Sizing a Replacement Steam Boiler Based on Building Heat Loss-NBP w/3 Drop Header Piping Diagrams

JUGHNE

I need to do a proposal to replace a 1955 schoolhouse Kewanee NG , nameplate of 1,080,000 BTUH input.
It has 2 zone valves (1 for old 1 pipe and 1 for newer 2 pipe) with a total of 1756 EDR connected.
Because of building improvements and radiation removed we are just about oversized by 2X.

First questions are about doing the room by room heat loss.
Using the simple Guide 2000 part 2 from the I=B=R guide, I am getting about 36 to 48 BTU/sq foot.
Also working backwards from installed EDR X240 and comparing that to my results I get a fairly consistent indication of new heat loss to be 65 to 73% of installed max EDR available.

The big variable is always the infiltration factor. I used 1 1/2 ACPH (.027 factor).
The build is fairly tight for it's age. In all the 6 class rooms to be heated, 168 sq feet of single pane windows have been replaced with insulated 2 x 6 walls that have 40 sq feet of double pane casement. The remaining walls are 12" of brick.
The ceiling has went from 1" 1955 roof "insulation" to 12 inches of blown in attic insulation.
Room sizes are from 620 to 814 sq feet with 10' ceilings.

So far does this seem to be way off base? Thanks in advance.

Mike_Sheppard

From what I have read, you size a steam boiler to the connected radiation, not the building heat loss. You’re not heating the building with steam you’re heating the pipes and the radiators. If you cut the output of the boiler in half but still have the same amount of radiation, you’ll be condensing steam before it can even reach all the radiators.

You would have to reduce the amount of radiation in the building.

Maybe this article can offer some insight. It talks about your situation.

https://heatinghelp.com/systems-help-center/taking-another-look-at-steam-boiler-sizing-methods/

JUGHNE

6 years ago I installed orifices in the 2 pipe convectors. They were sized for about 80% of connected EDR.
In effect the EDR (radiation) is already reduced, had I know more, the orifices would have been sized smaller than that.

This method has been used by others, I have done it on several other jobs without changing out the boiler.
Now I hope to size the boilers based on building heat loss.
Thanks.

The Steam Whisperer

For the two pipe, if the pressure doesn't get up to the 80% design pressure the convector output will be downsized. The one pipe steam side is the side that can be challenging. However, if the system is rather evenly split between sides and everything is high mass, you can probably install a timer to switch from one zone to the other every 30 minutes and this will allow a smaller boiler to be installed.

Steamhead

Why not install two smaller boilers, one for each zone? That way you could run each at the appropriate pressure, and only heat part of the building if needed. Here is one such job we did, and they love it:

https://forum.heatinghelp.com/discussion/167918/splitting-a-church-steam-system

https://forum.heatinghelp.com/discussion/170284/all-steamed-up-inc-installs-a-weil-mclain-480-steam-boiler-with-a-carlin-commercial-gas-burner

https://forum.heatinghelp.com/discussion/170152/weil-mclains-sgo-steam-boiler-installed-and-fired-with-a-carlin-ez-gas-burner

JUGHNE

David, I am not sure what you mean by 80% of design pressure.
In my mind I have already downsized the convector EDR with the orfices. Thank you.

Steamhead, yes, I plan to install a boiler just for the old single pipe, it is CI rads, about 414 EDR. I just did not want to clutter up my first posting with that info. The zone valves will to to heaven with all Cycle guards.

Actually I want to install 2 boilers for the 2 pipe side, hoping that they can be staged by pressure controls once the pressure is up.
Double drop risers on each into a 3" header with 2 3" risers dropped into a 4" header feeding the existing 4" main.

So far it is looking like 2 Peerless 63-05's or even 63-05L for the 2 pipe side. Thinking of parts interchangeably and redundancy.
Most boilers I work on are of the 1M size and old. As I look at them I keep thinking that just one leak will condemn them.

The single pipe side will maybe get a 63-04.

These seem friendly to me, only about 700 lbs for the bigger ones.

I don't need to work, but just want to do this install.
Just short of 70 by a month.

If the price isn't friendly then they can look elsewhere.
No one out here even wants to look at steam.
And if they do they are not 6 blocks from the school.

But what do you think of my heat loss calc's with the back engineering based on existing EDR and the 35-45 BTUH/Foot??

JUGHNE

Pictures are always good, I always ask for pictures

The Steam Whisperer

Orifices will flow a certain amount of steam at particular pressure difference. So if you sized the orifices to supply the radiators so they were 80% full at 2 psi on the coldest day of the year, then reducing the max pressure to 1 psi will drop the capacity of the radiators to 60% full. Running the system at a maximum of 1 psi will effectively reduce your radiation load to only 60%. Varying the supply pressure to the orifices will vary the amount of heat delivered which allows you to run outdoor reset on a steam system pretty much like any hot water system.
This works very effectively with stage fired equipment or modulating burners. We've done both.
I am working on doing this at my own church where we will eventually be replacing a 2,100,000 btku/hr input Weil LGB. We have already pulled a small load off by installing a 150,000 btu/hr input hot water boiler to feed a 1950's wings radiant floor that was on a heat exchanger. My calcs show installing two boilers, one at 275,000 input to carry the main building when in setback nearly all winter (45F interior temps and about 90% of the heating season) , with an additional 575,000 input boiler for warm ups on Sunday morning and for extra capacity in extreme weather. The orifices will allow us to run the low input boilers and still provide even heating to all the radiators and convectors since the orifices will meter the steam to each heating unit based on the pressure difference.
Orifices allow you to do amazing things with two pipe systems. On one of the earlier larger buildings we worked on, The heating plant was split into two boilers: 1 hi -low at 500,000 and 1,000,000 input and the second modulated from 1,000,000 to 2,000,000. In typical winter weather we were able to run at 500,000 input to provide silent, steady and even heating to the whole complex.

Steamhead

Hmmmm..... if you like Peerless, you might want to check out the SC-06 for the 2-pipe zone and see if any of the gas burners available have lo-hi-lo- firing. This would certainly simplify the steam piping.

The Steam Whisperer

I'e been staying away from the SC series.... too little water and too little steaming space with too much flame. Almost any impurities and you start having water line troubles. I think the Peerless CC is just a rebranded Smith 19 HE and would probably be a better choice. However, if set up properly, a couple stage fired atmospherics will probably save as much fuel as power burner. When we used to do more work on Hot water, stage fired atmospherics would save a lot of money versus the large single power burner boilers they replaced. Of course we also were running less overall input and added outdoor reset and often were not keeping the boilers hot all the time like the old,large water content boilers.

Mike_Sheppard

I never heard of using orifices and reducing boiler capacity. Pretty neat.

JUGHNE

Mike, there is a posting with good discussion by many about this, also is the orifice chart that i used for sizing.
Look for the title posting "Steaming" by Steve Minnich 3-12-19.

The first I ever read of this was Henry Gifford....How to Make a Two-Pipe Steam Heating System Really Work.
IIRC, he just almost eliminates the pick up factor to size a boiler after the orifice install. (from 1.6 to 1.1)

In 2 projects I was able to remove the rad steam trap guts as with the orifice on the inlet the steam would not get to the end of the rad.

The Steam Whisperer

I first came across the orifice concept with the Moline Vapor/Vacuum systems...Orificed radiators with to traps. These system work very well after 100 years. Also, if you dig into the literature in Dan's books you'll see that a number of manufacturer's ( Dunham for one, IIRC) were starting to use orifices because they balanced the system so well. I starting using them about 12 years ago and have them on a number of systems....some standing radiation, some convector, a number of formerly vacuum pump systems, and some running outdoor reset on the boilers. There are sometimes distribution issues when running boilers at very low firing rates.... typically under about 25 to 30% of the orificed radiator capacity. If you look at the piping you will often see why... such as some mains feeding off the bottom of the supply instead of the top. WE have found if your run at higher firing rates to "prime" the system with steam on cold start ups and then drop to the outdoor reset low firing rates things work well.

JUGHNE

David, that is one reason to use 2 smaller boilers in this case.
Hoping to stage the units with pressure controls.
Now the Kewanee runs up to 2.25 PSI to cycle off.

Just an idea of short cycling;
12-6-2013;.... -20 ODT overnight......-10 ODT daytime;
Building IDT average of 70 degrees
Boiler cycles:
4 minutes fire on
140 seconds off
4 minutes fire on
140 seconds off
The ODT design temp I use here is -10.
7246 HDD.

That short cycling is certainly showing the durability of the old HW RA890F and gas valve. Hopefully it makes it one more winter.

Steamhead, I am talking Peerless because my boiler Guru at the supply house (220 miles away) handles PB and Burnham.
The Burnhams have gotten a lot of bad reviews on the Wall.
Haven't seen much negative about PB.

And the Guru is a Wallie also and does post here.

Now another pressing issue; the dry return for the 2 pipe comes into the boiler room and connects 9 1/2" above the floor to the original cond pump. I will need to have a feeder pump.
These seem to have a high inlet connection.
Any ideas for this? Other than a pit?

The Steam Whisperer

If you could cut the firing rate of the old boiler it would probably really help.

Mike_Sheppard

> @JUGHNE said:
> Mike, there is a posting with good discussion by many about this, also is the orifice chart that i used for sizing.
> Look for the title posting "Steaming" by Steve Minnich 3-12-19.
>
> The first I ever read of this was Henry Gifford....How to Make a Two-Pipe Steam Heating System Really Work.
> IIRC, he just almost eliminates the pick up factor to size a boiler after the orifice install. (from 1.6 to 1.1)
>
> In 2 projects I was able to remove the rad steam trap guts as with the orifice on the inlet the steam would not get to the end of the rad.

Thank you, I will check it out!

JUGHNE

David, the old 1,000,000 BTUH boiler has only 1756 EDR remaining connected after years of remodeling.
So only about 529,000 is needed.
And also the 1 pipe is in a 100 year old tower with good north and west wind exposure. The 2 pipe is south and east with little wind exposure.
So the small zone of 414 EDR may call more than the 1342 EDR warmer building.
And the jacket losses are quite high. The flue pipe is 20" going into a pretty tall chimney.

This thing used to be a hot boiler sitting at +5 PSI waiting for zone valves to open. Since 1967....when converted from coal.
I redid controls about 10 years ago to change that.
Just think about 40 years of gas burned on the off cycle.

If the plan falls thru I will look at removing some burners and down firing.

When you orifice down a 2 pipe system and change out the boiler what pick up factor would you use?

The Steam Whisperer

If I see a lot of larger pipes ( or uninsulated pipes) I bump the pickup factor to 20 to 25%...which sounds like that this may be your case... lots of removed radiators but the pipes are still there. For more typical systems I give it 10 to 15%. I've seen that Henry Gifford uses 10%, but if you do set backs you probably want some more capacity to help bring spaces up to temp more quickly. Those cold rads in cold rooms can condense a lot more steam, so you might as well give it to them. I figure for the typical system you need to add 7% just for piping losses, so giving it some extra for recovery from setback can be a good thing.

JUGHNE

David, thanks for your input.
I have all winter to contemplate the numbers....almost too long to overthink things. But I enjoy doing this. The best hobby I ever had and sometimes get paid for it.

I need to come up with dollar amount within 3 weeks, main cost other than boilers is piping materials and that will stay close to the same with the boilers i am considering.

My brother restores cars as a hobby and that is a definite money pit......this however pays something.

Each main starts out at 4 ", the larger pipe with less load certainly allows less pressure but I understand more cold piping, maybe not needed, to pick up.
So having 2 boilers set up in staging is a definite advantage.
They will do a little set back overnight and certainly on the weekends.

The Steam Whisperer

If these two boilers are serving a single zone with orifices in the supply valves, then you can probably just use a two stage thermostat to stage them. I have a big 10,000 sq ft home that has been working that way for about 10 years now. No need to stage them on pressure.

JUGHNE

Thanks, that is an idea to consider.
Though limited conductors at t-stat.
Difficult to add more.
Also t-stat is accessible to everyone

The Steam Whisperer

If you want to keep the thermostat less accessible, just set a sensor where its at and put the 2-stage thermostat downstairs. That's what I just did at my church.

JUGHNE

Adding this diagram for all considerations.
The pump feeder-LWCO is still a little iffy location wise.
I have been doing search here for drop headers, more than 20 pages going back only to 2017. Found more started in 2004, it was very controversial at that time, much discussion. Today it is just a given IMO.
The pump inlet is on the opposite side of boiler from feeder control. I have a similar install by others where the feeder is influenced by pumped return.

Any comments, please.

The Steam Whisperer

I'd just run a single 3 inch riser for each boiler rather than 2 -2 inch. Less piping and a greater cross section on the piping to reduce velocity out of the boiler. your velocity with 3 inch will almost be slow enough to allow water to drop directly back into the boiler against the out flowing steam.

JUGHNE

David, thanks for you input.
The double 2" give 22' per second, the single 3" figures out to be almost 20'/second.
With the 30" riser i was hoping to lose most of the water in the risers.
Trying to find the point of diminishing returns on more expensive fittings and nipples.
Also the concern of using only a singe riser on one side of the boiler......maybe this is unwarranted?

The Steam Whisperer

With labor costs added in, a single 3 is cheaper than 2 -2inch. Peerless specs a single 3 inch riser all the way to the 345,000 input size, so using a single 3 inch on only 236,000 input should work great.

JUGHNE

Thank you, point taken.
If I had to be competitive that is most likely the route I would chose.
I am fortunate enough to not need to do this for profit....just don't want to lose money on it.
This is probably the only steam boiler I will get to replace or install.
I was in Kindergarten at this school when the Kewanee was installed.
Have done a fair amount of donated work there.
That is how small town schools stay alive out here.

Thanks again, input from all is greatly appreciated.