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Replacing oversized 1955 Steam boiler with Multiple with pictures!

JUGHNE Member Posts: 8,317
edited May 11 in THE MAIN WALL
Finally get to install new boilers. My school has given me the job of replacing the existing Kewanee.
For part of the building, 2 pipe convectors, I want to install 2 PB 63 series units.

There is 1342 EDR connected to this main.
I have done heat loss on the 7 rooms--area of 4172 sq feet-- that come up to be 172,859 BTUH which comes out to be 719 EDR. This is averaging 41 BTU/FT.
We are at 7075 HDD with -10 degree design ODT.
Before envelope improvements the design was 60 BTUH/FT.....1950's structure.

Five other areas that are heated include North has heated building attached, not opening to outdoors anymore.
East and South entries to outdoors.
Three story stairwell that now has reduced/upgraded or closed up windows.
The entries will retain the original EDR....the stair well will get 60% of original.

So with 719 EDR for the 7 rooms and 271 EDR for the 5 other areas, I see a total of 990 EDR needed.

In 2013 all traps were replaced and orifices installed in supply valves sized by the 2 PSI chart.

The boiler now runs at 2.25 PSI max and being meter clocked at 1,400,000 BTUH, it short cycles of course, even with the other 1 pipe building zone calling (414 EDR=99,360 BTUH).
The 1 pipe building will get a separate boiler.....another posting.

So with 2 boilers feeding the 2 pipe system needing 990 EDR, what would be the best guess on the 2 sizes? PB 63-04 is 458 EDR-----63-05L is 533 EDR----together is 991.

I want to stage these with pressure controls, both fire for recovery from minor overnight and week end setback. Which should be main lead boiler and which be 2nd recovery boiler?

Or should the sizes be farther apart but still adding up to near 990?
Our average daily temp in January is about 25 ODT.

There is 341' of steam main in a 350' tunnel.
Starts out 4" decreasing down to 2" EOM.
Fifteen 90's in that length.
Only 166 EDR of convector was removed and capped 24 years ago, it was in the first 4" main.
Otherwise all original EDR of 1342 convectors are still in use.

This piping was install new for a coal burner.
Hoping to run very low pressure on boilers with this piping sizing (coal design).

The orifices would need to supply only 69% of the 7 rooms of convectors.

So where does the pick up factor land for this situation?
Steam piping will get new 1" FG in the future.
All asbestos was abated last year.

Thanks for your attention.


  • leonz
    leonz Member Posts: 392
    As novice I have to ask, this do you have room for a dual drop header set up where one drop header feeds into the larger drop header to make more dry steam and deliver it faster(I think I have that right).
  • retiredguy
    retiredguy Member Posts: 408
    edited April 22
    MY only comment is that the sizing of a steam boiler is by counting the installed radiation and piping heat loss with little regard for the building's heat loss. Are you going the resize the radiation? I bet that that Kewanee is a beauty.
  • jumper
    jumper Member Posts: 1,623
    Pickup is for pipes not terminals, I believe. With multiple boilers you can effectively down fire after pipes are warm. Unless it is too far away consider incorporating other building with main boiler room.
    JUGHNE Member Posts: 8,317
    Leonz, yes the plan is to have a double drop header on each boiler with those then double dropping into a 4" header going to the steam main.

    Retiredguy, yes I understand the standard method of sizing boiler to connected EDR; however the existing convectors will be limited to only about 70% of rating with the use of orifices installed in the supply valve unions. This then reduces the radiation by then 30% of the convector just become part of the condensate return piping, steam never gets to the trap. I have done a couple of large jobs with no guts in the traps. As long as the pressure stays within the design parameters the steam only goes partially across the emitters and is enough to heat the room. The returning condensate is actually cool in some cases.

    Others have done this boiler sizing method with success. Some have dropped pick up factor to a factor of 1.1.

    IMO, I believe most steam systems have extra radiation connected, especially those designed for coal as this one is.

    Jumper, with the 2 boilers staged I can oversize on the 991 EDR somewhat. Real question is how much is needed for average winter day after pipes are heated and system is up to pressure. What size of primary boiler that would not short cycle much after warm up?

    The other building is from 1920's, is one pipe CI steam. It will have it's own system, boiler in same room as these 2. That part of the school may someday become storage area.....3 elevator
    JUGHNE Member Posts: 8,317

    JUGHNE Member Posts: 8,317
    edited April 23

    Actually built in 1958, was coal burner until late 1960's.
    The only thing on the gas train I have replaced in 10 years was the pilot solenoid gas valve.
    The shaft on the top of the diaphragm that runs the air shutter is leaky making the room a little gasey .

    I guess beauty is in the eye of the beholder.....I will miss her a little bit, but not for long.
  • mattmia2
    mattmia2 Member Posts: 3,008
    That looks like it was an antique when it was new. Are there zone valves on the convectors such that it rarely sees the full load?
    EBEBRATT-Ed Member Posts: 9,014

    To me which boiler is lead or lag doesn't matter. I would keep the sizes you picked that way if one failed you will still have about 1/2 capacity.

    The trick with two boilers is to control the water lines which is difficult in my opinion with out a boiler feed tank and 2 overflow traps.

    The idle boiler with it's steam supply valve open will fill with condensate. Two boilers if there returns are connected below the water line require check valves per ASME Code (a leak in one boiler will drain the other boiler)

    Do you have or are you planning on a feed tank or is this gravity return?

    I have a drawing for a manual lead lag system with manual switches so you can run both boiler lead, both boilers lag or either 1 lead and either one lag if you want it

    You can also do it with an alternating relay so it will alternate the lead boiler if you want
  • dopey27177
    dopey27177 Member Posts: 485
    The building load is little to small for multiple boilers,

    From what you describe about the radiator valves being re-orificed my bet is that the the system originally ran at about 1 Psi cutout and .5 psi cut in.
    Your real problem is no insulation.

    JUGHNE Member Posts: 8,317
    There are 2 zone valves--4" HW probably from the 1950's--motors replaced several times. No zone valves for new system....2 boiler systems instead.
    Now both are stuck partially open......another nail in the coffin for the old girl.
    Even with both valves open there is only about 1750 EDR (420,000 BTUH) connected.
    Boiler clocked at 1.3 to 1.4 Million btu.
    Between radiation removed and building improvements this is what is left.
    I count about 15 capped take offs. Boiler was sized correctly in 1958.

    Ed, will have feeder pump with electric solenoids and overflow traps for each boiler.
    I will have vaporstat on 2nd boiler to have it drop out on pressure rise. Will be an adjustment hobby next winter. School is only about 6 blocks away.

    Jake, true this is a small load. But we all know the single boiler is too big most of the time. The 2 small boilers cost about what a single larger one would. The smaller ones are package units. A single large one is split block and additional labor.
    There will be more cost in piping but I believe better efficiency and control results.
    Plus the stand by boiler in event of one failure.

    There were fairly large orifices in the convectors, original to the 1950's building.
    So with a coal fire I am thinking low pressure such as you suggested.
    Piping will get insulation in the future.
    JUGHNE Member Posts: 8,317

    Do you see the pressure relief screen door spring on the burner door?
    I was told that the latch was ground off and the spring held the door shut, in the event of serious delayed ignition that door could then be forced open rather than blow the breeching apart.
  • mattmia2
    mattmia2 Member Posts: 3,008
    Does that lever contraption on the gas valve allow it to modulate or is it just some sort of slow opening mechanism?
    JUGHNE Member Posts: 8,317
    The lever opens the air shutter to the burner.
    It is a slow opening diaphragm valve controlled by the small solenoid valve mounted on the top.
    The lever is moved by the shaft coming out of the top of valve.
    The shaft seal is leaky and just another reason of many to replace the boiler.
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,477
    Would you consider using one large header, into which both boilers feed with drops?
    Also, maybe Gifford loops would prevent the condensate from entering the lag boiler, by virtue of their higher point of connection.
    What will control the boilers-interior sensor, and multistage VisionPro?
    For sizing the boilers, “A” boiler sized to average heat loss, and “B” boiler sized to the difference between “A” and total EDR? In the morning, both boilers would fire until pressure, or thermostat cuts off the lag boiler.
    When the polar vortex hits, the thermostat cuts “B” back into operation. —NBC
    JUGHNE Member Posts: 8,317
    Each boiler would have it's own double drop header with supply off of it double dropping in larger header with F&T on end to remove any carry over water back to feeder pump.

    Dry return is only 9" off floor so feeder pump is needed. MM 150 LWCO pump controller on each boiler. Solenoid valve on each boiler.

    So far temp control will be single Tstat. Could need upgrade in the future.
    Pressure control to drop out lag boiler.

    Pegging average heat loss.... to be determined.

    Adjustment of pressure switches could pick smaller or larger boiler to be main lead, "A" boiler. TBD.
  • The Steam Whisperer
    The Steam Whisperer Member Posts: 657
    edited April 24
    This is very similar to the heating plant for my church I installed last spring. Originally 2.100,000 input LGB, 3 zones, 2 direct steam and 1 steam to HW convertor. We put in a small hw boiler to handle warmer weather heating for the hw system a few years ago so the main boiler would be kept off about 1/2 the heating season with the main zones in setback. Instead of installing 2- PB64-07 we installed 2- WM380. Since the 380 is only 350,000 input and the tapping are 4 inch, there is very low velocity in the riser, so little backpressure and little carryover. We used a single tapping on each boiler to a common 4 inch header. The PB would have required separate headers..... a whole lot more piping. We also orificed the system at the same time and balanced the steam flow to the steam/hw heat exchanger. The boilers are staged via relays and 2 stage thermostats. The HW boiler is brought on only when the thermostats go to second stage... this reduces the load on the steam boilers by closing the steam zone valve to the HW heat exchanger when the steam zones need more heat.

    Found a picture!
    To learn more about this professional, click here to visit their ad in Find A Contractor.
    EBEBRATT-Ed Member Posts: 9,014
    edited April 24
    Sounds like you have a good start on it!! Have fun!!

    One diaphram gas valve a little scary by today's standards!!!!!
  • mattmia2
    mattmia2 Member Posts: 3,008
    I think the thing to do is to think about what gives you options to change the controls and change how it behaves if you don't like how you configured it the first try.
  • clammy
    clammy Member Posts: 2,655
    Personally I think I would have looked again at a wet base boiler and installed a 2 stage gun either a 80 series Weil or a peerless . I like commercial boilers for commercial jobs seen guys do what your suggesting and in most cases there where a lot of issues low water content addition of f and t traps condensate pumps and of course flooded boiler after the boilers where shot We installed a semi commercial boiler removed condensate pumps and f and t installed a false water line and there’s fuel cost went down and a lot of the issue related to lower water level and small water content of the boiler and steam reaching dry returns due to lack of water seals disappeared . Up side much less near boiler piping and a similarly water line height ,either way w a 2 stage gas gun it would down fire after filing system w steam on pressure . But this is just my take on it not that I don’t ever think of using 2 steamers but when you really do the number w up keep and maintaince and not to mention the extra piping and the extra manual reset lwco and manual reset pressuretroll it s always cheaper to do one then two . That’s just my take in any case sounds like a great job and in any case we know that it will be installed properly either way . Peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating
  • ethicalpaul
    ethicalpaul Member Posts: 2,993
    I love your sizing process and reduction of the pickup factor. Wow, 15 capped supplies!! I get the idea one of your primary concerns is you don't want the system to be oversized and I agree completely. I like the backup the thinking that in normal operation just one boiler will be operating?

    May I ask about your double drop headers? Does the manufacturer suggest that piping? If not, do you suspect that the manufacturer is cutting it too close with their supply pipe sizing vs steam generation? I would be disappointed with a manufacturer if their recommended piping causes carryover, and in my visible boiler (admittedly tiny tiny compared to yours), I never see one drop of carryover. But maybe in larger boilers carryover occurs (I don't know hence all my questions)
    1 pipe Peerless 63-03L in Cedar Grove, NJ, coal > oil > NG
    JUGHNE Member Posts: 8,317
    Thanks to everyone for responses, the more discussion makes one think of other scenarios.

    Clammy, the boiler room is in the 1/2 basement of a 1920 3 story building.
    That older building has a 1 pipe system that will get a separate boiler.
    The 2 pipe system that the 2 boilers are feeding is a 1950 single story building built around the 3 story one.

    As far as needing a boiler feeder pump, (there is currently a cond pump for the old Kewanee...which holds about 100 gallons).
    The 2 pipe main is in a pipe tunnel, the 4" steam supply main loops up to 9.5' and then down to 40" (the ceiling of the 4' x 4' tunnel) and after 341' of supply the dry return is 9" above the boiler room floor.
    So to me I see the necessity of the feeder pump.
    Open to any other possibilities.
    I do have a low inlet feeder pump on order, it has the inlet about 6" above the floor.

    I am doing 2 boilers for the turn down ratio.
    The redundancy of 2 boilers available, 1 unit could heat the building most of the time.
    Also simplicity of parts to replace on a spark ignition system, much less than today's FAF. In the future any HVAC person could get the things to fire.
    The closest commercial boiler company that might work on gun systems is 100 miles away.....other than myself who services a handful of guns in my area.
    When this is completed I will have turned 72. So 10 years from now I may have forgotten how things should work.

    And thanks for the confidence Clammy.
    JUGHNE Member Posts: 8,317
    edited April 26
    Paul, hopefully my sizing calculations will prove out to work.
    There is some controversy of sizing steam boilers to heat loss versus connected EDR. I think there are only about 3 other Wallies who consider doing this.

    Of the 15 capped takeoff's 13 of them are on the 1 pipe system that will have separate boiler, only 2 capped on the 2 pipe system. Hoping one boiler will do the job after pick up is done.

    PB recommends individual boiler headers that then feed into a common header (using drop fittings) that feeds the 4" steam main.

    The double drop headers for the boilers are optional.
    Actually a single 3" riser off of each boiler would suffice.
    But I plan on 2 X 2" drop header on each boiler.
    Just a step up beyond I&O manual instructions.

    Just to show how much I have (over) analyzed this, close to home system, over 10 years or more: there is 341' of steam main that weights 2,395 pounds.
    Plus 19 hefty Tees.
    That piping has 16.7 cubic feet of air in it.

    I am fortunate to have the original blue print that shows all the piping for the 1950's building. It included the EDR, pipe sizes for supply and returns and lengths.
  • ethicalpaul
    ethicalpaul Member Posts: 2,993
    That's great that you have all the plans!

    I think doing the heat loss is totally said you can effectively reduce the EDR of any radiator by controlling the steam flow to it (if I read that correctly), so why not find out the real needs of the building and supply those needs?? Only 3 people here would do that?

    And the same can be done in residential homes, even in one pipe steam. Just do the heat loss, then either install boxes, or other insulation methods to the oversized radiators to reduce their EDR down to what each room/space needs. This can be made easily adjustable over time for comfort. Then install a boiler for the new, more correct EDR values.

    Thanks for sharing all this great information about this job! I look forward to the photos!
    1 pipe Peerless 63-03L in Cedar Grove, NJ, coal > oil > NG
    JUGHNE Member Posts: 8,317

    This is the nameplate on old boiler, very easy to see on the front.

    My best estimate of required BTUH's is 590,000.

    There were 2 other "estimates" for replacement.
    One was to use PB-GLC 11 sections, rated for 2,056,000 BTUH input, with power burner. Lo-Hi-Lo fire. I don't know how low this burner could go but fairly sure it would still be quite over sized.

    2nd company named a similar boiler size with power burner.

    Both included a 117 gallon boiler feed pump, the tank is 60" tall.
    The obvious wet return is 9" above the floor.

    Both companies are 100 miles away and considered the big dogs in their area.
    This type of expert company (from 200 miles away) had told the custodian years ago that he had to run 5 PSI has been working with 2.5 PSI for 10 years now.

    So it seems that oversizing is still popular.

    EBEBRATT-Ed Member Posts: 9,014
    edited April 29
    Estimating is a tough business in itself.

    You have had the opportunity to "live" with the building so you know what it needs. Most that come in to estimate can't afford to take the time to "learn" the building so they replace like for like.

    Not excusing it, it's just a fact.

    I did something similar once. Had a 5 story apartment building, steam, oil fired There was no way to access all the occupied units to do a radiation take off.

    We had a nasty cold spell (lucky). On my way to the office every morning I would stop and stick the oil tank and see how much oil they used. I did this for about a week.

    We also had some oil delivery records we could compare to the degree days.

    Ended up with a boiler just over 1/2 the size of the old boiler

    Worked out fine
    JUGHNE Member Posts: 8,317
    I understand these people had maybe 2 hours on site.
    But to ignore the nameplate and double the input seems outrageous.
    A walk around the basement of the old building would have shown about a dozen capped take offs, then a visit to the 4 class rooms would reveal only 4 radiators in use.
    There is even a third main, 2 1/2" pipe that goes into the tunnel and is capped.
    The custodian who accompanied them was aware of all of the above.
    A few questions posed to him would have revealed a lot. IMO, this is who you want to ask about the system, many times the person on site, being there maybe 10 years and hearing everything I pointed out to him in that time, does actually know something.

    I guess in my mind with only the 2 hours to investigate, I would have figured a boiler of the same size and included verbiage in the estimate that, if we would be considered for the project, further analysis would have to be done to the system.....what is quoted is the high end and possibly a lower price may be the result.

    What really stood out was the 60" tall feeder pump tank....looking at the wet return being only 9" off the floor.
    I did locate a feeder pump tank that has a 6" high inlet, a lot more money, but what other options would there be?
  • mattmia2
    mattmia2 Member Posts: 3,008

    I think doing the heat loss is totally said you can effectively reduce the EDR of any radiator by controlling the steam flow to it (if I read that correctly), so why not find out the real needs of the building and supply those needs?? Only 3 people here would do that?

    I think that is partly a function of that only being easy to do with heating related items on 2 pipe systems and there aren't a lot of residential 2 pipe systems and commercial 2 pipe systems tend to have zone valves which probably effectively reduces the peak size of the system.
    EBEBRATT-Ed Member Posts: 9,014
    edited May 1

    I know that Shipco can build you a tank that is not a stock tank. 9" off the floor is tough, if you raise the water line and come up into the tank you would make a trap and have to vent the return of air.

    The other option is a tank that is flush with the top of the floor.

    Or a condensate pump in a pit and have it feed the feed tank.MOre $$$$ I know From Shipco web site:

    Type DUMC
    Durable Underground Make-up Stainless Steel Boiler Feed Unit
    Boiler Feed Pumps & Surge Tanks

    A Durable Underground Make-up boiler feed unit with stainless steel receiver uses a patented design to pump water in applications where the return piping is at or below floor level. The underground basin is made of stainless steel in various sizes. Pumps are located above the basin cover plate allowing for easy maintenance with disturbing the cover plate. The propeller shaft and it high temperature patented (U.S. Patent #4,932,846) bearing design is more durable and simpler than most other designs.

    An electrical solenoid make-up water valve with float switch control is standard. Units available in either simplex or duplex configurations; motors are 3500 RPM, single or three phase. Unit equipped with bronze-fitted Model U pumps fitted with industry standard motors and with mechanical seals rated for temperatures up to 250°F. Higher temperature seals and special faces available upon request.

    Other accessories include gauge glass assembly, thermometer, inlet strainer, butterfly isolation valve, low-water cut-off and electrical control panels.


    Type DMS-MU & DMSS-MU
    Durable Steel/Stainless Steel Boiler Feed Pump, Low Inlet
    Boiler Feed Pumps & Surge Tanks

    Type DMS-MU and DMSS-MU use a patented design pump which handles up to 210°F condensate with a 2 ft. NPSH pump. Type DMS-MU is made with a rectangular steel receiver while Type DMSS-MU has a rectangular 300 series stainless steel receiver. Each has an inlet height of 6-1/2" from floor to centerline available to help with extremely low inlet issues. The top-mounted, close-coupled pump is bronze-fitted with an industry standard motor and utilizes a propeller shaft with its high temperature patented (U.S. patent #4,932,846) bearing design. Type DMS-MU and Type DMSS-MU are available in either simplex or duplex configurations with a variety of options. These units also eliminate the need for pump isolation valves since the pump is mounted on top of the receiver. As an added advantage these units can fit into a smaller floor space area than conventional Type DMS or Type PMS units. The standard mechanical seals are for 250°F. Higher temperature seals and special faces available upon request.
    JUGHNE Member Posts: 8,317
    Ed, thank you for your legwork.
    I had hoped I had made it clear that I do have that very DMS-MU on order.
    It has the 6 1/2" inlet AFF. Takes up a good size foot print of 30" X 30".
    And yes is more money.....but I don't want to dig a hole in the room....might hit water. ;)

    Don't like that it has an electric fill valve though.
    The float controlled water filler seems simpler.
    Maybe that application is not doable on a tank only 9" tall.

    The steam main itself is only 40" above the floor and the dry return is 9" above floor.
    Piping is in tunnel, steam main goes up over and down to enter tunnel.
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