Sizing help

saikosis

My boiler died, and I'm getting quotes for a replacement.

My existing radiators have 343 sq. ft. of EDR. I consulted the old manuals directly, so I'm pretty confident in that number.

At one point, we considered adding radiators back to one or two rooms that previously had them. I think we'd probably have slightly more even heat distribution if we added them back, but it's been fine without them. (I have no idea when or why they were removed.) Referencing the indentations on the floor where I assume the feet used to be, I estimated an additional 80 sq ft of EDR in total for the missing radiators. The odds that we ever add them back is pretty low, but not zero.

We have a 60-gallon indirect water heater and two teenagers.

Most of the piping in the basement is wrapped with 1" insulation, but the elbows and other connections are not insulated. There are also some pipes in a crawlspace that are not insulated, partly because of access issues and partly because there are water lines in there that I think deserve a little heat.

I know I could insulate better. I did what's there myself, which is why the more complicated stuff isn't wrapped. I actually got a quote earlier this year to finish the job, but the cost seemed very high for the expected payoff. I might have the contractor insulate the new near boiler piping and tackle the rest of the gaps myself.

The Peerless 63-03 is rated for 308 net sq. ft. of steam , 63-04L for 383, and 63-x-04 for 388. US Boiler's STMX125 is 321, IN5PVNI is 363, and STMX150 is 388. Weil-McLain's EG-40 is 321 and EG-45 is 388. There are probably other options too. Of course, I'll have to work with what's available and what the contractor likes to work with.

I'm between sizes, and that's just taking into consideration my radiators. Factor in the indirect water heater that isn't going anywhere, the missing insulation that could be fixed, and the missing radiators that may or may not reappear, and I'm not sure what I should do about sizing.

Suggestions?

Jamie Hall

Interesting dilemma! Ask six of us and you'll get twelve answers… but to start the ball rolling, in this particular instance, with your particular parameters, the best match is the INSPVNI — I'd consider the EG-45, but I'd also want to look at it (or ask my installer) if it can be downfired. Some boilers can. Some can't.

The indirect shouldn't be a factor.

EBEBRATT-Ed

Whatever you buy do NOT buy a BURNHAM INDEPENDENCE. Peerless and Weil McLain are ok. Burnham Steam MAX may be the best with the water you have.

ChrisJ

Peerless 63-03 is probably your best bet.

EG-40 is also fine but id be very tempted to go with an EG-35 if it was my house.

An EG-45 is too big.

Jamie Hall

Told you there'd be a variety of answers…

saikosis

I'm curious why you say the EG-45 would be too big. Aren't the EG-40 and especially the EG-35 too small? The EG-35 is 258 net AHRI to my 343 EDR. On a cold day, wouldn't that mean it would run forever and never get the job down? Are you guessing that design days are rare and that most of the time you don't need to fill every radiator completely? Is it that the EG-35 would be good enough 95% of the time and you can just put on a coat for those really cold days?

I'm also curious why the indirect water heater doesn't affect it. It's stealing heat. Don't I have to make up for that?

Jamie Hall

Couuple of thoughts. First, @ChrisJ and I have a sort of continuing running debate on just how big a boiler needs to be for a given system. I tend to go a bit on the bigger side, and tolerate some cycling if the boiler can't be downsized. @ChrisJ tends to go under, and prefers that the boiler be more exactly matched, once things are all warmed up, so that it minimizes cycling on pressure. It's a valid debate! In this case by reasoning is partly that crawlspace, but also it gives you an allowance to add those two radiators back if you wanted to.

EBEBRATT-Ed

Normally to heat domestic HW with a tankless coil or an indirect water heater off a boiler no addition capacity is added for the DHW.

The boiler if sized by the EDR already has 33% extra capacity built in.

If I remember right Burnham (as well as other mfgs) had a lot of steam boiler failures and the locations with the largest number of failures were located in RI and Eastern, MA. Burnham blamed this on "high chlorides" in the water along with locations in their boiler where you had flame on one side of the HX and combustion gas on the other side.

The new design of the "steam max" is supposed to prevent this type of failure.

You all know I would be the last person on earth to recommend any Burnham product.

But the OP stated (in his other post) he is in Eastern MA so the Steam Max may be the best boiler for him especially with the # of boiler failures he has already had. Steam Max 150 with 388 square feet or the Steam max 125 with 321 square feet

ChrisJ

https://forum.heatinghelp.com/discussion/comment/1905476#Comment_1905476

If you put all of the "rules" aside and look at the math alone you'll see why.

Look at the input and actual output of an EG-35. You have 100,000 btu/h input and a DOE rated output of 82,000 btu. Your radiation consumes 383 X 240 = 82,320 btu/h. Do you have an idea of the heatloss of your house? How big is it and how's the insulation?

You do not need extra energy to "heat all of the piping and radiation up together". If the system is properly balanced, the boiler will first heat all of the piping and then each bit of radiation section by section. Steam radiators never heat all at once, they heat bit by bit and if a certain radiator hogs all the steam it needs a slower vent.

You do not need to heat missing radiators because they do not exist. I'm not sure if this matters in huge systems with large piping, but in yours it doesn't for sure. Any existing runouts without radiators shouldn't heat at all because they can't vent air. This is especially true at reasonably low pressures that a smaller boiler will give you.

The EG-35 will almost certainly work fine for you as long as your piping is insulated, even with the indirect.

My system has 392sqft of radiation and I originally started with an EG-45. After several years I converted it to an EG-40 because I was tired of how sensitive it was to changes and I couldn't do any recovery without producing excess pressure. In fact, it would start to build pressure just maintaining a constant temperature when it was extremely cold out. Dropping it to an EG-40 got rid of all of that except during extreme cold if a lot of my TRV's are shut it still might start to creep up towards a 1/4 psi.

This is why I mentioned the EG-35, because there's a chance I'd choose that for my house if I have to replace my boiler again. I'm sure it would heat it just fine even with 392sqft.

@KC_Jones is running a negative pickup factor, his boiler is undersized for the load and his radiation is undersized for his house. I've been running 1.10 since I think 2013 or 2014 because 1.33 was too big, I didn't like it.

More boiler means a more sensitive system and larger overshoots and more hissing vents especially during a recovery. You never need 2 PSI, or for that matter 1/4 PSI in a typical single family house. A larger boiler is always bad.

Chances are your radiators are already oversized for the house. Don't make it worse by oversizing the boiler for the oversized radiators.

I think you want the Peerless 63-03, it's got a little more than the EG-35 but a little less than an EG-40 and from what I've heard it's a better boiler.

Sorry for the huge response…… but you asked a good question and I wanted to answer it as best I could.

pecmsg

Here on Eastern Long Island the design temperature is 5°F. Does it ge colder……………..Yes. Do we design for the few days a year (Last year 5 nights were lower than 5°F) that it gets lower…..NO.

95% of the nights are above 5°F so the boiler is in fact already oversized.

Jamie Hall

But remember, @pecmsg , steam boilers are sized on radiation, not on heat loss, and so the design outdoor temperature is completely irrelevant.

Steamhead

https://forum.heatinghelp.com/discussion/comment/1905460#Comment_1905460

This. Even here in MD I've replaced a lot of these. I'd go with the Peerless 63-04 or W-M EG-45, in case you decide to re-install those rads.

pecmsg

https://forum.heatinghelp.com/discussion/comment/1905515#Comment_1905515

I agree but we don't know how old this home is and what improvements have been made that cause the existing radiator EDR to be too large fro the room today.

I don't have issues with under sizing epically in older homes that have had major improvements.

Jamie Hall

Trying to balance a significantly underpowered steam system is… frustrating at best. At least with two pipe, it can be done. One pipe is a major challenge.

ChrisJ

https://forum.heatinghelp.com/discussion/comment/1905519#Comment_1905519

Have you tried it?

saikosis

I like the debate. There are lots of things to think about.

The house is from the 1850 or so and is kind of L-shaped. One part of the L is mostly uninsulated in the walls with blown-in insulation in the attic that has almost certainly settled by now. The other part of the L is probably in better shape for insulation due to more extensive renovations. This part of the L has the crawl space though. We used to get a breeze up through the floor, and spilled water would freeze on the floor on really cold days. We did spray foam in the joists above the crawl space and around the skirt, but it's still a little drafty.

Mostly original radiators. Two were removed, like I mentioned. They are both in the uninsulated L. One radiator was added when a back porch was enclosed and made into a kind of sunroom. That room is hard to keep warm because it's a little isolated from the rest of the house, so it doesn't really get carryover from other rooms. 343 EDR is what's there now for radiators.

Eight foot ceilings, except the sunroom has a sloped ceiling that goes from around 7 to probably 15 or so.

Jamie Hall

Yeah, I know what you mean. Spilled water on the floor freezing… we used to have a couple of rooms which had snowdrifts. Inside. Fun.

If you can figure out a way to keep the breezes from whistling through the crawl space it will help. Easier said than done. When I lived in Vermont we used to use hay bales for that, stacked against the foundations, but that's a little bit country for most people — and it's hard to get hay bales anymore in the more "civilized" parts of the country.

On powering a steam system. I suspect it is partly a more general almost philosophical debate. I have always liked to have available at least a little bit more power than what I needed — whether it was an airplane, a pickup truck, the family sedan, a lobster boat, a house heating system, a house electrical system… whatever. One can always back off the throttle a bit if you don't need all the horses in a particular situation. On the other hand, if you don't have them, you just don't have them. Tough luck. It's much easier in some applications to get it right — and a steam heating system is one of those, since you have a known load and the question amounts to how much extra margin you need above that to provide satisfactory power. I'm not in favour of wildly over-powering something, mind you — and that applies as much to a heating system as it does to the family grocery getter. But I do have an objection to the current trend of too little power and then every tweak tried to make it work. Just me, I guess.

saikosis

I'm generally in the "you might need it someday" camp too.

I know from 13 years of experience that the EG-50 has been fine. We maybe could have saved some fuel with a smaller unit. Maybe we would have been more comfortable. Maybe that one radiator in the sunroom wouldn't vent quite so aggressively. But it worked fine and kept us warm enough and comfortable enough.

The 45 would be just fine. The 40 too maybe. The 35 would make me nervous. I'd have to pay attention to it, which might actually be a fun hobby, but I worry about how much time I'd really be able to commit and how much my family would tolerate the early kinks.

This kind of makes me stress a little less about getting someone to do the replacement too. I'm not starting from scratch, so really anyone who can do boiler work could do a like-for-like swap without screwing things up (I hope). If I can get a steam head though, even better. I don't think I'd switch manufacturers without a real steam professional on the job. I assume that would involve more piping changes and have more opportunity for mistake.

KC_Jones

https://forum.heatinghelp.com/discussion/comment/1905519#Comment_1905519

I know I am only one system, but when I downfired my boiler to be 3% below the connected radiation I didn't change a thing and the balance remained the way I dialed it in previously.

saikosis

Regarding down firing, how does it work? Do you adjust some kind of regulator, yank out one of the burners, something else?

Your signature mentions EG-40. Is that the one you down fired?

KC_Jones

https://forum.heatinghelp.com/discussion/comment/1905533#Comment_1905533

I am doing things that would probably not be officially approved by any professional or manufacturer so I own it. For mine I removed burners. If I had it to do over again I would have installed an EG-30. I will be selling this house before this one needs replaced so what happens after that will be on the next owners. I will leave them detailed information about the quality of the system they will be getting and to not let the local knuckleheads mess it up when replacing it (they will if left to their own devices).

Jamie Hall

How you can down fire a boiler depends on the fuel, the type of burner, and the firebox in the boiler itself. Sometimes on gas it is as easy as removing a burner tube or two and adjusting the air and draught for best combustion. Other times you may have to change orifices or nozzles and air. And other times how far you can go depends on the fire box geometry, which may limit the minimum firing rate.

Also, depending on all of the above, you may wind up with slightly lower thermal efficiency.

EBEBRATT-Ed

@KC_Jones

I will give your boiler 8 years after the new owners get their mitts on it. Because you take care of it it will probably run 6 years with their neglect and 2 more years of that will finish it off.

ChrisJ

This morning my system fired up and heated the house for the first time this season and it was all still perfectly balanced as usual.

Obviously everything was cold and the EG-40 still had no problems with 392sqft.

Something else I'd like to add. I have TRVs on 5 out of 10 radiators and even those do not seem to effect the balancing even when all doing their little dance. Sometimes they're open, sometimes they're closed, sometimes they're open but only very little. Nothing else seems to care.

I added the TRVs to allow the system to cope with outside changes like solar loading, cooking etc. It's awesome to have the kitchen radiators stay ice cold on thanksgiving or Christmas day yet the rest of the house heats normally. They were not used to balance the system, it was balanced before them.

I can't speak for everyone, and certainly not large systems in huge apartment buildings and such, but my own single pipe system doesn't follow any of the rules or have any of the problems others talk about.

mattmia2

problems with balancing with a boiler that matches or is a little under the actual connected edr tend to happen when there are other system problems like mains that tee above the header instead of connecting individually or where there are some significant pockets of trapped water. Those sorts of things tend to make the steam prefer one path over another and make that path want to heat. When there is no excess steam the easier path wins. When there is a little excess steam it can fill both paths. I would argue to fix the problems rather than to oversize the boiler.

ChrisJ

https://forum.heatinghelp.com/discussion/comment/1905726#Comment_1905726

But how do you know that?

mattmia2

that's where a pro that has experience comes in. running the old system can help too

Jamie Hall

Mind you I'm not suggesting that a steam system which has a boiler exactly matched to the radiation (under normal conditions — it will be too small mismatched if the heated space is colder than normal, for instance) can't by made to work splendidly well. My own Cedric is matched to within about 3 percent, for example. What I am suggesting is that it is easier to balance a system if one has a little extra power to play with.

There is another aspect to this which pops up now and then, and applies as the mismatch between boiler power and radiation becomes greater: cycling. A good many discussions over the years have been had on that one. My contention was — and continues to be — that if the off time of a boiler which is cycling off and on to maintain pressure is short, the loss of efficiency is minimal — and may be very close to zero. It is somewhat inelegant, and some folks really are bothered by the cycling — but that is a psychological problem, not an engineering or thermodynamic one. (Note, however: if the off time is long enough for the boiler to drop below a simmer — say more than a minute or two — then there is an efficiency loss). Cycling does become problematic if the boiler is really seriously oversize — perhaps somewhere around a rated power output of half again the system power requirement.

saikosis

The thing that I think about is what am I going to regret more?

If I put in an undersized boiler and it can't heat my house, that's a big regret. I can buy a coat, but I can't easily put in a new boiler again.

If I put in an oversized boiler and it is inefficient or bangs or whistles or whatever, that's a small regret. And it sounds like I have options, like downsizing or even adding those other radiators that I always wanted.

That makes me lean more toward a slight oversize. I'd probably be fine with either. Smaller may be better, but bigger might be safer.

Considering that there's probably no right answer, does that sound like a reasonable way to think about it?

Steamhead

https://forum.heatinghelp.com/discussion/comment/1905792#Comment_1905792

Yes.

ChrisJ

https://forum.heatinghelp.com/discussion/comment/1905792#Comment_1905792

That's why my recommendation was the Peerless 63-03 or EG40.

Both of them are "slightly oversized" if you ignore the rules from almost a century ago. I later said I would use the 35, but I never meant to change my suggestion in your situation.

I don't know about the Peerless, but the EG40 may have a backup plan assuming WM didn't change anything.

Back when I did it the EG-40 and EG-45 shared the same block and only had different drafthoods , burner manifold and burner support. I think it cost me something like $300 to convert my EG-45 into an EG-40. That's not downfired etc, it's 100% legit an EG-40.

Even if that is true, I'd still highly urge you to go with the EG-40, do not start with the 45.

Jamie Hall

I think that's that is a very reasonable way to think about it.

Only I would add — unless you put in a much too large boiler, or control it poorly, you won't take a significant energy hit. Also, if it is installed correctly it won't bang or whistle or otherwise annoy you…

saikosis

In this particular case, I'm also thinking of ease of installing the new boiler. If I can't get a real steam pro and have to use a knucklehead, it'll probably be easier for a knucklehead to do a simple swap and tie into what's there. Even if I went from my EG-50 to a new EG-45, it might still be close enough.

I'd have to look at the manuals for other brands and compare their dimensions, but I assume they'd differ from the Weil-McLain just enough to require more repiping that could risk some knucklehead mistakes.

My boiler that was here when we bought the house was way oversized, had copper near boiler piping, and no hartford loop, so I know the damage a knucklehead can do.

ChrisJ

https://forum.heatinghelp.com/discussion/comment/1905800#Comment_1905800

30 and 35 should be identical.

40 and 45 as well.

The heights of all of them as well as taping side I believe are identical. But the distance between the outlet tapings will be different due to number of sections.

If you send me a PM I can show you pictures of what was involved in changing between the two, at least a few years back.

Steamhead

@saikosis , where are you located? We might know someone…………..

ethicalpaul

https://forum.heatinghelp.com/discussion/comment/1905792#Comment_1905792

It's nearly impossible for you to put in a truly undersized boiler. The boiler has a 1/3 extra slop factor. Never round up, the manufacturers already rounded up for you way too much.

In this particular case, I'm also thinking of ease of installing the new boiler. If I can't get a real steam pro and have to use a knucklehead, it'll probably be easier for a knucklehead to do a simple swap and tie into what's there. Even if I went from my EG-50 to a new EG-45, it might still be close enough.

I'm a very weak software engineer who never touched a boiler until I bought my house in 2017. In 2020 I installed a new steam boiler myself with only the knowledge I got from this forum. You don't need a real steam pro, you need anyone with a couple pipe wrenches who is willing to open the manual.

saikosis

I'm in Southeastern Mass. I got the two standard recommendations (Charlie from wmass and New England SteamWorks) in my other thread (https://forum.heatinghelp.com/discussion/204947/15-years-2-cracked-blocks-1-leaky-indirect-water-heater-coil) but might need more recommendations because of availability.

Charles put the boiler in, so I should be able to trust the near boiler piping, which is why a swap by a knucklehead might not be too bad if I can't get him back out here himself.

KC_Jones

https://forum.heatinghelp.com/discussion/comment/1905792#Comment_1905792

The possibility you will actually put in a too small boiler is zero, it's not going to happen no matter who you listen to on here. I have had too big, by a small amount and I now have "too small". From a comfort standpoint this is an absolute no brainer for me, the smaller is better by a huge margin. I went from Yugo to Cadillac, the difference is dramatic. In your case an EG-40 or similar would be the max I would go. Get it installed properly, balance it out and be happy. The EG-40 still give 25% pickup factor, which I feel is too much, but way better than going with the 45 which would be 50%, which is crazy.

ChrisJ

https://forum.heatinghelp.com/discussion/comment/1905810#Comment_1905810

If Charlie did it, I'm 100% sure the piping is good.

He's one of few I'd trust to work on my stuff.