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# Help with heat loss Btu/hr vs EDR

Member Posts: 129
I found my old CD from Slant Fin, Hydronic Explorer. I am in need of a new steamer this summer, so I have been putting a lot of info together from everyone here. I have entered in all my room dimensions and window/door sizes and glass type. I have a 1840 2 story brick Italianate with only very good attic insulation. I have set my outside temp. at zero degrees here in southern maine, my inside at 70 degrees. Some of the pulldown menus on the SF program didn't apply to this old place. I came with about 70,000 Btu\Hr. My question is how does this figure apply to boiler selection for this place, along with my EDR of my radiators?

• Member Posts: 1,484
How much EDR

is currently connected to the boiler?
• Member Posts: 129
• Member Posts: 15,953
You size steam

based on your EDR, never on the building heat loss.  It's ALWAYS based on the EDR.

An EDR of 404 works out to around net output of 100,000 btuh; with a pickup of 1.33 thats 130,000 btuh more or less.  That's what your boiler should be sized at.

All your 70,000 btuh from building heat loss tells you is that you did a decent job insulating, and your boiler won't be running all the time.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
• Member Posts: 8
knowing how u get the numbers always helps

1 edr equals 240 btus for steam-  So  404 X 240=96,960 and when sizing a steam boiler u would have to add 33% for the pick up factor the total 128,956. Pick up factor is the amount of heat required to heat the steam mains hopefully they are insulated
• Member Posts: 1,764
edited March 2011
And those numbers are Gross Output

Always confusing to someone who does not work with this stuff all the time.  We speak in terms of firing rate or Input BTU, Output BTU, Net BTU, and Steam Sq Ft., or EDR.

The guys went through the calculations to get you to the Output BTU.  Often boilers are sized by Input.  Assuming 80% efficiency, you'll need a boiler with an Input BTU rating of about 162,500.  Less if it is higher efficiency.

My main point I wanted to make is the previous responses were getting you to the Gross Output BTU of the system.   Or even easier, match a boiler and its EDR rating to your system EDR.

Now, if your system is a 2 pipe system, there are methods in which you can install orifices in the inlets to your radiators and actually effectively reduce your EDR to match the heat loss of your home.  If you have this as an option, you might be able to go to a smaller boiler.  I would ge the help of one of the pros on that subject.

There is an excellent article by Henry Gifford on the subject.  Here is the link     https://869789182725854870-a-energysavingscience-com-s-sites.googlegroups.com/a/energysavingscience.com/www/articles/henrysarticles/BSEOrifices.pdf?attachauth=ANoY7cqWR0eqwMQb3fPaAKcicpLMKIbtU3omBeOU2idWO8LrGl3LRxgDHR_6zZjMq3wEpqI27BCXC_-ilGp5hc80i03DmeagN9g0DXLHt6PVArEmvfBi0YuVBNbNwKnjrqJUJJickKnVPpnrTfE2_yOm1eNjiRHxJ4suHnL5MKR3cj2B8lcE_3S5FBpQ-32iM5qYixFZ7gz6jpgazNHVk1PFqc1WYZUXMM4zhy5rl29ZYrLDAKodRKI%3D&attredirects=0
Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
http://grandviewdavenport.com
• Member Posts: 129
Help with heat loss Btu/hr vs EDR

Thanks everyone for your input, very understandable. If I use Dave's advice as to my EDR to size my boiler. I am looking at a Weil Mclean SGO my EDR falls between a SGO-3 and a SGO-4 I believe. My question to Dave is, if I need Input rating of162,500 Btu is the SGO 3/4 going to be large enough? The net ratings on these are 85 and 108, I assume that is 85,000, and 108,000 am I correct? Jamie points me to a net of 130,000 Btu's if that is the case than the SGO-5 is the right size. Any thoughts?

Thanks Again

Model I=B=R Burner Cap (GPH) Net I=B=R Ratings: Steam (Sq. Ft.) Net I=B=R Ratings: Steam (MBH) Net I=B=R Ratings: Water (MBH) % DOE Seasonal Efficiency (AFUE) - Steam % DOE Seasonal Efficiency (AFUE) - Water Min. Chimney Size:

Rectangular (in) Min. Chimney Size:

Round (in) Min. Chimney Size:

Height (ft.)

SGO-3 0.95 354 85 100 83.8 85.3 8 x 8 6 15

SGO-4 1.20 450 108 126 84.0 85.0 8 x 8 6 15

SGO-5 1.45 546 131 152 83.9 85.0 8 x 8 7 15

SGO-6 1.75 658 158 184 83.7 85.0 8 x 8 7 15

SGO-7 2.00 750 180 210 83.6 85.0 8 x 8 7 15

SGO-8 2.30 833 200 231 0.0 0.0 8 x12 8 20

SGO-9 2.55 921 221 257 0.0 0.0 8 x12 8 20
• Member Posts: 14,514
edited March 2011
I'd go with the SGO-4

and down-fire it slightly if it short-cycles.

But if I were doing that job I'd use a Burnham MegaSteam, for its better efficiency, better warranty and easier servicing. You might be able to get away with a MegaSteam 396 if the system is extremely well insulated. The next size up from that is the 513, a bit big for your system but again you could down-fire slightly.
All Steamed Up, Inc.
Steam, Vapor & Hot-Water Heating Specialists
Oil & Gas Burner Service
Consulting
• Member Posts: 1,764
edited March 2011
gross output vs net output

You have an EDR of 404.  Conventional advice says go to the next largest size unless you are VERY near to the next lower size.  You are not, so you would go to the next larger size, rated for 450 sq ft steam, 108,000 Net BTU Steam, Ignore the 126 number, that is Net BTU Water.  It does not apply to your system.   From another chart,

http://www.weil-mclain.com/en/multimedia-library/pdf/weil-mclain-pdf/products/boilers/oil-boilers/sgo/SGO_SpecSheet_SprdR6_Lo.pdf

I find that the Gross output for the SGO-4 is 144,000BTU.  Isn't that magic how the formulas work out!  404 EDR(sq ft) x 240 BTU / Sq FT = 108,000 BTU Net x 1.34 piping and pickup = 144,720 BTU Gross Output (what is required to come out of the boiler to properly heat your system)

This boiler will do the job if you have calculated your EDR correctly and I'm sure you have.  You might also consider the Burnham Megasteam, MST396.  It is a little more efficient, 86%, and has a really superior design and is warranted against water corrosion, (unheard of!)  Here is a link http://www.usboiler.burnham.com/pdf/MegaSteam_lit.pdf

They are regarded by many of the pros on here as being the best oil fired steam boiler on the market.

And Steamhead spoke as I was typing my above message!
Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
http://grandviewdavenport.com
• Member Posts: 14,514
Great minds

think alike!
All Steamed Up, Inc.
Steam, Vapor & Hot-Water Heating Specialists
Oil & Gas Burner Service
Consulting
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