Boiler size

Haloyloy770

Hi I’m new here

I’m trying to get the right size boiler, I just bought a house that was vacant for over 10 years, the heating system is a one pipe steam system, the current boiler there is a oil fired burner, but in my eyes it looks small for the system, also there is no paper saying what size it is

I measured all radiators and got a total 341 EDR, (without adding any pickup factors)

So I’m looking to buy a mega steam boiler, but can’t decide if to get the 396 or 513, because I don’t know if the number from the manufacturer, for an example the 396 represents the systems EDR needed without including the pickup factor, (then ill need the 396 because I need 341 EDR) or the number from the manufacturer is including the pickup factor (then I’ll need the 513)

ethicalpaul

If anything the 396 is too big. See if people say the burner can be safely downfired.

Measure net sq ft (396) directly against your EDR.

 Good boiler, I hear, maybe the best. 

mattmia2

If you post some pictures of your current boiler and piping people here can probably tell you what it is and if it is piped properly and if it really needs to be replaced.

Haloyloy770

ethicalpaul, thank you
I have a “thought behind my head” that in the “near future” when I finish the attic and build an attached garage, to add radiators in thous spaces, I’m “wildly guessing“ that will be an “extra” 100 (or so) EDR bringing the total EDR 441 (or so)

Can I still go with the 396?

Mattmia
Yes I will try later on today to get some pictures

ethicalpaul

I have a “thought behind my head” that in the “near future” when I finish the attic and build an attached garage, to add radiators in thous spaces, I’m “wildly guessing“ that will be an “extra” 100 (or so) EDR bringing the total EDR 441 (or so)

Can I still go with the 396?

I will defer to the pros who will know a lot more about radiation in a garage.

They will also know the firing range of that boiler (how much it can be up- and down-fired). It might be that you can downfire it before you add radiation and then up-fire it after.

I will always go smaller rather than larger in an edge case. But the garage part of your scenario makes me unsure.

Jamie Hall

I think the smaller boiler would still be OK -- provided that all the mains are carefully insulated. Consider: garage or no, and one EDR can only put out 240 BTUh, no matter where you put it.

ethicalpaul

I think it depends on the garage. I would think one EDR in a cold space can use up way more steam than one EDR in a warm space.

Note the definition of EDR in TLAOSH, page 21 (my emphasis):

For steam, we say that one square-foot EDR will give up 240 BTU, when there is 70-degree Fahrenheit air on the outside of the radiator and 215-degree steam Fahrenheit on the inside of the radiator.

This doesn't mean I think the larger boiler would be better! It just means the garage might make things more complicated.

Jamie Hall

Well, technically you're right, @ethicalpaul . Indeed that's one of the unappreciated advantages of steam heat -- it will automatically rebalance between hot and cold rooms, up to a point. Oddly enough (you would think it would be out there, wouldn't you?) I haven't found a good reference to what the effect of space air temperature is on the output of a radiator. Obviously, if the space is at 212 (eek!) there would be no convection -- but there still could be radiation, depending on the temperature of the enclosing walls. But is the change in normal spaces linear with delta T? Or at a higher power? Going the other way around, with hot water, one is not too far off assuming a linear relationship between the hot water temperature -- with a subtractive constant -- and output. But...

If one were to assume that the relationship is linear between no output at a space air temperature of 212, and 240 BTUh/EDR at a space temperature of 70, then the relationship would be BTUh/EDR = 1.7 * (212-T), where T is the space air temperature. But I doubt that it's linear...

Now you've opened a can of worms. Thanks. I think!

ethicalpaul

"technically" is the best kind of correct

mattmia2

you have to remember that 70 f is 530 rankin. If the temp is 40 or 80 f, that difference is only a small fraction of the total energy and you are condensing steam in to liquid water so I think that the effect of a normal range of room temps has only a small effect on the amount of energy transferred.

ethicalpaul

I don't know what rankin is, but when I think of a 40 degree radiator hooked to a system of 70 degree radiators, I think of a lot of iron mass to heat up and then radiate into a 40 degree space, and I think that could consume a lot of steam, relative to all the other radiators in the system.

ChrisJ

mattmia2 said:

you have to remember that 70 f is 530 rankin. If the temp is 40 or 80 f, that difference is only a small fraction of the total energy and you are condensing steam in to liquid water so I think that the effect of a normal range of room temps has only a small effect on the amount of energy transferred.

Why did we need to know it's 530 Rankine?

Jamie Hall

mattmia2 said:

you have to remember that 70 f is 530 rankin. If the temp is 40 or 80 f, that difference is only a small fraction of the total energy and you are condensing steam in to liquid water so I think that the effect of a normal range of room temps has only a small effect on the amount of energy transferred.

This is quite true -- however, when playing with convective heat transfer we are dealing with delta T, not absolute T. For that matter, that's also true of radiation, only to a much higher power.

pecmsg

Haloyloy770 said:

ethicalpaul, thank you
I have a “thought behind my head” that in the “near future” when I finish the attic and build an attached garage, to add radiators in thous spaces, I’m “wildly guessing“ that will be an “extra” 100 (or so) EDR bringing the total EDR 441 (or so)

Can I still go with the 396?

Mattmia
Yes I will try later on today to get some pictures

That Finished Attic will need a little heat. If spray foamed then very little will be needed.

Attached Garage In Floor radiant Heat again if insulated properly Very little will be needed!

ted_p

Haloyloy770 said:

.....

I measured all radiators and got a total 341 EDR, (without adding any pickup factors)

So I’m looking to buy a mega steam boiler, but can’t decide if to get the 396 or 513, because I don’t know if the number from the manufacturer, for an example the 396 represents the systems EDR needed without including the pickup factor, (then ill need the 396 because I need 341 EDR) or the number from the manufacturer is including the pickup factor (then I’ll need the 513)

ethicalpaul said:

If anything the 396 is too big. See if people say the burner can be safely downfired.

Measure net sq ft (396) directly against your EDR.

 Good boiler, I hear, maybe the best. 

The MegaSteam MST396 has a Net AHRI rating of 396 sq ft. "Net AHRI ratings" for steam boilers already have a 1.333 pickup factor built-in so, as @ethicalpaul said, the MST396 has more capacity than needed for your existing 341 EDR of radiation.


I strongly encourage you to read Taking Another Look at Steam Boiler Sizing Methods in the System Help Center, by @The Steam Whisperer (Dave Bunnell).

Dave's approach involves the use of very slow radiator vents to achieve more even and efficient heat through long, slow heat cycles, using a boiler sized more closely to the heat-loss of the structure, rather than the conventional method of sizing the boiler to the (typically oversized) radiation. In my opinion, this is a must-read for anyone engaged in boiler selection.

One additional suggestion: If your house has gas, you might consider going with something like a Slant/Fin Intrepid TR30-1.10 with a gas burner. Although the MegaSteam is the most efficient small steam boiler available, in most areas nowadays gas is SO much cheaper than oil, that the cost to run a somewhat less efficient boiler on gas will be much lower.

Haloyloy770

Thank you all, you convinced me to go with the smaller one (396)

My plan is (I did not mention) to use a gas burner (like a riello) “but shhhh please don’t let Burnham (us boiler) know 😉”

I will send later on today some pictures of the current boiler there, and see if it’s “salvageable” or not

ethicalpaul

600 pounds wow!

Haloyloy770

Ok as promised here are some pictures of the boiler and piping (as you can tell I will have to work on thous main vents 😉🙄)

mattmia2

I think your instinct about replacement is correct. I would be concerned about rust on some of that piping too.

Haloyloy770

If anyone knows anything about this boiler please let me know, what size it is, if it’s worth “taking it apart” (clean it)? Or just dump it?

Haloyloy770

As you can tell from this radiator that it’s a one pipe steam system

ethicalpaul

From a fellow homeowner, replace that rustbucket

Haloyloy770

Ok Done ✅
Thank you guys

I’m located in Postville Iowa any suggestion where I can pick up (order) a Megasteam 396?

I want to set up the system ASAP because winter is coming 🥶

Steamhead

That boiler is a re-labeled American-Standard A-3 series unit. These boilers are built like tanks. But that burner is a re-labeled A-S DH series- a very early attempt at a higher-efficiency unit, which didn't work out too well.

The corrosion on the jacket would not affect the integrity of the cast-iron boiler sections.

If I were going to run that boiler for another couple seasons, I'd replace the burner with a Beckett AF- a current-model, high-efficiency burner. We've done this, and they run well, though not as efficiently as a MegaSteam or other modern boiler.

Haloyloy770

I hear you steamhead, maybe I’ll strip the boiler and see if there is any sign of a leak, if not then maybe I’ll give it a try

Did you try putting a gas burner in such a boiler?

I’m thinking of using a Riello 40 gas series, any thoughts?

Dave0176

Haloyloy770 said:

I hear you steamhead, maybe I’ll strip the boiler and see if there is any sign of a leak, if not then maybe I’ll give it a try

Did you try putting a gas burner in such a boiler?

I’m thinking of using a Riello 40 gas series, any thoughts?

You could run a gas burner. I would use a Carlin EZ gas.

Steamhead

Haloyloy770 said:

I hear you steamhead, maybe I’ll strip the boiler and see if there is any sign of a leak, if not then maybe I’ll give it a try

Did you try putting a gas burner in such a boiler?

I’m thinking of using a Riello 40 gas series, any thoughts?

Dave0176 said:

You could run a gas burner. I would use a Carlin EZ gas.

This. The Riello would be overkill for this boiler. And (I'm told, heh-heh) the EZ-Gas will run nicely in a MegaSteam if you decide to get one later. It will certainly run nicely in that Kewanee.

Haloyloy770

I hear you

I “was” thinking of the Riello 40 because I was advised by my uncle to use that, I used it in a Megasteam 396 back in NJ

But I don’t mind giving the EZ-Gas a try

Is there a specific model I should buy?
Remember I need to heat up 341 EDR

luketheplumber

Yikes!, just looking at the rusty flue pipe is giving me a headache. You should also get the rest of that chimney looked at before you even think about touching that boiler.

Steamhead

@Haloyloy770 , a pro will have to handle the installation. The standard EZ-Gas Pro will work. It uses an orifice which is drilled out to size.

And, what @luketheplumber said about the flue pipe.

Haloyloy770

Hi all

so after a “brief break” I’m back at “tackling” the boiler, yes I’m changing the flue pipe, and my plan is after the boiler is up and running, to call a pro to do a combustion test

I got a “unwanted surprise” when I found out that I have “almost” a full tank of oil (that will be between 240 and 250 gallons of oil 😕) I briefly turned the burner on and it gave “life”, so I’m guessing the burner still works, (obviously I’m planning to get a new oil filter and nozzle) the plan is to use up the oil then switch to gas (providing the oil is still good 😉)

my question is, what is the purpose (and how important is) the insulation “blanket” that is put in the boiler where the flame 🔥 is?