coal boiler with radiant heat

Ken_40

Great application! Yes, coal is okay w/radaint. The fuel is virtually immaterial; how it's piped up everything.

Is the system a hybrid? Meaning, part steam, part hot water? If so, a heat exchamger has to be in there somewhere. If straight hot water, some HWBB or HWRadiators and some radiant mixed in, an "absolute" control that prevents the boile from going to steam MUST be in place. The open expansion tank is a weak link unless the "control" is absolutely fail-safe and can absolutely prevent water temps from hitting 212F. This can be accomplished by either shedding load by over heating something, or turning off the coal flame in a few seconds - which ain't happenin'!

Oxygen in the water is a major problem. Even with an air scoop.

Before we pot-shot the solution to death, perhaps a few digital photos could be sent? Just make sure to reduce them to a max of 600 pixels wide and they'll travel nicely.

<A HREF="http://www.heatinghelp.com/getListed.cfm?id=504&Step=30">To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"</A>

Marty Wallace

coal boiler with radiant heat - operation questions

A cousin lives in Pennsylvania coal country and naturally burns coal in his home boiler. Recently renovated, he created 12 (yes, 12!) zones of heat - about 6 zones of radiant floor and 6 conventional cast iron baseboard radiation, plus a tankless heater. Supply comes off boiler and feeds all 12 zones at the same temp. In the radiant floor zones, he has both underfloor wood as well as concrete floors. I believe he has a mixing valve for the concrete floor zone, to keep it around 85 or so. He would normally run the boiler supply temp at about 180 deg, but was told that the radiant floor system plastic manifolds were only rated for 180, so he should run the boiler cooler. So he now runs at 140 supply, which I am told is still too hot for the underfloor zones. My thought is that this is too cool for the boiler - he will have condensation problems in the boiler and chimney (single wall galvanized to the masonry flue) with presumably a 120 or even 110 deg return temperature. Would anyone agree? I've suggested that he go back to running at 180 degrees and install a mixing valve (or valves) for the groups of zones - one for underfloor, one for concrete floors.

He also has a problem with the plastic manifolds leaking at the plastic - not the tubing/manifold joints. Seems like a crack develops. I didn't get the part manufacturer, unfortunately. Anyone have this problem before? Several have already been replaced within a year of installation.

He has an open expansion tank - his contractor didn't recommend a bladder tank, I guess he's (my cousin) had a lot of problems with the bladder types failing fairly quickly after installation. Does oxygen in the water have anything to do with this? I think he has an air scoop in the line somewhere, but not sure. Sorry I wasn't paying attention.

Any thoughts/comments would be greatly appreciated.