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Drop header benefit other than height?

cniessen1
cniessen1 Member Posts: 9
edited August 7 in Strictly Steam
I'm about to have a new boiler installed (likely Weil-McLain EG6), and I'm trying to understand the benefit of a dropped header if I don't have a height constraint. What is the benefit of a dropped header vs a non-dropped header that is installed at the same height as where the risers turn down to go to the dropped header?

I see lots of discussion about getting dryer steam because you can have taller risers with a DH, but if my steam mains are 36" above the top of the boiler, why wouldn't I just come up 30" into an oversize header, take the mains off of that just like is shown in lots of the diagrams in the Art of Steam Heating? Sure, if the mains were lower, I could get more height (I've seen the W-M video with the glass pipes so I get the problem) but I see lots of installation pictures where the risers aren't nearly as tall as they could be, but they turn down into a dropped header, then the feeds to the mains go up a lot from the header. What did the dropping do in this case? As long as I have the header at least as high as the risers would be for the dropped header, and I have swing joints, and I take the feeds off the header between the riser and the equalizer (so everything is going in the same direction), etc, what does dropping the header do for me?
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Comments

  • JUGHNE
    JUGHNE Member Posts: 9,908
    The drop header with the extra 90 ells for swing above the header makes the header assembly easier.
    That length of horizontal pipe for the header would have to be cut to an exact length.

    With the swing of the risers you may be possible to build that header with 2 standard nipples and a coupling.

    Then, also the taller the steam feed risers to your main add another drop out point for any water to fall out of wet steam into the horizontal header and out the equalizer pipe back into the boiler.
  • JUGHNE
    JUGHNE Member Posts: 9,908
    Also lowering the header itself, lets you get some distance between the existing steam mains and the header.

    You mention having 6" between header and mains, that can get close for fitting together.
    If there was more distance it might be easier to connect those.
    You would probably need unions at that point.
    That connection could also be built up with factory cut nipples.

    Also, assuming this is not a counterflow system, you can raise up your steam mains somewhat to get more slope down away from the boiler......within reason.
  • cniessen1
    cniessen1 Member Posts: 9
    Got it; thanks. So with plenty of height, there is some additional opportunity for dryer steam, but probably diminishing returns. Big win is that the install is quicker and (hopefully) cheaper if you can use standard nipples and not have to cut & thread custom pieces.

    Other than the slightly increased cost of material, should the riser be as tall as possible (either to the site height constraints, or the limits of length prethreaded pieces are available)? If more vertical to give a bigger chance for water to drop out is better, then going as high as possible before dropping to the header is always the right thing, no?
  • JUGHNE
    JUGHNE Member Posts: 9,908
    I was assuming double risers with 2 steam risers.

    What size of pipes are you talking about?

    Any pictures of existing boiler showing piping....floor to ceiling?
  • cniessen1
    cniessen1 Member Posts: 9
    This is what's there now; I'm sure all of the 2" copper will get replaced, but trying to get a handle on what the new install should look like.



    I look at finished installs like this one

    from this thread and I wonder why the risers didn't go higher. I'm sure if I ask for it, they'll do it, but is that something I should ask for?
  • Jamie Hall
    Jamie Hall Member Posts: 19,426
    Let's consider for a moment what happens inside those pipes. You have the riser or risers. The minimum height there allows the bigger -- really bigger droplets (let's call them blurps) to fall back into the boiler, but that leaves a lot of finer almost mist. If your header is really truly big enough -- and IMHO one size larger is not big enough -- and if your mains take off straight up and if your header is properly pitched most of that mist will not make the turn into the mains. Most of it. Now however, consider a dropped header. Not only does that mist now have to make two 90s to get over to the drops, the drops go straight down into the dropped header, and the mist impinges on the bottom of that dropped header (can't make the turn) and coalesces and, again if the pitches are good, makes its way happily to the equalizer, while nice dry steam goes along above it and up the risers.

    Bottom line -- significantly drier steam. There's another way to do this -- a big steam drum -- but that's not done any more.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • cniessen1
    cniessen1 Member Posts: 9
    Got it. Sounds like good reasons to add the drop header. Any reason not to make the risers as tall as possible?
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 12,362
    JMHO which many don't agree with.

    While a drop header may be easier to assemble you need xtra fittings which get expensive in larger sizes.

    I just don't like the way they look.

    I agree with low headroom they are the answer to that problem

    If your risers are tall so much the better. It keeps the water in the boiler.

    IMHO a standard header works fine if piped right and with the right size piping

    ethicalpaul
  • 109A_5
    109A_5 Member Posts: 276
    edited August 8
    @cniessen1, just curious, why are you replacing the boiler ? Has it failed ?

    I like the drop header, to me it fits in with the whole mystique of steam. For a one time cost if it provides drier steam and if drier steam is more efficient why not do it ?

    To all, was there a point in time, install manual, a text book, or just a very busy boiler installer that installed boilers with this type of near boiler piping ? Mine is very similar. I don't have any problems that I know of, but I bet my steam could be dryer.
    cniessen1 said:

    This is what's there now; I'm sure all of the 2" copper will get replaced, but trying to get a handle on what the new install should look like.



    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • cniessen1
    cniessen1 Member Posts: 9
    I think there's a hole in the boiler; late last winter it started need exorbitant amount of make up water and it wasn't able to keep the house warm on really cold days. I added a low pressure gauge to it and it never budges off of zero, so I think it never builds any pressure. Even in the summer now, the water level drops 1/2 way down the sightglass in a couple of weeks just from keeping the water warm enough for the DHW coil. FYI, the inspection label on the boiler seems to indicate its about 30 years old (based on what I think is the date on the "inspected by" manufacturer label). I converted it from oil to natural gas with a Carlin ez-gas gun about 5 years ago.
  • ethicalpaul
    ethicalpaul Member Posts: 3,759
    > so I think it never builds any pressure

    This isn't bad, it is actually the goal. But if the REASON it doesn't build pressure is due to a hole rusted in it, that is bad of course.

    If you can find an installer to properly install the near boiler piping according to the manufacturer's instructions (with very few exceptions), you don't need a drop header but they definitely don't hurt--unless your inspector is weird like mine and thinks they are improper.
    1 pipe Peerless 63-03L in Cedar Grove, NJ, coal > oil > NG
  • 109A_5
    109A_5 Member Posts: 276
    @cniessen1, Thanks. With the boiler off, you could temporally fill it over the top of the heat exchange and see if it leaks, just to be sure. When it was cold out and the boiler was running did you see what looks like white smoke from your chimney ?

    @ethicalpaul, And that what I don't like about inspectors...
    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • cniessen1
    cniessen1 Member Posts: 9
    edited August 10
    FYI I got the quote ($ for replacement with EG and near boiler piping). They quoted twin 2” risers going to a 2” dropped header. Seemed odd to me. Don’t I want a bigger header to slow the steam?  3”?
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 12,362
    @cniessen1

    Have you looked at the install instructions? What size boiler are they installing. 2" may or may not be correct
    clammy
  • 109A_5
    109A_5 Member Posts: 276
    @cniessen1, From OP "(likely Weil-McLain EG6)" would this be a EG-65 ?

    "They quoted twin 2” risers going to a 2” dropped header"
    Nothing in the chart matches their quoted pipe sizes.

    Maybe entertain other quotes. If you have not had the conversation of what you want and expect and why maybe you should. If they understand what you want and expect they may be more receptive to the idea. I'm thinking most homeowners are mostly clueless about boilers. Contractors just offer what they know, right or wrong. Also more labor and material costs will probably be passed along to you if you go above and beyond the norm (or their norm).







    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • Jamie Hall
    Jamie Hall Member Posts: 19,426
    I might add that using a dropped header does NOT mean it can be smaller than the manufacturer's recommended size! Also, the 24" rise applies, in the case of a dropped header, to where the risers turn to horizontal, and is not optional.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • STEAM DOCTOR
    STEAM DOCTOR Member Posts: 1,522
    Definitely time to look for a different installer. Needs to follow manufacturer recommendations at a minimum. Drop headers are great and they use them in every install, but they are secondary to the minimum requirements.
  • cniessen1
    cniessen1 Member Posts: 9
    Thanks all. The installer is quoting an EG-40
    which seems wrong to me. I calculate 400 sq ft of radiator so that seems too small. I want the DHW coil, but that doesn’t affect the sizing does it?  The EG-45 is rated for 388 sq ft, the -50 is 454. We might add a bathroom so my inclination is to go for the -50. 

    When I pushed back on the header size he told me that the -40 has a single 2” riser and the manufacturer specs a 2” header, both of which are clearly wrong. Anyone recommend a good installer in the Boston area?  I’ve contacted two from the companies listed here. One has ghosted me and the other doesn’t seem to want to read the manual. 
  • KC_Jones
    KC_Jones Member Posts: 5,114
    cniessen1 said:

    Thanks all. The installer is quoting an EG-40
    which seems wrong to me. I calculate 400 sq ft of radiator so that seems too small. I want the DHW coil, but that doesn’t affect the sizing does it?  The EG-45 is rated for 388 sq ft, the -50 is 454. We might add a bathroom so my inclination is to go for the -50. 


    When I pushed back on the header size he told me that the -40 has a single 2” riser and the manufacturer specs a 2” header, both of which are clearly wrong. Anyone recommend a good installer in the Boston area?  I’ve contacted two from the companies listed here. One has ghosted me and the other doesn’t seem to want to read the manual. 
    I wouldn't go up to the 50. The 45 rated for 388 still has 33% pickup factor "in reserve". The reality is it's gross output is 512 sq ft of radiation. A bathroom isn't going to add significantly to your number and going up to the 50 is just going to lead to short cycling. If you are comfortable with your 400 number I'd go with the EG-45.

    That does make me wonder though. The installer proposed an even smaller 40, which strikes me as odd. The reason being is it's typical for many installers to oversize, but we pretty much never hear of under sizing. I'm not there so I really can't question your numbers directly, just suggest maybe a recheck wouldn't hurt.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
    ethicalpaul
  • Jamie Hall
    Jamie Hall Member Posts: 19,426
    Did you contact @New England SteamWorks ? If you did, and you haven't heard from them, it's because they are incredibly busy -- they aren't ghosting you. Patience, or give them another e-mail. If you didn't, they're the best in your area/
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    mattmia2
  • pedmec
    pedmec Member Posts: 290
    call medford wellington service. we can get you a quote. 781-395-5279
  • cniessen1
    cniessen1 Member Posts: 9
    Thanks Jamie. They're the ones who are telling me to use a 2" header instead of the manufacturer's spec of a 2 1/2". When I asked about how they sized the boiler they said "Its sized right. This is what we do for a living." When I pushed back and asked about how they actually did it (since I measure 400sq ft and they are recommending a boiler with a net rating of 321 sq ft), they said "The average EDR of all of your radiators matched almost exactly the historical average of all the hundreds of homes we have done through the years." Um, you're saying you sized it because thats about right for every house you've done? They seem to be using a 5% pickup factor, which seems awfully low, but heaven forbid I ask why they are doing that.

    I'm getting a huge vibe of "stop questioning us. We know what we're doing and don't worry your pretty little head about what we'll do. Just fork over the money." The responses feel very condescending, and I don't think thats a relationship that will work.

    Any other suggested people? Or maybe a better contact at NE Steamworks?
  • Jamie Hall
    Jamie Hall Member Posts: 19,426
    edited August 13
    Yes -- Ryan himself. And get him to explain to you -- and to us here on the Wall -- his thinking. I have a feeling that there is something here which is being missed.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • cniessen1
    cniessen1 Member Posts: 9
    Ryan Curran? Thats the person I've been dealing with.

    Here's my email when I got the quote with the 2" header:
    Hi Ryan-
    Quick question. The quote mentioned twin 2” risers feeding a 2” header. I’m surprised the header isn’t 3” to lower the steam velocity to help ensure drier steam. Is the 2” dropped header intentional?
    Thanks-
    -chris


    And his response:
    It’s the size of the boiler that determines the size of the piping we use. The manufacturer’s piping specifications for the EG40 is one 2” riser. We use two, and add a dropped header. It is more than adequate for this size. As a rule, we do not go to 3” until the EG55. If you like however, we could quote a 3” header, or a 2” header feeding a 3” drop.

    So they added a 3" header option to the quote. (As was posted above, the manufacturer's spec says one 2 1/2" or 2x2" (if I'm reading the table properly) for the risers and 2 1/2" for the header.

    So I wrote back:
    Hi Ryan-
    Per the manufacturers specs they indicate a 2 1/2” header minimum for the EG-40.
    https://www.weil-mclain.com/sites/default/files/field-file/EG Series 6 Boiler Brochure 1120.pdf
    Couple more questions: does the quote include the DHW coil? I ask because I see a stand alone water heater as an option. If not please include it.

    Also can you let me know how you sized the eg-40? I calculate 400 sq ft of radiators; perhaps I entered the data wrong? Seems like I would need a 45 or a 50?

    Thanks for your help. I’m trying to make sure the quote makes sense.
    -chris


    and his response was:

    Hi Christopher,

    Here is your updated quote with requested options. The 2" header as originally specified with our dropped header is perfectly adequate, but you are free to upgrade if you wish.

    Your boiler is sized correctly. We do this for a living, to the exclusion of anything else. We are very good at it.

    Lead time is around 4-6 weeks after receipt of deposit. Clicking on Accept will then generate an electronic deposit invoice, which can be securely paid online.


    So I wrote back:
    Thank you for the changes. I’m sorry if I’ve offended you by asking about aspects of the quote that I don’t understand. I’m sure you have a lot of experience but your ability to size the boiler is only as accurate as the information I provided you on the form. I’m trying to understand if I might have entered the data wrong which is why I gave you the sq ft I had measured to see if what I provided was different from what I had intended. Or perhaps you’re using a different pick up factor. I don’t know, so I’m trying to head off any misunderstandings early.

    And the response was
    The average EDR of all of your radiators matched almost exactly the historical average of all the hundreds of homes we have done through the years. You did just fine. There is a 33% pickup factor included in boiler ratings, which was standardized in the 1920s and is excessive.

    Thanks.


    Am I being difficult with him? I'm really just trying to make sure that what they're going do makes sense in light of all of the advice I've seen on the board and in the books.
    Thanks-
    -chris
  • Jamie Hall
    Jamie Hall Member Posts: 19,426
    I would trust Ryan. First, on the header/riser size. There is some debate on that -- different strokes for different follks. I would probably prefer to go with the larger header -- as you have asked and he has said he would do. Others, far more qualified than I, would not feel a need to. I didn't realise that you were looking at 2 risers -- 2 inch is ample for the risers, in my view.

    A similar sort of comment appears on the sizing. Ryan pointed out that you would end up with a pickup factor of "only" 5%. Is this adequate? Most likely. It does depend somewhat on the rest of the system piping -- if there are several very very long mains, a larger pickup might be better. If your mains aren't insulated, then it certainly would be better -- but if the mains aren't insulated, there are a number of other downsides, so much better to get the mains insulated.

    Hope this helps.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    BobC
  • ChrisJ
    ChrisJ Member Posts: 13,258

    I would trust Ryan. First, on the header/riser size. There is some debate on that -- different strokes for different follks. I would probably prefer to go with the larger header -- as you have asked and he has said he would do. Others, far more qualified than I, would not feel a need to. I didn't realise that you were looking at 2 risers -- 2 inch is ample for the risers, in my view.

    A similar sort of comment appears on the sizing. Ryan pointed out that you would end up with a pickup factor of "only" 5%. Is this adequate? Most likely. It does depend somewhat on the rest of the system piping -- if there are several very very long mains, a larger pickup might be better. If your mains aren't insulated, then it certainly would be better -- but if the mains aren't insulated, there are a number of other downsides, so much better to get the mains insulated.

    Hope this helps.

    @Jamie Hall I would like to respectfully add this just so everyone is on the same page.

    What you're talking about is technically piping losses, not pickup. Yes, it has all been lumped into one term unfortunately but I feel it shouldn't be.

    The pickup factor is technically the ability for the system to pick up the building's temperature as fast as reasonably possible as well as taking advantage of increased EDR due to lower temperatures in the space. I.E. oversizing the boiler without causing too much pressure and losses to bring temperature back up after Christmas vacation at a school. This probably doesn't ever apply to residential systems really.

    That's why it was originally called the piping and pickup factor.


    This is why I find it amusing so many on here push for a pickup factor but then tell everyone not to do setbacks with the system because it'll build pressure. No reason for any pickup factor if you're never doing setbacks. Compensating for piping losses absolutely should be always done, but we can calculate that and add it to the load and it really doesn't need to be a set percentage.

    Of course............then comes the arguments that the boiler ratings and efficiencies are a complete lie and I have no clue what to say to that. I haven't figured out a way to accurately measure the output of my boiler.




    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
    ethicalpaul
  • STEAM DOCTOR
    STEAM DOCTOR Member Posts: 1,522
    Once upon a time, I took a few systems and actually calculated the heat loss from the mains and radiator risers. I was curious if the 33% is close to accurate. If memory serves me correctly, 25% or so was the number I came up with. Meaning that there was an additional 25% heat distribution /loss from the piping, above the heat distribution from the radiators. This was a while ago so I may be remembering incorrectly. And was only done to a small sample size. There's also the issue that presumably most houses have oversized radiators. So one does not necessarily need the full capacity of the radiators. It goes without saying that the 33% number is a wild estimation. The heat loss from the mains and radiator piping will change substantially if they're insulated or uninsulated. I have seen systems, with close to equal amounts of radiation, that had different numbers of mains, anywhere from 2-4. I have seen similar radiation on 2 inch mains and on two and a half inch mains and occasionally on 3-in mains
  • ChrisJ
    ChrisJ Member Posts: 13,258

    Once upon a time, I took a few systems and actually calculated the heat loss from the mains and radiator risers. I was curious if the 33% is close to accurate. If memory serves me correctly, 25% or so was the number I came up with. Meaning that there was an additional 25% heat distribution /loss from the piping, above the heat distribution from the radiators. This was a while ago so I may be remembering incorrectly. And was only done to a small sample size. There's also the issue that presumably most houses have oversized radiators. So one does not necessarily need the full capacity of the radiators. It goes without saying that the 33% number is a wild estimation. The heat loss from the mains and radiator piping will change substantially if they're insulated or uninsulated. I have seen systems, with close to equal amounts of radiation, that had different numbers of mains, anywhere from 2-4. I have seen similar radiation on 2 inch mains and on two and a half inch mains and occasionally on 3-in mains


    25% seems very excessive even with completely bare piping.
    I believe mine is around 3000 btu/h with 94,000 btu/h radiation. That's with 1" insulation some of which is in a cold crawl space.

    I thought even bare, it wasn't even remotely close to 33%.

    @KC_Jones Do you remember the numbers by any chance?


    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • STEAM DOCTOR
    STEAM DOCTOR Member Posts: 1,522
    I could be wrong. If time allows, I will try to take some numbers on next few systems 
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 12,362
    I agree with @ChrisJ no setback if the pipe doesn't cool you don't need much pick up unless you have unsual circumstances...long runs in unheated crawlspace, uninsulated pipe, large system connected to a small boiler etc.

    @cniessen1

    I would trust @New England SteamWorks
    ethicalpaul
  • ChrisJ
    ChrisJ Member Posts: 13,258

    I could be wrong. If time allows, I will try to take some numbers on next few systems 

    Me too, that's why I'm wondering if KC remembers.
    It's been a long time.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • KC_Jones
    KC_Jones Member Posts: 5,114
    ChrisJ said:

    Once upon a time, I took a few systems and actually calculated the heat loss from the mains and radiator risers. I was curious if the 33% is close to accurate. If memory serves me correctly, 25% or so was the number I came up with. Meaning that there was an additional 25% heat distribution /loss from the piping, above the heat distribution from the radiators. This was a while ago so I may be remembering incorrectly. And was only done to a small sample size. There's also the issue that presumably most houses have oversized radiators. So one does not necessarily need the full capacity of the radiators. It goes without saying that the 33% number is a wild estimation. The heat loss from the mains and radiator piping will change substantially if they're insulated or uninsulated. I have seen systems, with close to equal amounts of radiation, that had different numbers of mains, anywhere from 2-4. I have seen similar radiation on 2 inch mains and on two and a half inch mains and occasionally on 3-in mains


    25% seems very excessive even with completely bare piping.
    I believe mine is around 3000 btu/h with 94,000 btu/h radiation. That's with 1" insulation some of which is in a cold crawl space.

    I thought even bare, it wasn't even remotely close to 33%.

    @KC_Jones Do you remember the numbers by any chance?


    Your numbers? No I don't. ;)

    I think we need clarity for this discussion so we are all measuring the same thing. Are we talking only the mains, or all the piping in the whole house?

    For my system the mains add about 9.4% and the other piping to the radiators adds about 1.6% for a total of 11%. Since my mains are fully insulated at minimum 1.5" I don't feel they count for much except maybe a cold start that doesn't happen often and would only happen when it's mild and the entire system is essentially way over sized given the mild weather.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
  • STEAM DOCTOR
    STEAM DOCTOR Member Posts: 1,522
    I would think that we would want to count the means and all of the piping. And all the fittings and all of the shut off valves. Basically anything that gives off heat. Of course there is a guess factor involved
  • STEAM DOCTOR
    STEAM DOCTOR Member Posts: 1,522
    @KC_Jones has 11% with well insulated mains. Would not be surprised if that calculated to 25% range without insulation. Just a guess. We should probably start a new thread. 
  • KC_Jones
    KC_Jones Member Posts: 5,114

    @KC_Jones has 11% with well insulated mains. Would not be surprised if that calculated to 25% range without insulation. Just a guess. We should probably start a new thread. 

    No
    It's 11% without insulation
    with insulation it's less than 2%
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
  • STEAM DOCTOR
    STEAM DOCTOR Member Posts: 1,522
    Ok. Got it
  • Jamie Hall
    Jamie Hall Member Posts: 19,426
    edited August 15
    Chortle. On the whole, we al might be smarter to call it the "fudge factor" -- but I don't think anyone would like that. Although pickup factor is, perhaps, not a very accurate term, as it implies that somehow you need an extra boost of heat to get the system warmed up, which you don't, really. Piping loss factor is, perhaps, a little better. The reality, though, is that none of our measurements are that good, if one is honest about it. Does that radiator over there, painted shriek pink and with a load of old magazines on top really put out 240 BTUh per rated EDR value? How about that one painted shiny silver? How about the one which is all rusty but has a convection enhancing enclosure? Does anyone really sit down and measure the total effective radiating are of all the pipes? And then account for the effectiveness of their insulation -- if any -- or for being enclosed in a wall or a floor?

    Then let's look at the boiler. Is it really putting out the number of pounds of saturated steam per hour that its nameplate says? How about variations in installed real efficiency? Slight -- or not so slight -- changes in firing rate? If you're talking natural gas, variations in the BTU per CCF of the gas?

    All that kind of thing accounts for why an educated guess based on years of experience in specific kins of structures in specific geographic locations -- like Ryan's back up there -- is valuable.

    If one had the time one would install the thing -- or tune it -- and then sit there for a few days and adjust the firing rate to exactly match the system demand. Presto. No cycling, no build up of pressure beyond piping friction losses, Everyone goes home happy. Not practical. Or, if there were a market for it (there isn't, for residential uses) install a control system which would modulate the firing rate to control the pressure within a narrow, specified band for friction loss (big commercial boilers should do that -- and power boilers have been doing it, if in the beginning in a somewhat haphazard way, routinely since they first came into use). We do it on residential systems by the simple expedient of turning the boiler all the way off if the pressure gets to be higher than desired, and then turning it back on -- which is a form of modulation, if you will, of the firing rate.

    Oh dear. I sense a rabbit hole looming...

    Edit. For the rabbit hole, go read @STEAM DOCTOR 's new thread and add to it!
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • BobC
    BobC Member Posts: 5,317
    edited August 17
    About 13 years ago i ran the calculations for my system. I live in a small (1100sq ft) two story house with 6 rooms. The EDR of all my radiators is 198 sq ft. This house is 100 years old and the old Yankee builders were not about to oversize anything, any nickle they parted with bellowed long and hard.

    The header comes out of the boiler and circles the center chimney so it's only 14 ft long and the riser is probably 6 ft long. This means the radiator leadout's are long - 10 to 20 ft ea. The calculated area of all the piping (header, main and radiator leadouts and risers) is about 10 sq ft.

    That means my piping accounts for about 5% of the system EDR
    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • ChrisJ
    ChrisJ Member Posts: 13,258
    @Jamie Hall
    Perhaps using a fixed value for piping losses etc is similar to the guy standing in front of a house and seeing how my fingers wide it is to do a heat loss?

    :D
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • Gary Smith
    Gary Smith Member Posts: 405
    I agree with @JamieHall's comments. Also remember, the radiators were sized, approximately, based on the location's design winter temperature and the structure's heat loss. The whole sizing of both radiators and boilers is at best an educated guess guided by experience. I suspect too the pickup factor was arrived at, not by some exact engineering calculation, but by experience of suppliers/installers who hit on the 25% factor as a compromise point at which they didn't get too many complaints of too small or too large boilers. Because of all the factors involved, I don't think it pays, in either dollars or time, to get too precise, because on all days when the outside temperature is higher than the design day (most of the time) the boiler is oversized, on the few days the outdoor temp is colder, the boiler is undersized, so most of the heating season the system will operate outside it's perfectly and precisely selected design point.