HELP with new steam boiler

joe7

I’m relatively new to steam heat. (I’ve read some on this GREAT website…)



My 6 year old CROWN steam, oil powered boiler cracked and no longer works.  It’s 177,000BTU (input). The system is 1 pipe steam. (2 floor house 20x80, and (currently) unfinished basement. 3 family house)



I need to replace the boiler very soon, since we are still experiencing pretty cold weather :(



I’m thinking of replacing it with a GAS boiler (I have a gas line in boiler room).



I calculated the EDR of the radiators. I came up with: 472 (I erred on the generous side)



Several questions:



1)    Do I need to add any EDR for the piping?

2)    Someone told me that gas boilers give off less heat per BTU (compared with oil) and therefore if I currently have 177,000btu oil boiler, I should get at least 200,000btu gas.   Is there any merit to this?

3)    Bottom line: what size gas boiler should I get? 

4)    Does the boiler size have anything to do with the size of the house or EXCLUSIVELY the EDR of the radiators?



What brand boiler would you recommend:

a)    Green Mountain Boilers

b)    Williamson-Thermoflo

c)    Crown



Thank you very much in advance for your help and input.

DanHolohan

Some questions:

Are all your steam pipes insulated?



When you say "generous" what does that mean? How much have you already added to what's actually in the house?



A Btu is a Btu, whether it comes from burning oil or gas, so we look at the rating on the boiler.



The boiler's ability to produce steam has to match the system's ability to condense steam, which is why the measuring of the radiation is so important. If you're not certain, it would be good to get a steam-savvy pro in to do that for you.



Another issue is the piping of the new boiler. That has to be just right if you're going to be happy afterward.



I would also want to know why the Crown lasted only six years.

STEAM DOCTOR

Boiler

I wouldn't touch a green mountain with a ten foot pole. Its a side outlet boiler. Very hard to pipe adequately in best of circumstances and even harder in the small boiler rooms in most residential house. As Dan stated, boiler output needs to match heat output of radiators and piping. Typically the formula is heat output of rads plus an additional 33%. You also need to make sure that the gas line is adequately sized to handle the additional load of the boiler. Big question is, why did the boiler crack? Was the excessive addition of ne water? Did the boiler dry fire. Etc. You dont want a repeat performance with the new boiler. Might be worthwhile to contact Crown.

Jamie Hall

Slightly more direct...

answers.



1)    Do I need to add any EDR for the piping?

No.. But you need to insulate the piping.





2)    Someone told me that gas boilers give off less heat per BTU

(compared with oil) and therefore if I currently have 177,000btu oil

boiler, I should get at least 200,000btu gas.   Is there any merit to

this?

No.  Size by EDR, not BTU





3)    Bottom line: what size gas boiler should I get?

Match the EDR as closely as you can.  A bit over is a little better than under.

 



4)    Does the boiler size have anything to do with the size of the house or EXCLUSIVELY the EDR of the radiators?

No.  Exclusively EDR of the radiators is correct.

joe7

EDR calculation

1) about 80-90% of the main pipes are insulated with 1/2" insulation.

2) by "generously" I mean:  there are 2 bathrooms that their radiators are a floor to ceiling (9') pipe .  (since I don't know the EDR value of it), I calculated them as a 6 section 20" sunrad (2.25 EDR per section) = 13.5 EDR.

There are also 2 rooms that the radiators were removed by previous owner.  I may want to replace them.  I factored in an additional total 50 EDR for them.

I have another radiator that is currently 36 EDR.   The room was cut in half, so I can reduce the radiator size (and EDR) by almost half.

3) I was very puzzled as to why the relatively new Crown boiler failed.  Several months ago, I went to the basement to find it flooded.  The water came from the boiler (not from the return pipes). Apparently, it began in the middle of the night.  The automatic feeder kept filling in more water and this water in turn, leaked out of the chamber and gun.   Several friends (a contractor and plumber) advised me that the boiler is cracked and will need to be replaced.  but I should try to get it to limp until the end of this heating season by 'patching' the leak with boiler liquid/solder and/or oatmeal.   I used Hercules boiler liquid and solder several times.  It kept the boiler in operation for almost 2 months.  Now it seems to have finally 'died permanently'  

I have no idea what caused the boiler to crack.  I have a hunch (I have no expertise in boilers) that it has something to do with the automatic water feeder.

4) Regarding  calculating EDR to size a new boiler, Jamie Hall replied that I should not add anything for piping, only calculate the radiators themselves.  BN states that I should add 33% EDR.

what should I do?  add 33% or not?

thanks again!

ChrisJ

33%

Hi Joe,



That is a very good question and I asked the same thing recently.  Have a look at this thread and see what you think.



http://www.heatinghelp.com/forum-thread/149940/Pickup-factor-Help-me-understand



Right now my opinion is add 10-15% and no more above the radiation you have.  Please keep in mind I'm a homeowner, not a pro.

DanHolohan

All the metal in the system

and that includes the pipes between the boiler and the radiators, has to be brought from ambient temperature to 215 degrees. That's a function of specific heat. It takes so many Btu to raise a pound of iron or steel one degree Fahrenheit. Since the 1950s, manufacturers have suggested using a pick-up factor of 1.33 for the piping, and that assumes the steam piping is insulated with 1" of insulation. I'd use that factor.



As for the risers being used as radiators, here's the EDR:



1-1/4" = .63 EDR per linear foot

1-1/2" = .73 EDR per linear foot

2" = .88 EDR per linear foot

nicholas bonham-carter

Matching EDR

This would be a great application for a burner on the new boiler with an adjustable firing rate to match the present EDR all the way up to later increase in radiators etc.

I don't have any oil experience, as I only have a gas atmospheric, with more limited possibilities for adjusting the firing.--NBC

vaporvac

Here's an example for choosing a boiler:

I think the confusion stems from the difference between how much EDR one's system needs to take into account and what size boiler to buy. The boiler rating already includes this in their sizing, although they don't state this..

I posted an example on how I chose my boiler which some found useful:





500edr = 500sq ft of steam

500edr (without spick-up factor) = the boiler rated at 500sq ft. The boiler manufacturer has included it, but it isn't written. So really their edr is 500 plu30%, but they don't write that in because it's confusing. Just compare the edr to sqare feet of steam and you'll be fine.

ie. My combined edr is 1460 WITHOUT any pick-up factor and my pipes are insulated. I wanted two Slantfin boilers so I needed 730edr each. This is how we chose them:

http://www.slantfin.com/images/stories/Product-Literature/catalogsheet_intrepid_tr_10.pdf

Looking at the chart you can see that the TR50 is the closest with 767sq ft. ,so that's what we went with. That's it. There's nothing else to do. That boiler is able to account for the piping. End of story. (Although it IS confusing!)



I hope this helps.

P.S. i might also add that I can actually heat my house with only one boiler once the pipes are heated. This points out the total waste of oversizing and the beauty of an adjustable burner rate. If you're going for an atmospheric, many burners have a hi-lo--hi setting, but are often only set for one rate. I believe there's more flexibility with oil-burners.