New boiler time

Neild5

Our condo association is going to have to replace the boiler. It is an 11 year old Dunkirk rated at 1.5 million BTU and there are 8 or 9 cracks in 5 sections. All the cracks are about 2 inches from the top. So now I am having contractors look at it to quote a replacement. What a difference between the various guys that are coming out to size up the system. Had one look at the near boiler piping and comment how wrong it was done, but he recommended removing the boiler and replacing it with the same size/brand boiler so the piping doesn't have to be changed. He didn't ask how much radiation was connected, the boiler is rated for over 1100 sqft EDR more than is in the building. One more is coming out tomorrow, then the board will have to decide which one of the 4 to go with.

Neild5

The side outputs are 4 npt brushed down to 3. The cracks can be seen in 3 of the sections.

HVACNUT

Any blue prints that show all the rads and connected piping?
Otherwise they should be knocking on doors. With masks and gloves at the moment. Unfortunately.

Neild5

I have already done a full inventory of the radiators with pictures, if he had asked he would have been given a copy. I figured it would be a way to filter out the knuckleheads.

Steamhead

@Neild5 , those aren't "cracks". They're evidence of corrosion. That boiler series is not known for longevity or tolerance of a lot of make-up water, but it should have lasted longer than that.

You have leaks in that system- time to look for them. Look for bad vents, packing nuts that aren't tight or that need repacking, buried return lines etc.

Where are you located?

Neild5

I am in Chicago, the Steam Whisperer has been out and he was the one who pointed out the cracks. I have designed and machined cast iron parts and there are definite cracks 14 to 18 inches long in 8 places.

Steamhead

Well, if the sections had cracked from dry-firing, the cracks would be toward the bottom of the sections. You need to find the leaks.

And you've already found the right contractor.

JUGHNE

Knowing the connected EDR, I wonder if the boiler would be undersized to that point plus more for the radiation probably being oversized to the building heat loss.

Maybe 2 or 3 smaller staged boilers?

Neild5

Cracks are all at the top of the sections, about an inch below the top, even with the top of the side outlet fitting. I know I have the right contractor, just have to have additional quotes to appease the board.

The Steam Whisperer

That sure does sound like cracks from the header

JUGHNE

I noticed that the center burner section is shut off, is that the way it has been operated?

pecmsg

You need a Mechanical Engineer to go thru "Everything" with this system.

Agreed 2 or 3 separate boilers.
Lead / lag / standby

Find and fix the leaks.

Spend the money upfront finding the causes then save on the replacement over time.

Neild5

Yes, it is being run with 2 burner sections since the three are rated for 3633 and the radiator inventory is 2565. With all 3 sections running it cycles like crazy and the guy who installed it had the pressurtrol set to 8 psi. With 2 sections running it was running at 4 oz max pressure with it being -5 F.

EBEBRATT-Ed

Cheapest way out that will work is to change the boiler and install the same thing. Header is ok just fix the risers to the boilers with swing joints and make them 4". Monitor the make-up water and if it's adding excessive water find and fix the leaks.

Looks to me like there was another boiler there before this one, then they screwed up the piping when this boiler was installed.

Those risers are supposed to come off the boiler 4" and go straight up at least 20" then go to the header 4"

Neild5

The building was built in 1927, the coal boiler was replaced in the early 60's with gas, mid 80's and again in 08 or 09.

pecmsg

Neild5 said:

The building was built in 1927, the coal boiler was replaced in the early 60's with gas, mid 80's and again in 08 or 09.

So it was never sized properly to begin with!

Fred

Are the cracks in the middle of the boiler? I know the uneven heat distribution by not running all three burners, much like taking burner tubes out of a smaller boiler, runs the risk of causing sections to crack because of the uneven heating of those cast iron sections. I'm not sure if the cracks would show up on the top or bottom of the sections though.

Neild5

It was sold to the board to be multi stage without any type of special controls. He claimed that when fall came one section would heat the building, as it got colder section 2 would fire and section 3 on the worst days and be a backup in case one of the other 2 failed.

EBEBRATT-Ed

Yes that is the way those boilers operate. The burners are in sections. They don't all fire at the same time. Those boilers have been made for a long time. In you case it's 3 stage gas firing

Double D

Which model Dunkirk do you have? In the D249 manual there is no mention of stage firing. In the D247 manual page 17. They are recommending you do not stage fire with steam.
STAGE FIRING MULTIPLE BASEBOILERS
1.STEAMBOILERS Multiple base steamboilers should not be stagefired due to fluctuations in water line between fired and unfiredbases.The boiler should be all bases on or all bases off.When more precise control than a single thermostat offers is required, a weather responsive duty cycle control such as the Honeywell model ZG-54 or the HeatTimer model MP Cormode lEPU or a similar type of control should be used. These controls determine boiler runtime based on outdoor
temperature. Consult the various control manufacturers. It stage firing is required, consult the boiler manufacturer.

2.HOT WATER BOILERS Multiple base hot water boilers are ideal for stagefiring. Many controls are available for sequencing or stage firing multiple base hot water boilers. We offer a W7100J Outdoor Reset Stage Fire Control Package that will sequence up to six bases, with lead/lag, softstart, adjustable reset ratio and setpoint, and microprocessor control. This control will fire bases as required to maintain supply water temperature at a desired setpoint, which is automatically varied based on outdoor air temperature. Consult the boiler manufacturer for more information.

JUGHNE

There is often the warning for downfiring boilers by removing burners......official and otherwise......that this will harm the boiler.

There were early boilers that had one burner capped to drop the BTU size down. It was always the outer end burner(s).

So one wonders if no fire in the center but on each end would that be the possible source of cracking?

Double D

It would be nice to find out that is true that this boiler can be stage fired with only left and right base because I have a customer that has one that is grossly oversized.