Arcola Boiler

Alan (California Radiant) Forbes

I don't run into many of these. The serial number is 4AA.

A thing of beauty, but it's spewing CO like nobody's business.

Steamhead

What kind of gas was in use when that boiler was installed?

nicholas bonham-carter

I see a new hot water heater next to it. Could that installation have interfered with the chimney draft, causing more CO?--NBC

Charlie from wmass

Rusted burners could also be the culprit. I am assuming they are cast iron. By spewing you mean in the exhaust or out the hood into the room?

Alan (California Radiant) Forbes

Steamhead: It's in Berkeley and has probably always been natural gas.

NBC: Could be, but I doubt. It's drafting well.

Charlie: I placed my probe well inside the draft hood and got a 1,000 ppm CO reading. I also tested at the upper air holes in the jacket of the boiler and got 400 ppm. Could be a packing leak between the sections or at the collector at the top.

Steamhead

Alan (California Radiant) Forbes said:

Steamhead: It's in Berkeley and has probably always been natural gas.

Might wanna go digging and see what you find. Baltimore was supplied with Manufactured Gas up till the mid 1950s, so every appliance had to be retrofitted when "The Consolidated Gas and Electric Light and Power Company of Baltimore" made the switch to NG.

When I run into a boiler installed before the switch, there is a (puts on orange toupee) YUUUGE (removes toupee) possibility it's making high CO. The reason is, the length of the MG flame was a lot shorter than the current NG one. So, in a smaller firing zone designed for MG, the longer NG flame is a lot more likely to impinge on the cast-iron sections, which causes high CO (this info came from Tim McElwain, who encountered the same thing in Providence). And since they didn't have digital analyzers then, like we do now, very often the high CO went undetected. Adding primary air and reducing the firing rate brings the CO down, and since almost all of these units are oversized, they still heat the buildings just fine.

So: with the combustion analyzer set up and operating, the first thing I'd do is open the primary air shutters all the way. If this causes the flames to lift off the burners, close the shutters just enough to stop the lifting. This will shorten the flame length as much as possible. Then I'd clock the meter and see if the boiler is consuming more gas than it is rated to- if so, I'd dial it back. If the CO was still too high, I'd back off the gas pressure a bit until the CO drops. You want to get it down below 50 PPM air-free if you can. If your best efforts can't get it down below 100 PPM air-free, I would suggest replacing the unit.

Tim McElwain's manuals have the best discussion of CO from gas combustion I've ever seen. If you don't have them, you owe it to yourself to get them.