2" main does not match EDR load. Need some input here

Mark_72

Installing a new boiler and found that the EDR is 1236 Sq ft but the main is only 2". Should I still match the EDR?

Jamie Hall

I'll let the more experienced hands on folks comment on this one more authoritatively, but... a 2 inch main isn't even close to that BTU load. Not even remotely close.

If it's parallel flow, and if it is very carefully dripped, and if you don't mind a terrific pressure loss, you can probably push that much steam through it. But... it won't be happy. At all.

Steamhead

Is the entire main 2-inch, or just the piping around the boiler?

Mark_72

Hey Frank , Been awhile. So Installed at the moment is a EGH105 series 2 1125 sq ft EDR. Double 2 1/2 into 3" header. Take off is 2" and runs36' then jumps to 21/2" for 20' then back down to 2" another 20'
House built in 1920 But not sure when it was converted to apts. current boiler has been there apox 30 years and I've been involved since 2016.

EBEBRATT-Ed

Seems obvious that the somebody replaced some pipe probably in a emergency and used 2" because it was a faster fix to get the heat back on

Danny Scully

I agree with @EBEBRATT-Ed, 2” was a repair (or possibly a repipe when building became apartments?). You have to match the boiler to the EDR and additional address the current size of the steam main. 

Steamhead

@Mark_72 , forgive me but I'm drawing a blank- I know I know you from somewhere......

Mark_72

Steamhead said:

@Mark_72 , forgive me but I'm drawing a blank- I know I know you from somewhere......

Yea it's been that long. The fairfax apts in Philly 2010 maybe. So what do you think about this 2" main. They never had any problems with it in the past but I'm bothered installing a new EGH125 to it.

Mark_72

No water treatment?

GW

I wonder if you followed the main to see what happens, no bigger pipe outside the boiler room? 

—-ah yes 2 1/2” I guess that’s your answer. Go big or roll the dice 

Steamhead

Mark_72 said:

Steamhead said:

@Mark_72 , forgive me but I'm drawing a blank- I know I know you from somewhere......

Yea it's been that long. The fairfax apts in Philly 2010 maybe. So what do you think about this 2" main. They never had any problems with it in the past but I'm bothered installing a new EGH125 to it.

OK, I remember that place now. Definitely been a while!

So, what happens between the boiler, where the steam main leaves as 2", and the place the 2" expands to 2-1/2"? Are there any tees between these two points where radiators connect?

Mark_72

Steamhead said:

Mark_72 said:

Steamhead said:

@Mark_72 , forgive me but I'm drawing a blank- I know I know you from somewhere......

Yea it's been that long. The fairfax apts in Philly 2010 maybe. So what do you think about this 2" main. They never had any problems with it in the past but I'm bothered installing a new EGH125 to it.

OK, I remember that place now. Definitely been a while!

So, what happens between the boiler, where the steam main leaves as 2", and the place the 2" expands to 2-1/2"? Are there any tees between these two points where radiators connect?

Yes there are. I know I have to match the load but the main is my concern. The existing boiler in a egh105 series 1 at 1125 sq ft steam . It calls for a 3" header , 10" flue and that's what is there now. The new boiler is going to be a EGH 125s and call's for a 4" header , 12" flue. I feel the I'm over sizing. but the egh125 is about 59sq ft over my load and a egh115 is 69sq ft under. Thoughts?

Danny Scully

How well is the piping insulated? 

EBEBRATT-Ed

If the piping is insulated I would go with the smaller boiler your within the pick up factor. If not well insulated go with the larger size

ethicalpaul

Go with the smaller one no matter what your insulation condition IMO.

Here's why: when the boiler starts up, almost all the steam production is going to go toward filling up your main, none of it will go to your radiation load due to the main vent, right?

So why does it matter how insulated your main is? No main no matter how poorly insulated is going to take very long to fill and heat up with the full steam production of the boiler going into it. Then once the main is steam hot, it's not going to radiate very much and almost every bit of steam is going to be going to your radiators.

Both boilers figure plenty of extra to get to the "net sq feet of steam" so you are certainly not going to be undersized.

Finally, even if you think you will be undersized with uninsulated mains, just insulate the mains!

And out of curiosity, why are you moving up from the egh105? Was radiation EDR added to this building after that boiler was put into service? Or did someone in the past actually undersize a boiler??

Mark_72

ethicalpaul said:

Go with the smaller one no matter what your insulation condition IMO.

Here's why: when the boiler starts up, almost all the steam production is going to go toward filling up your main, none of it will go to your radiation load due to the main vent, right?

So why does it matter how insulated your main is? No main no matter how poorly insulated is going to take very long to fill and heat up with the full steam production of the boiler going into it. Then once the main is steam hot, it's not going to radiate very much and almost every bit of steam is going to be going to your radiators.

Both boilers figure plenty of extra to get to the "net sq feet of steam" so you are certainly not going to be undersized.

Finally, even if you think you will be undersized with uninsulated mains, just insulate the mains!

And out of curiosity, why are you moving up from the egh105? Was radiation EDR added to this building after that boiler was put into service? Or did someone in the past actually undersize a boiler??

Here is what's bugging me about this job.
There is a HB Smith boiler still in the basement and the SQ Ft rating is 1875. The WM EGH105 rating is 1125 and my total load comes out to 1235.75 or 1236. The HB Smith is still connected to the main and has a closed king on a 2" take off So I want to believe the 2" main should be there. The WM 105 is also connect to the 2" main. The Smith has been dead for at least 30 years. The mains are wrapped. Checking the the size of main against the connected load 386 sq ft for 2" and 635 for 2 1/2" and 1163 for 3" so I stopped and my brain said how can this be. Well now the building had no complaints when the 105 was working so I wanted to just replace it with the same. Now looking at the new WM EGH105 the sq ft rating is at 977 so the WM 125 comes to a bit over my load. I would like to stay with the 105 3" header and 10" flue but I think I'm making a mistake doing that. My numbers say I'll be 240sq ft under the load. This is why I started this thread. I need to order a boiler and I can't make up my mine.

ethicalpaul

Is it really 1236 sq ft of load? They don't have any radiators turned off? Like for decades?

Have you seen the performance of the 105? How is the pressure during the beginning of a call for heat? If it's not rising too much then it is apparent that a 2" main can in fact deliver 1125 sq ft of steam. Yes, the velocity is going to be high, but it will be less and less after each radiator runout.

So as long as the steam is dry, who cares if the velocity is higher for portions of the main? As long as the backing pressure is reasonable then the steam must be getting delivered, who can question it?

As for sizing, if your observations and their comfort level is satisfied with a 105, I'd get another 105. Installing a larger boiler when a 105 has been working for decades seems foolish to me. Do the near boiler piping like the manual says, maybe bump that 20ft section of 2" to 2.5" and I don't see what can possibly go wrong.

I've only installed one boiler, but I'd love to hear what the counter argument to this approach is.

Oh wait, I just remembered you said that the old 105s are 1125 and the new ones are 977? That is a drastic size difference for something with the same name! Does anyone know what happened there?

So then maybe the 115 is the new 105, I guess that would point to a 115 then. Weird.

Danny Scully

You’ve given them a proposal? Please don't tell me you haven’t and are going to order a boiler...

GW

Wow good luck. You’re quite sure the original boiler wasn’t parked over where the 2 1/2” is? And there’s rads coming off of the 2” main (on its way to the 2 1/2”?) All original? 

like Paul said I wonder if some of the rads are turned off. 

You’ll need to be on the ball with this one.

EBEBRATT-Ed

Don't know what kind of building this is but there is no reason that this building couldn't have been designed a higher pressure, as long as it's two pipe. Commercial buildings are often designed for 20, 30, 50 psi in the heating systems. Many commercial buildings Hospitals for example run 100 psi steam for their process loads, kitchen, laundry etc then go through a PRV and drop the pressure to 25 psi and send it to the heating system.

Why the pipe is 2" of the boiler and then increases makes no sense with any system

1236 EDR=296 lbs of steam.

2" pipe will carry 300 lb of steam with an initial pressure of 5 psi and the velocity is 80 feet/second

5 psi is the lowest pressure I found in my Sarco book. The velocity of 80 ft/second is the recommended velocity with 5psi pressure on 2" pipe. A lower pressure would not feed that much load

Mark_72

EBEBRATT-Ed said:

Don't know what kind of building this is but there is no reason that this building couldn't have been designed a higher pressure, as long as it's two pipe. Commercial buildings are often designed for 20, 30, 50 psi in the heating systems. Many commercial buildings Hospitals for example run 100 psi steam for their process loads, kitchen, laundry etc then go through a PRV and drop the pressure to 25 psi and send it to the heating system.

Why the pipe is 2" of the boiler and then increases makes no sense with any system

1236 EDR=296 lbs of steam.

2" pipe will carry 300 lb of steam with an initial pressure of 5 psi and the velocity is 80 feet/second

5 psi is the lowest pressure I found in my Sarco book. The velocity of 80 ft/second is the recommended velocity with 5psi pressure on 2" pipe. A lower pressure would not feed that much load

One pipe , 6 unit apartment building built in 1920. Not sure when it have been converted or if it was always this way. Steamhead has been a big help so thank you Frank if you're reading this. His thought is it was on city steam in the beginning and the the first boiler , a H.B. Smith was put in place. I guess we'll never know unless the Dean Men talk to me.
Thank you for the info, every little bit helps.