Need an EDR for this radiator- Carman's Pat. Apr. 28 1885

Theo_G

Hello all, my house (pre-1840s 1300sqft Greek Revival with later additions) has an 1880s-1890s one pipe steam system (two parallel flow perimeter mains with dry returns, no wet return), which is in need of a new boiler. Currently the boiler is a 1997 Burnham IN4 with a hole above the waterline. It is horribly piped in copper with no real header, a bullhead reducing tee at the equalizer, and a bullhead tee feeding both mains. One main is about 8ft long, the other about 20ft long. Both 2 inch. All of the soldered joints on the copper piping have lost their solder long ago and corroded. It all leaks badly.

I have experience replacing boilers, building proper near boiler piping, and tuning oil and gas power burners. I own several combustion analyzers, smoke testers, etc. The plan is to replace the boiler after heating season and make some other upgrades to the system at the time, like adding a unit heater for the cold basement which I spend more time in than nearly every other part of the house (workshop is down there). This is an unfinished basement although used as a living area, with stone walls and bedrock floor. I realize that the unit heater will affect the EDR, but it will be chosen before the exact model of boiler so as to match the system and boiler EDRs correctly. I would like to size for a 10-15% pickup factor due to the incredibly small piping and 3" fiberglass insulation throughout.

I would like a boiler with a power gas burner (Riello G120/200 or Carlin EZ Gas preferably) and the warranty is unimportant to me. Most likely I will go with a Megasteam or Crown Freeport 2 even though this is an unsupported conversion. There is just no reason for me to go with a pin boiler over a 3 pass in this day and age. I will go for a 3 inch drop header and 2 inch equalizer, figuring the pipe lengths from the difference in length between the MST288/396 and MST629, which requires a 3 inch header and 2 inch equalizer. The system will have king valves, return valves, the whole 9 yards. 

The plan is actually to switch the boiler back to oil in a couple years. We have a local supplier of B100 biodiesel and I have previously lived in 2 houses heated by B100 fueled burners. I prefer to be in control of my own fuel supply and infrastructure, I don't like being at the whims of the gas company, and I prefer a carbon neutral fuel if possible. It's not about price but rather just that I like the option of having a large fuel tank I am in control of, even if the fuel is more expensive.

So now for the EDR questions. I have one radiator I can not for the life of me figure out the EDR for. It's a W.W. Carman's, made in Portsmouth NH. This is a direct-indirect type radiator or hybrid radiator and convector. It uses hollow concentric tubes with steam in between. It is a huge radiator that contains so much air that it requires a varivalve set on full to remove all the air even on a 1 hour long cycle. Based on the surface area of the outer and inner tubes, I have figured out that the tubes themselves have an EDR of about 30 for the 14 of them combined. This does not factor in the possibility that the inner tubes may in fact be rated differently due to natural circulation and chimney effect pulling air through them. The base I just took a guess and said it is 10 EDR (It's huge) for a total of 40. Is there a better way of doing this than just guessing? For what it's worth, the radiator weighs about 350-400 lbs and is the size of a small Utica/Dunkirk atmospheric boiler. Pictures with dimensions included so you can see what I am dealing with.
With this radiator sized at around 40 EDR, the system with all radiators in their final positions and configuration, minus the unit heater, comes to 183 EDR. The other radiators include a Walworth wrought iron tube type of 24 EDR, an HB Smith Princess of 9 EDR, two 10 section tube types, branded SR CO, 30 EDR each, and two 5 sectiom 38" 3 column types, 25 EDR each. With a unit heater of 36Kbtu, or 150 EDR, or 2 18Kbtu units of 75 EDR each, that comes out to 333 EDR, well within the capabilities of an MST288 with reduced pickup factor. Given how small the piping is, and the fact that the unit heater fan will be controlled by a temperature switch on the piping, it shouldn't even influence the pickup factor in the first place. I could probably even go up to a 44k/175EDR unit and still have it work perfectly. It's not like there is much risk when the MST288 can be converted to an MST396 if it really ends up being undersized, but the system is working fine with an IN4 with a hole in the block downfired to 70,000 btu so as not to surge because of the horrible piping. Of course that is minus the unit heater but that boiler can't be putting out more than about 40,000 or so BTUs in that condition. 
The missing piece is the true EDR of that radiator. Can I do better than just guessing around like I have been? Does anyone have a chart showing EDR ratings for these?

Steamhead

That radiator proves that we'll never see it all in this business. The only mention I found for W.W. Carman was here:

https://www.newspapers.com/newspage/56484562/

You might look at the charts of similar rads. Here's Bundy:

https://www.heatinghelp.com/systems-help-center/bundy-radiators-for-steam-and-hot-water-also-heating-specialties-1894/

and some more:

https://www.heatinghelp.com/systems-help-center/ratings-for-gold-nason-bundy-and-reed-radiators/

Now, this is undoubtedly a "flue" type of radiator, which would increase its output. The only comparison I can find quickly between a flue and a non-flue rad is in this catalog:

https://www.heatinghelp.com/assets/documents/205.pdf

between the Rococo model, a standard column rad on page 12 of the PDF, and the Italian Flue model on PDF page 13. The 38" Rococo 3-column is 5 square feet per section, and the 38" Italian Flue is 7, which if my math is correct is a 40% increase. So, for example, you might take a comparable Nason or Reed radiator and add 40% to that rating for an approximation of yours.

BobC

Assuming those tube OD's are about 3" I think 40 is a pretty good estimate of the EDR for that old beauty.

Bob

Theo_G

Steamhead said:

That radiator proves that we'll never see it all in this business. The only mention I found for W.W. Carman was here: https://www.newspapers.com/newspage/56484562/ You might look at the charts of similar rads. Here's Bundy: https://www.heatinghelp.com/systems-help-center/bundy-radiators-for-steam-and-hot-water-also-heating-specialties-1894/ and some more: https://www.heatinghelp.com/systems-help-center/ratings-for-gold-nason-bundy-and-reed-radiators/ Now, this is undoubtedly a "flue" type of radiator, which would increase its output. The only comparison I can find quickly between a flue and a non-flue rad is in this catalog: https://www.heatinghelp.com/assets/documents/205.pdf between the Rococo model, a standard column rad on page 12 of the PDF, and the Italian Flue model on PDF page 13. The 38" Rococo 3-column is 5 square feet per section, and the 38" Italian Flue is 7, which if my math is correct is a 40% increase. So, for example, you might take a comparable Nason or Reed radiator and add 40% to that rating for an approximation of yours.

The Bundy Standard Enlarged loop seems like it would be the closest comparison, maybe in a slightly taller version such as the 42 inch to compensate for the smaller size of the loops vs the Carman's concentric tubes. That would give an EDR of about 60. I have a Walworth as well which is similar to a Nason, it is currently disconnected for refinishing, but its tubes are only around 1 inch in diameter each. The Carman's tubes are around 4 inch OD, inner tubes are 2.25 ID. It seems like the 2x7 Bundy at 60 EDR is probably the closest in actual size. Adding 40 percent for the convector portion per tube, for 14 tubes, that would result in an EDR of 89. Assuming the EDRs back then are inflated, we could say it's about 60 EDR. Unless we find a more precise EDR for the radiator, which I somehow doubt, this radiator seems to have been erased from history, the prudent thing to do seems to be to size the unit heater to allow for a bit of extra capacity on the boiler. Or to replace the bathroom radiator at the same time (needs to be done, the current one is 30 EDR in about an 8x10 room) and leave the unit heater the same size. I can also always go with 2 smaller unit heaters on opposite sides of the basement with dual speed fans allowing for different total EDRs/BTU output per heater.

It is a wonderful radiator and the airflow through the inner tubes is incredible. You can actually feel the cold air getting sucked under the base if you put your hand in front. You can also feel the radiant heat standing on the opposite side of the kitchen. It's directly across from an uninsulated wood front door so it does a good job of heating the house and the kitchen doesn't overheat.