Is This 'Storage Rust' on Section of New Boiler?

D107

Month-old install; I expect final tuneup and control tweaks to be finished tomorrow. Peerless MI-03; looking forward to seeing significant savings over old oversized boiler. Yesterday I took a look at the cast iron sections and found one apparently with rust. What does this look like? Should it be cleaned up? This section is on same side as the return. When boiler was first installed for a few days I did smell some kind of mild chemical steam-humid-smell but attributed it to the inhibitor and de-mineralizer installed in the system water.

Steamhead

Yes. It's just on the surface, won't affect the boiler's lifespan. Don't worry.

Tim McElwain

Watch out that it did not get hit with very low temperature on the return. That can sometimes cause this to happen. Other than that it is probably okay.

D107

@Tim McElwain thanks--how would I tell what the cause is? Or tell if it's surface rust or worse? The Hydrostat 3200+ has a circulator hold feature.

JohnNY

It's not a problem. I see it all the time.

Tinman

The two on the right are actually the unusual ones.

mikeg2015

It’s so even and consistent that I’d guess it rusted at the factory. They made a batch of left end sections that sat on a pallet all winter then humidity condensed on them that spring or something like that.

To save costs, they probably have to order batches of each section type (right, left, middle) in quantities of maybe 500 (total guess) or more or as long as a mold set will produce before rebuild/replacement or whatever determines a run length at the foundry.

D107

@mikeg2015 I took a look under the boiler and found what look like some rust spots on the cement block, and also--other photo not that clear--two rust marks on one of the firing tubes, which I would assume have come from the sections above.

Makes me wonder, maybe a leak between sections that has since sealed itself with rust? Or if somehow outside water touched the rusted section and dripped down? We have a water meter on the feed you can read down to .01 gallon showing no water lost at least in a few weeks since I noted the reading. See photos.

Tim McElwain

Is this on the return side of the boiler. If so there is a possibility of condensation if there is a drop in temperature of the water returning to the boiler. Anything less than 140 degrees can start to condense and cause evidence of water which is actually the condensate and not a water leak. What is the temperature of the water leaving the boiler and the water returning? It should typically be as close to a 20 degree (delta T) difference. As the return temperature drops from the 20 degrees the potential for condensing increases.

D107

Yes, on return side. I've always heard that as long as temp gets above 135 or so within 10 minutes there shouldn't be a problem. Peerless installs a hydrostat 3200+ on the boiler which has a 'circulator hold' feature which will not allow circ to run until boiler temp reaches 125, and will then shut it off when it falls to 115. Possibly similar to Buderus' Logamatic 'Pump logic'. I know those are low numbers but apparently Peerless sanctions it. Two of three of our zones are cast iron so there is quite an initial cold return, esp in shoulder season where heat cycles are farther apart. (Heat loss 38K, more likely 30K.) We don't have t-stat setbacks and I think within ten minutes or so return temps are ok but will have to watch this next season.

mikeg2015

Could add a aquastat in series with the circulator so it doesn’t come on until above 125 at the boiler.

Zman

D107 said:

Month-old install; I expect final tuneup and control tweaks to be finished tomorrow. Peerless MI-03; looking forward to seeing significant savings over old oversized boiler. Yesterday I took a look at the cast iron sections and found one apparently with rust. What does this look like? Should it be cleaned up? This section is on same side as the return. When boiler was first installed for a few days I did smell some kind of mild chemical steam-humid-smell but attributed it to the inhibitor and de-mineralizer installed in the system water.

I think the the factory stored those end sections longer or in a more humid warehouse than the others. You would have to be returning super cold water (50 degrees?) to get condensation on the outside. The water would then need to warm up instantly as it passed to the next section. I just don't see it.

If you wipe the 2 unrusted sections with mineral spirits to get the oils off and then spray them with a mist of water, you will get them to match nicely

D107

@Zman Thanks for clarifying the physics of this--something we homeowners can't always visiualize since we don't work with boilers everyday. So the other good news I take from your post is that even where there is condensate arising from low return temps, that is all external to the system water in boiler, piping, etc. --fire-side only..

The only question I have is that I have heard rust once started is a continual process that never stops, so should the rust on that section be removed/cleaned up? Or if it/s just from storage is the rust process so slow--and maybe inevitable with cast iron that is exposed to sometimes-humid summer ny air--that it's not an issue?

Zman

If you are getting low return temps, the damage would be on the fire side of the boiler and inside the vent.
I would not worry about light rusting on the outside of the sections.

Tim McElwain

@d107 you can reach me at my e-mail address timmcelwain@gastcri.com .