How to size a steam boiler

steamy58

Hi All

After having a plumber extensively examine the steam pipes in my home he concluded that my boiler may simply not be large enough to heat the home properly. He removed the main vent while steam was running and very little steam came out of the pipe. Some radiators get hot and some only halfway. We removed vents and valves from them as well and very little steam came out of the radiators.

House is a little under 3000 sq ft and boiler is 125,000 BTU weil mclain.

Does it make sense? Help

Rod

Sizing a Steam Boiler

Hi- Did he measure all the radiators and determine the total EDR? If he didn't, I would question if he really knows what he is doing. The first step would be to measure the EDR of each individual radiator and add them up so that you get a total EDR for your system. This is something you can do yourself. Attached is a work sheet to help you do this.

You might also tell us where you are located and perhaps we can refer you to a pro that understands residential steam heating. There is a lot of information on steamheating available on the website. Here's a link on sizing boilers:

http://www.heatinghelp.com/article/236/For-Homeowners/1490/How-to-have-a-boiler-replaced-without-getting-steamed

It would also help if you posted some pictures of your boiler so that we can see the attached piping. Take them from back away as we need to be able to trace out the piping. What is the model of your boiler?

- Rod

BobC

What is the EDR

A steam boiler has to be sized to drive all the radiators in the system. Each radiator has a surface area called it's EDR. The boilers EDR (sq ft of steam) should be equal to the sum of all the radiators EDR.



List all of your radiators by size (height, length, width) and the number of sections as well as the number of columns in each section. From that we can determine the EDR of each radiator.



Bob

jonny88

rod a ?please

Hi ,I was just about to ask a similar question.Ok my total sq ft edr is 647.5.Ok i get that,now when i multiply that by the conversion factor of 240 I get 155400.Fine I go to the boiler manufacturer and i see in the Input column a In6=175.

Now I get confused here,dans book ,Lost art of steam on page75 he says 1.add up radiation square foot.(mine is 647.5..Next multiply by 1.5 so i get 971.25...Next convert to MBH by multiplying by 240.I get 233100..then select boiler from D.O.E heating capacity.I am now up to an IN9 ...what am i doing wrong.Thanks,I know I am doing something stupid

AWA

EDR

The total EDR for my steam radiators is 400 * 240  = 96000

My boiler is a weil mclain 150000btu steam boiler with 380sq ft steam

Is it sized correctly for my 3000 sq ft home with little/no insulation as it is anolder home with plaster walls?

BobC

It should work.

Your boiler EDR is 95% of it's connected load. If it was installed correctly and the steam piping is insulated it should work. I suspect there are issues with the system piping. Are there any signs of radiators being removed?



Post some pictures of the boiler and the piping around it.



Bob

AWA

enought btu?

There is a section of the house that is baseboard water heat zoned off of the boiler but it does not seem that any radaitors were removed.

Problem is we removed the vents from the main pipe and no steam came out although the pipe is hot.

BobC

Pitch

Go over all the steam piping and make sure it is all pitched correctly, if there are any sags in the piping that will stop the steam in it's tracks. Don't trust your eyes, use a level.



How much baseboard is being fed by the boiler in addition to the 400 EDR radiators? If that load is significant it could be a problem.



Bob

BobC

Sizing steam

This is a good article about an alternative way to size a steam boiler



http://www.heatinghelp.com/article/323/Boilers/1551/Taking-Another-Look-at-Steam-Boiler-Sizing-Methods-by-Dave-Boilerpro-Bunnell



Bob

Paul48

Lost

Who's thread is this?

Rod

Boiler Sizing & Data Charts

Hi- You didn’t say what type or how big the building is that this system is in. For comparison I have an old 3 story house in rural Maine and my total EDR is about 550 sq.ft.   I just mention  this for your comparison as your  647.5 sq.ft of EDR means it must be a fairly good sized structure.  If this seems to be off a bit to you, you might want to check your EDR figures and calculations



Since we already have the total EDR of the system then let’s go to the next step and take a look at the attached Burnham Independence Data Sheet.  The input column can basically be ignored. What you are interested in in the I=B=R columns or the DOE Capacity (Gross) Column



The Short Method   (Comparing EDRs)            

If you look the the ratings chart in the columns under the section I=B=R Ratings you will see 3 columns . We’re only interested in the two columns:  Steam MB H and Steam Square Ft.    These  columns already have a 1.33 pickup factor included so you can just compare your total EDR  figure of you system to the nearest figure in the Steam Square foot column which would be 633 (IN 8)    



******************************************************************************

Long Method

This is the way to do it if you want to calculate it the long way or use a different “Pickup Factor”.

On Page 95 of the LAOSH,  Dan suggests using a 1.5 “Pickup Factor”  (rather than the standard 1.33) to allow for things like lack of insulation, removed radiators etc.



The calculation is : Total Measured EDR x  PickUp Factor x 240 = Total BTU Load

                                       647.5 sq.ft   x 1.5   x 240   =   233100 BTUs



We now take our 233100 figure and look on the Data sheet for the nearest figure DOE Heating Capacity* column which would be 231 (MBH) (IN9)



* Other manufacturer’s  data charts  will call this column: “Gross” or “Out put”                            

Looking at your figures I would say you are on the right track. You will just have to decide which “Pickup Factor” to go with in your situation.

I was going to include a link to Boiler Pro’s article but I see Bob  has already done that. It’s a really good article!

- Rod

Sorry Steamy 58 - I didn't mean to divert your thread though I thought this reply might also be useful to you too!

Rod

Need more Info

Hi- Do you have a figure for the EDR of your baseboard?  Has this system ever worked properly? If it has worked properly in the past was there something (maintenance etc.) done recently to the system?

Since your boiler seems reasonably sized, yet you aren't apparently producing steam, I'm wondering if it might not be a control problem. If you have an aquastat wired into the control circuits it might be cutting off the burner before any volume of steam is being produced.

  Where is the thermostat that controls the system located, in a room with steam radiators or in a room with baseboard?

- Rod

jonny88

thanks rod

Thanks for your time and explaination much appreciated.I didnt mean to hijack the thread as I thought your answer covered everything.Just in case there is a few wondering that" if he cant size a boiler why is he putting it in",I work for a company and work with a licensed plumber but usually there is not time for questions on the job,so again the people here who take time to answer questions make work more interesting and challenging as you know they work to a high caliber.

Fred Jordan

Boiler control

Does the LWCO have intermittent level check? If the cycle guard isn't wired in you might not make steam.