rads very hot at top but stone cold below - low pressure arco system

elfie

have an old arco system (ie. no traps or vents, only use an orafice opening into rads)



is it of concern to have top half of several rads very hot and radiating heat, and then lower half stone cold?  condensate return pipe is cold too.



rads are very old and will be tough to replace.



thanks

Jamie Hall

Not really...

steam rises, after all, when it gets into the radiator.



It could be indicative of a problem if the radiator never ever got hot most of the way down, even on a very long run.  In which case it might be that the lines leading to those radiators (or the returns to which they empty) aren't adequately vented.



There isn't much, after all, that can go wrong with a hunk of iron, assuming it doesn't leak.

ttekushan_3

perfectly normal

Steam heats sequentially. Every steam radiator fills this way.



The real question is, "Is the room comfortable?" If so, there is no other concern. If not, then it is an issue of distribution of steam effected by venting of mains and/or returns or boiler steam capacity vs radiator condensing capacity.



EDIT: and I will add that this is the hallmark of a well calibrated vapor system if the total percentage of each radiator being heated this way is about the same. Furthermore, orifice vapor systems with no traps really should never heat the entire radiator as the last 10% or so of the radiator is actually a "post condenser" to prevent steam from ever hitting the returns.

elfie

thanks

thanks for great comments, the rooms are getting warm just fine.  we just reduced the pressure in the system and are beginning to see how it was meant to be. 



these orafice systems are really remarkable (no traps, vents)



not sure i understand why the orafice styles rad are not more common



big question is, how long will these rads last?? what can be done to take care of rads to achieve a longer life?  a few have leaked and were removed.

Jamie Hall

There isn't much

that can go wrong with a radiator.  Most of the radiators in the place I care for are 83 years old, and very few problems.  One of the previous supers had a couple of radiators leak and removed them, sadly -- I've not been able to find replacements (yet -- haven't looked all that hard).  I've had a couple leak, but there are several different ways to repair them, ranging from absurdly simple (JB Weld sometimes works) to a bit difficult but not impossible -- taking the leaking sections apart and replacing the nipple which has rotted out.

elfie

rads used with coal boiler

these rads date back to when they used coal  so 80 yrs may be how old rads are.



there are 35 functioning rads in total and question is how best to evaluate them, or like AC compressors, they die when they die and its impossible to predict and then cure the damage.



the system may be gutted when they decide to install a/c to one floor of bldg, which means that a forced air heating system will be considered to share the central air ductwork.



and yes, they probably would gut/remove a good arco steam system.