steam boiler ratings

Glenn Sossin_2

These charts may prove helpful. There were alot of different radiators way back then.

Glenn

r. perry

boiler ratings

Would someone please explain what "square ft. of steam" ratings on boilers mean?
I'm trying to compare boilers and see a wide varience of rating for square foot of steam for boilers having almost identical mbh input ratings.
Example: the existing boiler rating plate reads "149mbh in" with a rating of 620 sq. ft. steam.
When I compare new boilers with a similar mbh "in" rating, the new boilers have rating of 354 sq. ft. steam, 287 sq. ft. steam, 164 sq. ft. steam and so on. ??????? THANKS!!

Mike T., Swampeast MO

The "square ft. of steam" refers to one square foot EDR (equivalence of direct radiation) of the radiators. The standard rating for one EDR of steam is for 240 btus @ 215F.

620 * 240 = 148,800 which rounds to 149 mbh (mbh = 1000 btu/hr) so it's just another expression of the input rating.

There should be other ratings as well. You should see an output rating both in mbh and sq.ft. of steam. This value will obviously be lower than the input.

If not ancient, there should also be an I=B=R rating, which is especially useful for steam systems as it includes a "pickup factor" to account for typical steam system piping. This value will be lower than the output.

Steamhead (in transit)

Actually

square feet of steam is another expression of the NET OUTPUT rating, not the Input. These ratings (whether marked IBR or not) include the pickup factor which is typically 1.33 for steam.

The DOE or Gross Output tells what is available at the boiler's outlet before it hits the piping.

The Input rating is expressed in BTU per hour of gas or gallons per hour of oil. One gallon of #2 fuel oil is good for 139,000 BTU, on average. This rating describes how much heat the burner puts into the boiler.

On a steam system, measure up your radiators and go for the closest square feet match.

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r. perry

boiler ratings

First, THANKS!! to Mike T & Steamhead for their replies.
I'm trying to replace an oil-fired steam boiler with a natural gas-fired steam boiler and just can not figure out the relationship between mbtu and sq. ft. of steam.
I've calculated the EDR ratings for all the radiators in the house. They add up to 447. If I take that number and multiply it by 240 I get 107,280. That should be the output mbtu size of the boiler I need to charge all the radiators, right?
Looking at a Crown boiler, model BSI138, it rates at 138mbtu in, 119mbtu out, 354 sq. ft steam (85mbh)
a Burnham boiler, model IN5 rates 140mbh in, 115mbh out, 358 sq. ft. steam (86mbh)
A New Yorker boiler rates 136 in, 118 out sq. ft. steam 164.
The existing OIL-fired boiler is an Axeman-Anderson Boiler-Burner No.149Po, installed January 1951 and rates mbtu/hr 149, steam sq. ft. 620. That's all the rating plate gives.
My question is will any of the natural gas-fired boilers mentioned above be adequate to power the system since the sq. ft of steam is less than half the capacity I have now, even though the mbtu's seem adequate?
Any comments/info would be greatly appreciated. Thanks. R. Perry.

Derheatmeister

How does the HP come into play?

Or, How many BTU's per HP ?

Steamhead (in transit)

Well, assuming your EDR count was accurate

your current boiler is way oversized.

You've been looking at the DOE output ratings rather than the NET output ratings. For example, the Burnham IN5's Net rating is 86,000 BTU per hour (also expressed as MBH). That corresponds with its rating of 358 square feet. You'd need the IN6, rated at 450 square feet if you went with an Independence boiler.

Go with the Square Feet rating, that's the easiest way. For another example, our company likes the Smith G-8 for its greater efficiency. The 4-section G-8 is rated 413 square feet, so that would be too small for your system. The 5-section is rated 525 square feet, which is a bit more than you'd need but we could dial the burner back a bit if it short-cycles.

For the record, the Input rating of the 4-section G-8 is 154 MBH (154,000 BTU per hour) and that of the 5-section is 196 MBH.

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Steamhead (in transit)

One boiler horsepower

equals 33475 Btu/hour or 9.8095 kW. This rating was used to determine how large a steam engine the boiler in question could operate.

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r. perry

steam boiler ratings

Men, agan, THANKS!! for your input. This has got me up all night. It's starting to get me steamed......HA1
O.K., Steamhead, would you be so kind as to check my arithmetic? For radiators I have:
1, 4 tube, 22 sections = 13,200
2, 4 tube, 24 sections = 28,800
4, 4 tube, 18 sections = 43,200
1, 3 tube, 18 sections = 8,640
1, 3 tube, 16 sections = 7,680
1, 3 tube, 12 sections, = 5,760
Total 107,280

Does this add up correctly?????????? R. Perry.

r. perry

steam boiler ratings

Men, agan, THANKS!! for your input. This has got me up all night. It's starting to get me steamed......HA1
O.K., Steamhead, would you be so kind as to check my arithmetic? For radiators I have:
1, 4 tube, 22 sections = 13,200--
2, 4 tube, 24 sections = 28,800--
4, 4 tube, 18 sections = 43,200--
1, 3 tube, 18 sections = 8,640--
1, 3 tube, 16 sections = 7,680--
1, 3 tube, 12 sections, = 5,760--
Total 107,280

Does this add up correctly? Do you come up with 107,280? R. Perry.

r. perry

steam boiler ratings

Men, agan, THANKS!! for your input. This has got me up all night. It's starting to get me steamed......HA1
O.K., Steamhead, would you be so kind as to check my arithmetic? For radiators I have:
(1) 4 tube, 22 sections = 13,200--
(2) 4 tube, 24 sections = 28,800--
(4) 4 tube, 18 sections = 43,200--
(1) 3 tube, 18 sections = 8,640--
(1) 3 tube, 16 sections = 7,680--
(1) 3 tube, 12 sections, = 5,760--
Total 107,280

Does this add up correctly? Do you come up with 107,280? R. Perry.

r. perry

steam boiler ratings

Men, again, THANKS!! for your input. This has got me up all night. It's starting to get me steamed......HA!!!
O.K., Steamhead, would you be so kind as to check my arithmetic? For radiators I have, ALL 23" tall....
(1) 4 tube, 22 sections = 13,200--
(2) 4 tube, 24 sections = 28,800--
(4) 4 tube, 18 sections = 43,200--
(1) 3 tube, 18 sections = 8,640--
(1) 3 tube, 16 sections = 7,680--
(1) 3 tube, 12 sections, = 5,760--
Total 107,280

Does this add up correctly? Do you come up with 107,280? R. Perry.

Steamhead (in transit)

It depends

on whether they are large-tube or small-tube rads. Check the width of one section on each- the easiest way to do this is to measure from the center of one section to the center of the next one.

If the section width is 2-1/2", they're "large-tube". I checked the figures on the first one you listed and they apply to a large-tube type.

If the section width is 1-1/2" or 1-3/4", they're "small-tube" rads, which would have different ratings.

If the section width is an even 2", you have the original American Corto rads which would not only have different ratings, but are NOT shown in Dan's book "E.D.R." (though the later, 2-1/2" ones are).

Measure them up and let us know what you have. Post some pics too, we like to see radiators here ;-)

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Steamhead (in transit)

Nice pics!

couple of corrections though..... the "new style square top" (a.k.a. large-tube) and "Slenderized" (a.k.a. small-tube) don't have "columns"- they have "tubes".

Also, the large-tube type came out in the early 1920s and the small-tube just before World War 2.

I believe the original tube radiator was the Corto, a.k.a. the French radiator, made by American Radiator Co. It was originally designed with slimmer sections (2" spacing instead of 2-1/2") and was even made in a steam-only version with no push nipples across the top! No kidding, Gordo and I saw these in a 1921-vintage house where we were looking at a boiler replacement. We'll have our camera with us next time we go there ;-)

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r. perry

boiler ratings

Thanks for the replies. I'm going to guess the radiators are American Standard because the same radiators are in many of the houses in this neighborhood, all built by the same builder and he seems to have favored American Standard as all the plumbing fixtures in all the houses are American Standard. My house was built in 1940 as were most of the others in this area. Built between late 20's thru the late 40's. The ones built after WW II really stand out though..
Anyway, I measured the tubes and they are 1.5" on center, so I'm guessing again they'd be considered small. I won't be able to take a good picture until Monday. The wife is gone for the week-end and has the camera, but I did find this picture with a radiator in the background. What do you guys think the radiatore are??? R. Perry

Steamhead (in transit)

That's a small-tube rad

to the rear of Cujo. Here's the list of the ones you posted earlier:

1- 35.2 square feet

2- 38.4 (2 of these)

3- 28.8 (4 of these)

4- 23.4

5- 20.8

6- 15.6

The total of these is 287 square feet, or 68,880 BTU per hour. You need a SMALL boiler! My choice for your house would be a 3-section G-8, based on these figures.

Are there any rooms where radiators were removed?



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r. perry

No radiators have been removed. I've insulated the attic. R32. Cleaned up/rehabbed the aluminium triple track storm windows (I carefully replaced all the pile weatherstripping on the storm panels which had disintegrated over the years)and the existing tru-divided lite wood douple hung windows all have been cleaned up, painted and all the glass lites removed and reset using a latex caulk to set the glass and new putty to finish the glazing. In addition, the window units themselves seem to be quality material. They're marked "Curtis Silentite" and have this somewhat elaborate weather stripping/counterbalance system. They're not pully/sash cord balanced and still run tight and seal up well. I've been toying with the idea of trying to downsize the steam system to economize on heating cost. I have a neighbor who ripped out his steam system and still has all the radiators sitting in his garage and told me I could have anything I could use. He just hasn't gotten around to hauling them off to the scrap dealer. I've had no problems keeping the house warm. Im fact, the rear of the house on the first floor is always about 5 degrees warmer than the rest of the house, so I thought I could easily downsize the 3 radiators in that area. I really want to keep the steam heat. I like it, and someone had a ducted AC System installed in '94, so that's still in good working order. It's just trying to figure out the right size replacement boiler. I've always suspected the boiler now there was too big. When I first moved in, the 2nd floor was always cold and the first floor was hot, very hot. I finally got it somewhat balanced by replacing all the vents, then setting all the venting on the first floor radiators to "closed" and all the venting on the 2nd floor radiators to full open, but still, the first floor, especially the back of the house, stays warmer than the rest of it. Anyway, a very big THANKS!! again to all of you who have taken time to write and share your years of experience with me. I'm very grateful to all of you.
Best regards, R. Perry.

Steamhead (in transit)

Well, when you get rid of that oversized boiler

you'll see a huge difference, and your benighted neighbor will be jealous of your home's comfort and efficiency. Also, are the steam mains vented?

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r. perry

steam boiler ratings

The mains seem to be vented. I'm not a HVAC man, so I can't really say/don't want to say. There are two distinct "vent-like" objects, rising above the main, at the far ends of the main, one looks exactly like an air vent on a radiator, only larger, the other looks very different, larger still. I'm just assuming they're vents, but I know all too well the very real danger of assuming anything is anything. I assumed the radiators were mfg. by American Standard, but after getting more curious yesterday, I got out some paint stripper and went to work on one of the radiators. I've found raised lettering on them reading, "National Art Radiator" so now I feel like I'm back to square one, wondering if the rating no's I've calculated, along with the rating no's "Steamhead" was so generious to have calculated for me are accurate. I can't find any info on National Art Radiator when I Google it, soooo....r. perry.

Steamhead (in transit)

The \"Art\" radiator

was a amall-tube, just like the Arco. The ratings were standardized, so no changes need be made to those I posted.

Measure the length and diameter of each of your steam mains and post pics of the vents that you found. We can tell you if they need upgrading.

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r. perry

boiler ratings

Once again, much Thanks! to "Steamhead" for all this advice. I've learned so much from this dialog that sometimes I want to say, Stop! My brain if full....HA!!
Anyway, I've got some pics taken ..........

r. perry

steam boiler ratings

Another very grateful Thanks! to "Steamhead" for advice. Here are pictures of the mains and what I'm guessing are vents..........

r. perry

And here are a couple views of the existing boiler. Note the lack of a Hartford Loop (thanks to this site I now know what a Hartford Loop is!!!)........

r. perry

Here are pictures of a typical branch take-off from the mail run. One pipe will feed the radiator on the 1st floor, the other pipe will feed the radiator on the 2nd floor.........as you can see, the main line is marked "2", I'm assuming 2 inches, and the branch take-offs are marked "1-1/4", again assuming 1-1/4 inches. There are only 4 of these configurations. This is a small house, 1560 sq. ft., 2 bedrooms, full bath upstairs and 1/2 bath down. There are a total of 10 radiators in the house. The living room has 2 radiators and the big bedroom, directly above the living room, also has 2 radiators. All the rooms are fairly big, at least on the big side for 1940 standards.

r. perry

And last, here are a couple pics of the radiators themselves. The "National Art Radiator" probably can't be read, but I'm sure you guys will recognize them immediatly.........

Steamhead (in transit)

Have you

had a chance to measure the steam mains yet?

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r. perry

steam mains & risers

If my arithmetic is correct, I should have 81 ft. of steam main labled "2" and 48 ft of riser labled "1 1/4". (calculated by assuming there are 5 radiators on the 2nd floor, and the 1st floor rooms have 8 ft. ceilings) The risers run inside the 1st floor walls with a 45 at the 1st floor ceiling, then another 45 to bring the riser up through the floor of the 2nd floor.
I don't know if and how 45 degree elbows figure into any of this, but I can easily go back and count those. It's really a very simple layout.
So Mr. Steamhead, what do you think?
If I manually calculate the steam main and risers, do I then subtract that number from the total or do I just not add the 30% to the radiator EDR and add the total footage for the piping? THANKS!!! R. Perry
The attachment is a crude drawing of what's in the basement.

r. perry

steam main & risers

If my arithmetic is correct, I should have 81 ft. of steam main (labled "2") and 48 ft. of risers, (labled 1 1/4") based on the 1st floor having 8 ft. ceilings. The risers run up inside the walls then 45 at the 2nd floor, then 45 again to come up through the 2nd floor. I don't know if and how any 45 degree bend figures into the total area of radiation. Also, if you add up all the footage of steam pipe, do you then add that to the total EDR of the radiators or do you just not add the 30% of the radiator EDR when figuring the total btu requirement? THANKS!!! R. Perry

Steamhead (in transit)

That's an unusual layout

the steam mains usually end near the drips and main vents, rather than being looped together like that. I'd use a Gorton #2 vent at each of the two venting points- watch how fast the steam distributes with this setup. If no one in your area carries Gorton vents, you can order them online from State Supply (www.statesupply.com) or PEX Supply (www.pexsupply.com).

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r. perry

boiler ratings...

Much THANKS!! to "Steamhead" and others who have so generiously offered valuable information and even more valuable advice. I can't express how grateful I am. Again, THANKS! Guess it's time to roll up my sleves and start getting dirty.......HA! Best regards to all, R. Perry

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