amount of balancing (sung the original hand valves)to account for the fact the second floor finally got an insulated ceiling. Fuel usage was also exceptionally low, they topped out at about $350 midwinter for natural gas to heat a 4,500 sq ft home with huge, leaky windows, no storms, no wall insulation, 11 ft ceilings down, and 10 up.

I suspect that many,many two pipe systems could be completely refitted with orifices to "resize the radiation" to new heating loads and the boiler size cut in half. Unfortunately, I don't get too many two pipe systems my way, mostly one pipe.

Now whether you can "undersize" boilers for one pipe systems is a little less apparent. I have seen several systems that the owners say are very comfortable and use little fuel that have undersized boilers (one I installed myself) However, every radiators uses an adjustable vents, and that, I believe, is the key.

Boilerpro

Boilerpro_3

It's already being done

I was in touch with T.P. Tunstall and he forwarded me an article about a company out east that has been retrofitting existing 2 pipe system with oricfice plates in the valves to meter steam to the current heating load and installing TRV's. I believe the number of systems done successfully in the past 5 to 10 years is in the hundreds.
In fact, I believe they even pulled out the Pick up factor for the systems, since the orifices restrict flow to the rads until pressure could build a little in the main after the mains finally filled. What this all means, is that we may finally be able to size steam boilers to heat loss on two pipe steam instead of radiation. On a typical install, you will probably be looking at a boiler that is half the size. Imagine the improvement in seasonal efficiency when a steam boiler is finaly loaded on the typical day to 50% load or greater, rather than cycling on and off at 25% load. This change in operating characteristics alone is probably worth about 20% reduction in fuel usage. It's been awhile since I read the article, but payback on the upgrade was in the range of 3 to 5 years, I beleive.

The concept is nothing new, like Gerry said, and was put into practice all over the country quite successfully. This is one of the reasons I love the old Moline systems. They metered the steam with orifices, limited the pressure supplied, and eliminated all the traps on the system. You end up with a system that is low maintainance and very efficient. The Moline system I worked on extensively a few years back heats very evenly, even with an "undersized" boiler, and required a small amount of balancing (sung the original hand valves)to account for the fact the second floor finally got an insulated ceiling. Fuel usage was also exceptionally low, they topped out at about $350 midwinter for natural gas to heat a 4,500 sq ft home with huge, leaky windows, no storms, no wall insulation, 11 ft ceilings down, and 10 up.

I suspect that many,many two pipe systems could be completely refitted with orifices to "resize the radiation" to new heating loads and the boiler size cut in half. Unfortunately, I don't get too many two pipe systems my way, mostly one pipe.

Now whether you can "undersize" boilers for one pipe systems is a little less apparent. I have seen several systems that the owners say are very comfortable and use little fuel that have undersized boilers (one I installed myself) However, every radiators uses an adjustable vents, and that, I believe, is the key.

Boilerpro