Too Small or Too Big

Murph2

my 28 year old Wild-Mclain steam boiler is leaking (Oil Fired).I am converting to gas.Both contractors given to me by gas company walked around the house and measued. One sez I need a 4 section boiler the other sez I need a 5 section boiler.Now my wife (retired math teacher) and I (retired phone co.) Found a chart on line and did our own measuring. We came up with a 4 section,but if you add the pipping lost factor of 1.33 we come up with a 5section requirement.We have 10 radiators . house built in 1927. Half col. radiators and half tube type.Steam main is covered for the length of the house and the pipes coming off the top of the old boiler were covered with insulation.28 years ago the oil company took out coal to oil boiler ad installed an oil fired steam Weil-Mclain model p-466E 144000DOE,450 sq ft of steam.Ran great all radiators in the house got hot almost at the same time Using Gorton valves thru out.So now we are getting a Burnham gas fired steam boiler. One cotractor measured 229 sq ft of steam. the other guy who I like is measuring oer 300 something sq ft. The over 300 sq ft uy is adding a loss factor of the pipes so he sez.it is hard to ID  the ra. diators and apply a chart to do our own cal.My question is how do we determine who is right or who is maybe to conservative or to over the top. Your ideas would be appreciated. i wish I had read your book 30 years ago.Thanks murph

crash2009

That's a pretty big spread.

If you post a couple pictures of the 2 kinds of radiators you have, we could help you identify them, and possibly direct you to the area of the library here, that contains the charts you need.  While you have the camera out, take a couple shots of the boiler.  Show the pipes up in the ceiling and the ones near the floor.

What city or state are you in?  Have you tried to get a 3rd contractor in there yet?

I am not 100% sure, but I thought that the pickup factor of 1.33 is allready built in to the boiler.  I thought that it should be as simple as measure the square feet of the radiators and match that number to the square feet of the boiler.  If you add 1.33 to your radiator EDR you will have a boiler 1.33 too big. 

BobC

Pipes insulated?

I agree 100% with what crash said, you can just size the boiler by matching the IBR boiler radiation with the connected radiation (in sq ft of steam). I would add that the steam pipe coming out of the boiler, and all the steam pipes in the basement, should be insulated with a minimum of 1" pipe insulation. that will make the basement get chilly but make the fuel bill go down and the boiler will work much better. The insulation is not cheap but you can do it yourself and save the labor cost.



Please post some pictures so we can see if anything else has to be corrected while they replace the boiler.



Bob

Rod

Boiler Replacement

It looks like your approaching the boiler replacement the right way by doing your homework first. As others have mentioned, post some pictures of your boiler. Take them from several angles and include the piping connected to the boiler in the pictures so we can trace the piping. (We can blow them up if we need more detail.)  Having the near boiler piping  properly configured is extremely important to success operation of the your steam system. Here are some links below that may be of use to you.

Have a great 4th!

- Rod



Links:

Steam Heating Primer

http://www.heatinghelp.com/article/11/Hot-Tech-Tips/128/A-Steam-Heating-Primer



Replacing a Steam Boiler 1

http://www.heatinghelp.com/article/11/Hot-Tech-Tips/186/How-to-replace-an-old-steam-heating-boiler



Replacing a Steam Boiler 2

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



Importance of Insulating Steam pipes

 http://www.heatinghelp.com/article/11/Hot-Tech-Tips/300/Why-you-should-insulate-steam-pipes



Video on Importance of Near Boiler Piping

http://www.heatinghelp.com/article/107/Steam-Heating/118/Steam-boiler-near-boiler-piping



Boiler Ratings Explained

http://www.heatinghelp.com/article/11/Hot-Tech-Tips/143/Boiler-Ratings-Explained



History of  Boiler Sizing (Why you need to calculate your systems boiler size)

http://www.heatinghelp.com/article/11/Hot-Tech-Tips/180/How-that-steam-boiler-got-to-be-so-big

Dave in QCA

SQ FT EDR RATINGS

Crash, you are absolutely correct.



The EDR or SQ FT rating on the boiler already has the pickup factor included.  The rating is intended to be matched to the actual radiation of the system.  Usual practice on a system with insulated pipes of normal sizes and lengths for a system of its size, is to select the boiler with the nearest rating that is larger than the actual radiation of the system.

Greg Maxwell

Boiler Swap

While that is a big spread, bear in mind that square footage of steam multiplied by 240 = BTU, so you are still in the range of a 3 section, even with adding for piping loss. Are these guys well versed in steam? Dont go with anyone who isnt. If you are curious about their eval, call and ask them why they did what they did.

Also, look on line for steam radiator sizing. There are charts available that should help you in your sizing efforts.