How do steam and hydronic boilers differ in construction?

Forest

Hi, all, are steam and hydronic boilers built any differently from one another? I've read enough to understand how some of the apparatus around the boiler differs, but I haven't seen any discussion of how the design of these boilers might differ.

Thanks!

Forest

delcrossv

Leaving condensing hot water boilers out of the mix, then no. The heat exchangers are identical.

Intplm.

https://forum.heatinghelp.com/discussion/comment/1834478#Comment_1834478

Or to put it another way, the sections on boilers via manufacturers are the same.

Big Ed_4

A proper steam boiler would have a large chest to collect the dry steam .

EBEBRATT-Ed

Back in the day it was common for steam & water boiler to be 100% the same boiler.

The boiler brochure would state steam rating and hot water rating. The only thing that changed was the controls and trim.

delcrossv

https://forum.heatinghelp.com/discussion/comment/1834491#Comment_1834491

If only. Not these days.

Long Beach Ed

While most hot water boilers can produce steam, there are characteristics that will make one boiler produce better, dryer steam than another. Ideally, a steam boiler:

Will accommodate a sufficient size outlet(s) to limit the steam's exit velocity minimizing carry-over of water into the header.

Will be configured to retain a stable water line while steaming.

Will have sufficient steam volume in the sections above the water line to enable the departure of steam at the water line.

Will have sufficient size connecting nipples to assure a contiguous steam chest space above the water line.

Have sufficient water capacity to permit the rated steaming capacity.

Will be configured to control fireside temperatures above the water line reducing damage to the iron from mineral deposits and reactions.

Some manufacturers' boilers satisfy these goals better than other manufacturers. Many simply slap a gauge glass on their water boilers, print a manual specifying huge header piping and sell their water boiler as steam boilers. There was an age when steam boilers were rated for their steam quality. Since those ratings are no longer published, the boiler quality was diminished. Recently some manufacturers have returned to designing small residential boilers with qualities favoring steam.

delcrossv

Recently some manufacturers have returned to designing small residential boilers with qualities favoring steam

@Long Beach Ed care to name some names?

Long Beach Ed

Burnham has made a huge effort to design two boilers specific to steam, and has done a great job: MegaSteam for oil and SteamMax for gas. True steam-only boilers of beautiful design.

Unfortunately Burnham also had serious casting and design problems a decade ago with some earlier designs which caused many of them to fail prematurely with tainted water qualities. Those failures precipitated the design of these improved models. To their credit, they voluntarily offered some compensation to owners years after the expiration of their warranties.

Everyone here has their favorite. I'm sure they'll tell you.

ethicalpaul

Peerless 63/64. I don't know if it has different castings for its water and steam boilers, but I can say with complete certainty that it delivers steam with no visible water to its supplies with nothing more (and actually considerably less) than manufacturer-specified piping.