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Help Please with Piping and Pickup Factor for Unusual Setup.

SteamHeat Member Posts: 159
What number should I use for Piping And Pickup Factor ???


I am trying to figure out the proper size boiler for an oil to gas conversion.

It is for a single family home Single Pipe Steam with 8 radiators on main floor and 2 on second floor. No radiators in basement.


Using Dan’s "E.D.R. Every Darn Radiator," book and info I just found in another postI have determined the total radiation of the radiators to be 382 sq. ft. I will append the radiator descriptions and calculations below in case anyone spots an error I have made in determining this total.



The house was built in the 1930’s. The basement pipe wrap has been removed by an abatement company. Fiberglass wrap has been placed only in small sections to protect adjacent electrical wiring. The majority of the basement piping is unwrapped and uninsulated. We would like to leave it unwrapped to give heat to the basement and to control voc / mildew odor. Piping appears extensive and circuitous. It is believed that the two second floor radiators (EDR 125 sq. ft.) were added after the original construction. The in-wall pipes to the second floor may have no insulation other than being in the wall. Wall feels warm to the touch in pipe areas when heat is on and there has been noticeable re-plastering.



The original boiler is a Thatcher Red King 1.48 gallons per hour maximum firing rate. Using 140,000 BTU per gallon oil this calculates to be a 210,000 BTU/H boiler. Net Steam on the plate is 380 sq. ft. Obviously efficiency was lower and piping and pickup factor was higher in 1930’s. Even before insulation was removed, boiler had a hard time keeping up with load.



All the radiator vents and the main vent have been replaced with Gorton’s. (Gorton is very helpful on the telephone and Ken is especially nice and considerate.) The main vent currently is a #1. Eventually we will menorah to 2 or 3 #D’s or #1’s whatever will fit, but for now it is just one #1. There are two 4’s, three 5’s two 6’s, and three C’s on the radiators.



It takes the Red King approximately 25 minutes from cold start, ( room temperature about 66 degrees Fahrenheit ), to get the first radiator warm. 40 minutes from cold start to get all radiators warm. Approximately 1 hour to get to 1.5 psi. One radiator, the Sunrad, hisses inside as the pressure gets past 1 psi. It may have a small leak. We’re unsure.



The standard 1.33 as piping and pickup factor seems inappropriate for this setup. Dan in “The Lost Art of Steam Heating” talks about using 1.5 for old houses with no pipe wrapping. William Bobenhausen in “Simplified Design Of HVAC Systems” recommends 1.5 or 1.6 for uninsulated piped houses.


I do not want to under or oversize. I have enough grief with what I’ve got without adding “water hammer” or any other oversize issues to the pile.



382 sq. ft. x 240 BTU / sq. ft. x 1.5 piping and pickup factor  =  137,520 BTU / H   D.O.E. Heating Capacity



At 81% efficiency: 137,520 BTU/H  /  0.81 efficiency  =  169,778 BTU/ H  C.S.A. Input



With 1.6 Pickup Factor I get:  146,688 BTU / H   D.O.E Heating Capacity

                                               181,096 BTU / H   C.S.A Input



If I used the 1.33 Pickup Factor I get:  122,240 BTU / H   D.O.E. Heating Capacity

                                              150,914 BTU / H   C.S.A. Input


Thank you in advance for any helpful advice you can offer.



Radiators Description:

Six of the Ten radiators were painted with room paint in the past and smell really bad when they are brought up to operating temperature. We will strip / remove the paint in the near future but I give this info to make the times listed above meaningful. Radiators Two through Nine have carpeting underneath them. Radiators One through Six have wooden boxes with screen fronts and cutouts at bottom surrounding them.



Radiator One:  American Corto Tube Type

                        10 Tubes Across

                          4  Deep

                        25  Inches Height

                        EDR = 10 x 2.75 = 27.5 sq. ft.



Radiator Two:  American Corto Tube Type

                         22 Tubes Across

                           4  Deep

                          24  Inches Height

                          EDR = 22 x 2.75 = 60.5 sq. ft.



Radiator Three:  American Corto Tube Type

                           20 Tubes Across

                             4  Deep

                           24  Inches Height

                           EDR = 20 x 2.75 = 55 sq. ft.



Radiator Four:  American Corto Tube Type

                           6 Tubes Across

                           3  Deep

                          24 Inches Height

                          EDR = 6 x 2.33 = 13.98 sq. ft.



Radiator Five:   Not Sure About This. It looks like a Column Type to me. See picture.

                          It resembles a Peerless or Princess.

                          But the top endcap says "American Radiator"

                          and the bottom endcap says "Corto Patented 1921"

                          12 Columns Across

                            4  Deep

                           25.5 Inches Height

                           EDR = 12 x 5 = 60 sq. ft.



Radiator Six:     Not Sure About This. It looks like a Column Type to me. See picture.

                          It resembles a Peerless or Princess.

                          But the top endcap says "American Radiator"

                          and the bottom endcap says "Corto Patented 1921"

                          13 Columns Across

                            4  Deep

                           25 Inches Height

                           EDR = 13 x 5 = 65 sq. ft.



Radiators Seven, Eight, and Nine:

                                Arco Convectors in Semi Recessed Wall Boxes.

                                3 Elements Per Radiator, Each 10 Inches Wide

                                Box is 32 Inches Wide

                                Box is 26 Inches Tall

                                Convector is 5.5 Inches Deep Made Up of 3 Rows

                                Convector is 6 Inches Tall

                                On Legs Overall Height of Convector is 15 Inches

                                EDR is by lookup from a post I just found

                                between 26.6 and 28 sq. ft.

                                I am using 27.3 sq. ft. to split the difference evenly.



Radiator Ten:  Sunrad On Legs With Bottom Cutout.

                        18 Inches Wide  8 Sections  7 Openings

                        Seems like 3.25 Inches Deep but cannot measure inside wall.

                        4 Slots Vertically

                        20 Inches Tall

                        EDR = 8 x 2.25 = 18 sq. ft.



Total = 381.88 sq. ft. => 382 sq. ft.




  • Jamie Hall
    Jamie Hall Member Posts: 23,426
    Most boilers

    have an EDR rating as well as a BTU rating; check both.  You're certainly on the right track -- except for one thing: those uninsulated mains in the basement.  You will get quite adequate basement heat after they are insulated.  But -- if you don't insulate them, you may have -- in fact, are rather likely to have -- some serious balancing and water hammer problems, because what happens is that a good bit of the steam will condense in the mains, rather than condensing where it belongs, in the radiators.  I have heard of situations where one or more radiators at the end of longer mains never got heat at all on normal runs, because the steam never made it past the uninsulated main.

    Bottom line: get some good (preferably 1") fiberglass insulation for steam pipes --  it's easy to put on and install it.  You'll be a lot happier in the long run.

    If you do, then your 1.33 to 1.5 pickup factor should work fine.  If still don't want to insulate, you should treat those exposed mains as radiation, and add their square footage in -- and then add the 1.33 to 1.5 pickup factor.

    I might add that water hammer etc. problems are much less likely to be caused by oversizing a boiler -- unless it's really grossly oversized -- than they are by either poor near boiler piping -- or uninsulated or improperly pitched mains.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • SteamHeat
    SteamHeat Member Posts: 159
    edited October 2009
    Heat Leaks Through Insulation ? Insulating Unions ?

    Thank you for your reply. You wrote...

    "You will get quite adequate basement heat after they are insulated."

    Could you elaborate ? If I insulate them, won't that keep most of the heat within the pipe ? Isn't that the idea ? Or is it that some gets out past the insulation, and that heat escaping is enough to heat the basement ? There are no real radiators in the basement.

    What would you recommend for the Couplings, T's and Elbows (135 and 150 degree angles I think) ? I know that Dan has written that even wrapping fiberglass wool around them and securing it with duct tape will work, but I'd like to do it as neat as possible if we're going to do it. In the areas where we are protecting wires I've used an oversized piece just to surround these pipe unions. It probably does not insulate very well. I was just trying to protect our wires from getting cooked.

    Thanks again.
  • Jamie Hall
    Jamie Hall Member Posts: 23,426

    the boiler itself, and the heat loss through the insulation (there always is some) the basement will probably be warm.  Whether it will be warm enough for you, I wouldn't care to say -- but if it isn't, you'll get much better results with putting in a deliberate heat source (lots of options) than depending on uncontrollable heat leakage from your steam pipes.

    There are a number of options for insulating fittings like elbows and T's and unions and the like, depending on the type of insulation one is using for the pipes.  Some types have prefabricated covers.  Some types one can make a cover rather easily by cutting and joining the insulation pieces, or pieces from a section the next size up.  Just depends on what you are using and what's there -- and, often, your ingenuity.  The fiberglass and duct tape works, but it does tend to look a little tacky!  The insulation doesn't have to fit glove tight around fittings, although the tighter the better, of course.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Unknown
    edited October 2009
    Insulate your mains!

    You must insulate your mains! Here's a good article of Dan's on the subject.


    Before I got involved with steam I was having the boiler updated and the piping close to the boiler redone.  I was told the same thing by my local knucklehead, that I didn't need the boiler piping insulated as it warmed the basement anyway.  Well I finally did insulate the near boiler piping and that made a huge difference in comfort and economics,so I can only imagine how detrimental leaving the whole mains and near boiler piping without insulation would be. The only have the wet return non insulated and that keeps the basement quite warm.

    As for mildew, my basement is damp only in the summer when the boiler is off and I'm using a dehumidifier and circulating fan to keep that under control.
  • SteamHeat
    SteamHeat Member Posts: 159
    edited October 2009
    What Are Realistic Run And Off Times ?

    Thank you for the link. It was helpful. I am reading Dan's books as fast as I can. They are excellent. But links to articles that directly address the most pressing issues for me are very much appreciated.

    Even when the asbestos pipe wrap was in place it still took 25 minutes for the first radiator to get warm. That has not changed even with the wrap removed.

    Could someone give me an idea for a correctly sized boiler in a single family house what amount of time should elapse from a cold start till the first radiator gets warm and total time to all the radiators geting warm?

    I am asking this so that when the boiler gets replaced I will have some idea on installation day what to expect when they first fire it up.

    Also, about how long should it take from cold start to get up to 1 or 1.5 psi?

    I am assuming that since I've read that boilers generally cycle 2 or 3 times per hour that a cycle should be around 15 to 25 minutes on and about 5-15 minutes off.

    Am I correct in that assumption?

    Thanks to all for your help.
  • Unknown
    edited October 2009
    Time/Pressure Buildup

    The length of time it takes steam to get to the first radiator only tells you how long it takes for the boiler to make steam and from a cold start your times are about par for the course. At the first radiator there is still a lot of reserve steam which hasn't been exposed to the main as yet so the affect of lack of insulation is minimal. The real comparison would be how long it takes the last radiator on the main to heat up.

    Keep in mind if we didn't have to insulate mains why would we be using radiators? Actually in the first steam systems they did this (just strung pipes down the walls) but found it was not as practical as to comfort and economy as radiators.

    As to how much time it takes to get pressure to 1or 1.5 PSI doesn't really have a viable answer.   In a perfect theoretical steam system, at a fixed ambient temperature, the system will be be providing just enough steam to adequately heat the radiators and build practically zero pressure (just enough pressure to move the steam through the pipes). When you build pressure you are wasting fuel!    Since there isn't such a thing as a fixed ambient temperature throughout the year, we have to design the steam system to keep us warm in the coldest of conditions. 

     If the ambient temperature is very cold and the steam system is cold when you start your boiler, the steam when it enters the radiators will be condensing at an extremely rapid rate when it hits those cold radiator surfaces.(Keep in mind the 1 cubic inch of water makes 1700 cubic inches of steam and vice versa.)  With all this condensing going (with the accompanying vacuum) you probably won't see an increase on your pressure gauge for quite some time. As the radiators heat up, the condensing slows, and after a time the system will gradually build pressure til the pressure control stops the burner. Either that or the thermostat, having had it's set temperature satisfied, stops the burner. When the ambient temperature is warm the radiators, won't condense steam as quickly and therefore  pressure will build fairly quickly. You can see now why time /pressure build up is so variable.

    Here's a post you might be interested in since you want to go from oil to gas. http://www.heatinghelp.com/forum-thread/127940/Stay-with-one-pipe

    Steamhead discusses gas boiler replacement . If it were me I'd pay close attention to the models he recommends. You would then just have to figure out just which one you wanted and the size you need.

    - Rod
  • SteamHeat
    SteamHeat Member Posts: 159
    Pressure Readings May Be / Probably Are Inaccurate.

    Thanks for your reply.

    I just tried reseting my pressuretrol, a P404A type. It does not shut down the boiler. I have been acting as a human pressuretrol, but I thought the pressuretrol was just set wrong. The problem is worse. When the boiler gauge starts to read 2 psi, my brand new Gorton valves start to vent. There is no pigtail on this 70+ year old boiler, so both the pressuretrol and the boiler gauge have been cooked thousands of times and who knows how much crud may be lodged in the pipe that feeds both of them. Therefore the times I stated to get up to 1.5 psi may be off considerably because it may not really be 1.5 psi. Ah the joys of old boilers. :-)

    I am limited to boilers that are available as knockdowns, because like many old houses, the stairway to the basement is very narrow with sharp turns. I am told Weil Mclain and Peerless are my only choices as knockdowns for 175,000 BTU/H.

    The Pressuretrol IS A SAFETY ISSUE! DON'T OPERATE the system until you have pressuretrol and the gauge replaced!  This isn't something you want to mess around with. You want to call a Pro in to check this out for you.  Somethings are better left to the pros!   Don't try to limp by because you're going to get a new boiler and don't want to fix the old one. Besides from an economic standpoint, .you can use this pressuretrol as an upper limit safety on the new boiler which isn't a bad idea in itself.
  • SteamHeat
    SteamHeat Member Posts: 159
    OK. Understood.

    Ok. Understood.

    Incidently, the previous owner tells me now that it has been that way for about the past 5 years possibly longer. The venting of steam from the old ruptured vent valves warmed the house very well apparently, and neither of the previous owners realized anything was amiss.

    To avoid things like this in the future, is there any value in putting a pressure gauge at the end of the main steam line where the main vent ( or vent menorah) goes. Or is that too far down the line to have any value as a safety check?
  • Pressure Relief Valve.

    The excess pressure is probably what wrecked those vents. As you can see by the news on the right of the Ottawa boiler blast, one doesn't want to ignore the safety issues! You have two pressure safeties on your boiler :1. The pressuretrol 2. The pressure relief safety valve. You don't want to operate a steam system with less than these being fully operational.  Obviously no pro has looked at the system in years otherwise he would have found the bad pressuretrol which then makes one wonder as to the operational status of the safety valve. You might want to read this link. It makes you respect safety issues.


    I can't see any benefit of putting a gauge near the vents.  What you need is a good low pressure gauge ( 0-3 PSI) and a bronze pigtail.  residental steam systems never`operate at over 2 PSI.     Lower pressure = Better operation.
  • SteamHeat
    SteamHeat Member Posts: 159
    edited October 2009
    Source For Bronze Pigtail ?

    The articles are sobering.

    I am going to buy the Wika 3 psi gauge from the gaugestore.com that seems to be often mentioned in heatinghelp.com posts. I will ask the plumbing contractor to put it in alongside the pressuretrol on the new boiler.

    Do the pressuretrol and the gauge (and the vaporstat if I can get him to install one) all need their own pigtails? Or is one pigtail with Tee's, nipples, and elbows to connect all the devices sufficient?

    Where is a good source for a bronze pigtail?

    Thank you for the education.
  • Pigtails

    Tees will work fine as you're not using the steam, just "sampling " it.

    Sources for bronze/brass pigtails -   Pex Supply , Mc Master Carr

    Sometimes you'll see bronze pigtails listed as "red brass"

    McMaster has a greater assortment of configurations - straight  & 90 degree.

    If convenient ,you want to try and mount you pressuretol, gauges etc as high as possible on the boiler to keep them out of the water.

    - Rod
  • SteamHeat
    SteamHeat Member Posts: 159
    Red Brass.

    Thanks for the mounting tips and source info.

    I'll get the red brass from McMasterCarr. I can't find bronze listed at either. Maybe I'm not searching correctly.

    Bronze and Red Brass are described as different on McMasterCarr 's website.

    Bronze is described as copper + tin.

    Red Brass is described as copper + zinc.

    But since they look similar, I would not be surprised if vendors use the words interchangeably. :-)

    The Help Is Much Appreciated.
  • djthx
    djthx Member Posts: 52
    Thatcher Red King


    I also have a Thatcher Red King "Oil" Boiler that was (somewhere along the line) converted to a gas-fired boiler.  However, I can't seem to find the boiler's specs.  Can you please let me know where to find them (pictures or links will be great)?

This discussion has been closed.