Sizing up gas boiler -- edr for exposed risers?

sanblas

Hi. I am trying to figure out what size gas boiler i need.
Its a 6 family bldg (5 units 2br + 1 1br) in nyc 3 floors height, almost fully detatched (one side only touching another house 2 flrs only). I have an old oil boiler and doing a conversion soon.

I went in each apt to measure radiators. I came up with 539.25 sq.ft of steam -- is this number also referred to as EDR?

All apts have exposed steam risers in kitchens, bath and one of the larger bedrooms -- should i calculate these risers in my calculation? If yes how do i do that?

Looking at a burnham independence boiler with a seperate hot water tank working on its own.

Any help here is appreciated!!

Fred

I assume those risers feed radiators on the floors above them? If yes, don't count them in your EDR calculation. The boiler has a 33% piping and Pick-up factor built into it to cover that requirement. Just be sure to use the Net Sq. Ft. of steam output on the boiler plate and match that, as closely as possible, to your EDR.
Make sure your EDR calculation is correct.

EDIT: If you want to double check your EDR Calculation, Use this chart: http://www.columbiaheatingsupply.com/page_images/Sizing Cast Iron Radiator Heating Capacity Guide.pdf

BobC

The boiler sq ft of steam should be the same as the radiator EDR (sq ft). The boiler sq ft of steam does not include a pickup factor of 33%, that hidden pickup factor is to take care of piping so you do not have to calculate piping EDR.

Some think the 33% is excessive so they try to undersize the boiler to better match the building to the boiler. make sure your measured radiator EDR is correct before deciding on which boiler.

Bob

sanblas

Thank you for the help.

Exposed risers in kitchen and baths do not feed any radiators, the ones in the bedroom they do. So should i count kitchen/bath risers, if yes how do i do thar?

Below is a list of how i did the calculation:

Apt 3F:
Livingroom. 38"h 3 columns 7 sections (35edr)
Large Bedroom 26" 3 columns 10 sections (37.5 edr)
Small bedroom 38" 3 columns 4 sections (20 edr)

Apt 3R:
Livingroom. 38"h 3 columns 8 sections (40edr)
Large Bedroom 26" 3 columns 10 sections (37.5 edr)
Small bedroom 38" 3 columns 4 sections (20 edr)

Apt 2F:
Livingroom. 38"h 3 columns 7 sections (35edr)
Large Bedroom 26" 3 columns 9 sections (33.75 edr)
Small bedroom 20" 4 tubes 10 sections (22.5 edr)

Apt 2R:
Livingroom. 38"h 3 columns 7 sections (35edr)
Large Bedroom 26" 3 columns 10 sections (37.5 edr)
Small bedroom 38" 3 columns 4 sections (20 edr)

Apt 1R:
Livingroom. 26"h 4 tubes 14 sections (38.5edr)
Large Bedroom 26"h 4 tubes 14 sections (38.5edr)
Small bedroom 20" 4 tubes 10 sections (22.5 edr)

Apt 1F:
Livingroom. 23"h 5 tubes 7 sections (21edr)
Bedroom 20"h 4 tubes 10 sections (22.5edr)

Lobby:
20"h 4 tubes 10 sections (22.5edr)

Fred

Your calculations look good. What is the total length and diameter of each of those pipes that do not feed radiators and how many of them are there? They obviously are there for added radiation. Once you provide the sizes, I'm sure we (or someone on this forum) can tell you what thee sq. ft of radiation should be for those. I assume they have vents near the tops of them. Is that correct?

sanblas

Thanks Fred. See attached pic of a riser, they are all the same size and 9' high. How much edr for one riser?

BobC

If the exposed pipe is 1-1/4" it will have an EDR of 2 for a 10ft length of pipe if my calculations are correct. The pipes EDR is not significant even if it is vented.

Bob

sanblas

So to calculate correct size boiler i add 33% to the 539.25? That will bring it up to (33% of 539.25 = 177.95) 717.20 ?

Fred

@BobC, they look closer to 2" pipe to me. @sanblas , can you tell us the outside circumference of that pipe? 1 in the kitchen and 1 in the Bathroom X 6 apartments X 9ft each is 108 ft. of pipe. If 1-1/4, about 24 EDR total, per BobC's calculation. If its bigger maybe BobC can calculate that as well.

vaporvac

NO!!!!! Compare the 539sq ft to the boiler rating plate sq feet. do not add in the 33% at either end. I think a prior comment meant to say it's INCLUDED in the boiler sq ft already.

sanblas

Its actually 2" pipe

Fred

vaporvac said:

NO!!!!! Compare the 539sq ft to the boiler rating plate sq feet. do not add in the 33% at either end. I think a prior comment meant to say it's INCLUDED in the boiler sq ft already.

I think BobC simply meant that the 33% was hidden from the Net Sq. Ft. of steam but is aready built into the boiler.

Fred

sanblas said:

Its actually 2" pipe

I would add about 50 sq. ft of EDR (total) for those pipes.

vaporvac

Oh yes, I'm sure @BobC knows that! It's just a confusing thing at first and I just wanted to clarify; or he may have merely mis-typed. That's something I often do.

Fred

sanblas said:

So to calculate correct size boiler i add 33% to the 539.25? That will bring it up to (33% of 539.25 = 177.95) 717.20 ?

I missed this comment!!! Per Vaporvac's comment, the 33% pick-up factor is already built into the boiler. All you want to do is match, as closely as possible the Radiator EDR to the Net Sq. Ft of steam on the boiler plate. 539 + 50 for the pipe radiators = 589 EDR. Find a boiler with a Net Sq. ft. of steam as close to 589 as possible.

sanblas

Ok got it, sorry i have no experience in this sector! So burnham IN7 is 542 sqft steam and the IN8 is 633 --- any suggestions on which one to purchase?

Fyi see attached plate of the existing oil boiler -- sqft steam is ALOT!! Why?

Fred

sanblas said:

Ok got it, sorry i have no experience in this sector! So burnham IN7 is 542 sqft steam and the IN8 is 633 --- any suggestions on which one to purchase?

Fyi see attached plate of the existing oil boiler -- sqft steam is ALOT!! Why?

All the older boilers were so much over-sized (when they used coal) and then when they were replaced or converted from coal, many installers just installed exactly what was there and took no measurements of the EDR.
If it were me, I'd go with the IN8, which is about 7% to 8% percent over-sized and I'd have the installer use a combustion analyzer and down-fire the burner by that much so that you get a perfect match.

Fred

I don't know where you are located but please, please use an installer that knows steam and knows what he is doing. We see so many horror stories here when it comes to steam boilers that are not installed correctly. Near boiler piping (Header, boiler risers, main tie-ins and equalizers and Hartford loops is as important as having a properly sized boiler. If you go to the "Find a Contractor" tab on this site, you will probably find a good Steam Pro in your area. Post what you find and we can all confirm they know thier business

Fred

As a matter of fact, I see you are in NYC. I don't know if @JStar does any work in NYC but he is one of the best. Here is his info: https://heatinghelp.com/find-a-contractor/detail/thatcher-heating-and-air-conditioning

BobC

This shows how a boiler should be piped and it shows several common mistakes.

http://www.comfort-calc.net/Steam_Piping_Donts.html

I would use both boiler risers into a 3" header so you get dry steam, the use of a drop header would also be a good idea.

Bob

sanblas

Thanks to all of you for all the answers!

I wanted to use gateway but they dont do work in long island city ny. I will reach out to jstar.

I will go with IN8 burnham.

What is the best way to control this boiler? I currently use a heat timer model EPU-CH. Should i stick with that ?

Fred

You can use a heat timer or a thermostat with remote temp sensors but, if you are able to get Jstar to look at your requirements, I'm sure he will have much better options for you to consider than I could ever suggest.

sanblas

Do you guys have a better recommendation than the burnham IN8? What boiler would you install and why?

ChrisJ

Contact @JStar and let him choose the boiler. Chances are his sizing will be slightly smaller than yours as well. An IN6 or IN7 or equivalent is likely plenty for the building, but let Jstar decide.

KC_Jones

Out of my own curiosity, you say these pipes don't feed any radiators? So that means at some point you can see the end of the pipe with a cap on it, essentially a pipe to nowhere. Is this correct?

sanblas

The riser disappears in the ceiling but at that point im sure its capped.

Just emailed jstar to see if he works in my area.

As fas as boiler wanted to get feedback from you guys if you would recommend another brand than burnham in this application and the reason why ?

Fred

Burnham makes a great boiler. Weil Mclain also makes a good boiler (the only thing I don't care for about weil Mclain is they use a rubber or composite nipple between sections where Burnham uses metal but they seem to hold up well. Just my personal reservations). Slant Finn also makes a good boiler and is a good company.
I don't think you can go wrong with either of these but Burnham is probably the most popular brand.

EDIT: I have a Burnham myself. It is 32 years old and still going strong. My replacement would likely be another Burnham.

JStar

If the risers are in the room, I'll typically add 0.5ft2 EDR per linear foot of 2" steel. Doesn't usually add up to much.

ChrisJ

@JStar
I wish there was an easy chart like that for pipe with 1" fiberglass on it. I have not found any easy way to figure out heatloss from an insulated pipe.

JStar

ChrisJ said:

@JStar
I wish there was an easy chart like that for pipe with 1" fiberglass on it. I have not found any easy way to figure out heatloss from an insulated pipe.

Yellow line. Multiply Watts x 3.412 to get BTU's.

ChrisJ

JStar said:

ChrisJ said:

@JStar
I wish there was an easy chart like that for pipe with 1" fiberglass on it. I have not found any easy way to figure out heatloss from an insulated pipe.

Yellow line. Multiply Watts x 3.412 to get BTU's.

Wow so what I came up with is about right.
Both of my steam mains waste around 2000 btus. Uninsulated I think it was around 8500.

Still seems odd to me that everyone wanted me to have a boiler that was 31,000 too big when my piping at most only wastes a fraction of that even uninsulated.

JStar

In heating-industry terms, "waste" is a safety factor for those who don't pay the fuel bill.

vaporvac

JStar said:

In heating-industry terms, "waste" is a safety factor for those who don't pay the fuel bill.

Well put!!! Can we quote you on that?

JStar

vaporvac said:

JStar said:

In heating-industry terms, "waste" is a safety factor for those who don't pay the fuel bill.

Well put!!! Can we quote you on that?

Of course. Just send me the royalties.