Mouat vs. Boiler Feed Pump vs. Reservoir Tank

Steam Bunny

We have a Mouat gravity feed vapor system 3000 EDR Net, powered by a 1913 1,500,000 btu Ideal Boiler. I discovered a *few* years ago it runs more efficiently at 750,000 BTU but that’s probably because I’ve insulated, turned off most of the radiators, etc., etc. In love with my Mouat system and fond of my walk-in boiler, I unwittingly became a vapor geek resisting the addition of a boiler feed pump (or any other alien device) on the system without due cause.

Slow learner that I am, last night, after perusing The Wall for the umpteenth time I went to bed trying to redesign a differential loop. This morning I woke up dreaming if the new boiler’s piped correctly I not only don’t need a boiler feed pump, the differential loop becomes obsolete, and as Dan (The Wall 10/27/02) indicates, the reservoir tank “is silly”. …. The clues are all on THE WALL, but you guys never actually get around to saying the BIG why & how to make a passive system work more reliably.

I’d like to give it a try & that’s because I have an original *SYSTEM* that *WORKS*, and am convinced the only thing that can screw it up & force me to succumb is the new *^%$)$# boiler and it’s *&%$#* near boiler piping!

I’ve concluded Boiler manufacturers & salesmen forgot about vapor systems long ago- why, you ask? Because these beauties were so well engineered their inventors forgot to include “planned obsolescence”. And when you can’t sell a repair part why would you have an ongoing knowledge of the system? So today’s boiler manufactures have focused on the 1-2 pound + steam systems (with all the breakable bells and whistles) rising to the top because they’ve *not* doomed themselves into becoming the proverbial Maytag repairman (a convoluted survival of the fittest).

Our new boiler’s a given- it’ll hold 1/10 (if that) of the water of my faithful Ideal- even $ can’t replace her gallon for gallon. So the remedy has to come from the near boiler piping- & it can be….. maybe.

If you go to your bible and turn to page 22 you’ll see the “transparent U” Dan uses to explain pressure. Cut one of these U’s in half vertically to make a J & a backwards J. Mentally screw one to the bottom side of an open pot and screw the other up to the bottom side of a pressure cooker (so both look like they’re pots wagging their tails). Place into each the same amount of water. THE AMOUNT DOESN’T MATTER. It can be 1 cup or 3 gallons- just so long there’s water showing in the J (that’s our return). Put them on the stove & what happens? As the water begins to boil in the pressure cooker- *visually*, not much…..but in the open pot? As the water gently steams away, the water level in its J begins to drop. No muss, no fuss.

Now let’s turn those pots into boilers and turn your Bible to pg.45. In the lower left hand column, Dan says “Try increasing a 2-inch header to a 3-inch and a 3 inch header to a 4-inch and you’ll see what I mean.” But, what we all lose sight of here is, Dan isn’t a Dead Man, even his book indicates he’s straddled between the deceased experts and those 1-2 pound + guys. He appreciates vapor systems, but when push comes to shove it’s not really his thing. Note: He finds nothing really wrong with using the boiler feed pump that will turn our returns into mere drains (pg. 133), force us to install F&T’s and suck us vapor owners into “planned obsolescence.” (After an $800 *rebuild* 35 years ago, my 92 yr. old system has cost about $250 in repairs).

But forgive him I do, for on page 46 is his salvation. Here he introduces us to Steam Velocity (the difference between boiling water in an open pot and a pressure cooker). Previously (pg. 43) he has quoted Mr. A. M. Daniels “the velocity should be relatively low- not be over 15 feet per second- if the carrying of water with the steam is to be avoided.” I love it because I woke up this morning dreaming we vapor people also need to do what we can to MINIMIZE/nullify/obliterate the, perhaps virtual, A Dimension between the boiler and its return, especially during startup.

Not being a heating expert, the only thing I can relate it to is a 5/8”garden hose with an on/off ball valve at it’s end. This *experiment* suggests even a restricting orifice can make a difference. If the valve is wide open (big orifice) the water dribbles out, drops to the ground & the pressure gauge reads very little if any pressure. If I close the valve halfway (smaller orifice) I begin to get considerable/faster but less water volume, the hose begins to stiffen, and the pressure gauge begins to rise. Close it further (smallest orifice) I get a cutting spray, hose is stiffer still and pressure gets closer to the 50 60 lbs of the city water supply. I realize 50-60 lbs is a far cry from 2 to 3 ounces, but is there an engineer out there who might be able to prove or disprove my *dream*, or at least show me why I'm entering the realm of diminishing returns (sic)??

If I were to get 1 Weil McLain boiler, an LGB-10 would be the correct choice for 3000 net EDR. Recommended minimum piping for an LGB-10 (single riser) is 5”. If I plug my 3000 EDR into the pg.46 formula for 5”, 6”, & 8” piping I come up with the following (if my math is correct) steam velocities: 5” = 39‘/sec, 6” = 27‘/sec, and 8” = 15.24‘/sec.

So when Weil McLain recommends a minimum 5” piping, and Dan ups it by 1x, if we want a Vapor gravity feed system to coexist with a present day boiler wouldn’t a 2x size increase get us closer to (is it?) atmospheric pressure & make for more reliable gravity returns?

Noel (6/27/02) says: “To think that a vaporstat prevents the water from staying in the pipes every bit as well as those components”

Yes, the vaporstat keeps the boiler from turning into a 1 lb+ pressure cooker, but could that be a bandaid?

Steamhead (6/29/02) wrote:

1) “You could do the same thing by installing a slightly bigger boiler and down-firing it to match the load”


Yep, especially successful if the near boiler piping is 1” bigger in size. If it’s not down-fired too much wouldn’t there be additional on/off cycles to *help* the condensate return?

2) “Most of the condensate in a Vapor system comes back thru the dry return, and unlike wet returns these are rarely clogged.”

Great point! But, in *my* system, the Mains drip to the wet returns & I think the dry returns activate only after the radiators begin to condense.

Noel, (6/29/02) I think you scratched the surface when you trustingly wrote

“……..(snip & taken out of context) If the water isn't coming back, there is a problem. It isn't in the supplies, because the boiler is piped properly”

But, if it's not upsized, the piping might not be proper for a vapor gravity feed system. Living designers don’t generally communicate with the dead, they communicate with the bottom line.

And Gerry (6/30/02) did get the fruitlessness of the reservoir tank, but what’s the solution Mr. Gill?.

“Noel, i think the ''light bulb'' in my head just went on. So if the boiler pressure was exerted down on its water the water in the wet return would not slide into the boiler till enough water returned to ''stack'' up the vertical returns to weigh enough to push it into the boiler. i think. and that’s why the tank or fat pipe idea wouldn't work. ‘cause if the water's coming back, it then doesn’t matter if there is 10 gallons or 100 gallons in the wet returns. i think....did i get that right Noel?”

Do you think it’ll *appear* to be working if tank’s big enough & there are enough on/off cycles? The proverbial oversized (safe bet) boiler might be an answer to that one, eh?

Any comments would be deeply appreciated.

Just a woman who has a perverted impulse to recycle the old & wonders if she could have dreamt a more tenable solution.

Steam Bunny

Unknown

I think we got off on the wrong foot.

I'm only a manufacturer, one of the 1-2 pound guys, as you say.

Noel

c.t.kay

input

what type of fuel is available to fire the boiler and what size is the chimney or breeching connection?

gerry gill

well, i'll tell you...

there is absolutly nothing wrong with the reservoir tank next to the boiler..or in an A dimension..i saw one put in as the hartford loop the other day..works great..put in by the master of masters around here..its physics..its just a manometer, in effect, and it HAS to work..it just must..why? because its PHYSICS..every day is a learning experiance, and i've been bleesed to be able to hang out with this local 82 year old master of plumbing physics and i've not only learned an enormous amount thats no longer taught, i've also reversed many ''taught'' ideas and re- thought many decisions based upon his insights into steam and water from a physics angle..oh, the differential loop just keeps the water from stacking up a B dimension..never stop learning..

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Steam Bunny

Mouat input/output

Fuel is Natural Gas
2 Flues are 13x17, Chimney 40'high
2 12" Stacks- one to each flue

Preservationist that I am, original vent pipe (disconnected)is still in tact.

jeff_51

put in a call

to steam head or eberatt ed or hot rod. No offense to anybody else, I know there are many other really great guys on this site, but they along with others here are REALLY sharp of some of this. I pretty much a hot water guy so I think I will shutup now

gerry gill

this may help you

maybe..page 17

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Steam Bunny

Steam Bunny

Mouat vs. Boiler Feed Pump vs. Reservoir Tank

Thanks Gil,

Took a bit of rethinking but you helped me formulate, then answer my biggest dumb question of the day! You're lucky if you only have to rethink what you once learned. I've formed a habit of forgetting what I knew and then have to start all over again. 'Tis Frustrating.

A manometer? Vertical? Horizontal? Gallons/EDR? To me a manometer is as attached, am baffled.

The creative old timers are just amazing, aren�t they?

Steam Bunny

Mouat

Jeff, Thank you for your input.

I got into a long 2002 thread last night. It offered some good stuff so I ended up quoting a few players whose thoughts tended to parallel my desire to keep a Mouat system as passive as possible.

I'd call everyone if I could just come up with coherent questions. Although I tend to focus on the Mouat Vapor System, I've lurked on other topics to find, in general, the contributors on the Wall all tend to be remarkable individuals.

Steam Bunny

reservoir piping

Thanks Gerry,

Certainly looks innocuous, until you start estimating size for 3000 EDR. (roughly 27' @ 30 min) Figure the final product might double as an interesting massage table. Oh Well.

gerry gill

thats the idea, yup

the boiler is one side of the monometer, and the tank is the other..only difference is there is boiler pressure exerted down on one side, and close to boiler pressure exerted down on the other..its basically a ''fat'' A dimension.. but the tank has to sit horizontal at the waterline.

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Rodney Summers

After spending the

time it takes to drink 6 mugs of coffee reading your tome, I am still not certain if there's a question, or a statement involved.

Be that as it may, I want to throw a concept at you that soemone else may have already mentioned, but I didn't see.

The principal shortcoming of todays' boilers to replicate the coal fire dynamics all vapor systems require, is the on-off nature of replacement boiler/bruners.

Your focus has been boilers. Have you considered a modulating burner arrangement? Here's the solution I envision as a true home-run solution.

If you replicate the gentle nature of coal fires, almost all other issues become moot. Take a look at this:

1) Weil McLain model 980.

2) Instead of the suggested (for 1-2 # steamers) 2- 4" riser tappings/sections, order the boiler with an ADDITIONAL 4" tapped center section, making it have three risers instead of just two!

3) Order it with PowerFlame's HTD (High Turn Down) fully modulating gas power burner, controlled by the ubiqutous Honeywell L91B1019 "modulating vaporstat" as the operating controller.

4) The burner is the secret, not the boiler or near boiler piping. Having a burner capable of staying lit in the ounce range of pressure, and making it gentle and nearly a constant "steaming rate" is the secret. This will eliminate all the side baggage of most of the "issues" you are legitimately conerned with IMHO.

Imagine a boiler/burner that could maintain EXACTLY 5 ozs. of pressure for HOURS, without cycling on or off - on a cold day. Can you hear the angels singing?

Make any sense?



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Steam Bunny

Mouat, vapor w/ Full Modulation?

You are absolutely AMAZING! How you read my post and extracted what you did is beyond my comprehension!

Exactly! Beyond having something that works, my fantasy is to be able to "stoke" the new boiler. Except for cost, had been contemplating ganging a couple of LGB's together.

Then, because it has a lower water line, a gentleman mentioned the Burnham 5B. When I pulled their brochure off the Internet I noted the full modulation capability which- to a novice- sure sounds attractive. Before I know ANYTHING about it I find myself *wasting time* contemplating the piping.

This a.m. I find your post and am so EXCITED to even think full modulation could be where it's at. I think I have a bit of homework to do.

Don't wander too far, I've got a feeling I'll have a lot of questions.

Many many thanks!!!!

gerry gill

Ken is correct

Ken is 100% correct..the firing rate is what matters on vapor..not the boiler..great point, easily overlooked..

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c.t.kay

boiler/burner

kens post is the way to do this installation.look at smith 19 series,weil mclain 80 or 88 series ,etc.boiler/burner combinations, not atomspheric boilers.

Steam Bunny

Mouat Vapor w/ Full Modulation

Yes, I finally feel we might be on the right track.

Have been having difficulty locating Ken's suggested Weil McLain 980 over the Internet. Will look at what you list so I can at least get my feet wet.

Good timing- thanks

c.t.kay

980

the 9 is the amount of sections, the 80 is the series.

Steam Bunny

Mouat vs. Boiler Feed Pump vs. Reservoir Tank

Got it!

Thank you again

Steamhead

SteamBunny

Can you post some pics of your current boiler installation? This may help us answer your questions better...... Also (unless I missed it) where are you located? Cleveland area maybe?

Rodney Summers

The secret lies in the burner,

Not the boiler!

I just happen to like W/M steam boilers. The 80 series is simply a minor variation and the latest incantation of an old proven cast iron steamer. I would expect actual/real AFUE numbers around 86% with the Power Flame full mod HTD (high turn down) burner. They claim it will go as low as 10:1 firing rate on the lowest firing rate. The best I ever got was about 6:1 Even that is remarkable IMHO and extremely reliable and efficienct throughout the entire firing range. With the computer E-PROM type Honeywell independent air/gas train chipset controller, we have one we installed about 6 years ago on the NY/NJ border that never required more than an annual service and check out. The damn thing never lost the initial program we programmed with our laptop in all those years.



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Steam Bunny

Angels Singing

Ken,

I can't hear the angels singing, but I think that's 'cause they're all on the Wall. In the meantime, I think I must of gone to heaven! Keep pinching myself to make certain I'm not havin' 'nother dream.

SteamHead,

I'm developing another *tome* as Ken calls them.
Will post as soon as it's in some sort of ordely fashion.
Sorry to take so long.

Steam Bunny

Mouat vs. Boiler Feed Pump vs. Reservoir Tank

SteamHead,Ken, et al

Yes, I could take photos of any areas in question, but I'm not certain what I'd be taking and/or if it would provide any insight.

Awhile back I overlaid the main, wet, and dry returns over a blueprint of our basement, traced risers, etc. I also drew the critical heights on a plywood board using a water tube.

For starters, I've written down much of this information for you to scan/pick out what might appear to be relevant.
Attached is the .doc file with that information. Any and all questions would be welcome! If you or anyone else requires another format don't hesitate.

If Ken's Weil McLain 80 with power flame really exists, it'll be the first time I've seen a solution able to accommodate the heating lifestyles of a homes present and future occupants. As I've ruled the thermostat for so long, I'm a bit apprehensive re a computer chip taking charge, but there seem to be too many positives to be worrying about that right now.

I tentatively have a contractor who comes highly recommended by a number of sources, particularly Weil McLain. He is, however, reluctant to give it a go without a boiler feed pump- perhaps because of house size. As my intentions are to try to keep the gravity-feed portion of the system in tact, I find myself proposing to him rather than the other way around. Any suggestions regarding additions to or modification of the near boiler piping, to optimize its chances for success, would be deeply appreciated.

Ken's novel suggestion to order an extra tapping for the 980 with 4" risers appears to cut the steam velocity down to 20 ft./sec. (assuming my math is correct). Does getting it closer to 15 make any sense?

Steamhead

First of all

the system needs more venting. Each steam main should have its own vent. What pipe sizes are used on mains 1, 2A and 2B?

The dry return must be well vented too, this is what vents the air from the radiators. If the old Mouat setup is gone, you should be able to use maybe two Gorton #2 vents.

And you say someone put a vent on a wet return??!? Just when I thought I'd heard everything.....

In the Mouat, like in any Vapor system, there must be a way to keep steam out of the dry return. Mouat did this with water seals, but you can also use thermostatic traps for this.

The radiators that were converted to one-pipe may be using the original steam runouts. These are no doubt undersized for one-pipe operation, which is likely the cause of the banging. You need to change them back.

Ken's idea of a third tapping is good. If you run all the steam risers from the boiler into an oversized drop header, this will lower the steam velocity even more. If the original boiler had a proper header, and that header is still there, you can run a single pipe from the new header into the old, which will further reduce velocity to what it was originally at that location. We did this on a Kriebel system and it worked beautifully.

Steam Bunny

Wet Return 1 Starts at 1¾” & ends with 2” /is 130ft long/ radiators= 1936 edr
Wet Return 2a Starts at 1” & ends with 1¼”/ is 42ft long/ radiators= 626 edr
Wet Return 2b Starts at 1” & ends with 1¼”/ is 30ft long/ radiators= 558 edr
(cumulative transverse area = 6.36 sq. in)

Steam Bunny

Steam Bunny

Mouat vs. Boiler Feed Pump vs. Reservoir Tank

Size of mains are listed at their 1st down riser to dry return. I've listed the edr of each because I'm not certain if total load is a factor.

Main 1= 5” / radiators= 1796 edr

Main 2a=2 ½ / radiators= 626 edr

Main 2b=3” / radiators= 558 edr

Attached is photo of Main 1 and how it's vented. Couldn't get it in one shot. I'm standing in the center turning left {snap}, then right {snap).

Glad to hear you'd vent all the Mains! I look forward to doing that and putting the one on the wet return out of its misery. The vent piping to the chimney is still here a few inches from the dry return(s), so you're right on when you say he wanted lots of air.

Am I right in thinking this was never a vacuum system?

Rodney Summers

Without knowing

the existing wet and dry vent piping, I am NOT agreeing more venting is needed. The Kreibel system has one vent - period. It is not on the main, but on the dry/vent return.

True, you could stick a bowling ball through the system vent hole, but venting the main per se is not the best or only idea IMHO.

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Steamhead

Pics didn't come thru

try again?

Given the small air holes in those Mouat water seals, you would definitely find the radiators at the ends of the mains lagging those closer to the boiler if the mains aren't properly vented. I've done this to similar water-seal Vapor systems such as Broomell and VECO, with good results.

When boilers ran on coal, you could get away with fewer vents because once the air was out, it stayed out- so what if the process took an hour? Nowadays we don't have that kind of time with oil or gas firing.

gerry gill

yup,

steve and me have found we need to vent the crap out of the old mouat systems to get them to work right on gas..there just isn't any significant pressure to push the air out otherwise..his systems were basically designed to simmer rather than being inferno's..

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Steam Bunny

Mouat Main Vent

Sorry. repeat- couldn't get straight on, so had to turn left (snap) then right (snap). Vent downfeeds directly into wet return.

Re Ken's statement, Attached could have been an after thought/addition. Quickly visited "newer" Mouat system today; it was also vented at end of main, owner still has originals- Wish I could recall piping, as (in hindsight) it may have been one of those works of piping art.... eg won't vent if/while water in riser to wet is stacked.

I'm convinced our frozen returns were due to lack of venting- so have inclination/urge to vent everything; just hope there'll be some *me-steam* left over for tinkering once new boiler goes in.

Got a "sizing reservoir pipes" paper today. 'tis in poor shape, will attach once I've had a chance to clean it up.

gerry gill

isn't that vent

venting the dry return prior to its drop to the wet return? if so thats the way it should be..

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Steam Bunny

No, photo can be confusing, look again.

On right is Main 1 getting ready to reposition itself closer to the ceiling. But it unloads/drips first from the bottom. Rust colored pipe then carries condensate to T on left. Vent is straight up (near ceiling) and dry return is straight down near floor.

Dry return is hidden behind & parallels main. A condensate collector, it doesn't do any touchdowns until it gets to the boiler, as in condensate expressway. (I wonder if at sometime during the cycle, *boiler stacking* might force wet return to *stall*. In *my* boiler,the wet & dry returns seem to be isolated from one another & have separate tapings to the boiler. Maybe I have a "C" dimension?

Black Pipe above is a radiator down feed to dry. Alum. on left is one of the indirects I had to squeeze next to to get photos.

Steamhead

Actually

the vent in the photo is venting the steam main via the drip. The drip goes down to a floor-level return, that's the "wet" return. You probably don't need a vent there, all your venting capacity should be at the end of the steam main.

Which vent is on the dry (overhead) return? This is where the air from the radiators would end up.

Steam Bunny

Mouat Venting

A Mouat Vent is off horizontal piping at end of dry return. Althought it tends to *drool* it works, but I've long suspected it's not handling the combined 3 mains real well.

Unrelated question- as in am I missing something?:
Attached is what I believe I saw yesterday. Can you see vent accommodating(???) end of Dry & Main? Can you explain what happens when/if the water stacks in the wet return??? Or doesn't it?

Steam Bunny

Mouat venting

A Mouat vent is off dry return via horizontal pipe. It works, but tends to *drool*; I've long suspected it's not enough venting for the 3 mains.

An unrelated question as in, am I missing something?

The attached (scroll down to schematic) is what I believe I saw yesterday at another Mouat home- vent seems to accommodate both dry and main. Can you explain what happens when/if condensate begins to stack in the wet return? Or doesn't it?

Steamhead

It only vents the dry return

air from the steam main in this setup must pass thru the radiators to reach the vent. You could get away with this in the coal-fired days- once the air was out, it stayed out- but not with oil or gas, even if you used modulation firing. The burner would start at high fire and modulate down from there, instead of starting slowly like a coal fire. Starting at high fire would produce lots of steam quickly, and it wouldn't distribute thru the mains quickly without proper main vents.

Steam Bunny

so am I correct in presuming they have to add a vent to each and every main- presuming it's not there already?

gerry gill

yes,

thats correct..vent each main by some means, ie. air vents or crossover traps..

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patrick linhardt

vents in the wrong place

Hi Steamhead,

Couldn't resist telling you of a #75 Hoffman vent I found one day installed on the steam header. The previous installer put a tee on the equalizer drop off the header instead of an elbow, bushed the top run down to 3/4" and mounted a vent. You can't make this up. I think I'm getting a chance to look at this job again. If so, I will have to get a picture. You'll love it. What are people thinking?

Best regards, Pat

Jammer

One common mistake is sizing steam based on Low Pressure Standards (1 Square Foot Load requires 240 BTUH).

A properly functioning Vapor/Vacuum Steam system can operate anywhere from 120 BTUH per Square Foot to 240.

If you have insulated the building and the pipes well you may find the system will operate well with a smaller boiler PROVIDED the system functions well.

The first sign of a misfunctioning vapor-vacuum steam system is actually LOSS of heat in some rooms, etc.

Jammer Don