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EDR calculations for steam

movin2gas Member Posts: 25
I'm not 100% sure, of course, but I did my best to find out. I have 4 different types of radiators in the house:
3 column (2.5" columns)
2 column (3" columns)
5 tube(1.5" tubes)
5 tube (1" tube) (this is a newer "slenderized" radiator)

You can take a look a my calculations here if you want:


  • movin2gas
    movin2gas Member Posts: 25
    How to factor in the pipes?

    Using an article and EDR table I found on Colonial Supply's website [1], I calculated the EDR of my radiators. Boiler sizing must account for steam in the pipes as well, right? I saw a mention on another form of multiplying the radiator EDR by 1.5 to get the correct sizing for the whole system. Is this accurate, and if not, how does one account for the pipes?


    [1] http://www.colonialsupply.com/resources/radiator3.htm
  • Brad White_203
    Brad White_203 Member Posts: 506

    For most residential steam systems, a piping and pick-up factor of 1.33 is sufficient, especially if the piping is well-insulated. On older systems (where piping is somewhat larger for a given system), a 1.50 factor is commonly suggested.

    Keep in mind though, that if you are selecting your boiler based on the I=B=R "net SF" or "net EDR", that factor has already be taken into account. You match your connected radiation and select the boiler to meet it as closely as possible.

    What I do is to calculate the piping as well as the radiation. (I want to take off the piping too so as to get good venting data so none of this work is wasted.)

    I take my net connected radiation EDR and see what I get for a boiler based on the 1.33 factor.

    Then I take my piping converted to EDR and add that to the radiation EDR and compare the two totals.

    More often than not, the 1.33 factor is enough to cover the piping. On older systems, indeed, that 1.50 factor comes pretty close to reality.

    Do both and then you know, for everyone's piping layout is different.
  • movin2gas
    movin2gas Member Posts: 25

    I'm doing this because I suspect my new boiler was oversized, though the contractor did measure everything himself before ordering it. My calculations put the EDR of the radiators at about 280 sq/ft. My boiler is an Burnham IN6PV. The literature I just read at Burnham.com lists an I=B=R NET rating of 454sq feet. That's a pretty big difference (the IN4 puts out 271 sq/ft, and the IN5 puts out 363). I don't quite understand how the pickup factor can be taken into account by Burnham since the piping can differ from house to house.

    That, and the fact that my house is only 1450 sq/ft and the IN6 is the biggest PV boiler they make lead me to believe that the original calculation was flawed.
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,314

    are you sure of the radiators size and style you are using?
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • Dan C.
    Dan C. Member Posts: 248

    Burnham includes a pickup up factor for "normal" piping. I have always assumed that this meant an average steam system. If you have a larger than normal system or a lot of uninsulated pipes then you have to figure for that also.
  • Brad White_191
    Brad White_191 Member Posts: 252
    My gut says

    that your radiation potential (67,200 BTUH) works out to just over 46 BTUH per SF. In a location with a design of zero or single digits, that seems rational for an older, not well insulated house. So there is some basis there.

    The piping and pickup factor is always a guess, as you say, no one knows what your piping is. But the 1.33 factor does not belong to Burnham but to the industry, set forth years ago based on lots of experience.

    The IN4 might well have worked if your piping is not extravagant and if it is well insulated. Otherwise an IN5.
  • movin2gas
    movin2gas Member Posts: 25
    House meets those criteria

    Boston area, not insulated well at all.
    The question is, what can I possibly do about it now? I paid $6500 for this thing.
  • Jim_64
    Jim_64 Member Posts: 253
    Original Quote

    Was this boiler model number specified in the original contract?

  • mark ransley
    mark ransley Member Posts: 155

    why cant you change the boiler order, it hasnt been installed yet, smaller should be cheaper, insulating pipes is easy.
  • movin2gas
    movin2gas Member Posts: 25
    Yes it has...

    Been installed, that is. The proposal does not specify the model, just the make.
  • Brad White_191
    Brad White_191 Member Posts: 252
    Where in Boston?

    That is too bad that the model was not specified. Have you approached the contractor? If so, what did he say?
  • movin2gas
    movin2gas Member Posts: 25
    He's taking care of it

    I just talked to the contractor, he found an error in his calculations which put an extra 100sq/ft on the EDR. According to the Burnham rep (who I am going to talk to myself), the IN6 can be downsized to an IN5 equivalent (in terms of both input BTU and steam output) by replacing the nozzle, and contractor is going to take care of that. Warrantee is still valid. Does this seem reasonable?

    Thanks for everyone's advice.

This discussion has been closed.