Water content (capacity) new boilers

307TurboFire · February 2019

Can anyone help me compare and contrast the water capacity of, say, a 1980s 100K BTU input residential boiler with a modern 100K BTU input residential boiler? More specifically, I am wondering about a circa- 1985 Utica PEG-112AW compared to a current Utica PEG112EID. By the way, it seems to me the chassis footprint of these two Utica models is about the same.

With respect to today's generally smaller water capacities, doesn't that make blowing down even more important than it was, in order to get the crud out? And yet at the same time we are admonished not add make-up water? If we are supposed to be blowing down at least the low-water cut-off control "periodically" during a season, which I would take to mean about once a month, doesn't that mean we will have to add the make-up water we are admonished not to add?

If water capacity has become such an issue, why is that Peerless seems to be the only mfr including water capacity in their model chart?

Reminds me of a scene in Raising Arizona:

Gale:
Alright ya' hayseeds, it's a stick-up. Everybody freeze. Everybody down on the ground.

Old Man in bank:
Well, which is it young feller? You want I should freeze or get down on the ground? Mean to say, if'n I freeze, I can't rightly drop. And if'n I drop, I'ma gonna be in motion. You see...

Gale:
Shut up!

Old Man in bank:
Okay then.

Gale:
Everybody down on the ground!

ethicalpaul · February 2019

I'm so glad you asked this, because I have long wondered the same thing. Some references say to flush the boiler weekly or monthly and that must be the same (or worse) as adding water every couple days due to a leak which everyone says is really bad!

PS: if you want, I can measure the water in my old PEG 112, but I assume you have one of those already

Fred · February 2019

I have a 1983 Burnham boiler that has a water capacity of 25 gallons. I believe the new ones are in the 12 to 15 gallon range.
I also have a McDonnell and Miller #67 LWCO on this boiler and I blow it down once a week, during the heating season, for the 28 years I have been in this house. It only takes about a quart to half a gallon of water to blow it down to get clear water. The concern for a lot of "Fresh water" is with regards to a lot of make up water due to system leaks, bad vents and frankly pure neglect. It also should be noted that the concern for fresh water is due to the amount of oxygen added to the boiler water, which will add to the risk of rust/rot. If you look at all the posts regarding the addition of fresh water, the advice is to bring the water to a boil when added to boil off that excess oxygen. At 36 years old, my boiler owes me nothing at this point even though I hope it goes another 36 years or at least until I die, whichever comes first.

EBEBRATT-Ed · February 2019

As @Fred mentioned blowing it down occasionally during the heating season is no concern. Any oxygen in the water will be driven off on the next call for heat in a steam boiler.

On the commercial jobs I usually work on with a boiler feed tank it is common for the customer to neglect the steam traps. This results in steam blowing through the traps and out the boiler feed tank vent=lost water. The make up water is fed in to the boiler feed tank. I have seen brand new feed water piping between the feed tank and the boiler rot out in a year or two because the water hasen't been heated to drive out the oxygen.

It's the constant addition of feed water to guard against

Chris_L · February 2019

I wouldn't assume the water capacity has changed that much over the past 30 years. And you do have to compare the same size boiler.

I have a small (266 square feet) 30+ year old Burnham 4B boiler. The water content when used for hot water is 9.2 gallons, and for steam 5.6 gallons.

The closest equivalent boiler today is the Burnham IN4 at 271 square feet. Its water content for hot water is 10 gallons, and for steam 6 gallons. So the newer boiler actually contains a bit more water.

The 25 gallons @Fred cites equals that for an older Burnham 412B used for hot water. That's a big, 12 section boiler. The equivalent figure today for an IN12 on water is 27.6 gallons.

Fred · February 2019

@Chris_L close but not a home run. My boiler is a 411B, nine section, steam boiler. It would be equivalent to an IN9 which I think has a water capacity of around 15 gallons for steam. We're not comparing a steam boiler, which is 1/2 to 2/3 full to a hot water boiler that is completely full.

Chris_L · February 2019

@Fred, both the Burnham 4B and IN boilers can be used for hot water or steam. I am really not sure what you are comparing. Where do you get your 25 gallons from?

My manuals indicate that for the 4B boiler series, the number following the 4 is the number of sections. So if you have a 411B, you have 11 sections not 9.

My point is that the water content of these boilers has not changed over the past 30 years. The older, 9-section 4B boiler has a water capacity of 12.6 gallons when used for steam. The newer, IN-9I has a capacity of 13.5 gallons when used for steam.

Fred · February 2019

@Chris_L , I have a 411B and I'm getting the 25 gallon capacity from the I&O manual for steam (that I still have) when the water level is 23 inches from the bottom of the boiler and mine is 9 sections and is original. I can't say if they built to order back in 1983 but if they did, they would have had to build the burners to order as well.

Fred · February 2019

@Chris_L , here is a post from about 3 years ago. The 4th post down is from me and includes a scan of the boiler plate from my boiler. The original Poster was a Service Tech out of New York and was working on the very same boiler, but it was missing the boiler plate. Same number of burner tubes but if I recall he had not had a chance to count the number of sections. I counted mine and there are 9. I will say they are wide sections, much wider than what the IN sections appear to be but it's hard to tell from pictures. I don't know if any redesigns occurred during the life of the 4B series boilers. Clearly some have occurred with the IN series.
https://forum.heatinghelp.com/discussion/comment/1410052#Comment_1410052

Chris_L · February 2019

@Fred, I too am wondering if they might have changed the design.

My "Series '4B' Gas Boiler" I/O manual, Table VI, specifies the 411B water content at 15.4 gallons on steam. It doesn't say anything about measuring from the bottom of the boiler. (The normal water level for this series is specified as 26" from the floor.) It also says the water content is 23.2 gallons when the 411B is used as a water boiler.

Based on the boiler plate from the post you linked, I'd say your boiler is closest to an IN11. It has a nearly identical gas input, but slightly more steam output. The IN11's water content is 16.3 gallons as a steam boiler.

For what it is worth, here is my boiler plate.

Looks the same as yours except that it is a much smaller boiler.

mikeg2015 · February 2019

Last I checked my HB Smith G300 was pushing 20 gallons. The eventually replacement, while 20-40% smaller, will be closer ot 10 gallons.

The big advantage to me is faster warm-up time for better response to heating calls, and less heat wasted to the unfinished basement space after shutdown in mild weather. More heat goes where you need it.

DOwnside is they hold less water so any leaks drain them faster. I suspect the castings are less durable. This old beast is build like a tank. Just 6 sections. Each one is probably pushing 150lbs I’d guess.

307TurboFire · February 2019

Appreciate the comments. I am totally mystified as to the make-up water oxygen concern. Even before reading the comments here, I was thinking, if you are adding make-up water, that is probably because the thermostat is calling for heat, and you want heat then and there when you add make-up water, so isn't surplus oxygen being boiled off essentially immediately? And if that is not the case, these are not sealed systems. Earth's atmosphere is found everywhere inside the system. Earth's atmosphere contains oxygen. The boiler water, either in steam or liquid form, is constantly exposed to atmospheric oxygen, wherever it is flowing throughout this system, through dozens of feet of pipe on return. I would think whether the water is fresh make-up water or has been inside the system for months, it must, at all times it is not being actively boiled, have roughly the same dissolved oxygen content.

PMJ · February 2019

Actually many times boiled water has far less oxygen in it than fresh water. Getting oxygen dissolved in water takes much agitation - as in waves, waterfalls, rain falling through the atmosphere, or pumping aerating systems in ponds. The life of condensate returning to the boiler is far more sedate than all that. It is also too warm to absorb much oxygen.

Jamie Hall · February 2019

PMJ said:
Acutally many times boiled water has far less oxygen in it than fresh water. Getting oxygen dissolved in water takes much agitation - as in waves, waterfalls, rain falling through the atmosphere, or pumping aerating systems in ponds. The life of condensate returning to the boiler is far more sedate than all that. It is also too warm to absorb much oxygen.

And furthermore -- most of the air which does get into most steam systems when they shut off is promptly driven out by the advancing steam when the boiler next fires up (or in one of @PMJ 's vacuum systems, never gets in there at all!) So the only real contact with air, if it occurs at all, occurs in the rather small surface area in the boiler when it isn't firing -- which surface area is perfectly still. Not much chance for oxygen to get in.

ksd99 · February 2019

@Fred what does it mean to blowing it down? This all very interesting, I was told by both former owners and repair guy to clean out any dirty water weeekly thru the boiler drain valve , which I know now is not why to do. So much to learn.

Fred · February 2019

ksd99 said:
@Fred what does it mean to blowing it down? This all very interesting, I was told by both former owners and repair guy to clean out any dirty water weeekly thru the boiler drain valve , which I know now is not why to do. So much to learn.

If you have a probe type Low Water Cut-off, you don't need to blow it down. I assumed if you were told to clean out the dirty water, weekly, that you have a McDonnell Miller low water cut off with a manual valve of the side of it that should be "Blown down" weekly or at least once every couple weeks. It is called a "Blow Down" because you should do it when the boiler is running. That way, the little pressure in the boiler will force some water and crud out through the bottom and at the same time, when blowing out a quart to a half gallon of water, the level in the unit will drop enough that it should shut the burner down, as a test that the LWCO is working properly. When doing the Blow down, be careful that you don't splash boiling water up onto yourself. Won't happen if the system pressure is low but if, for some reason the Pressuretol is set to high or not working like it should, it will have enough pressure to splash out of your bucket.

ksd99 · February 2019

@fred I actually have a McDonnell Miller electric probe -so I don't need to do blow down it but who knows why they wanted me to drain the dirty water. Knuckleheads.

Fred · February 2019

ksd99 said:
@fred I actually have a McDonnell Miller electric probe -so I don't need to do blow down it but who knows why they wanted me to drain the dirty water. Knuckleheads.

If all you have is a drain valve on the boiler, you can drain a little water out once or twice a heating season. Just let it run until the water is clear. That washes out any sediment in the boiler's mud leg and also keeps the drain valve from clogging.

Water content (capacity) new boilers

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