Sanity check on sizing a steam boiler for 3rd floor apartment?

radsteam1870

Long time lurker, first time poster, thanks so much in advance for any help you guys can provide.

We live on the top floor of a 150-year-old triple-decker where each apartment has its own separate heating system. We urgently need to replace our old steam boiler (25 years old, rated for 273 sqft/88k gross BTUs, worked great until it developed a massive crack in the heat exchanger).

Our plumber recommended the ForceSTEAM05 (5 sections, 113000 gross BTUs and 354 sqft of steam). But I've calculated the EDR of all our radiators at 207. We may add another tiny radiator for the office, but that would only bring us to 223. Which looks like the 4-section model (84000 gross BTUs, 263 sqft of steam) would be more appropriate.

I asked our plumber why the difference and he said nobody uses straight EDR numbers for an old triple-decker like our house. He said the rule of thumb is to add up the EDR for all the radiators, and then add in again the EDR of the largest radiator if you're calculating for the second floor, or 1.5 the EDR of the largest radiator if you're calculating for the third floor, and compare that to the net sqft of steam the boiler was rated for to compensate for all the piping. The biggest radiator is 75 EDR, so that would give us 320 (or 330 with the new radiator).

On the one hand, this guy has been installing heating systems for longer than I've been alive, and he's not wrong that this system is over 100 years old and probably has a lot of poorly-insulated pipes. On the other hand, he also told me that a larger boiler would be better because "you need enough steam pressure to get it all the way up to the third floor," which makes me a little nervous.

Ordinarily I'd try to get a couple more opinions, but you can't get a plumber in my area right now, and this guy is only squeezing us in because he's a friend of a friend. Is his recommendation reasonable?

ethicalpaul

Counterpoint: Someone can be installing the wrong boilers for longer than you have been alive

If it were me, I'd be looking at the very smallest steam boilers around.

the Peerless 63-03L at 233 sq ft

The Weil-Mclain EG-30 at 196 sq ft

The 30% pickup factor already baked into these numbers is plenty, and even more than plenty.

354 is absolutely insane and I'd question his other knowledge based on that recommendation

Beware plumbers when shopping for steam installers. If you must use one, make sure they explain to you in the quote how they will pipe in the boiler. Look in the installation manual and compare what you see there to what he proposes. This forum can help if you have questions.

PS: your nervousness about his pressure comment is completely justified. His statement is dangerous (because it shows his knowledge of steam systems is poor).

PPS: don't get rushed into this. You may be able to limp along until spring

PPPS: Where are you located? We might know someone

ethicalpaul

(this post no longer relevant)

KC_Jones

You need pretty much the smallest steam boiler made, period. Your plumber is factually incorrect I don't care how many years they have been doing it, they have been doing it wrong that whole time.

The metric they will use is "all the houses heat" and if that's the only criteria, I could size a boiler for any house, without even seeing the house or the system.

We see this on here all the time. Sizing a steam boiler is simple, and yet tons of professionals can't get it right.

So looking at the Force boilers you mention, they actually have one rated for 175 and one for 263. By classic sizing standards one would select the 263, so let's see what that bad boy can do.

So you need 200, it will have 63 extra, plus the pickup factor. Let's skip the 63 for now and look at the pick up factor.

Input is 103,000, after subtracting for efficiency we have 84,000 BTU usable capacity for the system. Now 33% of that is for the pickup which (according to Force) gives 21,000 BTU for piping. If we divide that by 240 btu per EDR we get 87.5 EDR that can be supported by the pick up factor.

2" pipe has a circumference of 7.46", and an EDR per foot of .622 sq ft/foot of pipe. So that pick up factor will support 140' of 2" pipe.

Now if we also add in the 63 extra that you will have since your rads only need 200, that "properly sized" boiler will support a total of 241' of 2" pipe. If the pipe is smaller for runouts and risers, the length goes up...dramatically.

Now, anyone looking at this can clearly see what your plumber is proposing is ludicrous, as he's proposing 91 EDR more than what I just showed. It's literal insanity.

I'd challenge him to run the actual numbers and justify what he proposes to do with that big boiler. The system can only output 48,000 BTU's, the rest of the boiler output is essentially useless.

As for water volume. If we go on the high end your radiation has a volume of 5.8 cubic feet, which is ~43 gallons, if we divide that by 1700 (expansion rate of steam from water) we get .4 ounces of water to fill up all your radiation with steam. Even with all the piping and such, I don't see how water volume will be any kind of issue, no matter how small you go.

@ethicalpaul can attest to the tiny amount of condensate there is as he has a sight glass on his return piping and has watched it. @ethicalpaul want to post the video link again?

ethicalpaul

(this post no longer relevant)

ChrisJ

tommay said:

Well, having enough is better than not having enough. Water levels can be adjusted. And the cost of an extra section is minimal.

This is horrible advice.
Literally horrible.

Please stop.

pecmsg

tommay said:

Well, having enough is better than not having enough. Water levels can be adjusted. And the cost of an extra section is minimal....Even the OP calculated 4 sections easily knowing he's adding on at some point.

With that reasoning add 2 sections, maybe 3!

Dan_NJ

ethicalpaul said:

the Peerless 63-03L at 233 sq ft

@radsteam1870 - Peerless 63-03L is the lower fired version of the 63-03, meaning it has one fewer burner tubes than the next higher output model (the L is for Lower). It should be possible if the 63-03L turned out to need more output to add that extra burner tube manifold, vent hood, maybe a few more parts to get you to a whopping 308 Sq Ft of steam output. Sure seems like you wouldn't need any more though. But you'd have heat and an option to expand later on (that you would probably never need or use)

DanHolohan

@tommay, I agree with @ChrisJ. You’re giving bad advice. You need to learn more before you try to help. This also applies to the thread on how steam vents work. I suggest you get a copy of The Lost Art of Steam Heating and study it. Thanks. 

Jamie Hall

In addition to the remarks above -- I'm completely with @ethicalpaul and @ChrisJ -- and @DanHolohan ! I'll add this: where are you located? If "triple decker" suggests you are in cental Massachusetts somewhere, the @Charlie from wmass .

Charlie from wmass

Your plumber is incorrect and misinformed. There's nothing to discuss truly. 

DanHolohan

Please read the book I suggested, @tommay. Some of your posts are making me think of the guy who had his electrician read his electrocardiogram.

When a lot of people are telling you that you are giving bad advice, it would be good for you to be quiet.

SteamingatMohawk

@tommay I am a mechanical engineer that worked in the US Nuclear Navy program for 38 years, including qualifying on and operating a submarine prototype power plant, going through 2 power plant refueling/overhauls. I've had my steam system for 33 years and I can tell you outright, many of the guys on HH are absolutely right on and there is some "magic" in steam heat.

If you don't listen to me, listen to Dan. You can message him privately using the envelope thingy at the top of the screen.

This is not being disrespectful, just candid and looking out for all of us.

DanHolohan

You don’t have the right to post bad or incorrect advice on this site. It’s dangerous. 

Charlie from wmass

My father was a great plumber and he started the trade in 1953. He and I fought constantly until my late twenties about how to install steam boilers. My father had decades more experience than me and finally realized he had been doing it wrong and I was doing it better. There is no magic involved with steam heating. There is only physics. And the original post was about boiler size and whether or not their plumber was oversizing the boiler. Grossly oversized boilers provide heat and very few people complain when they have an oversized boiler as far as adequate he goes. What they don't realize is they are wasting fuel every day that boiler runs. Since they have nothing to compare it to they never know the difference. Advice to install a larger boiler due to the fairy tale of water content is a disservice to the consumer and is perpetuation of falsehoods that exist in our trade. I have spent the last 20 years of my career fixing the mistakes of people that should have known better but refused to accept the knowledge they were given often for free.

Erin Holohan Haskell

Well said, @DanHolohan and @Charlie from wmass. Thank you.

DanHolohan

Exactly, Charlie. Thank you. A cup of water becomes 1,700 cups of steam at 0 psi. How much steam do you need to fill the system?  

I can’t believe we’re having this ridiculous conversation. 

Erin Holohan Haskell

@radsteam1870, I'm sorry your post got off track. It sounds like you need a steam pro. Where are you located?

radsteam1870

Thank you all for your helpful comments, especially @KC_Jones for providing such a clear breakdown, and @ethicalpaul for the video demonstration.

@Jamie Hall @Charlie from wmass Close -- I'm in Somerville, actually, which you wouldn't think would be short of heating contractors, but there's been terrible weather here lately and everyone was booked weeks out dealing with the aftermath.

HVAC guy (he's not a plumber, my bad) has followed up that while we *could* install a 4 section boiler and nothing terrible will happen, it'll be less efficient because the low-powered burner will be on all the time, instead of a larger boiler where it will turn on for a bit and make enough steam that it can turn off for a while and save energy.

That... does not sound right to me. Am I missing something here? Is there a read where that makes sense, and if not, is there something I could have misheard that sounds like that but makes sense?

My mom, Jen, and I share and co-own the apartment and we both have to sign off on any repairs. Jen is *very* committed to hiring this guy, because he is honest (I agree, he believes what he's saying) and he has a reputation for being responsive when something he installs has issues, so if we hire him to install the boiler we will have someone reliable to service it. I argue that we will not get *good* service, because if we go with the smaller boiler after he's doubled down on the 5-section, then everything that goes wrong will always be because we didn't go with the 5-section boiler, forever and ever amen.

HVAC guy suggested getting a 5-section boiler and shutting off one of the burners if we decide we don't need it. Jen thinks we should go with that plan as a compromise. She also wants me to stop antagonizing her friend's HVAC guy. At this point I want to just get out the space heaters and wait the three weeks for another plumber, but I am exhausted.

How much of an efficiency loss would this plan plausibly be vs just installing a correctly sized boiler?

DanHolohan

This is why I majored in Sociology. 

Do it right and you only have to do it once. My advice. 

mattmia2

Run.

EDIT:This was my comment on your original post. It is even more relevant to your second post. This person doesn't understand the basics of energy much less all the details you need to get right to make a steam system work well.

Chris_L

@radsteam1870 I can't help you with your mother, but I do have a couple thoughts.

Are you sure you calculated the EDR of your radiators correctly? It seems a bit high to me.

I am on the first floor of a two-family in a nearby town, and my radiators total 165 EDR (to heat 1200 square feet). The radiators in my tenant's unit total 207 EDR (for 1800 square feet on1.5 stories). But I wouldn't expect a typical floor of a Somerville 3-family to be more than about 1100 square feet.

In any case, if none of the pros on this site are available to help with a new boiler install, send me a PM and I can suggest some people locally (with no guarantees on their availability).

Jamie Hall

Difficult situation. You will lose efficiency with an oversized boiler, the only question is -- how much. If you leave all the burner tubes in place as designed, probably not much. If you "shrink" it by taking some of the burner out, potentially quite a bit. Also having it cycle on and off -- which it will have to, to match its output to the load -- may shorten its life some (probably not all that much) and may be annoying -- but if it's in the basement and you're on the third floor... maybe not.

But as @DanHolohan says, that's why he majored in Sociology, and why I'm a monk -- to deal with people problems, not heating problems!

DanHolohan

Jamie, you always make me smile. Thanks. 

KC_Jones

This website was started by a man that has written the books on steam heating and he is commenting on this thread. Some of the greatest steam men in the country are on this site. They are giving you the best advice there is.

Ask your mother how much money she wants to pay someone to do their job wrong. Personally I take pride in the work I do, so I’d have a hard time giving someone my hard earned dollars to do their job incorrectly.

His analogy about saving energy is wrong, it’s going to build pressure, building pressure in a steam system is always a waste of energy. As Jamie said, how much is debatable.

So to summarize, you pay more for a bigger boiler you don’t need, it will be less efficient costing more over its life and I can easily argue it will not run as well due to building unnecessary pressure which typically leads to noisy vents and discomfort. I would also be leary about him piping it correctly given his lack of knowledge on the sizing.

No matter how hard I try I can’t think of a single upside other than stroking the contractors ego.

Out of curiosity, how does the system work now? Steam should be silent and comfortable.

DanHolohan

So well said @KC_Jones. Thanks. 

EBEBRATT-Ed

@radsteam1870

I agree with all the above comments about installing the correct size boiler.

It's not my intention to add fuel to the fire but when you have decided which boiler to install please download the manual.

Find the piping diagram and see that the installer follow it closely. And copper tubing for the steam portion (anything above the water line) isn't the best choice.

radsteam1870

@Chris_L I calculated based on the values in an ASHRAE chart Dave_in_QCA posted in another thread. In total, it's two 26" high 3x20 columnar radiators (75x2), one 25" high thin-tube 4x20 radiator (40), and one 25" thin-tube 3x10 radiator (17). I tried the local contractors listed on this site first thing, so I will definitely ping you about those recommendations.

@KC_Jones Yeah, that's pretty much it. There are short-term benefits (getting it done now instead of several weeks from now, about 2k cheaper than we expected), but it's mostly about the social repercussions of pissing off a family friend. That last bit obviously isn't relevant to the forum, and I only mentioned it in my last post because, well, several very smart and knowledgeable people have taken the time to explain to me in great detail that hiring this guy is a bad idea, and I figured I should explain why on earth I was still considering it before asking you all yet more questions.
Honestly, if I had gotten "this plan is dumb and pointless, but probably won't make things worse" in response to the last post, I would have gone along with it to keep the peace. That is not what I'm hearing.
In response to your question about the heating system now: it's still the quietest steam heating system I've ever had, but my gas bill has more than doubled this year from last and now if you turn the auto-fill off the LWCO kicks in in about three hours. The burner tubes are solid rust and will just refuse to light every couple of days. We had a brief outage last year, and we had two different contractors in to check it out, both of whom told us the boiler just needed to be flushed. It's been a learning experience.

KC_Jones

My grandfather was, without a doubt, the wisest man I’ve known, one thing he told me is never do business with friends or family.  You are experiencing exactly why it’s bad.

When hiring a contractor the only thing that should be considered is what’s right for you the customer, it’s your money.

It won’t continue to operate as you describe if he installs that oversized boiler.  It’s going to build more pressure and faster, most likely make the vents loud and annoying, it will short cycle, and you may even end up with balance issue due to the increase in steam production and constant cycling.

Did he explain in detail why he thinks the building needs a bigger boiler than it’s had for the past 25 years?  I can’t imagine the mental gymnastics he would go through to explain that.

Just a few more points to complicate the situation.

If you’d like, send a link to this thread to your mom, we’d be more than happy to explain.

For me, looking at the facts, this is a no brainer.

BTW, I’m just a homeowner, but I experienced the pains of contractors that don’t know what they are doing so I ended up installing my own.  You aren’t alone, there really aren’t many contractors doing steam correctly.  That is perhaps a key point that not many understand.

SteamingatMohawk

@DanHolohan Yes, I agree there is science to this, but to me the interaction of air and steam/water in a phase changing environment within a building that faces all four directions and has heated and unheated rooms scattered throughout is some of the "magic".

DanHolohan

I like magic. 

Nothing to do with steam, but my seven-year-old grandgirl, Quinn, recently said, “Did you know that wizards are really just old men with some glitter in their pockets?”

mattmia2

So it was probably leaking above the water line for a while before you noticed liquid water and those that looked at it somehow missed that.

STEAM DOCTOR

radsteam1870 said:

Thank you all for your helpful comments, especially @KC_Jones for providing such a clear breakdown, and @ethicalpaul for the video demonstration. @Jamie Hall @Charlie from wmass Close -- I'm in Somerville, actually, which you wouldn't think would be short of heating contractors, but there's been terrible weather here lately and everyone was booked weeks out dealing with the aftermath. HVAC guy (he's not a plumber, my bad) has followed up that while we *could* install a 4 section boiler and nothing terrible will happen, it'll be less efficient because the low-powered burner will be on all the time, instead of a larger boiler where it will turn on for a bit and make enough steam that it can turn off for a while and save energy. That... does not sound right to me. Am I missing something here? Is there a read where that makes sense, and if not, is there something I could have misheard that sounds like that but makes sense? My mom, Jen, and I share and co-own the apartment and we both have to sign off on any repairs. Jen is *very* committed to hiring this guy, because he is honest (I agree, he believes what he's saying) and he has a reputation for being responsive when something he installs has issues, so if we hire him to install the boiler we will have someone reliable to service it. I argue that we will not get *good* service, because if we go with the smaller boiler after he's doubled down on the 5-section, then everything that goes wrong will always be because we didn't go with the 5-section boiler, forever and ever amen. HVAC guy suggested getting a 5-section boiler and shutting off one of the burners if we decide we don't need it. Jen thinks we should go with that plan as a compromise. She also wants me to stop antagonizing her friend's HVAC guy. At this point I want to just get out the space heaters and wait the three weeks for another plumber, but I am exhausted. How much of an efficiency loss would this plan plausibly be vs just installing a correctly sized boiler?

My mother is very honest. I would not allow to install a steam boiler in my home and neither should you 

radsteam1870

Sanity check #2:

Good news: Jen has agreed to sign off on whoever and whatever I want for the install as long as it happens in the next 10 days, I pay for it all, and I never, ever try to have a conversation about steam heating systems with her ever again. Thank you all, I could not have done it without you.

And thanks to a local referral from @Chris_L (thank you), I have found a guy who is not trying to get me to short-cycle my boiler as an efficiency measure and who has proposed... the Weil-McLain EG-30 that @ethicalpaul mentioned in the first response to this post.

(Several people on this thread have suggested the Peerless 63-03L. It looks ideal but also seems to be universally unavailable.)

@ethicalpaul and @KC_Jones, your posts have been extremely helpful so far, and I wanted to ask about the recommendation for the WM EG-30 (196sqft). We have about 140' of pipe in the system: 70 feet of insulated 2" pipe running along the basement ceiling, and 4 ~20' risers each going up 2 floors, all of them on exterior walls with poor insulation. I don't know the width of all the pipe in the system, but all the risers are the same diameter as the 2" header when they take off from the unheated basement for as far up as I can see, and one of those risers is 2" when it feeds into the radiator, so I don't want to assume the others narrow before the third floor.

Also, if it matters later, there are no main vents and based on the piping never have been. The basement pipes are shaped more-or-less like a cross with an elbow and a single riser going up to a single radiator at each end, plus they all have less than 2" clearance to the unfinished ceiling, so it's not clear where main vents could even be installed.

So, copying KC_Jones' calculations, the EG-30 gives us 47k BTUs net, and 62.5 BTUs total usable capacity. The radiators as they currently are require 207 x 240, or about 50k BTUs, and a small 15-EDR radiator would bring it up to 53k BTUs, with about 9K BTUs for piping/pickup. But the 140' of piping has an EDR of 87, or 20880 BTUs. So the EG-30 is 12K BTUs short for the system as a whole. Right?

Now, obviously, 1. we only care about heating the radiators and 2. steam rises, so in a frictionless physics-textbook world this would still be vastly overpowered. But in our imperfect world, is it still enough? Our radiators already heat unevenly no matter how I set the vents, and I worry that my dining-room radiator, which is always the last to heat even if I remove the vent entirely, would simply not heat with this configuration, or that I'd spend a half-hour just warming up the pipes every time the heat turned on. Am I overthinking it?

Thanks again for your time and expertise.

KC_Jones

Your balance issues are most likely directly related to lack of main venting, or not enough venting for the risers. That second one has been discussed on the forum several times as a way to improve balance. If neither one of those ideas interest you, then we will just move on and say, your balance will only get so good, regardless of boiler size.

That is a lot of piping for a system with only 200 EDR. Did there used to be a lot more radiation connected on other floors? Seems strange, but let's look at your numbers.

First, if the mains are fully insulated, I wouldn't factor them into this discussion. For the EDR to count the pipe is acting as a heat emitter, which, when insulated, it's not, or at least very little. So that would reduce your calculations accordingly. Without running the numbers you can see how this would work out just fine.

My calculations were based on the Force brand of products you mentioned at the beginning which is a bit bigger, but that Weil Mclain EG-30 should be fine as well. IMHO.

mattmia2

You can go a little under the calculated EDR as long as it is still more heat than the heat loss of the building and the system is relatively well balanced. The radiators may not fill completely but will produce enough heat to heat the building. You really should fix your main and riser venting, that will cost you a lot in additional energy as well as poor comfort.

radsteam1870

@KC_Jones Yes, it's a lot of piping; based on how it's laid out we think that the building originally had a single heating system with a single boiler where ours is now, and that there was a radiator coming off each riser on each floor, but that that it was chopped up when the building was converted to condos in the 80s. There may even have been riser vents at some point, although since the risers are walled up on the first and second floor they probably (hopefully?) aren't there now.

Entirely discounting the mains, that leaves a (pretty tiny) 3k BTU deficit. Your original post about the FORCE line communicated (quite effectively) that there's no need to run an overpowered system. I gather a deficit this small isn't going to compound into an issue either.

radsteam1870

mattmia2 said:

You really should fix your main and riser venting, that will cost you a lot in additional energy as well as poor comfort.

So I'm learning. My mains venting options are limited and my riser venting options are nil, so I'll probably be posting here again in a few months trying to figure out how to attach a Big Mouth to my bathroom radiator.

mattmia2

It isn't ideal but you can put a main vent in a drip below the main if you have to. Is the return at the boiler or at the far end of the system?

delcrossv

You can (almost) always vent risers right before the radiator valve. Replace the angle valve with a reducing tee and a straight valve and put the vent in the top of the tee on a nipple.. There's lot of pictures of that type of rig on here.

radsteam1870

mattmia2 said:

It isn't ideal but you can put a main vent in a drip below the main if you have to. Is the return at the boiler or at the far end of the system?

Far end. Right where the pipe bends up into the first-floor wall, there's three elbows forming a trap with a drip leg coming out the bottom. The wet return runs from there back along the floor all the way to the boiler.