Sizing

Coolmen

I replaced a steam gas boiler with a similar Btu type. Being I only had access late evening and did not have access to measure the radiators.
They complained that in cold morning pipes are noisy .
Today I went back and pitched a few rads replaced a few vents and measured the EDR.
Total was 200 edr x 240 comes to 49,000 Btu
Where I installed a crown 138 or 85,000 Btu
So I’m 36% oversized it seems. Any adjustments could I do before deciding to put in a 60,000 Btu and be 19% oversized. Maybe a couple air vents? Has anyone else had to deal with this ?

mikeg2015

Dimensionally the smaller boiler is probably the same on critical connection points. Might be money ahead to switch it out rather than a dozen call backs and installing vents.

What does the near boiler piping look like?

EBEBRATT-Ed

If your EDR is 49000 you need to add the piping and pick up and the boiler efficiency to that #

49000 x 1.33 (piping & pick up)=65,170/ .80 (boiler efficiency)=81,462 would be the correct BTU input

Your boiler is 138,000 input.

Every one has dealt with this. All the boilers in old houses were over sized.

It would have been a lot better if you had access to size it properly.

The boiler size has nothing to do with the banging.

If the piping is right and the venting is right and the boiler has been skimmed it will work .......but it will short cycle on pressure

You have to keep the pressure down to 1 psi, 2psi max

gfrbrookline

My boiler is similarly oversized. Mass out the main venting with Big Mouths, it may take multiples of them, and add gorton vents to the radiators, sized to match the radiator and run out edr.

Doing this made my system quiet, heating is even, and eliminated the short cycling. I also run 2 cph when the outside temp drops below 20 which reduces overall boiler run times.

Hap_Hazzard

The new boiler probably has a smaller steam chest that the one it replaced, which would make any marginal near boiler piping issues more critical. Can we see some pictures?

Coolmen

What I found is while running system yesterday with 3 pm 40* temp out door, No banging. They have been setting thermostat back at night 67* and at 5:30 am kick in at 70*. On the very cold mornings is when they here it.
I will replace all rad vents with adjustable types
Inform them to simply leave at 70* with no set back. Also 2 rads were not pitched near noisy side of house.
I could add a air vent to the main fairly easy to connect to a unused cap pipe where a rad once
Was connected to. (My thinking is this would slow down the velocity of the steam some)?
System was installed back in November and wasn’t an extrem problem. None likes being waken up 5:30 in the morning to ticks , bangs
Been doing hvac for 28 yrs and winter time I’ll do a dozen or more water boilers Replacement a yr.
I replaced maybe 5 steam

Coolmen

I reconnected my 2” in away that was done previously. Being the water heater is smack up against the main I couldn’t run the tee the other way.

Coolmen

So 49,000 Btu x 1.33 = 65170. Btu
Shouldn’t this be matched to the out out of my boiler but not the IBR rating since I calculated the piping all ready.

ethicalpaul

How did that compare to the diagram in the manual?

That's a hard question to ask, and maybe to answer, but I ask it plainly because I can tell that you are interested in the topic and want to improve your steam knowledge.

That piping will likely result in water being carried into the main which can cause a lot of different problems.

The job of the near boiler piping is to let (force!) water droplets to separate from the steam. This piping does not do that, but it can be corrected pretty easily I think, especially since the joints haven't gotten to rigor mortis yet.

Also regarding the sizing, why bring BTU into it? Just compare the EDR of the radiation to the net EDR on the boiler plate.

And I wouldn't say the boiler size has nothing to do with the banging. The faster steam production/velocity of an oversized boiler (especially with this piping) will result in more water getting thrown into the main, right @EBEBRATT-Ed ? (I realize I say this with the benefit of having seen the photos, and you hadn't seen them yet)

PS: Plus the copper isn't great. I think to do an install you have to follow the manual's instructions regarding pipe material and layout. Otherwise there's a risk of the term "cut and slide" that I've seen some folks use.

mattmia2

The existing copper if nothing else is a red flag that you better check the existing system is correct before installing a new boiler.

Coolmen

This is the current layout. I took my time exam it all yesterday and did not do this first time around .
I am hear for knowledge and knew that the connection supply although was reconnected as before was not to the install manual.
Bottom drawing was what I believe to be the right take off.
It would not take much to repipe that connection.

KC_Jones

Crown boiler with 138k input is rated for 354 sq ft of steam. That boiler is 77% over sized, that's crazy.

measured EDR 200
Rated EDR 354
oversized by 154 EDR
154/200=.77
.77x100=77%

The near boiler piping is completely wrong and will amplify the sizing issues. The existing system piping (doesn't appear to be original since it's copper) was done improperly at some point. Returns are supposed to connect below the water line on a one pipe system. System take offs are to come off of header individually. You don't even have a header to come off of.

Serious question, there was a diagram in the manual, is there a reason you didn't follow it? We see installs like this all the time, but I think this is the first time I've seen an installer post for us to ask the question.

I'm glad you are here for knowledge, so please soak it all up.

If you are going to keep that over sized boiler, I would suggest you need to add the second riser and an oversized 3" header to dramatically slow down the steam at the boiler. In all honesty you have an uphill battle on your hands versus a properly sized boiler.

A Weil Mclain EG-30 would pretty much be a perfect size for that system.

Coolmen

I have no problem removing and down sizing.
In 28 yrs this would be a first screwup design for me and will own up to it. Looking at the chart for crown going down to a BSI 103 seems still over sized and not as much . The BSI069 seems a little undersized.

ChrisJ

Coolmen said:

I have no problem removing and down sizing.

In 28 yrs this would be a first screwup design for me and will own up to it. Looking at the chart for crown going down to a BSI 103 seems still over sized and not as much . The BSI069 seems a little undersized.

Why didn't you follow the manual?

Coolmen

Thank you all for your info that I will take with me for future reference. I will be downsizing bsi103 and repiping my header.

ethicalpaul

Your customer will be in good shape! Please come back and post the results and bask in the glory! Then advertise in this site's Find a Contractor tool and use your install photos to show off your install. If you are in Westchester Co, NY, or southern Michigan, people will beat a path to your door!

EBEBRATT-Ed

@ethicalpaul

Well the piping is all wrong, that will make any boiler bang sized right or over sized.

Also, I don't think the size of the boiler has anything to do with velocity, yes it can make more steam in a given period of time, but it's the piping leaving the boiler and the radiation load and how much steam it will condense that determines the flow through the piping.

jmho

ChrisJ

EBEBRATT-Ed said:

@ethicalpaul

Well the piping is all wrong, that will make any boiler bang sized right or over sized.

Also, I don't think the size of the boiler has anything to do with velocity, yes it can make more steam in a given period of time, but it's the piping leaving the boiler and the radiation load and how much steam it will condense that determines the flow through the piping.

jmho

With a hot system yes.
With a cold system, the cold mains, piping and cold radiators can suck down a whole lot more if the boiler will supply it.

Jamie Hall

ChrisJ said:

EBEBRATT-Ed said:

@ethicalpaul

Well the piping is all wrong, that will make any boiler bang sized right or over sized.

Also, I don't think the size of the boiler has anything to do with velocity, yes it can make more steam in a given period of time, but it's the piping leaving the boiler and the radiation load and how much steam it will condense that determines the flow through the piping.

jmho

With a hot system yes.
With a cold system, the cold mains, piping and cold radiators can suck down a whole lot more if the boiler will supply it.

Hence... pickup factor!

ChrisJ

Jamie Hall said:

ChrisJ said:

EBEBRATT-Ed said:

@ethicalpaul

Well the piping is all wrong, that will make any boiler bang sized right or over sized.

Also, I don't think the size of the boiler has anything to do with velocity, yes it can make more steam in a given period of time, but it's the piping leaving the boiler and the radiation load and how much steam it will condense that determines the flow through the piping.

jmho

With a hot system yes.
With a cold system, the cold mains, piping and cold radiators can suck down a whole lot more if the boiler will supply it.

Hence... pickup factor!

Exactly correct Jamie, and it's there for just that. Pickup. It was determined to give faster recovery times while not building pressure excessively. From what I recall, in schools after winter shut down, churches etc.

But then, members on here who tell people they need a "pickup factor" say not to do setbacks. So...........it's kind of counter productive. Oversize the boiler to do a more rapid recovery but then say not to ever do setbacks because of it.................

Gerry Gill shared an article on it a while back as well as it's original name. Piping and Pickup factor.

Meanwhile, I can easily do a 10 degree recovery and never cycle on pressure.

EBEBRATT-Ed

In a normal sized house with little to no set backs the pick up factor of 1.33 can probably be reduced safely if the piping is insulated.

A church or other large building not so much

Coolmen

About 18” above water line I’d need to elbow as shown to get around the chimney then to a header is ok ?

Jamie Hall

You know, if you had turned that boiler 90 degrees clockwise, so the controls were facing the room, you might have had a chance to do some decent piping. As it is... yes, the riser would have come up under the stairs, but as best I can judge you could probably have managed a usable drop header arrangement.

Also... do I see copper?

I'm sorry to say this, but I think I would just take the whole thing apart, turn the boiler 90 degrees, and put in a proper drop header and all in black iron. Lose the copper.

mikeg2015

The water heater just needs to move.

If the main and returns are insulated decently, id go with the smaller size. You still have 10-20% pickup.

I’m of the opinion that EDR gets overestimated. It’s based on 2psi steam temp, and a fairly cool indoor ambient temp, unpainted radiators and doesn’t always take shape, floor coverings, wall clearance and floor clearance all impact output negatively. Plus traps and vents usually close before the very last section is fully heated.

But main venting needs to be good if your a little tight on sizing.

KC_Jones

Coolmen said:

About 18” above water line I’d need to elbow as shown to get around the chimney then to a header is ok ?

It isn't clear what you are proposing, but by your mark up it still won't be correct. You currently do not have a header. The header is supposed to be horizontal. So the boiler take off comes up, turns 90°, horizontal pipe that has the system take off coming from the top, then after the last take off a 90° elbow down to the equalizer. Also the entire header is to be, at minimum, 24" above the water line.

The system mains are to tie into the header individually, not be connected then have a single connection into your header. If this is single pipe steam the returns are not to be tied above the water line like they are, that creates difficulty balancing the system.

And I agree with the above get rid of all the copper above the water line.

Charlie from wmass

Down-firing a gas boiler by simply removing the orifices and plugging off where the burners are creates negative combustion effects which can greatly increase carbon monoxide production and increases condensing at startup through the heat exchanger which will lead to increased corrosion of the heat exchanger and greatly shorten the life of the boiler. It is known as hackery to do such things unless you are in desperate straits. The only time of boiler should be down fired by removal is if you are removing the manifold and replacing it with a proper manifold for allure fire rating approved by the manufacturer of the boiler. I don't care how many years somebody does something wrong or incorrect it doesn't make it right. the only way to size of boiler is by radiation if you're using any other method please stop. If you'd be to use to tell me what size of steam boiler you need please stop.

Coolmen

This is how I’m proposing the new riser and header.
Right side of boiler is a storage right to boiler is why equalizer did not go out other side.

Coolmen

Any problems with my diagram

KC_Jones

If I am interpreting it correctly I think you are ok.

Just to reiterate the header need to go in this order from one end to the other, without combining connections like you had on the original.

Boiler riser(s), system take off(s), equalizer, in that order from one end to the other with the highest point being the boiler riser and sloping down towards the equalizer.

Coolmen

the header pitched slightly towards equalizer. None of my books or diagrams show this but would assume to. If level would the force of stream push it in the direction.

KC_Jones

Level in theory will be ok, but keep in mind the pitch is slight. 1" in 20', I use 1/16" per foot which is slightly more.

Water runs down hill. There is water in that header and it needs to flow to the equalizer, hence the need for some slope. I doubt any manufacturer feels the need to explain this in their manual.

Coolmen

Removed copper and repiped.

KC_Jones

Much better.