Proper steam boiler size

mben

Sorry, this is my first time posting here and I am not familiar with the procedure.

My radiators are all 5 'tubes' deep -- based on information on page 43 of the reference suggested. They are all 8.75" wide. The radiators are 80 years old. The boiler is 10 years old. The reason for my posting here is to figure out whether the water overflow I am getting is due to improper sizing of the boiler, or some other reason.

I am just a homeowner who cannot understand the significance of some of the technical terms used in steam heating, other than at a very high level. I would much appreciate any help I could get on this. Thanks.

mben

sizing steam boiler

I would like to figure out whether the steam boiler I now have in my home is too small for the existing piping. The reason I am asking is because water flows over and out of the vent on top of the boiler when the system cools down. If I reduce the water in the boiler, the low water level cutoff causes the automatic water feeder to add water. How can I figure out the proper size? I now have a Utica PEG187B unit, with 187,500 AGA Input BTU/hr and 151,000 heating capacity BTU/hr. The steam rating is 113,000 BTU/hr (475 sq. ft.).

mben

Some additional information

There are 10 radiators on the steam boiler system I described in my previous message. 5 radiators have 1.25" valves and the remaiming 5 have 1" valves. All except for one radiator (which is 36" tall) are 26" tall. The 36" radiator has 7 sections and 1.25" valve. The other four 1.25" radiators have 8, 13, 13 and 14 sections, respectively. The five 1" radiators have 4, 4, 7, 7, and 7 sections, respectively. I hope this additional information will help answer my earlier question about the proper size steam boiler for my house. Thanks again.

Ken_40

Mmm.

What previous message?

We need to keep one thread per topic here.

If you multiple post under more than one "Title/topic", the continuity is lost.

Go back and resurrect your original post, which I assmue.all the pertinent info therein.

If it's gone from the display, Typically if no one hits a a post for 3 days, its gone...

Anna Conda

Ummm....

He meant the message that starts this thread. He bumped it with additional information, not unreasonable to do.

Unknown

mben

As you already have the capacity of your steam boiler, you are a little confused about the "load" on it(radiation sizes), right? I don`t size steam replacement boilers by the valves, its by the rads. Perhaps Dan`s book, EDR (Every Darn Radiator) will help you with this. Just look at the top here, under "SHOP".

Garret

I'm just a homeowner, but I believe I can help you figure out the EDR of your rads... In the shop here, Dan sells a book with radiator EDR data, but you might get enough info for now out of Burnham's free Heating Helper PDF. (check page 40 or so)

http://www.burnham.com/pdfs/htghelper.pdf

The key thing you're missing in your list of rads above is how many columns/tubes the radiators have. Sections go left to right as you look at the radiator, the columns or tubes are the "depth." Columns are really wide (2" or so diameter), and found on older style rads. Tubes are 1" or so diameter, and found on newer slimline rads.

Is this a new boiler, recently installed? One thing to be aware of is that modern high efficiency steam boilers have low water content compared to old boilers... so it's possible your boiler can make the EDR, but doesn't have enough water in it to wait out the lag for condensate to return. I believe some ways around this problem are installing a boiler feed pump, turning off your autofeeder (letting the system shut down on LWCO for a few minutes to wait for condensate to return), or upgrading to a better autofeeder (the Hydrolevel VTX is supposed to be smarter).

Here's some info from the Library about what causes boilers to shut off on low water... (which I thik is what your boiler is doing, except instead the feeder is compensating and causing the boiler to flood later).

http://www.heatinghelp.com/steam_burnershutsoffonlowwater.cfm

-Garret

Unknown

Your doing..........

just fine!! Have you read the previous messages? Garret has some good suggestions there also.

Unknown

the B and B

U need to get the books about steam heating and buy some bricks from Dan's list.... That will make u a very knowledgeable person when come to dealing with ur steam system and any helpful pros working on same...

Garret

Great, that's what I needed... I'll show you how to figure things when I get a sec (trying to get this newborn to sleep right now, to spell his mom).

Another thing that might help... if you have a digital camera, take a few pictures of the boiler, including all the controls and near-boiler piping, and attach them to a post in this thread.

If nothing else, folks here love to see an old steam system... but in all likelihood they'll see something you can change that will help your system.

Congrats on the old house, btw... mine's a similar vintage (1923). We just fired up our new boiler a few weeks back, and it's running so great I can't keep from coming back here to thank the pros for their help, and handle a few questions to spell em a bit.

Definitely get Dan's We Got Steam Heat book.. it's designed for homeowners. You'll probably also want the Lost Art of Steam, which is much more details than you'll need, and is actually a fascinating read.

-Garret

Garret

Okay here's the math. Short answer from my calculations is, your boiler is definitely not undersized.

Here's how it works... the maximum heat output of a radiator is specified by it's EDR, the equivalent direct radiation. It's a measure of the surface area of the radiator.

You calculate the EDR for each of your radiators, and add them up. That gives you the total load of radiation that your boiler is driving.

From radiator charts for tube-style rads, you find the sq foot EDR per section that matches your radiator(s). If you're between sizes in the charts, just average out the values. Then you multiply by the number of sections in each particular rad.

You'll have to check my math, because I'm doing it quickly...

For your ten rads:

3.5 EDR x 4 = 14

3.5 EDR x 4 = 14

3.5 EDR x 7 = 25

3.5 EDR x 7 = 25

3.5 EDR x 7 = 25

3.5 EDR x 8 = 28

3.5 EDR x 13 = 46

3.5 EDR x 13 = 46

3.5 EDR x 14 = 49


4.75 EDR x 7 = 33

Add em up, and you get 305 sq foot EDR. Your boiler is rated quite a bit higher than that (475 sq foot EDR). So your boiler is not undersized at all.. it's oversized by about 50%.

So post some pictures, and see if we can come up with a better idea for why it's flooding. I'm curious to see what make/model of autofeeder and low water cutoff (LWCO) you have.

-Garret

mben

Shut-off valve may be leaking...

Garret,

Thanks so much. Since your calculations show that my boiler is more than adequate, this eliminates one possible explanation for the overflow I am getting.
I was concerned that the boiler was shutting off on low water, before the condensate had a chance to return to the boiler to keep it within the operating range, as it is called in one of the references you mentioned earlier. If the feeder kicked in before the condensate returned to the boiler I would have overflow. Since the low water cut-off point was set at the factory, and they should know what they are doing, the only logical conclusion was that the boiler was too small.

The other possibility is that one of the shut off valves in the water feeder controls is leaking. I did an experiment last night: I shut off Valve 1 in the diagram I attached. There was no overflow. This suggests that Valve 2 may be leaking. I will try replacing it and see if the problem goes away.

Garret

Makes sense.... from your diagram, valve #2 seems to be your manual feed control... if it's not shut all the way, you'll slowly add water to the boiler all day long.

mben

Backflow control dripping

I fixed the manual feed valve and the overflow stopped.

I now notice that the release pipe from the backflow control valve is dripping. What does that mean? What should I do other than put a bucket under the release pipe?

Thanks.