radiators half hot - traps or vents?

johnd

I was looking at two pipe  residential unit yesterday. When the boiler fired one radiator heated up very quickly (less than five minutes), but the other six radiators got warm slowly and grdaually ( more than ten minutes, and you could feel the supply pipe get hot, then the heat slowly moved across the rest of the radiator).

All of the radiators only got hot in the top half, the bottoms stayed cool. the main vent on the return seemed to be working. I'm wondering if  the problem may be at the radiator traps, or if i should take another look at the venting. 

Jamie Hall

That one radiator

that gets hot quickly -- in about the length of the time all of them should, in fact -- may have a failed trap.  That would do it...

Dave in QCA

uneven distribution

Most 2-pipe steam systems have small radiator supply pipes, usually 3/4 or 1".  This tends to create a little bit of an orifice effect and helps to even out the distribution.  Another thing that can cause problems is if a trap or traps are replaced with one that has different venting characteristics than the rest of the system.  Are your traps all the same make and model?   I recently installed inlet orifice plates to even out my 2-pipe system and was surprised when I found that one of my radiators, it a system of 32 radiators, had an orifice in it.  As would be expected, it was not heating very well.  I would advise looking in the valve of the slow radiator.   Also, there were some valves from the past that had orifices built into them.  What type of valve is on this radiator.   Pics always help!  Please post some pics of your system and the radiator, valves, traps, etc.