New Steam Boiler or not

M Ransley

We have a 40-50 yr old Kewanee heating 16 units. It has always been maintained, and does not break down and works fine but needs tubes. Several repairmen have said keep it, keep it repaired as a new unit will have the same running efficiency. But efficiency may increase 1 - 3 % due to new units holding less water to heat to steam. For the cost of a new boiler I can not see a payback unless it is more than that. Well our repairman changed his mind to salesman of a new boiler. Is efficency of new units basicly the same, why would I want a new unit since mine is upgraded, maintained and works fine.

J.C.A._3

The payback....

May be a little longer than the makers would like you to believe, but with the price of fuel (any fuel) going up, it may be a quicker payback.

The biggest factor being, that you'll have less water that has to be steam.As long as the manufacturers piping instructions are followed, the unit will provide the necessary heat faster, thereby saving you money.

The biggest thing you should be worrying about is the INSTALLER.Will he follow the directions and do it right...or will he come up with some shortcut and make matters worse?The manufacturers have far more time to play with boilers than any installer will ever dream about having. They've been there and tried that. What is written in their instruction manuals isn't guess work. Any alteration of the suggested piping IS guesswork. Make yourself informed about the proposed boiler and make sure the installer will follow the recomendations of the manufacturer. P.S. I would dump the Kewanee boiler if it was mine. Things have moved forward and the numbers you're getting are only combustion efficentcy, not system efficency . Chris

M Ransley

JCA What % efficiency increase do you feel I will get with a new unit

J.C.A._3

M,

just edited my previous post to say SYSTEM efficentcy. That will be the key.
Are all the steam pipes still insulated? Are the main vents proper for the system? Are all the radiator vents/traps working properly? Is the boiler sized properly?

These are the things that make the SYSTEM efficent. The combustion process is but a part of the equation.

As to how much %age you'll save...it all depends on the other factors being, or being done right. Chris

M Ransley

Yes everything is insulated even the boiler has an extra 12 - 16" of fiberglass I put on. Vents are new or good Gordon, System is balanced. I just spoke to my repairman and he said my efficiency is apx 50 % for the Kewanee { a lie? } . Another Tech I had out last year said it was near 74- 80% and used a Bachrach gas analyser and set burners up right. So what do old Kewanees run in efficiency when set right as mine is ? Someone is lying to me. I know new units are 80-82% efficient are there higher eficiency units that are good and trouble free ? My repair guy who is good said I am calcified up, But If I install new tubes and decalcify I wont be- right? So what is the truth about my efficiency and if you are qualified and work Chicago south side I would be interested. To save 5 % on utilities is not logical on an investment of this size. 50 yr old forced air was 50% efficient, now up to 94.5% avg. (96.7% one model one brand } . 50 yr old H.W. heat was 65-73% now it is up to 99% [ one model] but averages 93-95%. I research before I buy but any help is apreciated. This is a good group of Pros, unlike the rude people at alt. Hvac " Hacks R Us " Thanks" Wall"
I am in Chicago and looking for Qualified help. If you are real good and have the right information contact me.

Steamhead

Boiler Efficiency ratings

There are two commonly in use: Combustion efficiency and Annual efficiency (a.k.a. AFUE).

Combustion efficiency just measures how efficiently the burners are working. This is what your tech measured with his digital analyzer. It has nothing to do with what happens to the heat after it is released from the combustion process.

Annual efficiency is the amount of heat released from the boiler to the system piping, measured over the course of a "typical" heating season. This includes any losses incurred when the burners are off. As you might expect, Annual efficiency is usually lower than Combustion efficiency. Good luck trying to determine annual efficiency on your Kewanee- it was made long before the test was introduced.

You might compare Annual efficiency to the EPA's miles-per-gallon ratings for vehicles. The test may or may not reflect real-world conditions, but it gives you a way to compare one unit to another.

Also, once the boiler has released the heat to the system piping, its job is done. From there the system must move the heat to the radiators. Depending on what type of steam system you have, you may be able to make this process more efficient too.

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Ken_8

If you have a typical

3-pass, scotch marine Kewanee from 50 years ago you will gain nothing by changing the boiler - unless you replace it with a battery of condensing boilers!

A 50 year old scotch marine Kewanee was and is still state of the art for fire tube boilers and can easily attain 85+ S.S. efficiency. With a full mod burner, you can retube that thing forever. The end of that boiler will be apparent when the outer shell or tube sheet goes bad. Retubing is inexpensive and borders on once every ten years maintenance. Had cathodic or chemical treatment been done more often - the tubes would still be fine.

A large condensing boiler would be a home run with fueld costs where they are. But a conventional boiler will be nearly identical as what you already have.



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oil-2-4-6-gas

.

take that Kewanee out and instal a nice 4-pass Cleaver Brooks that would be the only single-scotch marine that would give you increased efficiency or just retube the Kewanee--treat and monitor the water --unless you never had treatment /if you never had treatment after 20-30 years of not having it-this would be a problem ---what size boiler are we talking 50 hp? gas or oil ?

M Ransley

How do I tell if it is a 3 pass Scotch Marine. It has 2 groups of tubes separated by 6 ? " inches. What is 3 pass? 4 pass? Thanks.

M Ransley

My installer said the real high efficiency units units are 3 times as much, I think he is full of it and scared of the instal. I did not know Condensing steam was made

Ken_8

Sorry!

I did not read thoroughly enough to see you mentioning the system was steam. Or did you?

Three pass scotch marine boilers are rather typical and common forms. The Kewanee you mentioned is most certainly of that configuration. The three passes are comprised of what I call the "morrison" tube (the first "pass," where the flame occurs and is frequently refracted to allow reflected radiation to aid in complete combustion; the second "pass" which is simply the first "bank" of lower tubes that starts at the back door and by virtue of a door baffle (prevents the hot gasses from simply going out the last/third pass), back through the boiler via tubes and then around a similar baffle plate on the front door - only to be forced through the next (upper) bank of tubes, and then to a breech cavity where the gasses discharge from the boiler - typically with most of the heat being extracted along the passes.

Two and four pass fire tube boilers also exist however. Scotch marine type simply means horizontal, entirely wet backed and tubular in HX formation.

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M Ransley

Since I have a Scotch Marine Kewanee of 85% efficiency what will a new small steam unit save me by heating a smaller amounts of water? Are not new boilers 82% efficient. Therefore I do not see a savings, just a way to put 17 - 20,000 in my installers greedy fat pocket.

Boilerpro_3

MY thoughts and experiences...fwtw

Kewanee made a great boiler! They were more or less just down the road and I see them regularly. However, I have also replaced many and other large firetube boilers.
First off, I believe that these boilers were designed for industrial applications for heavy continuous loads and work very efficiently for that application....85 to 87 % firing efficiency. However, putting that same boiler into a heating application, especially steam, where the load is very light most of the time can kill the seasonal efficiency because of the potential for huge standby losses. How light that load is depends on a few things
1) Was the boiler sized to the radiation or greatly oversized (most are)
2) Steam boilers have large pick up factors, typically, that "oversize" the boiler when sizing it according to traditional methods
3) The original radiation was also likely to be oversized for the heating load, but not always. However, if you have insulated, added storms, etc, you now have oversized radiation.
4) Radiation is sized to heat the structure assuming no internal gains due to people, susnlight etc. In most apartment buildings these internal gains are significant, and greatly reduce the heat load. IE. I have a 10 unit building built in the 1970s.. typical insulation.... that is heated on all but the most extreme days by a single 100,000 btu/hr input 80% boiler. You can figure between 10 to 20 % of the buildings peak heat load will be met by internal gains and the bigger the structure the higher the percentage. The big buildings downtown run cooling almost all winter.

When combining all these factors together, it is not uncommon for a steam boiler to run at about 20% capacity or less nearly the whole winter... which really hurts your efficiency.

That being said, I am pretty positive that your burner setup will make a big difference ( I don't work on industrial power burners). If you have atmospehric, your losses are probably huge, if you have a sealed power burner that greatly decreases air flow through the boiler during off cycles, losses will be less, even though you still loose a bunch with the atmospheric damper.

My experience with hot water boilers of your type is when I have replaced them with 80% step fired boilers and added good controls to the system, I have seen savings from 35 to 75%. The 75% number was on a Kewanee with atmospheric burner installed in a church that maintained water temp continuously, with much of the structure at setback temperature. Boiler input was right on for heat load. Was replaced with 2 small cast iron power vent boilers with a full set of system controls. They say they now keep the sturcture at higher temps now that the fuel bills are so low.

I suspect you may see some significant savings if you go to a similiar setup in steam (small step fired boilers). I expect to be installing one of these setups in a system soon. I am also looking at setting up to do work in Chicago during my lighter season, so E-mail me if you'd like.

Boilerpro, a former southsider.

John Mills_3

I don't think you are understanding

what the guys are saying about efficiency.

Perfectly tuned & clean, you may be able to get over 80% combustion efficiency. That means after fully warmed and no cycles, it could do that well. But reread what Boilerpro said about using that boiler in a space heating situation:

"However, putting that same boiler into a heating application, especially steam, where the load is very light most of the time can kill the seasonal efficiency because of the potential for huge standby losses."

Annual efficiency rates what the real efficiency is. It looks at how inefficient the boiler is during startup until fully warm, it also looks at those pesky standby losses. Could it be as low as 50%? No way of knowing. You certainly are far less of the 82% or whatever AFUE of today's equipment. Will it pay to replace? Maybe not.

Might want to see if Boilerpro can check out the situation in the future and see what he has to say after seeing it in person. Then let us all know!

M Ransley

I need to do more research obviously. The Tech said condensing boilers are 3 times the cost, unreliable and unperfected, which I do not believe. The boiler has an additional R 45 insulation around it and I am sure it is oversized. But the amount of water it heats is to great for efficiency. 2 things come to mind for improving efficency, changing the burner to a modern outside air intake and an automatic damper that closes the chimney when unit is shut off. Those 2 alone Ive read may save 10- 20% on gas. So how does one calucalate overall efficiency, can it be done, or done for a fair cost.

M Ransley

Boiler pro what is your E Mail address. This is a south side building